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Pharyngeal electrical stimulation (PES), a novel noninvasive peripheral nerve stimulation technique, can effectively improve neurogenic dysphagia and increase the safety and effectiveness of swallowing in the clinic. However, the lack of animal models for dysphagia has limited the mechanistic research on PES, which affects its wide application. Therefore, determining optimal parameters for PES in rats is needed to enable mechanistic studies. Modified PES (mPES), which has different waves and pulse widths from PES, was used; in previous studies mPES was found to have a neurological mechanism like that of PES. A poststroke dysphagia (PSD) model was established, and rats with dysphagia were grouped into three different intensities (0.1 mA, 0.5 mA, and 1 mA) for the selection of optimal intensity and three different frequencies (1 Hz, 2 Hz, and 5 Hz) for the selection of optimal frequency based on a stimulation duration of 10 min in the clinic. A Videofluroscopic Swallow Screen (VFSS) was used to assess swallowing function in rats before and after mPES treatment. The results showed that the 1 mA group had better swallowing function (p < 0.05) than the model group. Compared with the model group, the 1 Hz and 5 Hz groups had the same improvement in swallowing function (p < 0.05). However, the increase in excitatory signals in the sensorimotor cortex was more pronounced in the 5 Hz group than in the other frequency stimulation groups (p < 0.05). Combining the clinical findings with the above results, we concluded that the optimal stimulation parameter for mPES in rats is "frequency: 5 Hz, current intensity: 1 mA for 10 min/day", which provides a basis for future basic experimental studies of mPES in animals. • mPES was firstly confirmed to improved swallowing function significantly in PSD rats. • 1 mA intensity of mPES has more pronounced improvement of swallowing in PSD rats. • 1 Hz and 5 Hz frequency of mPES carry out significant effect on swallowing function. • 5 Hz frequency of mPES exhibits maximal cortical excitatory activation in PSD rats. • Ischemic stroke rats showed significant swallowing disorders. [ABSTRACT FROM AUTHOR]

A central goal of neuroscience is to understand how populations of neurons coordinate and cooperate in order to give rise to perception, cognition, and action. Nonhuman primates (NHPs) are an attractive model with which to understand these mechanisms in humans, primarily due to the strong homology of their brains and the cognitively sophisticated behaviors they can be trained to perform. Using electrode recordings, the activity of one to a few hundred individual neurons may be measured electrically, which has enabled many scientific findings and the development of brain-machine interfaces. Despite these successes, electrophysiology samples sparsely from neural populations and provides little information about the genetic identity and spatial micro-organization of recorded neurons. These limitations have spurred the development of all-optical methods for neural circuit interrogation. Fluorescent calcium signals serve as a reporter of neuronal responses, and when combined with post-mortem optical clearing techniques such as CLARITY, provide dense recordings of neuronal populations, spatially organized and annotated with genetic and anatomical information. Here, we advocate that this methodology, which has been of tremendous utility in smaller animal models, can and should be developed for use with NHPs. We review here several of the key opportunities and challenges for calcium-based optical imaging in NHPs. We focus on motor neuroscience and brain-machine interface design as representative domains of opportunity within the larger field of NHP neuroscience.

While the majority of children with febrile seizures have an excellent prognosis, a small percentage are later discovered to have cognitive impairment. Whether the febrile seizures produce the cognitive deficits or the febrile seizures are a marker or the result of underlying brain pathology is not clear from the clinical literature. We evaluated hippocampal and prefrontal cortex function in adult rats with a prior history of experimental febrile seizures as rat pups. All of the rat pups had MRI brain scans following the seizures. Rats subjected to experimental febrile seizures were found to have moderate deficits in working and reference memory and strategy shifting in the Morris water maze test. A possible basis for these hippocampal deficits involved abnormal firing rate and poor stability of hippocampal CA1 place cells, neurons involved in encoding and retrieval of spatial information. Additional derangements of interneuron firing in the CA1 hippocampal circuit suggested a complex network dysfunction in the rats. MRI T2 values in the hippocampus were significantly elevated in 50% of seizure-experiencing rats. Learning and memory functions of these T2-positive rats were significantly worse than those of T2-negative cohorts and of controls. We conclude that cognitive dysfunction involving the hippocampus and prefrontal cortex networks occur following experimental febrile seizures and that the MRI provides a potential biomarker for hippocampal deficits in a model of prolonged human febrile seizures.

Silent information regulator 1 (SIRT1) plays a beneficial role in cerebral ischemic injury. Previous reports have demonstrated that transcutaneous electrical acupoint stimulation (TEAS) exerts a beneficial effect on ischemic stroke; however, whether SIRT1 participates in the underlying mechanism for the neuroprotective effects of TEAS against ischemic brain damage has not been confirmed. The rat models of middle cerebral artery occlusion/reperfusion (MCAO/R) were utilized in the current experiment. After MCAO/R surgery, rats in TEAS, EC and EX group received TEAS intervention with or without the injection of EX527, the SIRT1 inhibitor. Neurological deficit scores, infarct volume, hematoxylin eosin (HE) staining and apoptotic cell number were measured. The results of RNA sequencing were analyzed to determine the differential expression changes of genes among sham, MCAO and TEAS groups, in order to investigate the possible pathological processes involved in cerebral ischemia and explore the protective mechanisms of TEAS. Moreover, oxidative stress markers including MDA, SOD, GSH and GSH-Px were measured with assay kits. The levels of the proinflammatory cytokines, such as IL-6, IL-1β and TNF-α, were detected by ELISA assay, and Iba-1 (the microglia marker protein) positive cells was measured by immunofluorescence (IF). Western blot and IF were utilized to examine the levels of key molecules in SIRT1/FOXO3a and SIRT1/BRCC3/NLRP3 signaling pathways. TEAS significantly decreased brain infarcted size and apoptotic neuronal number, and alleviated neurological deficit scores and morphological injury by activating SIRT1. The results of RNA-seq and bioinformatic analysis revealed that oxidative stress and inflammation were the key pathological mechanisms, and TEAS alleviated oxidative injury and inflammatory reactions following ischemic stroke. Then, further investigation indicated that TEAS notably attenuated neuronal apoptosis, neuroinflammation and oxidative stress damage in the hippocampus of rats with MCAO/R surgery. Moreover, TEAS intervention in the MCAO/R model significantly elevated the expressions of SIRT1, FOXO3a, CAT, BRCC3, NLRP3 in the hippocampus. Furthermore, EX527, as the inhibitor of SIRT1, obviously abolished the anti-oxidative stress and anti-neuroinflammatory roles of TEAS, as well as reversed the TEAS-mediated elevation of SIRT1, FOXO3a, CAT and reduction of BRCC3 and NLRP3 mediated by following MCAO/R surgery. In summary, these findings clearly suggested that TEAS attenuated brain damage by suppressing apoptosis, oxidative stress and neuroinflammation through modulating SIRT1/FOXO3a and SIRT1/BRCC3/NLRP3 signaling pathways following ischemic stroke, which can be a promising treatment for stroke patients. • Transcutaneous electrical acupoint stimulation (TEAS) alleviated brain injury following ischemic stroke. • TEAS inhibited oxidative stress by activating SIRT1/FOXO3a signaling pathway in MCAO/R rat model. • TEAS suppressed neuroinflammation through modulating SIRT1/BRCC3/NLRP3 signaling pathway in MCAO/R rat model. [ABSTRACT FROM AUTHOR]

Abstract Peripheral nerve regeneration following injury is often incomplete, resulting in significant personal and socioeconomic costs. Although a conditioning crush lesion prior to surgical nerve transection and repair greatly promotes nerve regeneration and functional recovery, feasibility and ethical considerations have hindered its clinical applicability. In a recent proof of principle study, we demonstrated that conditioning electrical stimulation (CES) had effects on early nerve regeneration, similar to that seen in conditioning crush lesions (CCL). To convincingly determine its clinical utility, establishing the effects of CES on target reinnervation and functional outcomes is of utmost importance. In this study, we found that CES improved nerve regeneration and reinnervation well beyond that of CCL. Specifically, compared to CCL, CES resulted in greater intraepidermal skin and NMJ reinnervation, and greater physiological and functional recovery including mechanosensation, compound muscle action potential on nerve conduction studies, normalization of gait pattern, and motor performance on the horizontal ladder test. These findings have direct clinical relevance as CES could be delivered at the bedside before scheduled nerve surgery. Highlights • Conditioning crush lesions promote sensorimotor nerve regeneration but are not clinically feasible. • Conditioning electrical stimulation promotes nerve regeneration and sensorimotor recovery superior to the conditioning crush. • Electrical stimulation is clinically safe, well-tolerated, and can be performed prior to a scheduled nerve repair surgery. • Conditioning electrical stimulation may significantly improve clinical outcomes for patients with peripheral nerve injuries. [ABSTRACT FROM AUTHOR]

Highly varying patterns of electrostimulation (Dynamic Stimulation, DS) delivered to the dorsal cord through an epidural array with 18 independent electrodes transiently facilitate corticospinal motor responses, even after spinal injury. To partly unravel how corticospinal input are affected by DS, we introduced a corticospinal platform that allows selective cortical stimulation during the multisite acquisition of cord dorsum potentials (CDPs) and the simultaneous supply of DS. Firstly, the epidural interface was validated by the acquisition of the classical multisite distribution of CDPs and their input-output profile elicited by pulses delivered to peripheral nerves. Apart from increased EMGs, DS selectively increased excitability of the spinal interneurons that first process corticospinal input, without changing the magnitude of commands descending from the motor cortex, suggesting a novel correlation between muscle recruitment and components of cortically-evoked CDPs. Finally, DS increases excitability of post-synaptic spinal interneurons at the stimulation site and their responsiveness to any residual supraspinal control, thus supporting the use of electrical neuromodulation whenever the motor output is jeopardized by a weak volitional input, due to a partial disconnection from supraspinal structures and/or neuronal brain dysfunctions. • Two epidural MEAs simultaneously stimulate motor cortex and record spinal CDPs. • Selective cortical stimulation evokes multiple CDPs before contralateral EMGs. • Stronger cortical pulses progressively recruit CDP waves and full muscle contraction. • Spinal DS selectively potentiates the P 2 peak of CDPs while facilitating MEPs. [ABSTRACT FROM AUTHOR]

The delivery of a nerve insult (a “conditioning lesion”) prior to a subsequent test lesion increases the number of regenerating axons and accelerates the speed of regeneration from the test site. A major barrier to clinical translation is the lack of an ethically acceptable and clinically feasible method of conditioning that does not further damage the nerve. Conditioning electrical stimulation (CES), a non-injurious intervention, has previously been shown to improve neurite outgrowth in vitro. In this study, we examined whether CES upregulates regeneration-associated gene (RAG) expression and promotes nerve regeneration in vivo, similar to a traditional nerve crush conditioning lesion (CCL). Adult rats were divided into four cohorts based on conditioning treatment to the common peroneal (fibular) nerve: i) CES (1 h, 20 Hz); ii) CCL (10 s crush); iii) sham CES (1 h, 0 Hz); or iv) naïve (unconditioned). Immunofluorescence and qRT-PCR revealed significant RAG upregulation in the dorsal root ganglia of both CES and CCL animals, evident at 3–14 days post-conditioning. To mimic a clinical microsurgical nerve repair, all cohorts underwent a common peroneal nerve cut and coaptation one week following conditioning. Both CES and CCL animals increased the length of nerve regeneration (3.8-fold) as well as the total number of regenerating axons (2.2-fold), compared to the sham and naïve-conditioned animals (p < 0.001). These data support CES as a non-injurious conditioning paradigm that is comparable to a traditional CCL and is therefore a novel means to potentially enhance peripheral nerve repair in the clinical setting. [ABSTRACT FROM AUTHOR]

Individuals with pharmacoresistant epilepsy remain a large and under-treated patient population. Continued technologic advancements in implantable neurostimulators have spurred considerable research efforts directed towards the development of novel antiepileptic stimulation therapies. However, the lack of adequate preclinical experimental platforms has precluded a detailed understanding of the differential effects of stimulation parameters on neuronal activity within seizure networks. In order to chronically monitor seizures and the effects of stimulation in a freely-behaving non-human primate with idiopathic epilepsy, we employed a novel simultaneous video-intracranial EEG recording platform using a state-of-the-art sensing-enabled, rechargeable clinical neurostimulator with real-time seizure detection and wireless data streaming capabilities. Using this platform, we were able to characterize the electrographic and semiologic features of the focal-onset, secondarily generalizing tonic-clonic seizures stably expressed in this animal. A series of acute experiments exploring low-frequency (2 Hz) hippocampal stimulation identified a pulse width (150 μs) and current amplitude (4 mA) combination which maximally suppressed local hippocampal activity. These optimized stimulation parameters were then delivered to the seizure onset-side hippocampus in a series of chronic experiments. This long-term testing revealed that the suppressive effects of low-frequency hippocampal stimulation 1) diminish when delivered continuously but are maintained when stimulation is cycled on and off, 2) are dependent on circadian rhythms, and 3) do not necessarily confer seizure protective effects. [ABSTRACT FROM AUTHOR]

Rat models of complete and partial injuries are the most frequently used models for analysis of the cellular and molecular processes of nerve regeneration and axon sprouting. Studies of nerve regeneration and axon sprouting after complete and partial nerve injuries, respectively, are reviewed. Special consideration is made of the peripheral nerves chosen for the studies and the outcome measures that were utilized in the studies. The studies have made important contributions to our knowledge of the degenerative and regenerative processes that occur after the peripheral nerve injuries, why functional recovery is frequently compromised after delayed surgery, the positive effects of neurotrophic factors on nerve regeneration after delayed nerve repair or after insertion of autografts between transected nerve, and how axon regeneration may be accelerated by brief periods of electrical stimulation and/or by administration of androgens. [ABSTRACT FROM AUTHOR]

Noxious input can sensitize pain (nociceptive) circuits within the spinal cord, inducing a lasting increase in spinal cord neural excitability (central sensitization) that is thought to contribute to chronic pain. The development of spinally-mediated central sensitization is regulated by descending fibers and GABAergic interneurons. The current study provides evidence that spinal cord injury (SCI) transforms how GABA affects nociceptive transmission within the spinal cord, recapitulating an earlier developmental state wherein GABA has an excitatory effect. In spinally transected rats, noxious electrical stimulation and inflammation induce enhanced mechanical reactivity (EMR), a behavioral index of nociceptive sensitization. Pretreatment with the GABA A receptor antagonist bicuculline blocked these effects. Peripheral application of an irritant (capsaicin) also induced EMR. Both the induction and maintenance of this effect were blocked by bicuculline. Cellular indices of central sensitization [ c-fos expression and ERK phosphorylation (pERK)] were also attenuated. In intact (sham operated) rats, bicuculline had the opposite effect. Pretreatment with a GABA agonist (muscimol) attenuated nociceptive sensitization in intact, but not spinally injured, rats. The effect of SCI on GABA function was linked to a reduction in the Cl − transporter, KCC2, leading to a reduction in intracellular Cl − that would attenuate GABA-mediated inhibition. Pharmacologically blocking the KCC2 channel (with i.t. DIOA) in intact rats mimicked the effect of SCI. Conversely, a pharmacological treatment (bumetanide) that should increase intracellular Cl − levels blocked the effect of SCI. The results suggest that GABAergic neurons drive, rather than inhibit, the development of nociceptive sensitization after spinal injury. [ABSTRACT FROM AUTHOR]

Myelinated axons efficiently transmit information over long distances. The apposed myelin sheath confers favorable electrical properties, but restricts access of the axon to its extracellular milieu. Therefore, axonal metabolic support may require specific axo-myelinic communication. Here we explored activity-dependent glutamate-mediated signaling from axon to myelin. 2-Photon microscopy was used to image Ca 2 + changes in myelin in response to electrical stimulation of optic nerve axons ex vivo . We show that optic nerve myelin responds to axonal action potentials by a rise in Ca 2 + levels mediated by GluN2D and GluN3A-containing NMDA receptors. Glutamate is released from axons in a vesicular manner that is tetanus toxin-sensitive. The Ca 2 + source for vesicular fusion is provided by ryanodine receptors on axonal Ca 2 + stores, controlled by L-type Ca 2 + channels that sense depolarization of the internodal axolemma. Genetic ablation of GluN2D and GluN3A subunits results in greater lability of the compact myelin. Our results support the existence of a novel synapse between the axon and its myelin, suggesting a means by which traversing action potentials can signal the overlying myelin sheath. This may be an important physiological mechanism by which an axon can signal companion glia for metabolic support or adjust properties of its myelin in a dynamic manner. The axo-myelinic synapse may contribute to learning, while its disturbances may play a role in the pathophysiology of central nervous system disorders such as schizophrenia, where subtle abnormalities of myelinated white matter tracts have been shown in the human, or to frank demyelinating disorders such as multiple sclerosis. [ABSTRACT FROM AUTHOR]

Functional recovery after peripheral nerve injury and surgical repair declines with time and distance because the injured neurons without target contacts (chronic axotomy) progressively lose their regenerative capacity and chronically denervated Schwann cells (SCs) atrophy and fail to support axon regeneration. Findings that brief low frequency electrical stimulation (ES) accelerates axon outgrowth and muscle reinnervation after immediate nerve surgery in rats and human patients suggest that ES might improve regeneration after delayed nerve repair. To test this hypothesis, common peroneal (CP) neurons were chronically axotomized and/or tibial (TIB) SCs and ankle extensor muscles were chronically denervated by transection and ligation in rats. The CP and TIB nerves were cross-sutured after three months and subjected to either sham or one hour 20 Hz ES. Using retrograde tracing, we found that ES significantly increased the numbers of both motor and sensory neurons that regenerated their axons after a three month period of chronic CP axotomy and/or chronic TIB SC denervation. Muscle and motor unit forces recorded to determine the numbers of neurons that reinnervated gastrocnemius muscle demonstrated that ES significantly increased the numbers of motoneurons that reinnervated chronically denervated muscles. We conclude that electrical stimulation of chronically axotomized motor and sensory neurons is effective in accelerating axon outgrowth into chronically denervated nerve stumps and improving target reinnervation after delayed nerve repair. Possible mechanisms for the efficacy of ES in promoting axon regeneration and target reinnervation after delayed nerve repair include the upregulation of neurotrophic factors. [ABSTRACT FROM AUTHOR]

The present review focuses on the physiological states of spinal networks, which are stochastically modulated by continuously changing ensembles of proprioceptive and supraspinal input resulting in highly redundant neural networks. Spinal epidural interfaces provide a platform for probing spinal network dynamics and connectivity among multiple motor pool-specific spinal networks post-injury under in vivo experimental conditions. Continuous epidural low-frequency pulses at low intensity can evoke motor responses of stochastically changing amplitudes and with an oscillatory pattern of modulation. The physiological significance of this oscillatory pattern, intrinsic to "resting" spinal networks and observed in both uninjured and injured locomotor circuits, is unclear. This neural variability among spinal networks appears to be a fundamental mechanism of the network's design and not a "noise" interfering with movement control. Data to date also suggest that the greater the level of stimulation above motor threshold, the greater the loss of modulation over the motor output that is physiologically provided by interneuronal networks, which integrate naturally occurring proprioceptive and cutaneous input generated during movement. Sub-motor threshold spinal electrical stimulation experiments demonstrate a range of functional improvements of multiple physiological systems when used in concert with sensorimotor training after spinal cord injury. Although our understanding of the systemic, cellular and molecular modulatory mechanisms that trigger these activity-dependent adaptive processes remain incomplete, some basic physiological principles have evolved, at least at the systemic and neural network levels and to some degree at the cellular level. [Display omitted] • Spinal sensorimotor networks are stochastically modulated, particularly by highly varying proprioceptive input. • The continuous arrival of multiple sensory modalities provides highly redundant neural networks that, at the systems level, are continuously in highly dynamic states. • An epidural interface can be used as an effective site to trigger spinally evoked potentials to probe activity levels of multiple motor pools simultaneously via muscle specific EMG. • Sub-motor threshold spinal neuromodulation amplifies and enables a wide range of voluntarily triggered motor activities after spinal cord injury and can acutely and selectively elevate the excitability of different neuronal networks to facilitate use-dependent mechanisms. • Use-dependent mechanisms can then be engaged to transform the reorganization of spinal-supraspinal networks to higher functional states. [ABSTRACT FROM AUTHOR]

Following a cerebral cortex injury such as stroke, excessive inhibition around the core of the injury is thought to reduce the potential for new motor learning. In part, this may be caused by an imbalance of interhemispheric inhibition (IHI); therefore, treatments that relieve the inhibitory drive from the healthy hemisphere to the peri-lesional area may enhance motor recovery. Theta burst stimulation delivered by transcranial magnetic stimulation has been tested as a means of normalizing IHI, but clinical results have been variable. Here we use a new rat model of synaptic IHI to demonstrate that electrical intracranial theta burst stimulation causes long-lasting changes in motor cortex excitability. Further, we show that contralateral intermittent theta burst stimulation (iTBS) blocks IHI via a mechanism involving cannabinoid receptors. Finally, we show that contralesional iTBS applied during recovery from cortical injury in rats improves the recovery of motor function. These findings suggest that theta burst stimulation delivered through implanted electrodes may be a promising avenue to explore for augmenting rehabilitation from brain injury. [ABSTRACT FROM AUTHOR]

Abstract: The relationship between dysmyelination and the progression of neuropathy in Charcot–Marie–Tooth (CMT) hereditary polyneuropathy is unclear. Mice heterozygously deficient for the myelin protein P0 gene (P0+/−) are indistinguishable from wild-type (WT) at birth and then develop a slowly progressing demyelinating neuropathy reminiscent of CMT Type 1b. Accumulating evidence suggests that impulse conduction can become lethal to acutely demyelinated central and peripheral axons. Here we investigated the vulnerability of motor axons to long-lasting, high-frequency repetitive stimulation (RS) in P0+/− mice as compared to WT littermates at 7, 12, and 20months of age. RS was carried out in interrupted trains of 200Hz trains for 3h. Tibial nerves were stimulated at the ankle while the evoked compound muscle action potentials (CMAPs) and the ascending compound nerve action potentials (CNAPs) were recorded from plantar muscles and the sciatic nerve, respectively. In 7-month old mice, there was recovery of CMAP and CNAP following RS. When mice were about one year old, electrophysiological recovery following RS was incomplete and in P0+/− also associated with morphological signs of partial Wallerian degeneration. The effect of RS was larger in P0+/− as compared to age-matched WT. When mice were about 2years old, the effect was stronger and became similar between WT and P0+/−. RS was followed by a transient hyperpolarization, which decreased with age and was smaller in P0+/− than in WT. Our data suggest that both aging and the dysmyelinating disease process may contribute to the susceptibility to activity-induced axonal degeneration. It is possible that in aging mice and in P0+/− there is inadequate energy-dependent Na+/K+ pumping, as indicated by the reduced post-stimulation hyperpolarization, which may lead to a lethal Na+ overload in some axons. [Copyright &y& Elsevier]

Abstract: Activity treatments are useful strategies to increase axonal regeneration and functional recovery after nerve lesions. They are thought to benefit neuropathy by enhancing neurotrophic factor expression. Nevertheless the effects on sensory function are still unclear. Since neurotrophic factors also play a fundamental role in peripheral and central sensitization, we studied the effects of acute electrical stimulation and early treadmill exercise on nerve regeneration and on neuropathic pain, and the relation with the expression of neurotrophins. After sciatic nerve section and suture repair, rats were subjected to electrical stimulation (ES) for 4h after injury, forced treadmill running (TR) for 5days, or both treatments combined. Sciatic nerve section induced hyperalgesia in the medial area of the plantar skin in the injured paw. TR and ES differently but positively reduced adjacent neuropathic pain before and after sciatic reinnervation. ES enhanced motor and sensory reinnervation, and combination with TR induced strong agonistic effects in relieving pain. The differential effects of these activity treatments were related to changes in neurotrophic factor mRNA levels in sensory and motor neurons. ES speeded up expression of BDNF and GDNF in DRG, and of BDNF and NT3 in the ventral horn. TR reduced the levels of pro-nociceptive factors such as BDNF, NGF and GDNF in DRG. Combination of ES and TR induced intermediate levels suggesting an optimal balancing of treatment effects. [Copyright &y& Elsevier]

Abstract: Mesial temporal lobe epilepsy (MTLE) is a common medically refractory neurological disease that has been treated with electrical stimulation of gray matter with limited success. However, stimulation of a white matter tract connecting the hippocampi could maximize treatment efficacy and extent. We tested low-frequency stimulation (LFS) of a novel target that enables simultaneous targeting of bilateral hippocampi: the ventral hippocampal commissure (VHC) with a novel in-vitro slice preparation containing bilateral hippocampi connected by the VHC. The goal of this study is to understand the role of hippocampal interplay in seizure propagation and reduction by commissural fiber tract stimulation. LFS is applied to the VHC as extracellular and intracellular recording techniques are combined with signal processing to estimate several metrics of epilepsy including: (1) total time occupied by seizure activity (%); (2) seizure duration (s); (3) seizures per minute (#); and (4) power in the ictal (V2Hz−1); as well as (5) interictal spectra (V2Hz−1). Bilateral epileptiform activity in this preparation is highly correlated between hippocampi. Application of LFS to the VHC reduces all metrics of epilepsy during treatment in an amplitude and frequency dependent manner. This study lends several insights into the mechanisms of bilateral seizure reduction by LFS of the VHC, including that depolarization blocking, LTD/LTP and GABAA are not involved. Importantly, enhanced post-stimulation 1-Hz spiking correlates with long-lasting seizure reduction and both are heightened by targeting bilateral hippocampi via the VHC. Therefore, stimulating bilateral hippocampi via a single electrode in the VHC may provide an effective MTLE treatment. [Copyright &y& Elsevier]

Abstract: Many types of electrical stimulation (ES) devices have been shown to promote the survival of degenerated neural cells, such as dopaminergic neurons in the medial forebrain bundle-transected rats, ischemic-injured cortical neurons and inner-and outer-nuclear-layer cells in degenerated retina. Using a rat photic injury model, our lab previously proved the neuroprotective effect of transcorneal electrical stimulation (TCES) on apoptotic photoreceptor cells. To delineate the mechanisms that might underlie this process, the effects of ES on light-damaged photoreceptor degeneration-induced microglia and Müller cell activation were investigated in the present in vitro study. Our data showed that ES (3ms, 20Hz, 300–1600μA) increased survival among light-reared cone-derived cells (661W) cultured alongside microglia or Müller cells analyzed by LDH and TUNEL assays. The degree of rescue was found to depend on the different intensities of the ES current. The immunocytochemistry revealed that ES significantly decreased the numbers of activated microglia cells with ameboid shapes and increased the numbers of reactive gliotic Müller cells with larger soma when they were co-cultured with light-damaged 661W cells. Real-time RT-PCR and Western blotting indicated that ES which was applied to different co-cultures and 661W cell-conditioned media (661WCM)-treated glia cultures had a prominent inhibitive effect on the secretion of interleukin (IL)-1β and tumor necrosis factor (TNF)-α in microglia and a positive regulative effect on the production of brain-derived neurotrophic factor (BDNF) and ciliary neurotrophic factor (CNTF) in Müller cells. The death rate of light-exposed 661W cells cultured with microglia was decreased significantly by the addition of neutralizing antibodies against IL-1β and TNF-α. On the other hand, the death rate of light-exposed 661W cells cultured with Müller cells was prominently increased when the co-culture was incubated in the presence of neutralizing antibody against BDNF while anti-CNTF neutralizing antibody did not induce additional exacerbation of the cell death among those 661W cells. These findings indicate the feasibility of using ES to create a nurturing environment for light-damaged photoreceptor cells. This environment is characterized by diminished microglial activation and fortified Müller cells reactive gliosis, which may have great potential in ameliorating photoreceptor damage. In this way, ES was here determined to be a novel, potent therapeutic option for delaying the progression of photoreceptor degeneration in patients suffering from retinitis pigmentosa (RP). [Copyright &y& Elsevier]

Abstract: The selectivity of neurons in sensory cortex can be modified by pairing neuromodulator release with sensory stimulation. Repeated pairing of electrical stimulation of the cholinergic nucleus basalis, for example, induces input specific plasticity in primary auditory cortex (A1). Pairing nucleus basalis stimulation (NBS) with a tone increases the number of A1 neurons that respond to the paired tone frequency. Pairing NBS with fast or slow tone trains can respectively increase or decrease the ability of A1 neurons to respond to rapidly presented tones. Pairing vagus nerve stimulation (VNS) with a single tone alters spectral tuning in the same way as NBS-tone pairing without the need for brain surgery. In this study, we tested whether pairing VNS with tone trains can change the temporal response properties of A1 neurons. In naïve rats, A1 neurons respond strongly to tones repeated at rates up to 10pulses per second (pps). Repeatedly pairing VNS with 15pps tone trains increased the temporal following capacity of A1 neurons and repeatedly pairing VNS with 5pps tone trains decreased the temporal following capacity of A1 neurons. Pairing VNS with tone trains did not alter the frequency selectivity or tonotopic organization of auditory cortex neurons. Since VNS is well tolerated by patients, VNS-tone train pairing represents a viable method to direct temporal plasticity in a variety of human conditions associated with temporal processing deficits. [Copyright &y& Elsevier]

Abstract: Administration of psychostimulants is often associated with increased seizure susceptibility. In our previous studies prenatal methamphetamine (MA) exposure increased seizure susceptibility of adult rats in models of primarily or secondarily generalized seizures induced by convulsant drugs. The effect of a single MA challenge dose in adulthood on chemically induced generalized seizures however, depends on the prenatal MA exposure history. Thus, the present study used a model of focal electrical stimulation to determine whether prenatal MA exposure with or without the adult challenge MA dose has the same outcome in a focal seizure model. Total of six groups of adult male rats were tested (prenatally MA-exposed, prenatally saline-exposed and rats without prenatal injections), each of these groups was either postnatally challenged with MA or with vehicle injection (MA-MA, MA-S; S-MA, S-S; C-MA, C-S). Seizures were induced by repetitive electrical stimulation (15s/8Hz) of sensorimotor cortex. Stimulation threshold, duration of afterdischarges (ADs), and presence and duration of spontaneous ADs (SAD) were evaluated. Additionally, behaviors associated with stimulation and ADs, and occurrence of wet-dog shakes (WDS) were analyzed. Our data demonstrate that daily injection of MA (5mg/kg) within prenatal period decreased the occurrence of WDS and SADs, and shortened the duration of ADs and SADs suggesting anticonvulsant effects. Moreover, the challenge dose of MA (1mg/kg) increased seizure threshold in all groups of rats, shortened duration of ADs in controls and prenatally saline-exposed animals, shortened duration of SADs in prenatally saline-exposed rats and totally eliminated WDS in all groups. Thus, the present study demonstrates that both chronic prenatal MA exposure and a single dose of MA in adulthood decrease focally induced epileptiform activity in adult male rats. [Copyright &y& Elsevier]

Abstract: Bladder reflexes evoked by stimulation of pudendal afferent nerves (PudA-to-Bladder reflex) were studied in normal and chronic spinal cord injured (SCI) adult cats to examine the reflex plasticity. Physiological activation of pudendal afferent nerves by tactile stimulation of the perigenital skin elicits an inhibitory PudA-to-Bladder reflex in normal cats, but activates an excitatory reflex in chronic SCI cats. However, in both normal and chronic SCI cats electrical stimulation applied to the perigenital skin or directly to the pudendal nerve induces either inhibitory or excitatory PudA-to-Bladder reflexes depending on stimulation frequency. An inhibitory response occurs at 3–10Hz stimulation, but becomes excitatory at 20–30Hz. The inhibitory reflex activated by electrical stimulation significantly (P<0.05) increases the bladder capacity to about 180% of control capacity in normal and chronic SCI cats. The excitatory reflex significantly (P<0.05) reduces bladder capacity to about 40% of control capacity in chronic SCI cats, but does not change bladder capacity in normal cats. Electrical stimulation of pudendal afferent nerves during slow bladder filling elicits a large amplitude bladder contraction comparable to the contraction induced by distension alone. A bladder volume about 60% of bladder capacity was required to elicit this excitatory reflex in normal cats; however, in chronic SCI cats a volume less than 20% of bladder capacity was sufficient to unmask an excitatory response. This study revealed the co-existence of both inhibitory and excitatory PudA-to-Bladder reflex pathways in cats before and after chronic SCI. However our data combined with published electrophysiological data strongly indicates that the spinal circuitry for both the excitatory and inhibitory PudA-to-Bladder reflexes undergoes a marked reorganization after SCI. [Copyright &y& Elsevier]

Abstract: Electrical stimulation of the dorsolateral periaqueductal gray (dlPAG) has frequently been shown to induce escape and freezing/decreased locomotion responses which mimic panic- and fear-like behaviour. In the present study we tested whether such spontaneous fear-like behaviour could be observed in an open-field test 12h after dlPAG stimulation. Further, we tested whether this fear-like behaviour could be attenuated by acute or chronic administration of buspirone and escitalopram. Our data demonstrate for the first time that animals showed fear-like behaviour 12h after dlPAG stimulation, which may possibly reflect panic disorder with anticipatory anxiety/agoraphobic symptoms. Acute and chronic escitalopram, but not buspirone, treatment attenuated the fear-related behaviour. Besides, our data also showed that the stimulation intensities to evoke an escape reaction, a panicogenic response, were significantly higher after chronic buspirone and escitalopram treatment. These results suggest that the fear-like response, which was observed 12h after dlPAG stimulation, could be considered as a relevant animal model for panic disorder with anticipatory anxiety/agoraphobic symptoms. [ABSTRACT FROM AUTHOR]

Abstract: The cerebral cortex is tightly and reciprocally linked to the cerebellum and the ascending dentato-thalalmo-cortical pathway influences widespread cortical regions. Using a rodent model of middle cerebral artery stroke, we showed previously that chronic, 20Hz stimulation of the contralateral lateral cerebellar nucleus (LCN) improved motor recovery, while 50Hz stimulation did not. Using motor evoked potentials (MEP) elicited by intracortical microstimulation, we now show the effect of LCN stimulation on motor cortex excitability as a function of pulse frequency in propofol-anesthetized rats. MEPs were recorded serially, at 15-s intervals, with cerebellar stimulation delivered in 10-min blocks at rates of 20, 30, 40, 50 or 100Hz. Stimulation at 20, 30, 40 or 50Hz enhanced the average MEP response across the block, with the maximal overall increase observed during 30Hz stimulation. However, the effect varied as a function of both repeated trials within the block and LCN stimulation frequency, such that 40Hz and 50Hz stimulation showed a reduced effect over time. Stimulation at 100Hz produced a transient increase in MEP amplitude in some animals; however the overall effect across the block was a trend towards reduced cortical excitability. These results suggest that direct stimulation of the LCN can yield frequency-dependent changes in cortical excitability and may provide a therapeutic approach to modulating cortical activity for the treatment of strokes or other focal cortical lesions, movement disorders and epilepsy. [ABSTRACT FROM AUTHOR]

Abstract: The long-term objective of this work is to understand the mechanisms by which electrical stimulation based movement therapies may harness neural plasticity to accelerate and enhance sensorimotor recovery after incomplete spinal cord injury (iSCI). An adaptive neuromuscular electrical stimulation (aNMES) paradigm was implemented in adult Long Evans rats with thoracic contusion injury (T8 vertebral level, 155±2 Kdyne). In lengthy sessions with lightly anesthetized animals, hip flexor and extensor muscles were stimulated using an aNMES control system in order to generate desired hip movements. The aNMES control system, which used a pattern generator/pattern shaper structure, adjusted pulse amplitude to modulate muscle force in order to control hip movement. An intermittent stimulation paradigm was used (5-cycles/set; 20-second rest between sets; 100 sets). In each cycle, hip rotation caused the foot plantar surface to contact a stationary brush for appropriately timed cutaneous input. Sessions were repeated over several days while the animals recovered from injury. Results indicated that aNMES automatically and reliably tracked the desired hip trajectory with low error and maintained range of motion with only gradual increase in stimulation during the long sessions. Intermittent aNMES thus accounted for the numerous factors that can influence the response to NMES: electrode stability, excitability of spinal neural circuitry, non-linear muscle recruitment, fatigue, spinal reflexes due to cutaneous input, and the endogenous recovery of the animals. This novel aNMES application in the iSCI rodent model can thus be used in chronic stimulation studies to investigate the mechanisms of neuroplasticity targeted by NMES-based repetitive movement therapy. [Copyright &y& Elsevier]

Abstract: Electrical stimulation (ES) of injured peripheral nerves accelerates axonal regeneration in laboratory animals. However, clinical applicability of this intervention has never been investigated in human subjects. The aim of this pilot study was to determine the effect of ES on axonal regeneration after surgery in patients with median nerve compression in the carpal tunnel causing marked motor axonal loss. A randomized control trial was conducted to provide proof of principle for ES-induced acceleration of axon regeneration in human patients. Carpel tunnel release surgery (CTRS) was performed and in the stimulation group of patients, stainless steel electrode wires placed alongside the median nerve proximal to the surgical decompression site for immediate 1 h 20 Hz bipolar ES. Subjects were followed for a year at regular intervals. Axonal regeneration was quantified using motor unit number estimation (MUNE) and sensory and motor nerve conduction studies. Purdue Pegboard Test, Semmes Weinstein Monofilaments, and Levine''s Self-Assessment Questionnaire were used to assess functional recovery. The stimulation group had significant axonal regeneration 6–8 months after the CTRS when the MUNE increased to 290±140 (mean±SD) motor units (MU) from 150±62 MU at baseline (p <0.05). In comparison, MUNE did not significantly improve in the control group (p >0.2). Terminal motor latency significantly accelerated in the stimulation group but not the control group (p >0.1). Sensory nerve conduction values significantly improved in the stimulation group earlier than the controls. Other outcome measures showed a significant improvement in both patient groups. We conclude that brief low frequency ES accelerates axonal regeneration and target reinnervation in humans. [Copyright &y& Elsevier]

Abstract: As functional recovery following peripheral nerve injury is dependent upon successful repair and regeneration, treatments that enhance different regenerative events may be advantageous. Using a rat facial nerve crush axotomy model, our lab has previously investigated the effects of a combinatorial treatment strategy, consisting of electrical stimulation (ES) of the proximal nerve stump and testosterone propionate (TP) administration. Results indicated that the two treatments differentially enhance facial nerve regenerative properties, whereby ES reduced the delay before sprout formation, TP accelerated the overall regeneration rate, and the combinatorial treatment had additive effects. To delineate the molecular mechanisms underlying such treatments, the present study investigated the effects of ES and TP on expression of specific regeneration-associated genes. Following a right facial nerve crush at the stylomastoid foramen, gonadectomized adult male rats were administered only ES, only TP, a combination of both, or left untreated. Real time RT-PCR analysis was used to assess fold changes in mRNA levels in the facial motor nucleus at 0 h, 6 h, 1 d, 2 d, 7 d, and 21 d post-axotomy. The candidate genes analyzed included two tubulin isoforms (α1-tubulin and βII-tubulin), 43-kiloDalton growth-associated protein (GAP-43), brain derived neurotrophic factor (BDNF), pituitary adenylate cyclase-activating peptide (PACAP), and neuritin (candidate plasticity-related gene 15). The two treatments have differential effects on gene expression, with ES leading to early but transient upregulation and TP producing late but steady increases in mRNA levels. In comparison to individual treatments, the combinatorial treatment strategy has the most enhanced effects on the transcriptional program activated following injury. [Copyright &y& Elsevier]

Abstract: Functional electrical stimulation (FES) can restore control and offset atrophy to muscles after neurological injury. However, FES has not been considered as a method for enhancing CNS regeneration. This paper demonstrates that FES dramatically enhanced progenitor cell birth in the spinal cord of rats with a chronic spinal cord injury (SCI). A complete SCI at thoracic level 8/9 was performed on 12 rats. Three weeks later, a FES device to stimulate hindlimb movement was implanted into these rats. Twelve identically-injured rats received inactive FES implants. An additional control group of uninjured rats were also examined. Ten days after FES implantation, dividing cells were marked with bromodeoxyuridine (BrdU). The “cell birth” subgroup (half the animals in each group) was sacrificed immediately after completion of BrdU administration, and the “cell survival” subgroup was sacrificed 7 days later. In the injured “cell birth” subgroup, FES induced an 82–86% increase in cell birth in the lumbar spinal cord. In the injured “cell survival” subgroup, the increased lumbar newborn cell counts persisted. FES doubled the proportion of the newly-born cells which expressed nestin and other markers suggestive of tripotential progenitors. In uninjured rats, FES had no effect on cell birth/survival. This report suggests that controlled electrical activation of the CNS may enhance spontaneous regeneration after neurological injuries. [Copyright &y& Elsevier]

Abstract: High frequency stimulation (HFS) is used to control abnormal neuronal activity associated with movement, seizure, and psychiatric disorders. Yet, the mechanisms of its therapeutic action are not known. Although experimental results have shown that HFS suppresses somatic activity, other data has suggested that HFS could generate excitation of axons. Moreover it is unclear what effect the stimulation has on tissue surrounding the stimulation electrode. Electrophysiological and computational modeling literature suggests that HFS can drive axons at the stimulus frequency. Therefore, we tested the hypothesis that unlike cell bodies, axons are driven by pulse train HFS. This hypothesis was tested in fibers of the hippocampus both in-vivo and in-vitro. Our results indicate that although electrical stimulation could activate and drive axons at low frequencies (0.5–25 Hz), as the stimulus frequency increased, electrical stimulation failed to continuously excite axonal activity. Fiber tracts were unable to follow extracellular pulse trains above 50 Hz in-vitro and above 125 Hz in-vivo. The number of cycles required for failure was frequency dependent but independent of stimulus amplitude. A novel in-vitro preparation was developed, in which, the alveus was isolated from the remainder of the hippocampus slice. The isolated fiber tract was unable to follow pulse trains above 75 Hz. Reversible conduction block occurred at much higher stimulus amplitudes, with pulse train HFS (>150 Hz) preventing propagation through the site of stimulation. This study shows that pulse train HFS affects axonal activity by: (1) disrupting HFS evoked excitation leading to partial conduction block of activity through the site of HFS; and (2) generating complete conduction block of secondary evoked activity, as HFS amplitude is increased. These results are relevant for the interpretation of the effects of HFS for the control of abnormal neural activity such as epilepsy and Parkinson''s disease. [Copyright &y& Elsevier]

Abstract: Direct electrical stimulation of neural tissues is a strategic approach to treat injured axons by accelerating their outgrowth [Al-Majed, A.A., Neumann, C.M., Brushart, T.M., Gordon, T., 2000. Brief electrical stimulation promotes the speed and accuracy of motor axonal regeneration. J. Neurosci. 20, 2602–2608] and promoting their regeneration [Geremia, N.M., Gordon, T., Brushart, T.M., Al-Majed, A.A., Verge, V.M.K., 2007. Electrical stimulation promotes sensory neuron regeneration and growth-associated gene expression. Exp. Neurol. 205, 347–359]. Recently, transcorneal electrical stimulation (TCES), a novel less invasive method, has been shown to rescue axotomized and damaged retinal ganglion cells [Morimoto, T., Miyoshi, T., Matsuda, S., Tano, Y., Fujikado, T., Fukuda, Y., 2005. Transcorneal electrical stimulation rescues axotomized retinal ganglion cells by activating endogenous retinal IGF-1 system. Invest. Ophthalmol. Vis. Sci. 46(6), 2147–2155]. Here, we investigated the neuroprotection of TCES on light-induced photoreceptor degeneration and the underlying mechanism. Adult male Sprague–Dawley (SD) rats received TCES before (pre-TCES) or after (post-TCES) intense light exposure. After fourteen days of light exposure, retinal histology and electroretinography were performed to evaluate the neuroprotective effect of TCES. The mRNA and protein levels of apoptotic-associated genes including Bcl-2, Bax, Caspase-3 as well as ciliary neurotrophic factor (CNTF) and brain-derived neurotrophic factor (BDNF) in the retinas were determined by real-time PCR and Western blot analysis. The localization of these gene products in the retinas was examined by immunohistochemistry. Both pre- and post-TCES ameliorated the progressive photoreceptor degeneration. The degree of rescue depended on the strength of the electric charge. Post-TCES showed a relatively better and longer-term protective effect than pre-TCES. Real-time PCR and Western blot analysis revealed an upregulation of Bcl-2, CNTF, and BDNF and a downregulation of Bax in the retinas after TCES. Immunohistochemical studies showed that Bcl-2 and CNTF were selectively upregulated in Müller cells. These findings provide a new therapeutic method to prevent or delay photoreceptor degeneration through activating the intrinsic survival system. [Copyright &y& Elsevier]

Abstract: Although injured peripheral axons are able to regenerate, functional recovery is usually poor after nerve transection. In this study we aim to elucidate the role of neuronal activity, induced by nerve electrical stimulation and by exercise, in promoting axonal regeneration and modulating plasticity in the spinal cord after nerve injury. Four groups of adult rats were subjected to sciatic nerve transection and suture repair. Two groups received electrical stimulation (3 V, 0.1 ms at 20 Hz) for 1 h, immediately after injury (ESa) or during 4 weeks (1 h daily; ESc). A third group (ES+TR) received 1 h electrical stimulation and was submitted to treadmill running during 4 weeks (5 m/min, 2 h daily). A fourth group performed only exercise (TR), whereas an untreated group served as control (C). Nerve conduction, H reflex and algesimetry tests were performed at 1, 3, 5, 7 and 9 weeks after surgery, to assess muscle reinnervation and changes in excitability of spinal cord circuitry. Histological analysis was made at the end of the follow-up. Groups that received acute ES and/or were forced to exercise in the treadmill showed higher levels of muscle reinnervation and increased numbers of regenerated myelinated axons when compared to control animals or animals that received chronic ES. Combining ESa with treadmill training significantly improved muscle reinnervation during the initial phase. The facilitation of the monosynaptic H reflex in the injured limb was reduced in all treated groups, suggesting that the maintenance of activity helps to prevent the development of hyperreflexia. [Copyright &y& Elsevier]

Abstract: Major Depression Disorder (MDD) is usually accompanied by alterations of cortical activity and excitability, especially in prefrontal areas. These are reflections of a dysfunction in a distributed cortico-subcortical, bihemispheric network. Therefore it is reasonable to hypothesize that altering this pathological state with techniques of brain stimulation may offer a therapeutic target. Besides repetitive transcranial magnetic stimulation, tonic stimulation with weak direct currents (tDCS) modulates cortical excitability for hours after the end of stimulation, thus, it is a promising non-invasive therapeutic option. Early studies from the 1960s suggested some efficacy of DC stimulation to reduce symptoms in depression, but mixed results and development of psychotropic drugs resulted in an early abandonment of this technique. In the last years tDCS protocols have been optimized. Application of the newly developed stimulation protocols in patients with major depression has shown promise in few pilot studies. Further studies are needed to identify the optimal parameters of stimulation and the clinical and patient characteristics that may condition response to tDCS. [Copyright &y& Elsevier]

Abstract: Although most spinal cord injuries are anatomically incomplete, only limited functional recovery has been observed in people and rats with partial lesions. To address why surviving fibers cannot mediate more complete recovery, we evaluated the physiological and anatomical status of spared fibers after unilateral hemisection (HX) of thoracic spinal cord in adult rats. We made intracellular and extracellular recordings at L5 (below HX) in response to electrical stimulation of contralateral white matter above (T6) and below (L1) HX. Responses from T6 displayed reduced amplitude, increased latency and elevated stimulus threshold in the fibers across from HX, beginning 1–2 weeks after HX. Ultrastructural analysis revealed demyelination of intact axons contralateral to the HX, with a time course similar to the conduction changes. Behavioral studies indicated partial recovery which arrested when conduction deficits began. In conclusion, this study is the first demonstration of the delayed decline of transmission through surviving axons to individual lumbar motoneurons during chronic stage of incomplete spinal cord injury in adult rats. These findings suggest a chronic pathological state in intact fibers and necessity for prompt treatment to minimize it. [Copyright &y& Elsevier]

Abstract: Electrical or chemical stimulation of the inferior colliculus (IC) induces fear-like behaviors. More recently, consistent evidence has shown that electrical stimulation of the central nucleus of the IC supports Pavlovian conditioning and latent inhibition (LI). LI is characterized by retardation in conditioning and also by an impaired ability to ignore irrelevant stimuli, after a non-reinforced pre-exposure to the conditioned stimulus. LI has been proposed as a behavioral model of cognitive abnormalities seen in schizophrenia. The aim of the present study was to determine whether dopaminergic mechanisms in the IC are involved in LI of the conditioned emotional response (CER). To induce LI, a group of rats was pre-exposed (PE) to six tones in two sessions, while rats that were not pre-exposed (NPE) had two sessions without tone presentations. The conditioning consisted of two tone presentations to the animal, followed immediately by a foot shock. PE and NPE rats received IC microinjections of physiological saline, the dopaminergic agonist apomorphine (9.0 μg/0.5 μL/side), or the dopaminergic antagonist haloperidol (0.5 μg/0.5 μL/side) before both pre-exposure and conditioning. During the test, the PE rats that received saline or haloperidol had a lower suppression of the licking response compared to NPE rats that received vehicle or haloperidol, indicating that latent inhibition was induced. There was no significant difference in the suppression ratio in rats that received apomorphine injections into the IC, indicating reduced latent inhibition. These results suggest that dopamine-mediated mechanisms of the IC are involved in the development of LI. [Copyright &y& Elsevier]

Abstract: The purpose of this study was to determine cerebral metabolic profile changes in response to electric stimulation to the right dorsal hippocampus (HPC) for the establishment of an epileptic rat model. Electroencephalogram measurements and behavioral results indicated that the experimental rats were in an early stage of epilepsy. Metabolites were determined by high-resolution magic-angle-spinning nuclear magnetic resonance (HR-MAS NMR) spectroscopy of the following intact brain tissue: bilateral hippocampi, entorhinal cortices (ECs), and temporal lobes (TLs). The NMR data was statistically analyzed using principal component analysis (PCA). Results demonstrated that metabolic profiles were significantly different between the experimental and sham rats in the bilateral hippocampi and the ipsilateral EC. Significant increases in total creatine in the ipsilateral HPC and alanine in the ipsilateral TL were measured (p <0.05). Some metabolite levels were disturbed in the bilateral HPC-EC loops. In the sham group, glutamate and choline concentrations were significantly higher or lower in the ipsilateral EC than bilateral hippocampi, respectively (p <0.01). However, such differences were not observed in the experimental group. In addition, N-acetylaspartate levels in the experimental group were significantly less in the ipsilateral HPC than in bilateral ECs (p <0.05). The level of myo-inositol in the ipsilateral EC significantly increased in the experimental group, compared to the contralateral EC (p <0.05). These results may provide metabolic information about temporal lobe structures to provide more knowledge about epileptic abnormalities at the early stage. [Copyright &y& Elsevier]

Abstract: Kindling is an essential operating paradigm of the nervous system extensively used both as a model of epileptogenesis and neuroplasticity. In a parallel study conducted on chronically implanted non-anesthetized kindled cats, we report the occurrence of long-lasting slow oscillatory patterns (1.5–2 Hz) called outlasting activities (OA) following the acute seizures (AS) induced by cortical stimulation. Here, we asked if OA observed in the neocortex of kindled animals are generated exclusively by the cortical networks or if they also rely on the burst firing of thalamic neurons. We analyzed the electrophysiological patterns of synchronization of cortical EEG (areas 4, 5, 7, 21, 17, 18, 22) and thalamic field (EThG) (ventral posterior lateral nucleus—VPL), and the influence of modulatory systems originating in the pedunculo-pontine tegmentum (PPT) and locus coeruleus (LC) on the discharge pattern of thalamic neurons during OA. Synchrony analysis of field recordings showed that during AS cortical paroxysmal activities preceded thalamic ones, while during OA this sequential order was reversed. During OA thalamic neurons regularly discharged bursts with the frequency of OA. Electrical stimulation of either PPT or LC during OA decreased both the probability of bursts in thalamocortical neurons and the amplitude of OA. Yet, neither of them was able to block completely the expression of OA. Following PPT/LC stimulation the burst firing of thalamocortical neurons was replaced by tonic firing. We conclude that the thalamus is involved in the mechanism of generation of OA but that it does not play an exclusive role. [Copyright &y& Elsevier]

Abstract: The clinical outcome of peripheral nerve injuries requiring surgical repair is usually poor and efficient therapies do not exist. Recent work has suggested that low-frequency electrical stimulation of the severed nerve which produces repeated discharges of the parent motoneuron perikarya positively influences axonal regeneration, even if applied once for a period of only 1 h. Here we provide the first evidence for locomotor functional benefits of such stimulation. We transected the femoral nerve of adult C57BL/6J mice proximal to the bifurcation of the quadriceps and saphenous branches and electrically stimulated the proximal nerve stump for 1 h at 20-Hz frequency prior to nerve repair with a silicone cuff. Three months later, the ability of the quadriceps muscle to extend the knee in sham-stimulated mice had recovered to 63% of the preoperative values as estimated by single-frame motion analysis. After electrical stimulation, the outcome was only slightly better (73%) but the rate of functional recovery was considerably accelerated. Near-maximum recovery was achieved 6 weeks earlier than in the control group. The beneficial effects were associated with larger motoneuron cell bodies and increased diameters of regenerated axons in the quadriceps nerve branch, but not with enhanced preferential reinnervation by motoneurons of muscle as opposed to skin. The observed acceleration of functional restoration and the positive effects on motoneurons and regenerated axons indicate the potential of a clinically feasible approach for improvement of nerve repair outcome in human patients in which delayed target reinnervation is a factor limiting recovery. [Copyright &y& Elsevier]

Abstract: Brief electrical stimulation enhances the regenerative ability of axotomized motor [Nix, W.A., Hopf, H.C., 1983. Electrical stimulation of regenerating nerve and its effect on motor recovery. Brain Res. 272, 21–25; Al-Majed, A.A., Neumann, C.M., Brushart, T.M., Gordon, T., 2000. Brief electrical stimulation promotes the speed and accuracy of motor axonal regeneration. J. Neurosci. 20, 2602–2608] and sensory [Brushart, T.M., Jari, R., Verge, V., Rohde, C., Gordon, T., 2005. Electrical stimulation restores the specificity of sensory axon regeneration. Exp. Neurol. 194, 221–229] neurons. Here we examined the parameter of duration of stimulation on regenerative capacity, including the intrinsic growth programs, of sensory neurons. The effect of 20 Hz continuous electrical stimulation on the number of DRG sensory neurons that regenerate their axons was evaluated following transection and surgical repair of the femoral nerve trunk. Stimulation was applied proximal to the repair site for 1 h, 3 h, 1 day, 7 days or 14 days at the time of nerve repair. Following a 21-day regeneration period, DRG neurons that regenerated axons into the muscle and cutaneous sensory nerve branches were retrogradely identified. Stimulation of 1 h led to a significant increase in DRG neurons regenerating into cutaneous and muscle branches when compared to 0 h (sham) stimulation or longer periods of stimulation. Stimulation for 1 h also significantly increased the numbers of neurons that regenerated axons beyond the repair site 4 days after lesion and was correlated with a significant increase in expression of growth-associated protein 43 (GAP-43) mRNA in the regenerating neurons at 2 days post-repair. An additional indicator of heightened plasticity following 1 h stimulation was elevated expression of brain-derived neurotrophic factor (BDNF). The effect of brief stimulation on enhancing sensory and motoneuron regeneration holds promise for inducing improved peripheral nerve repair in the clinical setting. [Copyright &y& Elsevier]

Abstract: Functional magnetic resonance imaging (fMRI) studies were performed for visualizing ongoing brain plasticity in Neurotrophin-3 (NT3)-treated experimental spinal cord injury (SCI). In response to the electrical stimulation of the forepaw, the NT3-treated animals showed extensive activation of brain structures that included contralateral cortex, thalamus, caudate putamen, hippocampus, and periaqueductal gray. Quantitative analysis of the fMRI data indicated significant changes both in the volume and center of activations in NT3-treated animals relative to saline-treated controls. A strong activation in both ipsi- and contralateral periaqueductal gray and thalamus was observed in NT3-treated animals. These studies indicate ongoing brain reorganization in the SCI animals. The fMRI results also suggest that NT3 may influence nociceptive pathways. [Copyright &y& Elsevier]

Abstract: Long-term potentiation (LTP) of synaptic transmission is a widely accepted model that attempts to link synaptic plasticity with memory. LTP models are also now used in order to test how a variety of neurological disorders might affect synaptic plasticity. Interestingly, electrical stimulation protocols that induce LTP appear to display different efficiencies and importantly, some may not be as physiologically relevant as others. In spite of advancements in our understanding of these differences, many types of LTP inducing protocols are still widely used. In addition, in some cases electrical stimulation leads to normal biological phenomena, such as putative memory encoding and in other cases electrical stimulation triggers pathological phenomena, such as epileptic seizures. Kindling, a model of epileptogenesis involving repeated electrical stimulation, leads to seizure activity and has also been thought of, and studied as, a form of long-term neural plasticity and memory. Furthermore, some investigators now use electrical stimulation in order to reduce aspects of seizure activity. In this review, we compare in vitro and in vivo electrical stimulation protocols employed in the hippocampal formation that are utilized in models of synaptic plasticity or neuronal hyperexcitability. Here the effectiveness and physiological relevance of these electrical stimulation protocols are examined in situations involving memory encoding (e.g., LTP/LTD) and epileptiform activity. [Copyright &y& Elsevier]

Abstract: This study examined whether epidurally delivered cortical electrical stimulation (CS) improves the efficacy of motor rehabilitative training and alters neuronal density and/or cell proliferation in perilesion cortex following ischemic sensorimotor cortex (SMC) lesions. Adult rats were pre-trained on a skilled reaching task and then received partial unilateral SMC lesions and implantation of electrodes over the remaining SMC. Ten to fourteen days later, rats received daily reach training concurrent with anodal or cathodal 100 Hz CS or no stimulation (NoCS) for 18 days. To label newly generated cells, bromodeoxyuridine (BrdU; 50 mg/kg) was administered every third day of training. Both anodal and cathodal CS robustly enhanced reaching performance compared to NoCS controls. Neuronal density in the perilesion cortex was significantly increased in the cathodal CS group compared to the NoCS group. There were no significant group differences in BrdU-labeled cell density in ipsilesional cortex. Staining with Fluoro-Jade-B indicated that neurons continue to degenerate near the infarct at the time when cortical stimulation and rehabilitation were initiated. These data indicate that epidurally delivered CS greatly improves the efficacy of rehabilitative reach training following SMC damage and raise the possibility that cathodal CS may influence neuronal survival in perilesion cortex. [Copyright &y& Elsevier]

Abstract: The neural substrate underlying the aversive effects induced by ethanol abstinence is still unclear. One candidate for such effects is the dorsal periaqueductal gray (dPAG), a core structure of the brain aversion system. The main aim of this study is to examine the role of the dPAG as a possible locus of the aversive effects following abrupt alcohol withdrawal. To this end, rats were subjected to an oral ethanol self-administration procedure, in which animals were offered 6–8% (v/v) ethanol solution for a period of 21 days followed by an abrupt discontinuation of the treatment on the two subsequent days. Control animals received control dietary fluid for similar periods of time. The effects of ethanol withdrawal were examined in the elevated plus-maze (EPM) (Exp. I), on the prepulse inhibition of startle to loud sounds (Exp. II) and on the freezing and escape responses induced by electrical stimulation of the dPAG (Exp. III). In Experiment III, rats were implanted with an electrode aimed at the dPAG and the number and duration of ultrasonic vocalizations (USVs) were also recorded in the rats that received dPAG stimulation at freezing and escape thresholds. Data obtained showed that ethanol withdrawal elicited significant “anxiety-like” behaviors, as revealed by the decrease in the number of entries into and time spent onto the open arms of the EPM. Startle reflex and prepulse inhibition remained unchanged in withdrawn animals. In addition, discontinuation from the chronic ethanol regimen caused a reduction in the stimulation thresholds for freezing and escape and in the number and duration of USVs. Together, these effects have been interpreted in the frame of a high fear state elicited by activation of the dPAG. These findings are indicative that ethanol withdrawal sensitizes the substrates of fear at the level of this midbrain structure. [Copyright &y& Elsevier]

Abstract: Functional recovery after peripheral nerve injury is often poor despite high regenerative capacity of peripheral neurons. In search for novel treatments, brief electrical stimulation of the acutely lesioned nerve has recently been identified as a clinically feasible approach increasing precision of axonal regrowth. The effects of this stimulation appear to be mediated by BDNF and its receptor, TrkB, but the down-stream effectors are unknown. A potential candidate is the HNK-1 carbohydrate known to be selectively reexpressed in motor but not sensory nerve branches of the mouse femoral nerve and to enhance growth of motor but not sensory axons in vitro. Here, we show that short-term low-frequency electrical stimulation (1 h, 20 Hz) of the lesioned and surgically repaired femoral nerve in wild-type mice causes a motor nerve-specific enhancement of HNK-1 expression correlating with previously reported acceleration of muscle reinnervation. Such enhanced HNK-1 expression was not observed after electrical stimulation in heterozygous BDNF or TrkB-deficient mice. Accordingly, the degree of proper reinnervation of the quadriceps muscle, as indicated by retrograde labeling of motoneurons, was reduced in TrkB+/− mice compared to wild-type littermates. Also, recovery of quadriceps muscle function, evaluated by a novel single-frame motion analysis approach, and axonal regrowth into the distal nerve stump, assessed morphologically, were considerably delayed in TrkB+/− mice. These findings indicate that BDNF/TrkB signaling is important for functional recovery after nerve repair and suggest that up-regulation of the HNK-1 glycan is linked to this phenomenon. [Copyright &y& Elsevier]

Abstract: The effects of cortical spreading depression (SD) on evoked dopamine release in mesolimbic (nucleus accumbens) and nigrostriatal (nucleus caudatus) terminal fields were studied by in vivo voltammetry in anesthetized rats. Dopamine release was evoked by electrical stimulation of medial forebrain bundle (20 Hz, 100 pulses). Local application of 3 M KCl on the dura initiated SD in the cortex. It was found that SD modulated evoked dopamine release in subcortical structures at the same time when the wave of depression of cortical activity reached reciprocally connected subcortical areas. This cortical depression increased stimulated dopamine release in the nucleus accumbens and decreased dopamine release in the nucleus caudatus. In agreement with these results, electrical stimulation of the prefrontal cortex at 20 Hz, synchronized with medial forebrain bundle stimulation, decreased evoked dopamine release in the nucleus accumbens. Areas of the cortex which modulated dopamine release in these two terminal fields were spatially separated by at least 5 mm from each other. It is proposed that depression and activation of evoked dopamine release in the nucleus caudatus and nucleus accumbens following SD are indicative of tonic activation of the nigrostriatal and tonic inhibition of the mesolimbic dopaminergic terminals by cortex in normal conditions. SD in the cortex, modulating neurotransmitter release in subcortical structures, may have a general impact on redistribution of oxygen supply in these subcortical areas and on behavior associated with brain trauma, migraine, insult or seizures, i.e. the kind of neuropathology which may cause SD type phenomena also in human brain. [Copyright &y& Elsevier]

Abstract: Electrical stimulation at the time of nerve repair promotes motoneurons to reinnervate appropriate pathways leading to muscle [Al-Majed, A.A., Neumann, C.M., Brushart, T.M., Gordon, T., 2000. Brief electrical stimulation promotes the speed and accuracy of motor axonal regeneration. J. Neurosci. 20, 2602–2608] and stimulates sensory neurons to regenerate [Geremia, N.M., Gordon, T., Al-Majed, A.A., Brushart, T.M., Verge, V.M., 2002. Brief electrical stimulation promotes regeneration of sensory fibers into cutaneous and muscle branches of femoral nerve. Neurosci. Abstr. 535.14]. The present experiments examine the effects of electrical stimulation on the specificity of sensory axon regeneration. The unoperated rat femoral cutaneous branch is served by 2–3 times more DRG neurons than is the muscle branch [Brushart, T.M., 1988. Preferential reinnervation of motor nerves by regenerating motor axons. J. Neurosci. 8, 1026–1031]. After transection and repair of the femoral trunk, equal numbers of DRG neurons project to both branches. However, 1 h of electrical stimulation restores the normal proportion of DRG neurons reinnervating skin and muscle. To ask if the redistribution of stimulated neurons results from enhanced specificity of target reinnervation, we developed a new technique of sequential double labeling. DRG neurons projecting to the femoral muscle branch were prelabeled with Fluoro Gold 2 weeks before the nerve was transected proximally and repaired with or without 1 h of 20-Hz electrical stimulation. Three weeks after repair, the muscle nerve was labeled a second time with Fluororuby. The percentage of regenerating neurons that both originally served muscle and returned to muscle after nerve repair increased from 40% without stimulation to 75% with stimulation. Electrical stimulation thus dramatically alters the distribution of regenerating sensory axons, replacing normally random behavior with selective reinnervation of tissue-specific targets. If the enhanced regeneration specificity resulting from electrical stimulation is found to improve function in a large animal model, this convenient and safe technique may be a useful adjunct to clinical nerve repair. [Copyright &y& Elsevier]

Abstract: Electroacupuncture stimulation (EAS) is known to change brain neurotransmitter release. In the present study, we investigated the effects of synchronous or asynchronous electroacupuncture stimulation with low versus high frequency on spinal opioid release and tail flick nociception. Rats were given “2/100 Hz” EAS, which stands for an asynchronous mode of stimulation, in which 2 Hz was alternated with 100 Hz, each lasting for 3 s, or “(2 + 100) Hz” EAS, a mode of stimulation in which 2 Hz stimulation was applied to the left hind leg simultaneously with 100 Hz stimulation on the right hind leg. The rats were subjected to the same total number of electrical stimulations in these two modes. Results were as follows: (1) 2/100 Hz EAS was 40% more potent than (2 + 100) Hz EAS (P < 0.01) in producing an anti-nociceptive effect. (2) Intrathecal (i.t.) injection of the μ-opioid receptor antagonist d-Phe-Cys-Tyr-d-Trp-Orn-Thr-Pen-Thr amide (CTOP) blocked in a dose-dependent manner the anti-nociceptive effect produced by 2/100 Hz EAS but not by (2 + 100) Hz EAS, whereas i.t. injection of the κ-opioid receptor antagonist norbinaltorphimide (Nor-BNI) blocked the anti-nociceptive effect induced by both modes of EAS. (3) I.t. injection of endomorphin-2 antiserum blocked in a dose-dependent manner the anti-nociceptive effect of 2/100 Hz EAS but not that of (2 + 100) Hz EAS, whereas i.t. injection of dynorphin antiserum blocked the anti-nociceptive effect induced by both modes of stimulation. (4) 2/100 Hz EAS increased the release of both endomorphin-2 and dynorphin, whereas (2 + 100) Hz EAS increased the release of dynorphin but not of endmorphin-2. We conclude that the more potent anti-nociceptive effect induced by 2/100 Hz EAS, as compared with that of (2 + 100) Hz EAS, was due, at least partly, to the synergistic interaction of endomorphin-2 and dynorphin in rat spinal cord. [Copyright &y& Elsevier]

Peripheral electrical stimulation (PES) has been utilized to manage chronic pain associated with nerve injury. However, the data on clinical effectiveness are conflicting and the neurophysiological mechanism is not well known. This study was designed to assess whether PES relieved neuropathic pain and its possible mechanisms. The neuropathic pain model was made with lumbar 5th (L5) and 6th (L6) spinal nerve ligations in rats. Nociceptive responses of the rats were assessed by the cold plate test (the number and duration of paw lifts that occurred in 5 min on a 5 ± 1°C cold plate). PES with a frequency of 2 Hz and at increasing strengths was given for 30 min via stainless-steel needles inserted into standard acupoints on the leg and back, respectively. Immunochemistry was used to examine the immunoreactivity of the NMDA receptor 1 (NR1) subunit in the spinal cord dorsal horn. The results are as follows: (1) PES relieved neuropathic pain and the effect was blocked by 1.0 mg/kg naloxone. (2) The effect of one session of PES lasted up to 12 h. (3) Repetitive PES showed a cumulative effect and no tolerance was observed. (4) There was a significant increase of NR1 immunoreactivity in the superficial laminae of the spinal cord of neuropathic pain rats as compared with naive rats. This increase could be reversed by repetitive 2 Hz PES. These results suggest that PES can relieve neuropathic pain, and that μ-opioid receptors and NMDA receptors are involved in the effect of PES. [Copyright &y& Elsevier]