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The functional relevance of sigma-1 (σ1 ) receptor expression in the rat hippocampal CA1 during adolescence (i.e., 35-60 days old) was explored. A selective antagonist for the σ1 receptor subtype, BD-1047, was applied to study hippocampal long-term potentiation (LTP) and spatial learning performance. Changes in the expression of the σ1 receptor subtype and its function were compared between castrated and sham-castrated rats. Castration reduced the magnitude of both field excitatory postsynaptic potential (fEPSP)-LTP and population spike (PS)-LTP at 35 days (d). BD-1047 decreased PS-LTP in sham-castrated rats, whereas BD-1047 reversed the effect of castration on fEPSP-LTP at 35 d. In addition, BD1047 impaired spatial learning and augmented σ1 receptor mRNA levels in castrated rats at 35 d. Surprisingly, neither castration nor BD1047 had an effect on fEPSP-LTP and PS-LTP, spatial learning ability or gene expression levels at 45 d. Castration had no effect on fEPSP-LTP but reduced PS-LTP at 60 d. BD1047 increased the magnitude of fEPSP-LTP, but had no effect on PS-LTP in castrated rats at 60 d. However, BD1047 reduced spatial learning ability, and σ1 receptor mRNA levels were decreased in castrated rats at 60 d. This study shows that σ1 receptors play a role in the regulation of both CA1 synaptic efficacy and spatial learning performance. The regulatory role of σ1 receptors in activity-dependent CA1-LTP is locality- and age-dependent, whereas its role in spatial learning ability is only age-dependent. Prepubertal castration-associated changes in the expression and function of the σ1 receptor during adolescence may play a developmental role in the regulation of hippocampal area CA1 activity and plasticity. © 2016 Wiley Periodicals, Inc., (© 2016 Wiley Periodicals, Inc.)

The effect of chronic administration of sodium salicylate (NaSal) on the excitability and synaptic plasticity of the rodent hippocampus was investigated. Repeated systemic treatment with NaSal reliably induced tolerance to the anti-nociceptive effect of NaSal (one i.p. injection per day for 6 consecutive days). Following chronic NaSal or vehicle treatment, a series of electrophysiological experiments on acute hippocampal slices (focusing on the CA1 circuitry) were tested whether tolerance to NaSal would augment pentylenetetrazol (PTZ)-induced long-term potentiation (LTP) and /or epileptic activity, and whether the augmentation was the same after priming activity with a natural stimulus pattern prior to PTZ. We noted an altered synaptic input-to-spike transformation, such that neuronal firing increased after a given synaptic drive. Population spike-LTP (PS-LTP) was increased in the NaSal-tolerant animals, but only when it was induced via a combination of electrical stimulation (theta pattern primed-burst stimulation) and the transient application of PTZ. Identifying and understanding these changes in neuronal excitability and synaptic plasticity following chronic salicylate treatment could prove useful in the clinical diagnosis or treatment of chronic aspirin-induced, or even idiopathic, seizure activity., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Studies have shown that following opiate withdrawal, the spontaneous discharge rate of locus coeruleus (LC) neurons remarkably increases. Combination of intrinsic mechanisms with extrinsic excitatory modulations mediates the withdrawal-induced hyperactivity of LC neurons. The nucleus paragigantocellularis (PGi) provides the main excitatory inputs to LC and plays a pivotal role in opiate withdrawal. In the present study the direct facilitatory role of PGi on opiate withdrawal-induced hyperactivity of LC neurons was investigated using a newly developed brain slice, containing both LC and PGi. HRP retrograde neuronal tracing was used to verify the existence of both LC and PGi neurons in the developed slice. The spontaneous discharge rate (SDR), resting membrane potential (RMP) and spontaneous excitatory post-synaptic currents (sEPSCs) were recorded in LC neurons using whole cell patch clamp recording. Results showed that the net SDR and the net RMP of LC neurons in slices containing both LC and PGi neurons are significantly higher than slices lacking intact (uncut) PGi inputs. Also, the frequency of sEPSCs in those LC neurons receiving PGi inputs significantly increased compared to the slices containing no intact PGi inputs. Altogether, our results propose that increase in PGi-mediated excitatory transmission might facilitate the opiate withdrawal-induced hyperactivity of LC neurons.

Alzheimer's disease (AD) is characterized by the formation of amyloid beta (Aβ) plaques in the brain. Dysfunctional excitatory synaptic transmission and neuronal plasticity are generally accepted as primary events in the development of AD. There is evidence to suggest that both COX-1 expression and COX-2 expression are changed in the brain of AD patients. However, the impact of COX-dependent mechanisms on synaptic dysfunction underlying the memory deficit is not fully elucidated. In the present study effects of non-selective NSAIDs (aspirin and sodium salicylate) on associated memory impairment as well as Aβ-mediated suppression of synaptic plasticity in the hippocampus were examined. Aβ1-42 (5μg/μl) and ibotenic acid (5μg/μl) were injected bilaterally into the dorsal hippocampus of rats and the spatial memory and long term potentiation (LTP) were assessed by water maze performance and in vivo field potential recording, respectively. Field excitatory post synaptic potentials (fEPSP) were recorded from stratum radiatum of area CA1 following Schaffer collateral stimulation. Behavioral study revealed that both sub-chronic high dose of sodium salicylate (SS) and chronic low dose of aspirin improved the spatial memory impairment of Aβ treated rats, however the effects of SS were lower than those of aspirin. Animals treated with SS and aspirin showed a significant decrease in escape latency (SS: F(1, 24)=15.85, p<0.01, aspirin: F(1, 22)=25.24, p<0.001, ANOVA). Furthermore, in probe test, animals treated with aspirin (p<0.05) but not SS (p>0.05) spent more time (one-way ANOVA) in target quadrant zone. Both applied drugs restored the suppression of fEPSP slope LTP that was induced by Aβ treatment (unpaired t-test, p<0.001). Aspirin showed a preventative effect also against Aβ-induced changes in LTP and memory task when applied before Aβ administration. Since aspirin and SS improved synaptic dysfunction, we can suggest that COX-dependent mechanisms may play a role in synaptic dysfunction in an experimental model of AD., (Copyright © 2015 Elsevier Inc. All rights reserved.)

The rostral ventromedial medulla (RVM) acts a key role in the descending inhibitory pain modulation. Neuropeptide orexin-A (ORXA) is confined to thousands of neurons in the lateral hypothalamus (LH). While RVM gets the orexinergic projections, the orexin receptors are also expressed in this structure. The aim of this study was to specify the cellular effects of ORXA on RVM neurons in vitro by using the whole cell patch-clamp recording. RVM neurons were classified into three types based on their electrophysiological characteristics. Type 1 neurons exhibited an irregular spontaneous activity which was interrupted by periods of pause in 25% of recorded neurons. Type 2 neurons did not show any spontaneous baseline activity (53.8% of recorded neurons). Type 3 neurons fired repetitively without interruption (51.2% of recorded neurons). ORXA had either inhibitory or excitatory effects on 53.8% (7/13) of type 1 neurons. ORXA excited 46.4% (13/28) of type 2 neurons and 27.3% (3/11) of type 3 neurons. The excitatory effect of ORXA observed in type 2 neurons was suppressed by an orexin 1 receptor (OXR1) antagonist, SB-334867. Briefly, we hypothesized that the ORXA mediated excitation and/or inhibition in RVM neurons might work as a mechanism to modulate pain processing by orexinergic neurons.

Aims: Attempts are aimed to introduce new approaches toward enhancing the brain's potential for repair in neurodegenerative diseases and traumatic injuries. Here we report an increased expression of pluripotency and progenitor markers within the brain following pretreatment with valproic acid (VPA) and in vivo transfection of inducible Oct4-expressing viral particles., Materials and Methods: Systemic administration of VPA was performed for one week prior to an intracerebroventricular injection of the Oct4-expressing vector into the right side of the brain. Oct4 expression was induced by doxycycline from day 1 post-transfection for an additional week. Real time-PCR and immunohistofluorescence were used for evaluation of marker expression., Key Findings: Real time-PCR analyses of samples collected from the area of transfection within the injected-lateral ventricle revealed increased expression of some stem cell and progenitor markers, which included endogenous Oct4, Nanog, Klf4, c-Myc, Pax6 and Sox1. Expressions of Oct4, SSEA1 and Nanog were further confirmed by immunohistofluorescence. The increased neural progenitor and pluripotency markers due to Oct4 overexpression did not lead to teratoma formation during a 100day follow-up., Significance: Our findings suggest that the application of Oct4 as a reprogramming factor in conjunction with VPA, an epigenetic modifier, might be a potential strategy for increasing the brain's capability to repair itself., (Copyright © 2014 Elsevier Inc. All rights reserved.)

The effectiveness of O-pulse stimulation (TPS) for the reversal of O-pattern primed bursts (PB)-induced long-term potentiation (LTP) were examined at the Schaffer-collateral-CA1 pyramidal cell synapses of hippocampal slices derived from rats chronically treated with morphine (M-T). The results showed that slices derived from both control and M-T rats had normal field excitatory postsynaptic potential (fEPSP)-LTP, whereas PS-LTP in slices from M-T rats was significantly greater than that from control slices. When morphine was applied in vitro to slices derived from rats chronically treated with morphine, the augmentation of PS-LTP was not seen. TPS given 30 min after LTP induction failed to reverse the fEPSP- or PS-LTP in both groups of slices. However, TPS delivered in the presence of long-term in vitro morphine caused the PS-LTP reversal. This effect was blocked by the adenosine A1 receptor (A1R) antagonist CPX (200 nM) and furthermore was enhanced by the adenosine deaminase (ADA) inhibitor EHNA (10 μM). Interestingly, TPS given 30 min after LTP induction in the presence of EHNA (10 μM) can reverse LTP in morphine-exposed control slices in vitro. These results suggest adaptive changes in the hippocampus area CA1 in particular in adenosine system following repetitive systemic morphine. Chronic in vivo morphine increases A1R and reduces ADA activity in the hippocampus. Consequently, adenosine can accumulate because of a stimulus train-induced activity pattern in CA1 area and takes the opportunity to work as an inhibitory neuromodulator and also to enable CA1 to cope with chronic morphine. In addition, adaptive mechanisms are differentially working in the dendrite layer rather than the somatic layer of hippocampal CA1., (© 2014 Wiley Periodicals, Inc.)

Orexins are produced from neurons which are restricted to a few regions of the lateral hypothalamus (LH), where they are important in pain modulation. The orexin receptors and orexinergic projections are localized in regions previously shown to play a role in pain modulation such as rostral ventromedial medulla (RVM). The effect of orexin-A (ORXA) microinjection into the RVM on nociceptive behaviors was examined using the formalin test. Microinjection of ORXA into the RVM, but not adjacent reticularis gigantocellularis (Gi) nucleus, decreased formalin induced nociceptive behaviors. Pretreatment with a selective OX1R antagonist, SB-334867 inhibited the antinociception produced by ORXA, while the administration of SB-334867 alone had no effect. These data demonstrate that ORXA-induced antinociception in the formalin test is mediated in part through orexin1 receptors in the RVM., (Copyright © 2014. Published by Elsevier Inc.)

Objective: It is well known that intracerebroventricular (ICV) and supraspinal injections of orexin-A elicit analgesia, but the mechanism(s) of action remains unidentified. This study aims to characterize the effect of orexin-A on rostral ventromedial medulla (RVM) neurons which are involved in the descending nociception modulating pathway., Materials and Methods: In this experimental study, we injected orexin-A or vehicle di- rectly into rats' ICV while the tail flick (TF) latencies were measured and the on- and off-cell firing activities were monitored for more than 60 minutes., Results: In response to noxious stimuli on the tail, we observed increased firing rate of on-cells and a decreased association with the firing rate of off-cells and in neutral cells the firing rate was unchanged just prior to tail flicking. ICV injection of orexin-A decreased the spontaneous firing rate of on-cells (the type of RVM neurons believed to have facilitatory action on nociception). Furthermore, orexin-A increased firing rate of off-cells (the type of RVM neurons believed to have an inhibitory action on nocicep- tion). Orexin-A reduced the TF-related responses of on-cells and TF-related pause duration of off-cells., Conclusion: These results have shown that the analgesic effect produced by orexin-A may be induced by brainstem neurons. It is suggested that the orexinergic system from the hypothalamus to the RVM may have a potential role in modulation of nociceptive transmission.

The current practical tests were designed to study in vitro interactions in the field potential between salicylate and morphine analgesics in the hippocampus area CA1 taken from morphine-(7 days) or salicylate (6 days)-treated rats. For this, morphine or salicylate was applied in vitro to the hippocampal slices derived from chronically drug-treated or saline-injected rats and drug-induced changes in evoked field potentials of area CA1 were evaluated. Chronic treatment in vivo of morphine or salicylate had no impact on baseline field EPSP and population spikes (PS) but a leftward shift in fEPSP/PS (E/S) curves and an increase in paired pulse ratio at 10 ms IPI were seen. Acute in vitro salicylate produced a durable PS potentiation in morphine-treated group, whereas an increase in PS of all groups was observed after long-term exposure to in vitro salicylate. Acute in vitro morphine caused a stable PS potentiation in control and salicylate treated groups, but not in morphine treated group. A potentiated fEPSP and a greater PS potentiation in salicylate treated group were observed after long-term exposure to in vitro morphine. It is concluded that the chronic treatment in vivo of salicylate or morphine incites lasting changes in the CA1 circuitry, which alters excitatory effects of subsequent salicylate or morphine tests in vitro in a way that an increase in reactivity or tolerance to the acute salicylate or morphine administration was observed., (© 2013 Elsevier B.V. All rights reserved.)

Hippocampus functions, including spatial cognition and stress responses, mature during adolescence. In addition, hippocampus neuronal structures are modified by circulating sex steroids, which dramatically increase during adolescence. Therefore, the effects of castration and the circulating levels of the main sex steroid testosterone on spatial learning and memory were examined across postnatal ages to test whether pre-pubertal castration affected rats' spatial ability in the Morris Water maze (MWM). Male rats were either castrated or sham-castrated at 22d (days of age), or left gonadally intact. They were then trained and tested in the MWM beginning at 28d, 35d, 45d or 60d. We found that all of the intact rats learned the spatial task; however, the males at 22d and 28d required more trials to acquire the task than the males at older ages. The males castrated at 22d and tested at 35d had significantly lower escape latency and traveled distance during training than the sham-castrated males trained at the same age. No differences were observed in mean values of escape latency and traveled distance at 45d even though they had comparable levels of testosterone. We conclude that adult-typical performance for male spatial memory emerges during mid-adolescence and that pre-pubertal castration appears to improve spatial learning during this time., (© 2013. Published by Elsevier Inc. All rights reserved.)

The effects of prepubertal castration on hippocampal CA3-CA1 synaptic transmission and plasticity were studied at different ages in vitro. The field excitatory postsynaptic potentials (fEPSP) and population spikes (PS) were simultaneously recorded from stratum radiatum and stratum pylamidale of area CA1 following stimulation of Schaffer collaterals in slices taken from sham-castrated and castrated rats at postnatal days (PND) 28, 35, 45, and 60. Castration had no effect on baseline responses at different ages except at PND 60 that a decrease in the fEPSP slope was seen. Prepubertal castration caused age-specific changes in CA1-long term potentiation (LTP) induction. The castration did decrease both fEPSP-LTP and PS-LTP at PND 35 but a decrease was seen only in PS-LTP at PND 60. NMDA receptor antagonist AP5 (25 µM) completely blocked both fEPSP-LTP and PS-LTP at PND 60 and only PS-LTP at PND 35 in both sham-castrated and castrated groups. Although AP5 blocked fEPSP-LTP at PND 35 in sham-castrated group, it failed to inhibit fEPSP-LTP at PND 35 in castrated one. These findings suggest that prepubertal castration causes the age-dependent changes in CA1-LTP induction, which might arise from alterations in the NMDA receptors., (Copyright © 2013 Wiley Periodicals, Inc.)

Tolerance and cross-tolerance for the effects of morphine (M) and sodium salicylate on nociception and learning were examined. The anti-nociceptive effects were measured by using the classic tail flick (TF) and hot plate (HP) tests and learning was measured with the Morris water maze (MWM). Tolerance or cross-tolerance was induced by daily injection (i.p.) of morphine sulfate (10mg/kg for 7 days) or sodium salicylate (300 mg/kg for 6 days). The injection of sodium salicylate increased both TF and HP latencies. This anti-nociceptive effect was progressively decreased across six injections and tolerance to sodium salicylate was developed. When M was injected to sodium salicylate-tolerant rats, a weakened anti-nociceptive effect was seen, indicating cross-tolerance to M. Acute treatment with M also increased TF latency. This anti-nociceptive effect was successively decreased across seven injections and tolerance to M was developed. When sodium salicylate was injected to M-tolerant rats, a diminished anti-nociceptive effect was seen, indicating cross-tolerance to sodium salicylate. Acute M impaired water maze performance, while chronic M and sodium salicylate had no effects on MWM performance. However, when M was injected to rats that had received sodium salicylate after each training trial for 7 days, these rats spent less time in target quadrant as compared to M and saline groups. It is concluded that chronic sodium salicylate induces tolerance to anti-nociceptive effects of M and vice versa. Also chronic salicylate may produce lasting metaplastic changes in brain mechanisms behind spatial learning and memory, which can be visualized in cross-sensitization to morphine., (Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.)

Herein the effect of orexin receptor type-1 antagonist SB-334867 on the development of tolerance to analgesic effects of morphine was studied in rats. To incite tolerance, morphine sulfate was injected intraperitoneally (i.p., 10mg/kg) once a day for 7 days. The tail flick test was used to evaluate antinociceptive effects of the morphine. A selective OxR1 receptor antagonist, SB-334867, was microinjected (i.c.v.) into the right cerebral ventricle (10 μg/10 μl) immediately before each morphine injection. Repeated morphine application resulted in tolerance to morphine analgesic effects as a decreasing trend during 7 days. Also, repeated administration of SB-334867 (i.c.v.) alone was without significant effect on the nociception as compared to control. Microinjection of SB-334867 prior to each morphine injection inhibited the development of tolerance, so that the analgesic effects of morphine were significantly higher in SB-334867 plus morphine treated rats than that of vehicle plus morphine treated ones on days 4-7. It is concluded that orexin receptor type-1 might be involved in the development of tolerance to morphine analgesic effects., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Withdrawal from chronic opiates is associated with an increase in anxiogenic-like behaviours, but the anxiety profile in the morphine-dependent animals is not clear. Thus, one of the aims of the present study was to examine whether morphine-dependent rats would increase the expression of anxiogenic-like behaviours in novel and stressful conditions. Additionally, recent studies have shown that voluntary exercise can reduce anxiety levels in rodents. Therefore, another aim of this study was to examine the effect of voluntary exercise on the anxiety profile in both morphine-dependent animals and animals experiencing withdrawal. Rats were injected with bi-daily doses (10 mg/kg, at 12 h intervals) of morphine over a period of 10 days in which they were also allowed voluntary exercise. Following these injections, anxiety-like behaviours were tested in the elevated plus-maze (EPM) model and the light/dark (L/D) box. We found reductions in time spent in, and entries into, the EPM open arms and reductions in time spent in the lit side of the L/D box for both sedentary morphine-dependent and withdrawn rats as compared to the sedentary control groups. The exercising morphine-dependent and withdrawn rats exhibited an increase in EPM open arm time and entries and L/D box lit side time as compared with the sedentary control groups. We conclude that voluntary exercise decreases the severity of the anxiogenic-like behaviours in both morphine-dependent and withdrawn rats. Thus, voluntary exercise could be a potential natural method to ameliorate some of the deleterious behavioural consequences of opiate abuse., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Effects of morphine on synaptic transmission and plasticity in the hippocampus area CA1 following in vivo sodium salicylate and the potential molecular mechanism were investigated. Population spikes (PS) were recorded from stratum pylamidale of area CA1 following stimulation of Schaffer collaterals in slices taken from control and sodium salicylate injected rats. To induce long term potentiation (LTP), a 100Hz tetanic stimulation was used. Acute in vitro morphine increased baseline PS amplitude in control slices but not in slices taken from sodium salicylate treated rats. In vivo chronic salicylate did slightly decrease and/or destabilize LTP of CA1 synaptic transmission. We also found that mRNA of NR2A subunit of NMDA receptor was reduced in the hippocampus of sodium salicylate treated rats as compared to control ones. Following LTP induction, the mRNA of NR2A and PP1 (protein phosphatase 1) in slices taken from salicylate-treated rats were more than those of control ones. After long-term exposure to in vitro morphine, high frequency stimulation (HFS) decreased NR2A mRNA level significantly in sodium salicylate treated slices. It is concluded that in vivo sodium salicylate causes tolerance to excitatory effect of morphine and changes the ability of HFS to induce PS LTP in the hippocampus area CA1 in vitro. These changes in synaptic response may be due to alterations in NR2A and PP1 expression., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Chronic exposure to opiates impairs spatial learning and memory. Given the well-known beneficial effects of voluntary exercise on cognitive functions, we investigated whether voluntary exercise would ameliorate the cognitive deficits that are induced by morphine dependence. If an effect of exercise was observed, we aimed to investigate the possible role of hippocampal brain-derived neurotrophic factor (BDNF) in the exercise-induced enhancement of learning and memory in morphine-dependent rats. The rats were injected with bi-daily doses (10mg/kg, at 12h intervals) of morphine over a period of 10 days of voluntary exercise. Following these injections, a water maze task was performed twice a day for five consecutive days, followed by a probe trial 2 days later. A specific BDNF inhibitor (TrkB-IgG chimera) was used to block the hippocampal BDNF action during the 10 days of voluntary exercise. We found that voluntary exercise blocked the ability of chronic morphine to impair spatial memory retention. A blockade of the BDNF action blunted the exercise-induced improvement of spatial memory in the dependent rats. Moreover, the voluntary exercise diminished the severity of the rats' dependency on morphine. This study demonstrates that voluntary exercise ameliorates, via a TrkB-mediated mechanism, the cognitive deficits that are induced by chronic morphine. Thus, voluntary exercise might be a potential method to ameliorate some of the deleterious behavioral consequences of the abuse of morphine and other opiates., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Curcuminoids are vital constituent of turmeric, with therapeutic potential in the treatment of Alzheimer's disease. Electrically, stimulus train-elicited plastic changes in hippocampal CA1 excitability were used as an experimental paradigm to study the effects of curcuminoid mixture and individual components on functional failure induced by Aβ peptide in vitro. Electrical stimulation was applied on Schaffer collaterals, and population spikes (PS) were recorded from stratum pyramidale. To induce long-term potentiation (LTP) of PS, primed burst stimulation (PBs) was used. Aβ peptide inhibited PS LTP induction. Sinking PS LTP due to Aβ peptide was rescued when curcuminoid mixture was applied before PBs only at lower dose (0.1 μM) resulting in PS potentiation to 127.42% ± 1.83% at 5 min and 123.98% ± 1.06% at 60-min post-PBs. Similarly, when bisdemethoxycurcumin was applied, PS LTP was induced and lasted only at a single dose (0.1 μM). Demethoxycurcumin was effective at a middle dose (1 μM), so that the PS amplitude was changed to 140.15% ± 2.68% and 129.82% ± 0.44% at 5 and 60 min, respectively. PS LTP was effectively induced in the presence of curcumin at middle and high doses (1 and 30 μM) with resultant PS LTP to 155.68% ± 1.23% and 127.72% ± 1.23%, respectively, at 60-min post-PBs. These results showed that curcuminoids can restore susceptibility for plastic changes in CA1 excitability that is injured by exposure to Aβ peptide and rescue sinking PS LTP in Aβ-peptide-exposed hippocampal CA1 neurons., (Copyright © 2010 Wiley-Liss, Inc.)

The impact of theta patterning of the stimulation on the kindling effects of pentylenetetrazol (PTZ) was studied in rat hippocampus area CA1 in vitro. A potential involvement of adenosine A1 receptors was also examined. Primed-bursts stimulation (PBs) and theta pulse stimulation (TPS) were used as patterned activities. Stimulus patterns were applied to the Schaffer collateral afferents of hippocampal slices from both control and PTZ-kindled rats, the field excitatory postsynaptic potentials (fEPSP) and population spikes (PS) were simultaneously recorded from stratum radiatum and stratum pyramidale, respectively. Experiments were carried out in the presence or absence of the adenosine A1 receptor antagonist CPX. The following changes in kindled vs. control slices were observed. PBs was unable to produce both fEPSP LTP and PS LTP in untreated slices. When A1 receptor antagonist CPX was applied before PBs, both fEPSP LTP and PS LTP were elicited. PS LTP was selectively depressed by TPS (applied at 60 min after LTP induction) exclusively when A1 receptors were blocked, while TPS failed to depress PS LTP in untreated PBs-exposed slices. These findings suggest that seizing entails lasting changes in hippocampus area CA1 so that LTP induction by PBs is masked due to intensive adenosine release which in turn prevents TPS to induce PS LTD in epileptic CA1 network., (2010 Wiley-Liss, Inc.)

Objective: Bone marrow stromal cells (BMSCs) were documented as a feasible candidate for cell therapy. Several protocols with one or more steps, using different chemicals, were used for inducing BMSCs differentiation into neuronal phenotype. Many of these chemicals were reported to be of mutagenic, teratogenic or carcinogenic properties. The purpose of this work was to evaluate the neuronal inductivity of selegiline to BMSCs., Methods: Selegiline was used to induce BMSCs following pre-induction with beta-mercaptoethanol and retinoic acid. The neuronal phenotype was evaluated using antineurofilament 200, neurofilament 68, anti-Map-2 and synapsin I antibodies. In addition, reverse transcription polymerase chain reaction was used for the expression of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), neurotrophin 3 (NT-3), neuroligin 1 and post-synaptic density protein 95 (PSD-95)., Results: The result of the work showed that the induced BMSCs were immunoreactive for neurofilaments 200 and 68. Moreover, anti-Map-2 and synapsin I antibodies showed a structure morphologically consistent with synapses. Reverse transcription polymerase chain reaction showed that the induced BMSCs could express BDNF, NGF, NT-3, neuroligin 1 and PSD-95. The time course used was 1, 3, 6, 12, 24, 36 and 48 hours, and the percentages of neurofilament 200 immunoreactive cells were analysed using the logistic growth curve., Discussion: The results showed that selegiline was efficient and a potent inducer for BMSCs into neuronal phenotype, which can be used in the cell therapy in neurodegeneration and traumatic nervous tissue injuries.

The effects of chronic morphine exposure on synaptic plasticity in the CA1 region of the hippocampal slice preparation using extracellular recordings of the population spike (PS) evoked in response to Schaffer collateral stimulation were studied. High frequency stimulation (HFS; 1X100 Hz) and theta pulse stimulation (TPS; 5 Hz trains for 3 min) were used as patterned activities. The results showed that in rats chronically treated with morphine (dependent group), TPS induced long-term depression (LTD) of PS in CA1 in the absence of in vitro morphine. This TPS-induced PS LTD was blocked in the presence of either AP5 (NMDAR antagonist) or CPX (A1 adenosine receptor antagonist) alone, but was not blocked when AP5 and CPX were co-applied. This TPS-induced PS LTD was also blocked in the presence of either 8-PT (a selective A1 adenosine receptor antagonist) or MRS1220 (a specific A3 receptor antagonist). Additionally, when TPS was applied prior to HFS, PS long-term potentiation (LTP) was blocked. However, when TPS was applied after HFS, there was no reversal of PS LTP in slices from dependent rats in contrast to controls which displayed reversal of LTP. Both the PS LTD and the absence of PS LTP reversal were blocked by in vitro application of morphine. It is concluded that morphine withdrawal was associated with greater depression of CA1 PS elicited by natural stimulus induced activity pattern. This effect was associated with changes in NMDA and adenosine receptors due to chronic morphine administration. Such an in vitro preparation could provide a novel paradigm to investigate withdrawal effects on synaptic plasticity.

This study was designed to investigate an interaction between acute restraint stress and corticosterone with verapamil, a blocker of L-type voltage-dependent calcium (VDC) channels on retrieval of long-term memory. Young adult male rats were trained in one trial inhibitory avoidance task (0.5 mA, 3 s footshock). On retention test given 48 h after training, the latency to re-enter dark compartment of the apparatus was recorded. In Experiment 1, verapamil pretreatment (5, 10, or 20 mg/kg) enhanced the impairing effects of acute stress (which was applied for 10 min in a Plexiglass tube 30 min before the retention test) on memory retrieval. The applied stress increased circulating corticosterone levels as assessed immediately after the retention test, indicating that stress-induced impairment of memory retrieval is mediated, in part, by increased plasma levels of glucocorticoids. Verapamil did not change this response. In Experiment 2, pretreatment of an intermediate dose of verapamil also enhanced corticosterone-induced impairment of memory retrieval. In Experiments 3 and 4, acute stress or corticosterone did not change motor activity with or without prior treatment of verapamil, suggesting that stress or glucocorticoid-induced impairment of memory retrieval is not due to any gross disturbances in motor performance of animals. These findings indicate that blockade of L-type VDC channels enhances stress or glucocorticoid-induced impairment of memory retrieval, and provide evidence for the existence of an interaction between glucocorticoids and L-type VDC channels on memory retrieval.

Riluzole has been shown to possess neuroprotective effects in a variety of neurological and animal model of diseases, including motor diseases. However, the mechanism(s) by which riluzole preserves the intrinsic electrophysiological characteristics of neuronal membrane has not been fully delineated. Ataxia is a clinical manifestation of disturbance in coordinated motor activity, which may be caused by cerebellar impairment. Here, the in vivo neuroprotective effect of riluzole on the intrinsic activity of Purkinje cells (PCs) in a rat model of cerebellar ataxia induced by 3-acetylpyridine (3-AP) was studied. Behavioural assessment tests, histological examination and whole cell patch clamp recording under current clamp conditions were used to explore the possible protective effect of riluzole against induction of ataxia with 3-AP treatment. Combined treatment with riluzole and 3-AP not only almost completely prevented the neuronal degeneration in cerebellar Purkinje cells layer but also the development of ataxia, which occurred following injection of 3-AP alone and partially improved the motor behaviour in comparison with ataxic rats. The normal firing behaviour and action potential characteristics of Purkinje neurones were preserved. The amplitude of both fast after hyperpolarization potential (fAHP) and post train after hyperpolarization potential, a marker of slow AHP (sAHP), along with the duration of post train AHP, which play an important role in regulating the firing behaviour were restored to the control conditions. These findings suggest that riluzole-induced neuroprotection may be mediated at least in part by activation of Ca(2+)-dependent K(+) channel function.

Purpose: Herein we used electrophysiologic approaches in hippocampal area CA1 to estimate how morphine treatment alters the pentylenetetrazol (PTZ) effects., Methods: Hippocampal slices taken from either control animals or animals made dependent via chronic morphine administration were examined. Changes in the population spike and epileptiform amplitudes were used as indices to quantify the effects of PTZ exposure in the control and morphine-dependent slices. Hippocampal slices taken either from control animals or from animals made dependent upon morphine were exposed to PTZ, either with or without morphine, naloxone, or morphine + naloxone., Results: Morphine dependence increased a PTZ-induced long-term potentiation (LTP) of the population spike in CA1 in vitro. This LTP was not found in rats that had spontaneously withdrawn morphine or withdrawn with naloxone in vivo after chronic morphine intake. Morphine or naloxone in vitro blocked the PTZ-induced LTP changes in control and morphine-dependent slices. However, PTZ-induced multiple population spikes (epileptiform activity) in CA1 was not blocked by naloxone., Discussion: It is concluded that dependence on morphine enhances PTZ-induced plastic and epileptic changes in CA1 excitability. We suggest that this model of neuronal activity in dependent slices could present an opportunity for studying the mechanisms underlying the increased likelihood of seizures in morphine users.

This study was designed to examine the effect of corticosterone on consolidation of contextual fear memory and hippocampal long-term potentiation (LTP) in rats. In Experiment 1, dose-response effects of corticosterone on consolidation of contextual fear memory were determined. Immediately after training in contextual fear conditioning task, rats received different doses of corticosterone. Testing 24 h later, it revealed that corticosterone enhanced memory consolidation in an inverted U shape as evidenced in increased freezing behavior of corticosterone-treated animals. The most effective dose was 3 mg/kg. In Experiment 2, LTP was examined in rats whose memory consolidation has been enhanced with corticosterone. The rats were trained as the above and received corticosterone (3 mg/kg) immediately after training. Immediately or up to one day after retention test, rats were anesthetized with urethane for LTP experiments. For LTP induction, three episodes of high frequency stimuli, 30 s apart, were delivered to the perforant path, each consisting of 10 stimuli at 250 Hz. LTP was assessed by measuring the increase in the initial slope of the population excitatory post-synaptic potentials and the amplitude of the population spikes. Data indicated that animals whose memory has been enhanced by corticosterone, also displayed enhanced hippocampal LTP. The above findings suggest that glucocorticoids may enhance contextual fear memory consolidation via enhancing hippocampal LTP.

Introduction: The hippocampus and piriform cortex have a critical role in seizure propagation. In this study, the role of adenosine A1 receptors of piriform cortex on CA1 hippocampal kindled seizures was studied in rats., Methods: Animals were implanted with a tripolar electrode in the right hippocampal CA1 region and two guide cannulae in the left and right piriform cortex. They were kindled by daily electrical stimulation of hippocampus. In fully kindled rats, N6- cyclohexyladenosine (CHA; a selective adenosine A1 receptors agonist) and 1,3-dimethyl-8-cyclopenthylxanthine (CPT a selective adenosine A1 receptor antagonist) were microinfused into the piriform cortex. The animals were stimulated at 5, 15 and 90 minutes (min) after drug injection., Results: Obtained data showed that CHA (10 and 100 microM) reduced afterdischarge duration, stage 5 seizure duration, and total seizure duration at 5 and 15 min after drug injection. There was no significant change in latency to stage 4 seizure. CPT at concentration of 20 microM increased afterdischarge duration, stage 5 seizure duration, and total seizure duration and decreased latency to stage 4 seizure at 5 and 15 min post injection. Pretreatment of rats with CPT (10 microM), 5 min before CHA (100 microM), reduced the effect of CHA on seizure parameters., Conclusion: These results suggested that activity of adenosine A1 receptors in the piriform cortex has an anticonvulsant effect on kindled seizures resulting from electrical stimulation of the CA1 region of the hippocampus.

To fill microelectrodes using backfilling method needs excessive time approximately 4-6 h. It is often difficult to fill microelectrodes without damage or leakage. A main problem is bubble formation in microelectrodes which has an impact on the electrical properties of the electrode and thus it influences the quality of the recording. Based on Archimede's principle there is a force within a solution which pushes insoluble material with a lower specific gravity upward and outside of the solution. Centrifugation can increase the force to eliminate the bubbles. We designed a microelectrode holder to protect microelectrode sensitive tips from mechanical damage due to the gravity tensions; it can help to eliminate the bubbles easily and simultaneously in 10 min or less. The tests were performed for 2000, 4000, and 8000 rpm centrifugation each one for 3, 6 and 12 min duration respectively, it was found that the bubbles were completely eliminated at 8000 rpm for 6-12 min and there were no significant differences for resistance, and the number of leaky or damaged electrodes between the two methods. In the new design of devices, the materials used and the design of the holder are simple and the approach is applicable to many laboratories worldwide.

Numerous studies have dealt with the role of opiate system in tasks aimed at measurement of cognitive behavior, but the role of morphine dependence on learning and memory is still controversial. In this study chronic exposure to morphine was employed to evaluate learning ability and spatial short-term memory (working memory) and long-term memory (reference memory) in the water maze task. Male albino rats were made dependent by chronic administration of morphine in drinking water that lasted at least 21 days. In Experiment 1, the performance of animals was evaluated in reference memory version of the water maze. Rats were submitted to a session of 6 trials for 6 consecutive days to find the submerged platform that was located in the center of a quadrant. Latency and traveled distance to find the platform were measured as indexes of learning. Memory retention was tested 24 h after the last training session in a probe trial (60 s) in which there was no platform and the time spent in each quadrant of the water maze was recorded. Results indicated that latency and traveled distance to find the platform were same in control and dependent rats during training days, but during the probe test morphine-dependent group spent significantly less time in the target quadrant. In Experiment 2, training on working memory version of the water maze task was started. Only two trials per day were given until the performance of animals was stabilized (at least 5 days). Final test was done at day 6. Acquisition-retention interval was 75 min. No significant differences were found on acquisition and retention trials between morphine and control groups. Our findings indicate that chronic exposure to morphine did not impair learning ability, but partially impaired retention of spatial long-term (reference) memory. Moreover, dependence on morphine did not affect either acquisition or retention of spatial short (working) memory.

Activation of hypothalamic-pituitary-adrenal (HPA) axis inhibits development of morphine tolerance. Also, the expression of CaMKIIalpha is increased following chronic administration of morphine. In the current study, we tried to examine the effect of epinephrine, on the development of morphine tolerance; and also evaluate the expression of CaMKIIalpha as a molecular index for tolerance development. Analgesic tolerance was induced by intrathecal (i.t.) injection of morphine 15 microg/rat, twice a day for 5 days. To study the effect of epinephrine on development or reversal of morphine tolerance, epinephrine was administrated 20 min before morphine injections. Analgesia was assessed using tail flick test. Gene expression assays were done using RT-PCR. Following 5 days of combined administration of morphine and epinephrine (2, 5 or 10 microg/rat), in day 6, morphine produced potent analgesia. Administration of saline and morphine during days 1-5, caused reduced analgesic effect of morphine on day 6. After tolerance induction during 5 days, co-administration of epinephrine and morphine for another 5 days, significantly reversed the tolerance. Both morphine and epinephrine increased the expression of CaMKIIalpha. The expression of CaMKIIalpha was highly increased following combined administration of epinephrine and morphine. Our results showed the inhibition and reversal of analgesic tolerance to local administrated morphine by epinephrine. We observed the increased expression of CaMKIIalpha without development of morphine tolerance in animals treated with combined epinephrine and morphine.

Low-frequency stimulation (LFS) is an antiepileptic and antiepileptogenic electrical stimulation. In this study the effect of changes in some LFS (1Hz, monophasic square wave) parameters (intensity, pulse duration and train duration) on piriform cortex kindled seizures was investigated both in fully kindled rats and during kindling acquisition. In fully kindled animals, application of different patterns of LFS immediately before kindling stimulation had no significant effect on seizure parameters. However, daily (15 min) application of LFS (0.1 ms pulse duration at intensity equal to after-discharge threshold (ADT) and 1 ms pulse duration at intensity equal to 1/4 ADT) during inter-seizure interval of 7 days significantly reduced the stage 5 duration of the next kindled seizure. Application of the same two LFS protocols for 3 days and 2 weeks had no effect on seizure parameters. The effect of LFS was also tested using different paradigms during kindling acquisition. When LFS (0.1 and 1 ms pulse duration, intensity equal to ADT and 1/4 ADT) was delivered daily after each kindling stimulation, it could significantly decrease after-discharge duration in various days during kindling development. In this experiment, only LFS with 0.1 ms pulse duration and intensity equal to ADT significantly delayed the appearance of seizure stages 1 and 2. According to obtained results, it may be concluded that in fully kindled rats application of different patterns of LFS before kindling stimulation has no anticonvulsant effect, but it can exert an inhibitory effect when applied during an inter-seizure interval of 7 days. In addition, LFS has antiepileptogenic effect during kindling acquisition. These effects depend on the applied LFS parameters (e.g. intensity, pulse duration and train duration).

Neonatal single whisker experience changes the response properties of spared barrel neurons to deflections of principal and adjacent whiskers. However little is known about the temporal characteristics of the paired whisker inputs. To address this issue we used computer controlled mechanical displacement of paired whiskers in control and plucked animals (plucking of all whiskers but D2 started at 0, 5 and 8 postnatal days). The principal whisker (PW) and its caudal adjacent whisker (AW) were deflected simultaneously or serially at different inter-stimulus intervals (10, 20, 30, 50 and 100 ms). Neuronal responses were recorded in D2 spared barrel both in layers IV and V. In the control group, combined deflection of AW prior to PW led to suppression of ON and OFF responses to PW deflection both in layers IV and V. The magnitude of this suppression was strongly dependent on the inter-stimulus intervals (ISIs). At almost all tested ISIs, whisker plucking from P0, P5 and P8 weakened suppressive interactions in layers IV and V barrel neurons for both ON and OFF responses. The most decrease in inhibitory interactions was observed in P5 plucked animals. Principal whisker-evoked ON responses were increased only in P0 plucked animals both in layers IV and V. AW-evoked ON responses are decreased in P5 plucked animals in layer IV. The available data suggest that sensory experience can modulate temporal aspects of response integration and receptive field properties of layers IV and V neurons in barrel cortex. These changes have different critical periods.

Low frequency stimulation (LFS) has an inhibitory effect on kindling acquisition. In the present study the effect of the perforant path LFS on induction of rapid perforant path kindled seizures and synaptic transmission in the dentate gyrus was investigated. Animals were kindled by perforant path stimulation in a rapid kindling manner (12 stimulations per day). In one group of animals LFS (0.1 ms pulse duration at 1 Hz, 200 pulses, and 50-150 microA) was applied to perforant path, immediately after termination of each rapid kindling stimulation. Application of LFS significantly retarded the kindling acquisition and increased the number of stimulations to achieved different kindled seizure stages. LFS also prevented an increment in the slope of field excitatory postsynaptic potentials and population spike amplitude during kindling. In addition, LFS significantly reduced the marked increase in early (10-50 ms intervals) and late (300-1000 ms intervals) paired-pulse depression induced by kindling. According to obtained results, it may be suggested that LFS of perforant path has a significant antiepileptogenic effect through inhibition of synaptic transmission in dentate gyrus. Meanwhile, LFS prevents an increase in the paired-pulse depression during kindling acquisition.

Adenosine exerts its anticonvulsants effect through different brain regions including piriform cortex. In this study, the effect of amygdala kindled seizures on adenosine A1 receptor-mediated neuromodulation in piriform cortex pyramidal neurons was tested at 24 h and 1 month after kindling. Animals were kindled by daily electrical stimulation of amygdala. Field potentials were recorded from layer II of piriform cortex pyramidal cells following stimulation of the lateral olfactory tract. Obtained results showed that N6-cyclohexyladenosine (CHA), a selective adenosine A1 receptor agonist (1, 10 and 100 microM; i.c.v.), reduced A1 slope and B1 amplitude of field potentials in both kindled and non-kindled (control) rats. However, its effects on kindled animals were more potent at 24 h, but not 1 month post-kindling. 8 cyclopenthyl-1,3-dimethylxanthine (CPT), a selective adenosine A1 receptor antagonist (50 microM, i.c.v.), had no significant effect on the field potential parameters. However, CPT (50 microM, i.c.v.) pretreatment eliminated effects of CHA (10 microM; i.c.v.) on the field potentials. These results indicate that activation of adenosine A1 receptors has an inhibitory effect on the field potentials of piriform cortex pyramidal neurons and the efficiency of adenosine A1 receptor neuromodulation in piriform cortex is increased at short-term (24 h) but return to normal at long-term (1 month) after kindling implementation.

In this study, the effect of A1 and A2A adenosine receptor activity of the piriform cortex (PC) on amygdala-kindled seizures was investigated in rats. Animals were kindled by daily electrical stimulation of the amygdala. In fully kindled rats, N6-cyclohexyladenosine (CHA, a selective A1 agonist), 8-cyclopentyl-1,3-dimethylxanthine (CPT, a selective A1 antagonist), CGS21,680 hydrochloride (CGS, a selective A2A agonist), and ZM241,385 (ZM, a selective A2A antagonist) were microinjected bilaterally into the PC. Rats were stimulated 5 min post-drug microinjection and seizure parameters were measured. Results showed that intra-PC CHA (10 and 100 micromol/L) decreased the duration of both afterdischarge and stage 5 seizure and significantly increased the latency to stage 4 seizure. Intra-PC CPT increased afterdischarge and stage 5 seizure duration at the dose of 20 micromol/L. The anticonvulsant effect of CHA (100 micromol/L) was eliminated by CPT (10 micromol/L) pretreatment. On the other hand, neither intra-PC CGS nor ZM had a significant effect on kindled seizures. These results suggest that activity of A1, but not A2A, receptors of the PC have anticonvulsant effects on kindled seizures elicited from electrical stimulation of the amygdala.

Previous research has shown that the hippocampus processes pain related-information, probably through hippocampal neurons that respond exclusively to painful stimulation. In the current experiments we tested whether blocking NMDA receptors in the hippocampal CA1 region and dentate gyrus could reduce nociceptive behaviors in rats. The competitive and noncompetitive NMDA receptor antagonists 2-amino-5-phosphonopentanoic acid (AP5; 3.75 microg/0.75 microl) and MK801 (1.5, 3, 6 microg/0.5 microl) were injected into the dentate gyrus and CA1 area of behaving rats 5 min before subcutaneous injection of formalin irritant. Pain behaviors in both acute and tonic phases of the formalin test were significantly reduced by AP5 (3.75 microg/0.75 microl) and MK801 (3 microg/0.5 microl, but not 1.5 and 6 microg/0.5 microl) injection to the dentate gyrus. In the CA1, injection of AP5 had no effect while injection of the effective dose of MK801 (3 microg/0.5 microl) had a significant antinociceptive effect. This effect was apparent only during the late phase of the formalin test. These results support the hypothesis that NMDA-sensitive mechanisms are involved in acute and persistent pain-related processing in the dentate gyrus and with tonic pain processing in the hippocampal CA1 region.

Neurohormones like testosterone and estrogen have an important role in learning and memory. Many biological effects of androgens in the brain require the local conversion of these steroids to an estrogen. The current research has conducted to assess the effect of testosterone, estrogen and aromatase inhibitor (anastrozole) on spatial discrimination of rats, using Morris water maze and also the pathway of the effect of testosterone by using anastrozole. Adult male rats were bilaterally cannulated into CA1 region of hippocampus and divided into 15 groups. Different groups received DMSO 0.5 microl and DMSO 0.5 microl + DMSO 0.5 microl as control groups and different doses of testosterone enanthate (TE) (20, 40 and 80 microg/0.5 microl), estradiol valerat (EV) (1, 2.5, 5, 10, and 15 microg/0.5 microl), anastrozole (An) (0.25, 0.5, 1 microg/0.5 microl), TE 80 microg/0.5 microl + anastrozole 0.5 microg/0.5 microl and EV 15 microg/0.5 microl + anastrozole 0.5 microg/0.5 microl all days before training. TE and EV were injected 30-35 min before training and anastrozole was injected 25-30 min before training. Our results have shown both TE 80 microg/0.5 microl and EV 15 microg/0.5 microl groups increase in escape latency and traveled distance to find invisible platform. Also we have shown that anastrozole dose dependently decreases escape latency and traveled distance. We resulted that both TE and EN impaired acquisition of spatial learning and memory but anastrozole improved it. Anastrozole also could be buffered TE-induced impairment effect but not EV.

In this study, the role of adenosine A1 receptors of the hippocampal CA1 region in entorhinal cortex-kindled seizures was investigated in rats. Animals were kindled by daily electrical stimulation of the entorhinal cortex. In fully kindled rats, N(6)-cyclohexyladenosine (CHA; a selective A1 receptor agonist) and 1, 3-dimethyl-8-cyclopenthylxanthine (CPT; a selective A1 receptor antagonist) were microinfused bilaterally into the hippocampal CA1 region. Rats were stimulated and seizure parameters were measured. Results obtained showed that CHA (10 and 50 micro moles) decreased the afterdischarge duration (ADD) in the hippocampal CA1 region and entorhinal cortex, stage 5 seizure duration (S5D) and seizure duration (SD) only at the dose of 50 micro moles, and significantly increased the latency to stage 4 (S4L). Intrahippocampal CPT increased ADD and S5D, and significantly reduced the latency to stage 4 (S4L) at the dose of 10 micromoles. Pretreatment of rats with CPT (5 micro moles) before CHA (50 micro moles), significantly reduced the effect of CHA on seizure parameters. The results suggest that the CA1 region of the hippocampus plays an important role in spreading seizure spikes from the entorhinal cortex to other brain regions and activation of adenosine A1 receptors in this region participates in the anticonvulsant effects of adenosine agonists.

Adenosine is an endogenous anticonvulsant that exerts its effects through A1 receptors. As the piriform/amygdala is a critical circuit for limbic seizure propagation, in this study, the role of basolateral amygdala A1 receptors on piriform cortex (PC)-kindled seizures was investigated. Rats were kindled by daily electrical stimulation of PC. In fully kindled animals, bilateral intra-amygdala N6-cyclohexyladenosine (CHA; 10-500 micromol/L, a selective A1 receptor agonist) had no effect on kindled-seizure parameters. However, bilateral intra-amygdala 2% lidocaine (reversal neuronal inhibitor) reduced the kindled seizure severity. There was significant increase in stage 4 latency and decrease in stage 5 duration. Bilateral lesion of basolateral amygdala of kindled animals (by electrical DC current) reduced the kindled seizure severity more dramatically. Our results showed afterdischarge duration, stage 5 duration, and seizure duration were decreased and stage 4 latency increased significantly. In addition, daily intra-amygdala CHA had no significant effect on PC kindling acquisition. Therefore, it may be concluded that although the basolateral amygdala neuronal activity has a critical role in the propagation of epileptic seizures from PC, the amygdala A1 receptors have no role in this regard. On the other hand, amygdala A1 receptors have no anticonvulsant or antiepileptogenic effect on PC-kindled seizures.

The present research aimed at investigating the opioid-adenosine interaction on regional cerebral blood flow (rCBF). Therefore rCBF in the sensory cortex of morphine-naive and -dependent rats was measured using the laser-Doppler flowmetry technique. The results showed that adenosine (10(-5), 10(-4), 10(-3) M) significantly increased rCBF in morphine-dependent rats (MDR) (P < 0.01). This effect was inhibited by theophylline (5 x 10(-5) M). Also systemic naloxone (0.5, 1.5 and 3 mg/kg, s.c.) significantly increased rCBF in MDR and it was accompanied by elevated blood pressure and heart rate. Local adenosine (10(-4) M) significantly augmented naloxone (0.5 mg/kg)-induced increase in rCBF of MDR but had no significant effect on naloxone's (1.5 and 3 mg/kg) increasing effect on rCBF. Theophylline also has no effect on naloxone increasing effect on rCBF. These data suggest that adenosine receptors responsiveness increase in sensory cortex of MDR. Naloxone also highly increased rCBF of MDR that probably not interfere with adenosine receptors. Also, it seems that adenosine acts as a modulator in rCBF regulation of morphine-dependent and morphine withdrawal rats.

The effect of ritanserin (5-HT2 antagonist) on scopolamine (muscarinic cholinergic antagonist)-induced amnesia in Morris water maze (MWM) was investigated. Rats were divided into eight groups and bilaterally cannulated into CA1 region of the hippocampus. One week later, they received repeatedly vehicles (saline, DMSO, saline+DMSO), scopolamine (2 microg/0.5 microl saline/side; 30 min before training), ritanserin (2, 4 and 8 microg/0.5 microl DMSO/side; 20 min before training) and scopolamine (2 microg/0.5 microl; 30 min before ritanserin injection)+ritanserin (4 microg/0.5 microl DMSO) through cannulae each day. Animals were tested for four consecutive days (4 trial/day) in MWM during which the position of hidden platform was unchanged. In the fifth day, the platform was elevated above the water surface in another position to evaluate the function of motor, motivational and visual systems. The results showed a significant increase in escape latencies and traveled distances to find platform in scopolamine-treated group as compared to saline group. Ritanserin-treated rats (4 microg/0.5 microl/side) showed a significant decrease in the mentioned parameters as compared to DMSO-treated group. However, scopolamine and ritanserin co-administration resulted in a significant decrease in escape latencies and traveled distances as compared to the scopolamine-treated rats. Our findings show that microinjection of ritanserin into the CA1 region of the hippocampus improves the scopolamine-induced amnesia.

Using field potential recording in the CA1 region of the rat hippocampal slices, the effects of eugenol on synaptic transmission and long-term potentiation (LTP) were investigated. Population spikes (PS) were recorded in the stratum pyramidal following stimulation of stratum fibers. To induce LTP, eight episodes of theta pattern primed-bursts (PBs) were delivered. Eugenol decreased the amplitude of PS in a concentration-dependent manner. The effect was fast and completely reversible. Eugenol had no effect on PBs-induced LTP of PS. It is concluded that while eugenol depresses synaptic transmission it does not affect the ability of CA1 synapses for tetanus-induced LTP and plasticity.

1H NMR spectroscopy was used to investigate the stoichiometry and stability of the drug ketamine cation complexes with some crown ethers, such as 15-crown-5 (15C5), aza-15-crown-5 (A15C5), 18-crown-6 (18C6), aza-18-crown-6 (A18C6), diaza-18-crown-6 (DA18C6), dibenzyl-diaza-18-crown-6 (DBzDA18C6) and cryptant [2,2,2] (C222) in acetonitrile (AN), dimethylsulfoxide (DMSO) and methanol (MeOH) at 27 degrees C. In order to evaluate the formation constants of the ketamine cation complexes, the CH3 protons chemical shift (on the nitrogen atom of ketamine) was measured as function of ligand/ketamine mole ratio. The formation constant of resulting complexes were calculated by the computer fitting of chemical shift versus mole ratio data to appropriate equations. A significant chemical shift variation was not observed for 15C5 and 18C6. The stoichiometry of the mono aza and diaza ligands are 1:1 and 1:2 (ligand/ketamine), respectively. In all of the solvents studied, DA18C6 formed more stable complexes than other ligands. The solvent effect on the stability of these complexes is discussed.

In this study the role of adenosine A1 and A2A receptors of the hippocampal CA1 region on piriform cortex-kindled seizures was investigated in rats. Animals were kindled by daily electrical stimulation of piriform cortex. In fully kindled rats, N6-cyclohexyladenosine (CHA; a selective A1 receptor agonist), 1,3-dimethyl-8-cyclopenthylxanthine (CPT; a selective A1 receptor antagonist), CGS21680 hydrochloride (CGS, a selective A2A receptor agonist) and, ZM241385 (ZM, a selective A2A receptor antagonist) were microinfused bilaterally into the hippocampal CA1 region. Rats were stimulated and seizure parameters were measured. Obtained results showed that microinjection of CHA (10 and 100 microM) decreased the afterdischarge duration (ADD), stage 5 seizure duration (S5D) and seizure duration (SD), and significantly increased the latency to stage 4 (S4L). Intra-hippocampal CPT increased ADD at the dose of 20 microM. Pretreatment of rats with CPT (10 microM) before CHA (10 microM), significantly reduced the effect of CHA on seizure parameters. On the other hand, microinjection of CGS (200 and 500 microM) increased ADD, but of ZM had no effect on seizure parameters. Pretreatment of rats with ZM (50 microM) before CGS (500 microM), significantly reduced the effect of CGS on seizure parameters. The results suggest that the facilitatory role of the hippocampal CA1 region in relaying or spreading of piriform cortex kindled seizures is decreased by the activation of adenosine A1 receptors and increased by A2A receptors.

In this study the effect of adenosine A(1) receptors of the entorhinal cortex (EC) and amygdala on kindled seizures was investigated. Animals were kindled by daily electrical stimulation of amygdala (group 1) or EC (group 2). In the fully kindled animals, N(6)-cyclohexyladenosine (CHA), a selective A(1) receptor agonist, and 1,3-dimethyl-8-cyclopenthylxanthine (CPT), a selective A(1) receptor antagonist, were microinjected bilaterally into the EC (group 1) or amygdala (group 2). The seizure parameters were measured at 5, 15, 60 and 120 min post injection. Obtained data showed that in group 1, intra-EC microinjection of CHA at concentration of 10 microM reduced amygdala- and, EC-afterdischarge duration and stage 5 seizure duration at 5, 15, 60 and 120 min post drug injection. It also increased the latency to stage 4 seizure but no alteration was observed in seizure stage. At concentrations of 0.1 and 1 microM, CHA reduced only EC-afterdischarge duration at 5 and 15 min post drug infusion. Bilateral microinjection CPT at concentrations of 5 and 10 microM into the EC did not alter seizure parameters. Intra-EC microinjection of CPT (5 microM), 5 min before CHA (10 microM), blocked the anticonvulsant effects of CHA. On the other hand, in group 2 animals, intra-amygdala CHA (10, 50 and 100 microM) or CPT (5 and 10 microM) had no significant effect on seizure parameters of EC-kindled rats. These results suggest that adenosine A(1) receptors activation of the EC may have an inhibitory effect on amygdala-kindled seizures. But, despite of reciprocal interconnections between these two regions, activation of the A(1) receptors of the amygdala has no effect on EC-kindled seizures.

In diabetic angiopathy, responsiveness of alphal-adrenoceptors in blood vessels increases. The aim of this study was to investigate the vasoconstrictor response of knee joint blood vessels to phenylephrine (a 1-adrenoceptor agonist) in diabetes and acute inflammation. Acute knee joint inflammation was induced by the intraarticular injection of a 3% kaolin/3% carrageenan suspension. Diabetes was induced by the intravenous injection of alloxan (70 mg/kg). Male albino rats weighing 70 to 90 g each were divided into the following 4 groups: untreated controls, diabetic, inflammatory, and diabetic inflammatory. The blood flow of the knee joint was measured using the laser Doppler flowmetry (LDF) technique. Vasoconstriction of the articular microvascular was measured in response to the topical application of different concentrations (10(-7) to 10(-3) mol) phenylephrine. The results of this study show that (a) increased knee joint diameter and circumference due to inflammation and the knee joint basal blood flow were significantly lower in diabetic than in control rats; (b) the responsiveness of alphal-adrenoceptors decreased in kaolin/carrageenan-induced acute inflammation; (c) carrageenan-induced acute inflammation did not decrease the responsiveness of alphal-adrenoceptors in diabetic rats. We conclude that diabetes inhibits the reductive effect of acute inflammation on the responsiveness of alpha1-adrenoceptors in rats.

Phencyclidine (1-(1-phenylcyclohexyl)piperidine, CAS 956-90-1, PCP) has shown analgesic effects. Some of its derivatives have been synthesized and their biological properties were studied. Since a hydroxyl group has been added to the position 2 of the cyclohexane ring of PCP, this compound would be more hydrophilic than PCP. This compound was synthesized using a different and improved method with a higher yield. Its analgesic effect was studied using the tail-flick test on rats and was compared with that of ketamine (CAS 1867-66-9). The results showed that 2-hydroxyphencyclidine can increase tail-flick latencies as compared to the control group and indicate that the maximum analgesic effect of this compound occurs 2-5 min after its injection while the effect of ketamine is observed 10-25 min after injection.

In this study we compared soleous and gastrocnemius muscles responses to paired stimulation in order to reveal the embedded information in H-reflex of these muscles. Four men with ages between 20 and 26 were tested. Since there was no ideal point based on the scientific rules to record H-reflex from gastrocnemius muscle, we were to determine an ideal point and electrode placement from anatomical and physiological point of view. Then, soleous and gastrocnemius muscles were subjected to paired stimulus and H-reflex recovery curve of these muscles were recorded To record the recovery curve, 11 pairs of stimulus were delivered to the posterior tibial nerve. Time interval between the 1st pair of stimulus was 50 ms and increased by 20 ms steps in the next pairs up to 250 ms. The second H-reflex amplitude was divided to the first H-reflex amplitude and expressed in percent, then the recovery curve was drawn accordingly. While the time interval of the paired stimulus was less than 110 ms, the behavior of the curves was similar. In this stage we guessed that the muscles were impressed by the renshaw cells inhibition and the induced fatigue by the first stimulus. When the interval in a pair was 110 ms or more, the recovery percent of soleous was significantly higher than that of the gastrocnemius. This behavior may be due to the less fatigability of soleous motoneurons and less renshaw inhibition on slow motoneurons of soleous. When the time interval of a pair stimulus increases to more than 170 ms, both of the curves behave alike. This may be due to the diminishing of renshaw cell inhibition and the reduction of fatigue. Because of motoneurons physiological properties, when we evoke H-reflex, smaller motoneurons recruit predominantly; but the comparison of the soleous (slow) and gastrocnemius (fast) recovery curves behavior shows that the information about the fast motoneuron are included in H-reflex using this procedure. So we can indirectly assess different motoneurons and renshaw cell activities.

This study investigated whether application of acute restraint stress or dexamethasone, as a glucocorticoid receptor agonist, impaired retrieval of long-term memory and if pretreatment with opiate antagonist naloxone blocked their effects on memory retrieval. Young adult male rats were trained in one trial inhibitory avoidance task (1 mA, 1.5 s footshock). On retention test given 48 h after training, the latency to re-enter dark compartment of the apparatus was recorded. Thirty minutes before retention test, the rats were exposed to a 10 min of restraint stress in a Plexiglass tube or were injected with dexamethasone (1 mg/kg) with or without prior treatment of naloxone (1 or 2 mg/kg). The results showed that both acute restraint stress and dexamethasone impaired retention performance. Both doses of naloxone were effective in blocking the impairing effect of stress, but only higher dose of naloxone blocked dexamethasone-induced impairment. The applied stress increased circulating corticosterone levels as assessed immediately after the retention test, indicating that stress-induced impairment of memory retrieval is mediated, in part, by increased plasma levels of glucocorticoids. These findings further indicate that acute restraint stress and glucocorticoids impair retrieval of long-term memory, and provide evidence for the existence of an interaction between glucocortioids and opiate system on this process.

The effect of theta pulse stimulation (TPS) on pentylenetetrazol (PTZ)-induced long-term potentiation of population spikes was studied in the CA1 region of rat hippocampal slices. The field excitatory postsynaptic potential (fEPSP) and population spikes (PS) were recorded from strata radiatum and pyramidale, respectively, following stimulation of Schaffer collaterals. A transient PTZ application produced a long-lasting enhancement of PS amplitude. A 3-min episode of TPS delivered at test-pulse intensity failed to reverse the PTZ potentiation. However, the same stimulation at a higher intensity produced complete reversal of the PTZ potentiation when delivered during the last minutes of PTZ application. Prior application of high-intensity TPS also decreased the amount of PTZ potentiation, whereas it had no long-lasting effect on baseline synaptic responses. High-intensity TPS induced reversal was blocked by adenosine A1 receptor antagonist and, furthermore, was reduced by protein phosphatase 1 inhibitor. The results suggest that mechanism of PTZ-induced LTP reversal involves activation of adenosine receptors and protein phosphatases., (Copyright 2003 Wiley-Liss, Inc.)

The effect of chronic morphine treatment on hippocampal CA1-long-term potentiation (LTP) was examined in vitro. The field excitatory postsynaptic potential (fEPSP) was recorded from stratum radiatum of area CA1 following stimulation of Schaffer collaterals in slices taken from control and morphine-dependent rats. To induce LTP, a 100-Hz primed burst stimulation (PBs) was used. Slices from rats exposed to chronic morphine showed no effect on baseline synaptic responses. Slices from control rats or rats exposed to chronic morphine maintained in ACSF with either morphine or naloxone also had no effect on baseline synaptic responses. Control slices perfused with medium containing either morphine or naloxone as well as both drugs exhibited hippocampal CA1 LTP. Similarly, slices from morphine-dependent rats maintained in ACSF with either naloxone or just morphine free ACSF also exhibited hippocampal CA1 LTP. However, slices from morphine-dependent rats maintained in ACSF with morphine significantly attenuated hippocampal CA1 LTP. These findings suggest that hippocampal CA1-LTP can still be achieved in slices from morphine-dependent rats exhibiting morphine withdrawal through mechanisms that may be inhibited by opiate exposure. Such studies can be helpful in understanding the neurophysiological substrate of memory deficits seen in opiate addicts.