Density Of Pyramidal Neurons Research Articles

Intramuscular Injection of BOTOX® Boosts Learning and Memory in Adult Mice in Association with Enriched Circulation of Platelets and Enhanced Density of Pyramidal Neurons in the Hippocampus

BOTOX® is a therapeutic form of botulinum neurotoxin. It acts by blocking the release of acetylcholine (ACh) from the synaptic vesicles at the neuromuscular junctions, thereby inhibiting the muscle contraction. Notably, many neurological diseaseshave been characterized by movement disorders in association with abnormal levels of ACh. Thus, blockade of aberrant release of ACh appears to be a potential therapeutic strategy to mitigate many neurological deficits. BOTOX® has widely been used to manage a number of clinical complications like neuromuscular disorders, migraine and neuropathic pain. While the beneficial effects of BOTOX® against movement disorders have extensively been studied, its possible role inthe outcome of cognitive function remains to be determined. Therefore, we investigated the effect of BOTOX® on learning and memory in experimental adult mice using behavioural paradigms such as open field task, Morris water maze and novel object recognition test in correlation with haematological parameters and histological assessments of the brain. Results revealed that a mild dose of BOTOX® treatment via an intramuscular route in adult animals improves learning and memory in association with increasednumber of circulating platelets and enhanced structural plasticity in the hippocampus. In the future, this minimally invasive treatment could be implemented to ameliorate different forms ofdementia resulting from abnormal ageing and various neurocognitive disorders including Alzheimer's disease(AD).

Morphological Changes of the Rat Hippocampal Neurons Following Excessive Fluoride Consumption

The purpose of present work was to characterize morphological alterations of rat hippocampal neurons after long-term (12-months) consumption of excessive doses of ionic fluoride (F – ). Material and methods. Male Wistar rats were assigned to four groups. Animals from control group were given drinking water with background F – content of 0.4 mg/L, rats from other groups received the same water with 5, 20 and 50 mg/L (as NaF). The morphology of neurons in CA 3 and CA 1 hippocampal areas was evaluated after staining of brain slices with toluidine blue according to Nissl’s method. Results . Long-term intoxication of rats with F – resulted in disorganization of cellular layer and decline in numerical density of pyramidal neurons in CA 3 and CA 1 hippocampal areas, which most probably indicates the death of a part of the cells. The neurons of both hippocampus zones exhibited such pathological changes as unequal distribution of Nissl substance, shifting of nuclei to periphery, cytoplasm vacuolization. Some neurons underwent swelling, other, in contrast, shrunk, spindle neurons or cells with spiral-like outgrowths were also visualized. In hippocampus of F – -exposed rats, the number of normochromic neurons decreased, but amount of hyperchromic and hypochromic cells increased. Conclusion . Long-term intake of excessive F – doses by the rats was established to induce dystrophic and necrobiotic changes of pyramidal neurons in CA 3 and CA 1 hippocampal zones. The revealed pathological processes can be a cause of disturbances in inter-neuronal communications in the hippocampus and lead to development of various neurological and cognitive disorders.

Delayed Effects of Surgery during Early Pregnancy on Brain Development in OXYS Rats

The aim of the present work was to study the effects of stress induced by surgical interventions in early pregnancy on neuron density in the prefrontal cortex and hippocampal fields CA1 and CA3 and on neurogenesis in the dentate fascia of the hippocampus in the adult offspring of OXYS rats. Female OXTS rats were paired with fertile males of the same strain and, 96 h after detection of spermatozoids in vaginal smears, underwent a surgical procedure imitating embryo transplantation. The offspring of these females (OXYS-PS) were studied in comparison with intact OXYS and WAG rats aged five months. The density of pyramidal neurons in the prefrontal cortex of intact OXYS rats was significantly greater than that in rats of the WAG control strain. Neuron density in hippocampal field CA1 in intact OXYS rats was smaller, while that in field CA3 was greater, than that in WAG rats. No significant differences in the intensity of neurogenesis were seen between intact WAG and OXYS rats. In rats of the experimental group, OXYS-PS, the density of pyramidal neurons was lower in the prefrontal cortex and hippocampal field CA1 than in both control strains, while in field CA3 it was lower only in comparison with intact OXYS rats. In addition, rats of the OXYS-PS group showed a higher level of neurogenesis in the dentate gyrus of the hippocampus than both control strains.

SAT-285 TSH/TSHR Signaling Deficiency Impairs Spatial Learning and Memory

Background: Subclinical hyperthyroidism is associated with cognitive impairment, but the mechanism has remained unclear. As subclinical hyperthyroidism is characterized by significantly decreased TSH levels, this study aimed to investigate whether TSH regulates cognitive function. Methods: The correlation between TSH and cognitive impairment was investigated in a cross-sectional population study. The role of TSH/TSH receptor (TSHR) signaling in spatial learning and memory was further examined by behavior tests in Tshr-/- mice. Dendritic spine, synaptic density and structure of hippocampal CA1 pyramidal neurons were detected by Golgi’s method and electron microscopy. The mRNA and protein expression levels of learning and memory-related genes were assessed by RNA sequencing, real-time PCR, immunoblotting and immunofluorescence approaches. Results: Serum TSH level correlated negatively with cognitive impairment in the current population. Consistently, Tshr deletion in mice led to significantly compromised performance in hippocampus-dependent tasks, reduced dendritic spine density and excitatory synaptic density as well as altered synaptic structure in CA1 subfield of the hippocampus. Furthermore, the mRNA levels of learning and memory-related genes were altered, and protein levels of CREB-regulated genes were downregulated in the hippocampus of Tshr-/- mice. Conclusions: These findings reveal that TSH/TSHR signaling ablation impairs spatial learning and memory, indicating a decline in TSH level might contribute to the increased prevalence of cognitive impairment in subclinical hyperthyroidism patients.

Inhibition of 5α Reductase Impairs Cognitive Performance, Alters Dendritic Morphology and Increases Tau Phosphorylation in the Hippocampus of Male 3xTg-AD Mice

Recent work has suggested that 5α-reduced metabolites of testosterone may contribute to the neuroprotection conferred by their parent androgen, as well as to sex differences in the incidence and progression of Alzheimer’s disease (AD). This study investigated the effects of inhibiting 5α-reductase on object recognition memory (ORM), hippocampal dendritic morphology and proteins involved in AD pathology, in male 3xTg-AD mice. Male 6-month old wild-type or 3xTg-AD mice received daily injections of finasteride (50 mg/kg i.p.) or vehicle (18% β-cyclodextrin, 1% v/b.w.) for 20 days. Female wild-type and 3xTg-AD mice received only the vehicle. Finasteride treatment differentially impaired ORM in males after short-term (3xTg-AD only) or long-term (3xTg-AD and wild-type) retention delays. Dendritic spine density and dendritic branching of pyramidal neurons in the CA3 hippocampal subfield were significantly lower in 3xTg-AD females than in males. Finasteride reduced CA3 dendritic branching and spine density in 3xTg-AD males, to within the range observed in vehicle-treated females. In the CA1 hippocampal subfield, dendritic branching and spine density were reduced in both male and female 3xTg-AD mice, compared to wild type controls. Hippocampal amyloid β levels were substantially higher in 3xTg-AD females compared to both vehicle and finasteride-treated 3xTg-AD males. Site-specific Tau phosphorylation was higher in 3xTg-AD mice compared to sex-matched wild-type controls, increasing slightly after finasteride treatment. These results suggest that 5α-reduced neurosteroids may play a role in testosterone-mediated neuroprotection and may contribute to sex differences in the development and severity of AD.

Activity-dependent death of transient Cajal-Retzius neurons is required for functional cortical wiring.

Programmed cell death and early activity contribute to the emergence of functional cortical circuits. While most neuronal populations are scaled-down by death, some subpopulations are entirely eliminated, raising the question of the importance of such demise for cortical wiring. Here, we addressed this issue by focusing on Cajal-Retzius neurons (CRs), key players in cortical development that are eliminated in postnatal mice in part via Bax-dependent apoptosis. Using Bax-conditional mutants and CR hyperpolarization, we show that the survival of electrically active subsets of CRs triggers an increase in both dendrite complexity and spine density of upper layer pyramidal neurons, leading to an excitation/inhibition imbalance. The survival of these CRs is induced by hyperpolarization, highlighting an interplay between early activity and neuronal elimination. Taken together, our study reveals a novel activity-dependent programmed cell death process required for the removal of transient immature neurons and the proper wiring of functional cortical circuits.

Treatment with gut bifidobacteria improves hippocampal plasticity and cognitive behavior in adult healthy rats

At the present time, gut microbiota inspires great interest in the field of neuroscience as a function of its role in normal physiology and involvement in brain function. This aspect suggests a specific gut-brain pathway, mainly modulated by gut microbiota activity. Among the multiple actions controlled by microbiota at the brain level, neuronal plasticity and cognitive function represent two of the most interesting aspects of this cross-talk communication. We address the possible action of two-months implementation of gut Bifidobacteria using a mixture of three different strains (B-MIX) on hippocampal plasticity and related cognitive behavior in adult healthy Sprague Dawley rats. B-MIX treatment increases the hippocampal BDNF with a parallel gain in dendritic spines’ density of hippocampal CA1 pyramidal neurons. Electrophysiological experiments revealed a significant increment of HFS-induced LTP formation on the CA1 hippocampal region in B-MIX treated rats. All these effects are accompanied by a better cognitive performance observed in B-MIX treated animals with no impairments in locomotion activity. Therefore, in adult rats, the treatment with different strains of bifidobacteria is able to markedly enhance neuronal plasticity and the CNS function influencing cognitive behavior, an effect that may suggest a potential therapeutic treatment in brain diseases associated with cognitive functions.

Early Sensory Loss Alters the Dendritic Branching and Spine Density of Supragranular Pyramidal Neurons in Rodent Primary Sensory Cortices.

Multisensory integration in primary auditory (A1), visual (V1), and somatosensory cortex (S1) is substantially mediated by their direct interconnections and by thalamic inputs across the sensory modalities. We have previously shown in rodents (Mongolian gerbils) that during postnatal development, the anatomical and functional strengths of these crossmodal and also of sensory matched connections are determined by early auditory, somatosensory, and visual experience. Because supragranular layer III pyramidal neurons are major targets of corticocortical and thalamocortical connections, we investigated in this follow-up study how the loss of early sensory experience changes their dendritic morphology. Gerbils were sensory deprived early in development by either bilateral sciatic nerve transection at postnatal day (P) 5, ototoxic inner hair cell damage at P10, or eye enucleation at P10. Sholl and branch order analyses of Golgi-stained layer III pyramidal neurons at P28, which demarcates the end of the sensory critical period in this species, revealed that visual and somatosensory deprivation leads to a general increase of apical and basal dendritic branching in A1, V1, and S1. In contrast, dendritic branching, particularly of apical dendrites, decreased in all three areas following auditory deprivation. Generally, the number of spines, and consequently spine density, along the apical and basal dendrites decreased in both sensory deprived and non-deprived cortical areas. Therefore, we conclude that the loss of early sensory experience induces a refinement of corticocortical crossmodal and other cortical and thalamic connections by pruning of dendritic spines at the end of the critical period. Based on present and previous own results and on findings from the literature, we propose a scenario for multisensory development following early sensory loss.

P: 74 Cholestasis Decreases Dendritic Spine Density in a Rat Hippocampal Organotypic Culture

BACKGROUND: Executive functioning impairment in children with cholestatic liver disease is increasingly recognized. Injury to developing neuronal networks could be an underlying mechanism. Given that the CSF of rat pups following bile duct ligation is highly concentrated in ammonia, murocholic and taurocholic acids, we hypothesized that cholestasis may significantly alter density of synaptic contacts onto pyramidal neurons, known to be essential in the development of executive functioning. METHODS: Transverse hippocampal organotypic slice (400 µm thick) were harvested from 6–7-day-old Wistar rats. They were maintained for 15 days in a CO2-incubator (33°C). pc-DNA3.1-EGFP plasmid biolistic transfection was performed 7 days after harvesting. 3 days following transfection, control medium or experimental medium containing 100 µM α-murocholic-acid, 200 µM taurocholic-acid and 2.5 mM ammonium was added to the culture (day 0 of exposure, MIX condition). Confocal microscopy using imageJ was used for to manually count CA1 pyramidal neuron dendritic spines as proxies for excitatory synapses. Static analysis quantified dendritic spines density each day. Dynamic analysis quantified dendritic spines turnover (loss and neo-formation) for each 24 h time-window. Statistical analysis was conducted using PRISM software for multiple t-test or mixed-effect ANOVA. RESULTS: Static analysis showed a biphasic profile in MIX condition. During early phase (first 3 days of exposure), we observed >50% decrease in dendritic spine density compared to control (cf Figure 1, P < 0.001). On days 3 to 4), spine density recovered to reach control value. Dynamic analysis showed 15% loss in dendritic spines stability during the early phase of exposure to MIX condition, compared to controls, with comparable low rates of spine turnover. During the late phase of MIX exposure, spine turnover increased significantly in favor of spine neo-formation: spine neo-formation was 10 times higher (0.280 vs 0.023 spines.µm-1, P = 0.033) than controls, while spine loss was 6 times higher in neurons exposed to MIX (0.154 vs 0.026 spines.µm-1, P = 0.0026) than controls. CONCLUSIONS: We demonstrate here that mimicking cholestasis ex vivo leads to a biphasic response in spine density of rat hippocampal CA1 pyramidal neurons. Spine density decreases during the first 3-days of exposure to a mix of bile acids and ammonium chloride-owing to decreased in spine stability. This is followed by increased spine turnover with spine neo-formation in excess of spine loss, yielding a final spine density similar to control animals. Whether these new spines are functionally equivalent to controls remains to be determined.

Close Homolog of L1 Regulates Dendritic Spine Density in the Mouse Cerebral Cortex Through Semaphorin 3B.

Dendritic spines in the developing mammalian neocortex are initially overproduced and then eliminated during adolescence to achieve appropriate levels of excitation in mature networks. We show here that the L1 family cell adhesion molecule Close Homolog of L1 (CHL1) and secreted repellent ligand Semaphorin 3B (Sema3B) function together to induce dendritic spine pruning in developing cortical pyramidal neurons. Loss of CHL1 in null mutant mice in both genders resulted in increased spine density and a greater proportion of immature spines on apical dendrites in the prefrontal and visual cortex. Electron microscopy showed that excitatory spine synapses with postsynaptic densities were increased in the CHL1-null cortex, and electrophysiological recording in prefrontal slices from mutant mice revealed deficiencies in excitatory synaptic transmission. Mechanistically, Sema3B protein induced elimination of spines on apical dendrites of cortical neurons cultured from wild-type but not CHL1-null embryos. Sema3B was secreted by the cortical neuron cultures, and its levels increased when cells were treated with the GABA antagonist gabazine. In vivo CHL1 was coexpressed with Sema3B in pyramidal neuron subpopulations and formed a complex with Sema3B receptor subunits Neuropilin-2 and PlexinA4. CHL1 and NrCAM, a closely related L1 adhesion molecule, localized primarily to distinct spines and promoted spine elimination to Sema3B or Sema3F, respectively. These results support a new concept in which selective spine elimination is achieved through different secreted semaphorins and L1 family adhesion molecules to sculpt functional neural circuits during postnatal maturation.SIGNIFICANCE STATEMENT Dendritic spines in the mammalian neocortex are initially overproduced and then pruned in adolescent life through unclear mechanisms to sculpt maturing cortical circuits. Here, we show that spine and excitatory synapse density of pyramidal neurons in the developing neocortex is regulated by the L1 adhesion molecule, Close Homolog of L1 (CHL1). CHL1 mediated spine pruning in response to the secreted repellent ligand Semaphorin 3B and associated with receptor subunits Neuropilin-2 and PlexinA4. CHL1 and related L1 adhesion molecule NrCAM localized to distinct spines, and promoted spine elimination to Semaphorin 3B and -3F, respectively. These results support a new concept in which selective elimination of individual spines and nascent synapses can be achieved through the action of distinct secreted semaphorins and L1 adhesion molecules.

Neuroglial Complex of the Prefrontal Cortex in Men and Women of the Senile Age

The aim of study was to investigate the neuroglial complex of the prefrontal cortex BA10 area in men and women of the senile age in comparison with the similar parameters in the elderly people. Material and methods. The study of the neuroglial complex was carried out on a series of frontal total sections of 5 male and 5 female brains in people of the senile age. Totally 20 male and female brain hemispheres were studied. The material was obtained no later than 24 hours after death and was fixed in 10% formalin solution. 20-micron-thick samples were stained with cresyl violet using Nissl method. The density of neurons, total glia, satellite gliocytes and neurons surrounded by them were investigated. Statistical data processing was performed in STATISTICA 12. Results. The study revealed gender age-related differences of the neuroglial complex morphometric parameters of the prefrontal cortex BA10 area in men and women. The decrease in the density of neurons, the proportion of satellite glia, the increase in the density of total glia were more significantly expressed in senile men than in senile women. These changes were more pronounced in the left hemisphere of the male brain and equally pronounced in both hemispheres in the female brain. Conclusion . Thus, this study detected features of the neuroglial complex of the prefrontal cortex BA10 area in men and women of the senile age. There was revealed the more significant decrease in the density of pyramidal neurons and satellite gliocytes in the cytoarchitectonic layer III of the prefrontal cortex BA10 area of the male brain compared with the similar layer of the female brain.

Postnatal nectin-3 knockdown induces structural abnormalities of hippocampal principal neurons and memory deficits in adult mice.

The early postnatal stage is a critical period of hippocampal neurodevelopment and also a period of high vulnerability to adverse life experiences. Recent evidence suggests that nectin‐3, a cell adhesion molecule, mediates memory dysfunction and dendritic alterations in the adult hippocampus induced by postnatal stress. But it is unknown whether postnatal nectin‐3 reduction alone is sufficient to alter hippocampal structure and function in adulthood. Here, we down regulated hippocampal expression of nectin‐3 and its heterophilic adhesion partner nectin‐1, respectively, from early postnatal stage by injecting adeno‐associated virus (AAV) into the cerebral lateral ventricles of neonatal mice (postnatal day 2). We found that suppression of nectin‐3, but not nectin‐1, expression from the early postnatal stage impaired hippocampus‐dependent novel object recognition and spatial object recognition in adult mice. Moreover, AAV‐mediated nectin‐3 knockdown significantly reduced dendritic complexity and spine density of pyramidal neurons throughout the hippocampus, whereas nectin‐1 knockdown only induced the loss of stubby spines in CA3. Our data provide direct evidence that nectins, especially nectin‐3, are necessary for postnatal hippocampal development of memory functions and structural integrity.

Pathological changes on basis of ischemia with associated virus infection in mice brain

The global literature constantly receives new data showing the infectious pathogens as factors for development of atherosclerosis and acute cerebrovascular pathology, and the data showing the predictors of pathology of the heart-vessels as markers of inflammation. The results of research about the connection between the infectious agents and atherosclerosis are ambiguous, and the attempts to prove such connection have encouraged the experiments where the infectious agents with atherogenesis are modeled in animals. The connection of this data with ischemic lesion of brain is not properly explored, but certain experimental research show progressive degeneration in brain hemorrhage in mice with herpes virus 1 (HSV1) due to the post-stroke immunosuppression and reactivation of the infectious agent. The aim of this work is to explore experimentally the possible connection between the herpetic infection and the ischemic lesion to the cortex of mice. To achieve this goal we formed 5 groups of experimental animals (mice) for investigation into the possibility of connection between herpes infection and ischemiazaition of brain: 1st group (n=52) - with cholesterol diet; 2nd group (n=23) - with HSV1; 3d group (n=30) - with unilateral occlusion of the common carotid artery; 4th group (n=10) - with HSV1 and occlusion of the common carotid artery; 5th group (n=6) - with cholesterol diet, HSV1, occlusion of the common carotid artery. The microscopic slides evaluated changes morphometrically in the density of the neurons of the neocortex in the ocular of parietal temporal fields of the brain and the hippocampus. The results were processed statistically with Origin Lab 8.0. A probable increase in structural changes was identified in group 5 (with three pathological factors respectively) of the combined model compared to models without association and/or with several pathological signs from the groups 1-4 (1, 2, 3, 4). Comparison of the results between the 1-4th and 5th groups showed a significant increase in the relative number of neurons with cytopathological signs (hemochromatosis, deformation of the perikaryon, karyopyknosis), which may testify in favor of a sufficiently rapid lesion of the pyramidal neocortex neurons influenced by two or more pathological signs. The reduction in the density of pyramidal neurons in the temporal and/or temporal cortex in the combined model with ischemiazaition and viral association in was had greater probability compared to the models formed with only one risk factor. The revealed increase in the degree of neocortex induction during brain cerebral ischemia in mice with herpes infection is an evidence of possible connection between the two.

Green tea polyphenols ameliorate ethanol-induced spatial learning and memory impairments by enhancing hippocampus NMDAR1 expression and CREB activity in rats.

The current research probed into the effects of green tea polyphenols (GTPs) on ethanol-induced spatial learning and memory impairments and inquired the potential molecular mechanism in rats. Thirty 8-week-old male Sprague-Dawley rats were randomly divided into three groups. The control group (control, n=10), ethanol group (ethanol, n=10), and GTPs intervention group (GTP, n=10) received gavage administration of saline, ethanol, and ethanol-GTP solution, respectively, for 8 weeks. Morris water maze was applied to assess the spatial learning and memory function of rats in each group at the last week of treatment. There was no dramatic change in body weight of rats in the different groups. Compared with rats in the control group, 8-week ethanol gavaged rats showed increased escape latency period and decreased time in the target quadrant. Moreover, 8-week ethanol gavage decreased the density of pyramidal layer neurons, expression of NMDAR1, and CREB phosphorylation in the hippocampus region. In contrast, GTP intervention decreased escape latency period and increased the time in the target quadrant, the density of pyramidal layer neurons, expression of NMDAR1, and CREB phosphorylation in the hippocampus region. The current findings indicated that GTP intervention can improve ethanol-induced spatial learning and memory impairments in rats after ethanol withdrawal, which is related to the upregulated density of pyramidal layer neurons, expression of NMDAR1, and CREB phosphorylation in the hippocampus region.

Restoring striatal WAVE-1 improves maze exploration performance of GluN1 knockdown mice.

NMDA receptors are important for cognition and are implicated in neuropsychiatric disorders. GluN1 knockdown (GluN1KD) mice have reduced NMDA receptor levels, striatal spine density deficits, and cognitive impairments. However, how NMDA depletion leads to these effects is unclear. Since Rho GTPases are known to regulate spine density and cognition, we examined the levels of RhoA, Rac1, and Cdc42 signaling proteins. Striatal Rac1-pathway components are reduced in GluN1KD mice, with Rac1 and WAVE-1 deficits at 6 and 12 weeks of age. Concurrently, medium spiny neuron (MSN) spine density deficits are present in mice at these ages. To determine whether WAVE-1 deficits were causal or compensatory in relation to these phenotypes, we intercrossed GluN1KD mice with WAVE-1 overexpressing (WAVE-Tg) mice to restore WAVE-1 levels. GluN1KD-WAVE-Tg hybrids showed rescue of striatal WAVE-1 protein levels and MSN spine density, as well as selective behavioral rescue in the Y-maze and 8-arm radial maze tests. GluN1KD-WAVE-Tg mice expressed normalized WAVE-1 protein levels in the hippocampus, yet spine density of hippocampal CA1 pyramidal neurons was not significantly altered. Our data suggest a nuanced role for WAVE-1 effects on cognition and a delineation of specific cognitive domains served by the striatum. Rescue of striatal WAVE-1 and MSN spine density may be significant for goal-directed exploration and associated long-term memory in mice.

Bisphenol A exposure remodels cognition of male rats attributable to excitatory alterations in the hippocampus and visual cortex

Bisphenol A, an environmental xenoestrogen, has been shown sex-specific adverse effects on cognitive function of rodents. However, the specific mechanisms underlying these outcomes remain elusive, limiting our understanding the differences in behavioral impairments due to BPA exposure between genders in humans. The present study chose the juvenile stage (with a stable estrogen level) as the exposure window to explore BPA effects on cognitive behaviors of male and female Sprague-Dawley (SD) rats and related mechanisms. Three dosages of BPA (0.04, 0.4 and 4 mg/kg/day) were chose to make BPA-exposed models. Especially, the mid-dose for rats was close to the current reference daily limit for human exposure given by the U.S. Environmental Protection Agency. Our results showed that male but not female juvenile rats had a marked decline in spatial memory after 0.4 mg/kg/day BPA exposure, which accompanied with downregulation of glutamate receptor (NR2) expression in their hippocampus and primary visual cortex (V1). In the high-dose BPA exposed groups (4 mg/kg/day), there was not only a deficit of spatial memory, but also an anxiety-like behavior of male rats. Additionally, those rats had a significant decline in spine density of pyramidal neurons and a decreased expression of glutamate receptor subtypes (NR2 and GluR1) in the hippocampus. Importantly, such impairments in the hippocampus of male rats were associated with a decrease of glutamate receptor (NR2) expression in the V1, which could perturb the visual information inputs. To some extent, altered ERβ expression within their hypothalamus could contribute to the anxiety-like behavior after high-dose BPA exposure. However, the low-dose BPA exposed juvenile rats didn’t present any structural and behavioral changes in our present study. Those results suggests that BPA exerts dose dependent and gender-specific effects on the cognition of juvenile animals. Our findings shed light on mechanisms underlying BPA effects on the juvenile animals.

Стуктурно-функциональные изменения нейронов неокортекса белых крыс после 20-минутной окклюзии общих сонных артерий

Цель исследования - изучение структурно-функциональных изменений нейронов сенсомоторной коры головного мозга белых крыс в норме и после 20-минутной окклюзии общих сонных артерий. Методика. С помощью световой (окраска гематоксилином и эозином, по Нисслю), флуоресцентной (окраска DAPI), иммунофлуоресцентной (нейронспецифическая енолаза - NSE) и электронной микроскопии была изучена нейроцитоархитектоника сенсомоторной коры (СМК) головного мозга белых крыс в норме (n =5) и в динамике - 1, 3, 7, 14, 21 и 30 сут.; после 20-минутной окклюзии общих сонных артерий (n =30). Согласно рекомендациям Nomenclature Committee on Cell Death (2009), проведено детальное описание и сравнение всех морфотипов измененных пирамидных нейронов СМК мозга белых крыс после острой ишемии. Морфометрический анализ проведен с помощью программы ImageJ 1.46. Результаты . Использование комплекса морфологических методов позволило классифицировать нейроны на основании четких структурных маркеров и доказать возможность апоптоза гиперхромных нейронов СМК после воспроизведения ишемии. Показано, что через 3 сут. в слое III 6-12% гиперхромных нейронов подвергалось апоптозу, 13,4-24,6% - коагуляционному некрозу, а остальные выходили из патологического состояния в отдаленном восстановительном периоде. Необратимо измененные клетки-тени составляли 11,5% (95% ДИ: 7,4-16,8%). Общая численная плотность пирамидных нейронов в течение 30 сут. постишемического периода в слое III СМК снижалась на 30,5% (95% ДИ: 24,2-38,7%), а в слое V - на 14,4% (95% ДИ: 9,9-20,0%). Заключение. Показана смешанная природа гибели нейронов - одновременное сочетание процессов некроза и апоптоза (парапоптоз). Однако основную роль в гибели нейронов играли процессы быстрого и отдаленного ишемического некроза.

MicroRNA-219 decreases hippocampal long-term potentiation inhibition and hippocampal neuronal cell apoptosis in type 2 diabetes mellitus mice by suppressing the NMDAR signaling pathway.

Type 2 diabetes mellitus (T2DM) is a complex polygenic disease that causes hyperglycemia and accounts for 90%-95% of all diabetes mellitus cases. Hence, this study aimed to examine the effects of microRNA-219 (miR-219) on inhibition of long-term potentiation (LTP) and apoptosis of hippocampal neuronal cells in T2DM mice through the N-methyl-d-aspartate receptor (NMDAR) signaling pathway regulation. The T2DM mouse models were established, after which LTP in vivo was recorded by means of electrical biology, and the fasting blood glucose of mice was measured. Next, the density of pyramidal neurons in each group was calculated. Additionally, the expression levels of miR-219, the NMDAR signaling pathway [NMDAR1 (NR) 1, NR2A, and NR2B), downstream target proteins [calmodulin-dependent protein kinase-II (CaMK-II) and cAMP response element binding protein (CREB)], and apoptosis-related factors [Bcl2-associated X protein (Bax), c-caspase-9 and c-caspase-3] in the hippocampal tissues were determined. Finally, immunohistochemistry was applied to detect and measure the positive expression of Bax, caspase-9, and caspase-3 proteins. The results showed that upregulation of miR-219 increases LTP and density of pyramidal neurons in the hippocampal tissues of mice, while it decreases blood glucose of db/db mice. In addition, miR-219 upregulation also leads to decreased mRNA levels of NR1, NR2A, NR2B, CaMK-II, and CREB and protein levels of NR1, NR2A, NR2B, CaMK-II, CREB, p-CREB, Bax, c-caspase-9, and c-caspase-3. Furthermore, upregulation of miR-219 inhibits positive expression of Bax, caspase-9, and caspase-3 proteins, leading to the suppression of hippocampal neuronal cell apoptosis. The findings from this study indicated that the upregulation of miR-219 decreases LTP inhibition and hippocampal neuronal cell apoptosis in T2DM mice by downregulating the NMDAR signaling pathway, therefore suggesting that MiR-219 might be a future therapeutic strategy for T2DM.

Gene expression profile associated with postnatal development of pyramidal neurons in the human prefrontal cortex implicates ubiquitin ligase E3 in the pathophysiology of schizophrenia onset

Schizophrenia is a neurodevelopmental disorder with the typical age of onset of overt symptoms and deficits occurring during late adolescence or early adulthood, coinciding with the final maturation of the cortical network involving the prefrontal cortex. These observations have led to the hypothesis that disturbances of the developmental events that take place in the prefrontal cortex during this period, specifically the remodeling of synaptic connectivities between pyramidal neurons, may contribute to the onset of illness. In this context, we investigated the gene expression changes of pyramidal neurons in the human prefrontal cortex during normal periadolescent development in order to gain insight into the possible molecular mechanisms involved in synaptic remodeling of pyramidal neuronal circuitry. Our data suggest that genes associated with the ubiquitination system, which has been implicated in the biology of synaptic plasticity, may play a major role. Among these genes, UBE3B, which encodes the ubiquitin ligase E3, was found to undergo periadolescent increase and was validated at the protein level to be upregulated during periadolescent development. Furthermore, we found that the density of UBE3B-immunoreactive pyramidal neurons was decreased in schizophrenia subjects, consistent with the result of a previous study of decreased UBE3B mRNA expression in pyramidal neurons in this illness. Altogether these findings point to the novel hypothesis that this specific ligase may play a role in the developmental pathogenesis of schizophrenia onset by possibly altering the synaptic remodeling process.

P.1.004 - Morphological substrates of abnormal activity patterns in a mouse model of mental illness

During the last years, a wealth of investigations has been dedicated to psychiatric diseases with developmental time course. However, the mechanisms leading to the devastating symptoms and specific adapted treatments are still poorly understood. The investigation of mouse models mimicking the etiology of disorders can expand the understanding of the ontogeny by determining the cellular substrates of mental illness [1]. To better comprehend the role and underlying molecular mechanisms of morphological deficits during early development of cortical dysfunctions, we investigated mice mimicking the genetic (Disrupted-In-Schizophrenia 1) and environmental (maternal immune activation) background of mental illness (dual-hit GE mice). We previously showed that they have an impaired maturation of prefrontal-hippocampal function [2]. To determine the cellular substrates of dysfunction we investigated the morphological and synaptic deficits of pyramidal neurons in the prefrontal cortex (PFC) of neonatal mice. For this, GE mice were in utero electroporated with pAAV-CAG-tDimer2 either at E12.5 or at E15.5 to target pyramidal neurons in layer V/VI and II/III of the PFC, respectively. We analyzed the complexity of dendritic arborizations by using the Sholl analysis method and spine density of tDimer2-expressing pyramidal neurons in layer II/III and V/VI. Furthermore, we quantified the layer- and age-specific density of pyramidal neurons and interneurons by immunohistochemistry with custom-written processing algorithms in ImageJ. Following a stream of recent investigations implying the involvement of microglial cells in synaptic pruning we investigated the maturation of the microglial population in GE mice using image processing algorithms in MATLAB. Data were tested for significant differences using t-test or two-way ANOVA. The GE mice showed major layer specific morphological deficits in the PFC including abnormal migration and an increase of interneuronal density in layer II/III at neonatal age (control: 322.2 ± 11.73 cells/mm2, GE mice: 407.1 ± 20.17 cells/mm2; p=0.0012). This layer II/III specific disruption was confirmed by a reduction of dendritic arborization complexity (20-130 μm p 0.05) and spine density (mino GE mice: 4.709 ± 0.1493 spines/10 μm; control vs. mino GE mice p=0.3945) of pyramidal neurons in layer II/III. These data reveal that the functional deficits of local circuits in the PFC of GE mice at neonatal age result from abnormal anatomy of pyramidal neurons and microglia maturation.