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Background Lipocalin 2 (Lcn2) is an acute-phase protein implicated in multiple neurodegenerative conditions. Interestingly, both neuroprotective and neurodegenerative effects have been described for Lcn2. Increased Lcn2 levels were found in human post-mortem Alzheimer (AD) brain tissue, and in vitro studies indicated that Lcn2 aggravates amyloid-β-induced toxicity. However, the role of Lcn2 has not been studied in an in vivo AD model. Therefore, in the current study, the effects of Lcn2 were studied in the J20 mouse model of AD. Methods J20 mice and Lcn2-deficient J20 (J20xLcn2 KO) mice were compared at the behavioral and neuropathological level. Results J20xLcn2 KO and J20 mice presented equally strong AD-like behavioral changes, cognitive impairment, plaque load, and glial activation. Interestingly, hippocampal iron accumulation was significantly decreased in J20xLcn2 KO mice as compared to J20 mice. Conclusions Lcn2 contributes to AD-like brain iron dysregulation, and future research should further explore the importance of Lcn2 in AD. Electronic supplementary material The online version of this article (10.1186/s12974-018-1372-5) contains supplementary material, which is available to authorized users.

Background: Whole body vibration (WBV) is a form of physical stimulation via mechanical vibrations transmitted to a subject. It is assumed that WBV induces sensory stimulation in cortical brain regions through the activation of skin and muscle receptors responding to the vibration. The effects of WBV on muscle strength are well described. However, little is known about the impact of WBV on the brain. Recently, it was shown in humans that WBV improves attention in an acute WBV protocol. Preclinical research is needed to unravel the underlying brain mechanism. As a first step, we examined whether chronic WBV improves attention in mice. Material and Methods: A custom made vibrating platform for mice with low intensity vibrations was used. Male CD1 mice (3 months of age) received five weeks WBV (30 Hz; 1.9 G), five days a week with sessions of five (n=12) or 30 (n=10) minutes. Control mice (pseudo-WBV; n=12 and 10 for the five and 30 minute sessions, respectively) were treated in a similar way, but did not receive the actual vibration. Object recognition tasks were used as an attention test (novel and spatial object recognition – the primary outcome measure). A Balance beam was used for motor performance, serving as a secondary outcome measure. Results: WBV sessions of five (but not WBV sessions of 30 minutes) improved balance beam performance (mice gained 28% in time needed to cross the beam) and novel object recognition (mice paid significantly more attention to the novel object) as compared to pseudo WBV, but no change was found for spatial object performance (mice did not notice the relocation). Although 30 minutes WBV sessions were not beneficial, it did not impair either attention or motor performance. Conclusion: These results show that brief sessions of WBV improve, next to motor performance, attention for object recognition, but not spatial cues of the objects. The selective improvement of attention in mice opens the avenue to unravel the underlying brain mechanisms.

Sleep is important for brain function and cognitive performance. Sleep deprivation (SD) may affect subsequent learning capacity and ability to form new memories, particularly in the case of hippocampus-dependent tasks. In the present study we examined whether SD for 6 or 12 h during the normal resting phase prior to learning affects hippocampus-dependent working memory in mice. In addition, we determined effects of SD on hippocampal glutamate alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors and their regulatory pathways, which are crucially involved in working memory. After 12 h SD, but not yet after 6 h, spatial working memory in a novel arm recognition task was significantly impaired. This deficit was not likely due to stress as corticosterone levels after SD were not significantly different between groups. In parallel with the change in cognitive function, we found that 12 h SD significantly reduced hippocampal AMPA receptor phosphorylation at the GluR1-S845 site, which is important for incorporation of the receptors into the membrane. SD did not affect protein levels of cyclic-AMP-dependent protein kinase A (PKA) or phosphatase calcineurin (CaN), which regulate GluR1 phosphorylation. However, SD did reduce the expression of the scaffolding molecule A-kinase anchoring protein 150 (AKAP150), which binds and partly controls the actions of PKA and CaN. In conclusion, a relatively short SD during the normal resting phase may affect spatial working memory in mice by reducing hippocampal AMPA receptor function through a change in AKAP150 levels. Together, these findings provide further insight into the possible mechanism of SD-induced hippocampal dysfunction and memory impairment.

Vinpocetine (ethyl-apovincaminate, Cavinton), a synthetic derivative of the Vinca minor alkaloid vincamine, has been used now for decades for prevention and treatment of cerebrovascular diseases predisposing to development of dementia. Both vinpocetine and its main metabolite cis-apovincaminic acid (cAVA) exert a neuroprotective type of action. Bilateral N-methyl-D-aspartate (NMDA)-induced neurodegeneration in the entorhinal cortex of rat was used as a dementia model to confirm the neuroprotective action of these compounds in vivo. NMDA-lesioned rats were treated 60 min before lesion and throughout 3 postoperative days with a 10 mg/kg intraperitoneal dose of vinpocetine or cAVA. Behavioral tests started after termination of drug treatment and consisted of novel object recognition, social discrimination, and spontaneous alternation in a Y-maze, and spatial learning in the Morris water maze. At the end of behavioral testing brains were perfused with fixative and the size of the excitotoxic neuronal lesion and that of microglial activation around the lesion were assayed quantitatively on brain sections immunostained for neuron-specific nuclear protein (NeuN) and integrin CD11b, respectively. Entorhinal NMDA lesions impaired recognition of novel objects and the new social partner, and suppressed spontaneous alternation and spatial learning performance in the Morris maze. Both vinpocetine and cAVA effectively attenuated the behavioral deficits, and significantly decreased lesion size and the region of microglia activation. Both lesion-induced attention deficit and learning disabilities were markedly alleviated by vinpocetine and cAVA. The morphological findings corroborated the behavioral observations and indicated reduced lesion size and microglia activation especially after vinpocetine treatment which supports an in vivo neuroprotective mode of action of vinpocitine and a less potent action of cAVA.

Neural progenitors in the subgranular zone of the hippocampal formation form a continuously proliferating cell population, generating new granule neurons throughout adult life. Between 10 days and 1 month after their formation, many of the newly generated cells die. The present study investigated whether a partial lesion of one of the main nuclei projecting to the hippocampus, the medial septum (MS), affects survival and differentiation of cells during this critical period. Rats were injected with BrdU and 5 days later excitotoxic lesion of the MS was applied by infusion of either 30 or 60 nmol of N-methyl-D-aspartate (NMDA). One week after the lesion, quantification of immunopositive cells revealed that the number of GABAergic cells was significantly reduced in both lesioned groups, whereas a decline in cholinergic cell number was observed only after injection of 60 nmol of NMDA. The partial septohippocampal denervation significantly reduced hippocampal neurogenesis. Survival of newly generated neurons was decreased by approximately 40%. The MS lesion did not affect proliferation of hippocampal progenitors. The present study points out the importance of a functional septohippocampal pathway for the regulation of hippocampal neurogenesis and highlights the potential role of GABA as a mediator in this phenomenon.

Clinical trials show beneficial effects of acetylcholinesterase (AChE) inhibitors, including galantamine, on cognitive functions in patients with mild to moderate Alzheimer's disease. Galantamine shows a dual action profile by also acting as an allosteric modulator of nicotinic acetylcholine receptors. Nevertheless, its in vivo mechanism of action is only partly understood. Here, we first established a novel lesion model provoking significant functional impairment of the septo-hippocampal projection system without triggering massive neuronal death in the rat medial septum. Next, we studied whether galantamine, administered in doses of 1 and 3 mg/kg post-lesion, promotes functional recovery of spatial navigation behaviors, and affects the output of septal cholinergic projections. Infusion of N-methyl-D-aspartate (NMDA; 30 nmol/l mu l) in the medial septum resulted in spatial learning deficits associated with significant shrinkage of cholinergic neurons and reduced AChE activity in the hippocampus at 7 days post-lesion. Galantamine treatment alone significantly increased the hippocampal acetylcholine concentration and attenuated the NMDA-induced spatial learning impairment. Galantamine post-treatment also affected NMDA-induced changes in AChE and choline-acetyltransferase activities. In conclusion, our data show that galantamine attenuates experimentally-induced cognitive impairments underscored by mild neuronal damage. (C) 2005 Elsevier B.V. All rights reserved.

Although the rabbit brain, in particular the basal forebrain cholinergic system, has become a common model for neuropathological changes associated with Alzheimer's disease, detailed neuroanatomical studies on the morphological organization of basal forebrain cholinergic nuclei and on their output pathways are still awaited. Therefore, we performed quantitative choline acetyltransferase (ChAT) immunocytochemistry to localize major cholinergic nuclei and to determine the number of respective cholinergic neurons in the rabbit forebrain. The density of ChAT-immunoreactive terminals in layer V of distinct neocortical territories and in hippocampal subfields was also measured. Another cholinergic marker, the low-affinity neurotrophin receptor (p75(NTR)), was also employed to identify subsets of cholinergic neurons. Double-immunofluorescence labeling of ChAT and p75(NTR), calbindin D-28k (CB), parvalbumin, calretinin, neuronal nitric oxide synthase (nNOS), tyrosine hydroxylase, or substance P was used to elucidate the neuroanatomical borders of cholinergic nuclei and to analyze the neurochemical complexity of cholinergic cell populations. Cholinergic projection neurons with heterogeneous densities were found in the medial septum, vertical and horizontal diagonal bands of Broca, ventral pallidum, and magnocellular nucleus basalis (MBN)/substantia innominata (SI) complex; cholinergic interneurons were observed in the caudate nucleus, putamen, accumbens nucleus, and olfactory tubercule, whereas the globus pallidus was devoid of cholinergic nerve cells. Cholinergic interneurons were frequently present in the hippocampus and to a lesser extent in cerebral cortex. Cholinergic projection neurons, except those localized in SI, abundantly expressed p75(NTR), and a subset of cholinergic neurons in posterior MBN was immunoreactive for CB and nNOS. A strict laminar distribution pattern of cholinergic terminals was recorded both in the cerebral cortex and in CA1-CA3 and dentate gyrus of the hippocampus. In summary, the structural organization and chemoarchitecture of rabbit basal forebrain may be considered as a transition between that of rodents and that of primates.

The chronic dietary intake of essential polyunsaturated fatty acids (PUFAs) can modulate learning and memory by being incorporated into neuronal plasma membranes. Representatives of two PUFA families, the n-3 and n-6 types become integrated into membrane phospholipids, where the actual (n-6)/(n-3) ratio can determine membrane fluidity and thus the function of membrane-bound proteins. In the present experiment we studied hippocampal neurotransmitter receptors after chronic administration of n-3 PUFA enriched diets in a brain hypoperfusion model, which mimics decreased cerebral perfusion as it occurs in ageing and dementia. Male Wistar rats received experimental diets with a decreased (n-6)/(n-3) ratio from weaning on. Chronic experimental cerebral hypoperfusion was imposed by a permanent, bilateral occlusion of the common carotid arteries (2VO) at the age of 4 months. The experiment was terminated when the rats were 7 months old. Three receptor types, the muscarinic 1, serotonergic 1A and the glutaminergic NMDA receptors were labeled in hippocampal slices by autoradiographic methods. Image analysis demonstrated that 2VO increased muscarinic 1 and NMDA receptor density, specifically in the dentate gyrus and the CA3 region, respectively. The increased ratio of n-3 fatty acids in combination with additional dietary supplements enhanced the density of the serotonergic 1A and muscarinic 1 receptors, while n-3 fatty acids alone increased binding only to the muscarinic 1 receptors. Since the examined receptor types reacted differently to the diets, we concluded that besides changes in membrane fluidity, the biochemical regulation of receptor sensitivity might also play a role in increasing hippocampal receptor density.

Cholinergic neurons of the basal forebrain form one of the neuron populations that are susceptible to excitotoxic injury. Whereas neuropharmacological studies have aimed at rescuing cholinergic neurons from acute excitotoxic attacks, the short-term temporal profile of excitotoxic damage to cholinergic nerve cells remains largely elusive. The effects of N-methyl-D-aspartate (NMDA) infusion on cytochemical markers of cholinergic neurons in rat magnocellular nucleus basalis were therefore determined 4, 24 and 48 h post-lesion. Additionally, the influence of excitotoxic damage on the efficacy of in vivo labelling of cholinergic neurons with carbocyanine 3 . 1921gG was investigated. Carbocyanine 3-1921gG was unilaterally injected in the lateral ventricle. Twenty-four hours later, NMDA (60 nM/mul) was infused in the right magnocellular nucleus basalis, while control lesions were performed contra laterally. Triple immunofluorescence labelling for carbocyanine 3 1921gG, NMDA receptor 2A and B subunits and choline-acetyltransferase (ChAT) was employed to determine temporal changes in NMDA receptor immunoreactivity on cholinergic neurons. The extent of neuronal degeneration was studied by staining with Fluoro-Jade. Moreover, changes in the numbers of ChAT or p75 low-affinity neurotrophin receptor immunoreactive neurons, and the degree of their co-labelling with carbocyanine 3-1921gG were determined in basal forebrain nuclei. The effects of NMDA-induced lesions on cortical projections of cholinergic nucleus basalis neurons were studied by acetylcholinesterase (AChE) histochemistry. Characteristic signs of cellular damage, as indicated by decreased immunoreactivity for NMDA receptors, ChAT and p75 low-affinity neurotrophin receptors, were already detected at the shortest post-lesion interval investigated. Fluoro-Jade at 4 It post-lesion only labelled the core of the excitotoxic lesion. Longer survival led to enhanced Fluoro-Jade staining, and to the decline of ChAT immunoreactivity reaching a maximum 24 h post-surgery. Significant loss of p75 low-affinity neurotrophin receptor immunoreactivity and of cortical AChE-positive projections only became apparent 48 h post-lesion. Carbocyanine 3-1921gG labelling in the ipsilateral basal forebrain exceeded that of the contralateral hemisphere at all time points investigated and progressively declined in the damaged magnocellular nucleus basalis up to 48 h after NMDA infusion.The present study indicates that excitotoxic lesion-induced alteration of cholinergic neuronal markers is a rapid and gradual process reaching its maximum 24 h post-surgery. Furthermore, in vivo labelling of cholinergic neurons may be applied to indicate neuronal survival under pathological conditions, and enable to follow their degeneration process under a variety of experimental conditions. (C) 2001 IBRO. Published by Elsevier Science Ltd. All rights reserved.

Sleep is important for brain function and cognitive performance. Sleep deprivation (SD) may affect subsequent learning capacity and ability to form new memories, particularly in the case of hippocampus-dependent tasks. In the present study we examined whether SD for 6 or 12 h during the normal resting phase prior to learning affects hippocampus-dependent working memory in mice. In addition, we determined effects of SD on hippocampal glutamate alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors and their regulatory pathways, which are crucially involved in working memory. After 12 h SD, but not yet after 6 h, spatial working memory in a novel arm recognition task was significantly impaired. This deficit was not likely due to stress as corticosterone levels after SD were not significantly different between groups. In parallel with the change in cognitive function, we found that 12 h SD significantly reduced hippocampal AMPA receptor phosphorylation at the GluR1-S845 site, which is important for incorporation of the receptors into the membrane. SD did not affect protein levels of cyclic-AMP-dependent protein kinase A (PKA) or phosphatase calcineurin (CaN), which regulate GluR1 phosphorylation. However, SD did reduce the expression of the scaffolding molecule A-kinase anchoring protein 150 (AKAP150), which binds and partly controls the actions of PKA and CaN. In conclusion, a relatively short SD during the normal resting phase may affect spatial working memory in mice by reducing hippocampal AMPA receptor function through a change in AKAP150 levels. Together, these findings provide further insight into the possible mechanism of SD-induced hippocampal dysfunction and memory impairment.

The brain 5-HT1A receptor system in male wild house mice selected for high and low offensive aggression was investigated by autoradiographic analysis of in situ hybridization and radioligand binding. In high-aggressive mice, characterized by a short attack latency, the rise in plasma corticosterone concentration during thr early dark; phase was reduced, At that time the level of 5-HT1A mRNA in the dorsal hippocampus (dentate gyrus and CA1) was twice the amount measured in low-aggressive mice that had long attack latency and high plasma corticosterone level. Increased postsynaptic 5-HT1A receptor radioligand binding was found in dentate gyrus, CA1, lateral septum, and frontal cortex. No difference in ligand binding was found for the 5-HT1A autoreceptor on cell bodies in the dorsal raphe nucleus. In conclusion, genetic selection for high offensive aggression co-selects for reduced (circadian peak) level in plasma corticosterone and increased postsynaptic 5-HT1A receptor number in limbic and cortical regions.

In this study, testosterone secretory capacity of testicular Leydig cells during ontogeny was determined in males of an aggressive and a nonaggressive genetic selection line of wild house mice. Neonates, 23-day-old prepubertals, and adult male mice were studied. A morphometric method was used to quantify 3-beta-hydroxy steroid dehydrogenase (3-beta-HSD)-stained Leydig cells in testicular sections to determine testosterone secretory capacity. We consider this parameter to reflect circulating testosterone in the plasma. The results of this study show that the testosterone secretory capacity of Leydig cells in the testis changes differentially during development in males of the aggressive and nonaggressive selection lines. This capacity is highest in the aggressive selection line males at adulthood and at the prepubertal age of 23 days. Surprisingly, at birth, the highest T-secretory capacity was observed in the males of the nonaggressive selection line. The significance of an interaction between genetic factors and differences in perinatal testosterone for the individual variation in adult aggressive behavior is discussed.