The effects of antipsychotic drugs administration on 5-HT1A receptor expression in the limbic system of the rat brain

Increasing evidence suggests that 5-HT1A receptors are involved in the pathophysiology and treatment of schizophrenia. This paper investigated 5-HT1A receptor mRNA expression and binding density in female rats treated with aripiprazole (2.25 mg/kg/day), olanzapine (1.5 mg/kg/day), haloperidol (0.3 mg/kg/day) or vehicle (control) orally three times/day for 1 or 12 weeks. Animals were sacrificed 48 h after the last administration. Aripiprazole significantly increased 5-HT1A receptor binding density by 33% in the CA1 region of the hippocampus and by 21% in the medial posterodorsal nuclei of posterior amygdala (MeP) compared to the control group after 1 week of treatment. Olanzapine significantly decreased 5-HT1A receptor binding density by 17–22% in Layers I–IV of the cingulate cortex after 1 week of treatment. Neither of these antipsychotic drugs affected 5-HT1A receptor binding density after 12 weeks drug treatment. As expected, haloperidol treatment did not have any significant effect on 5-HT1A binding density after 1 or 12 weeks of treatment. 5-HT1A receptor mRNA expression was not altered by antipsychotic treatment in any brain region. The results indicate that aripiprazole and olanzapine have differential effects on 5-HT1A receptor expression, which may contribute to their distinct profiles in improving negative symptoms and cognitive deficits in schizophrenia. Aripiprazole and olanzapine may produce adaptation and desensitization of 5-HT1A receptor expression after long term treatment.     

Maternal immune activation during pregnancy increases limbic GABAA receptor immunoreactivity in the adult offspring: implications for schizophrenia

Prenatal exposures to a variety of infections have been associated with an increased incidence of schizophrenia. We have reported that a single injection of the synthetic cytokine releaser PolyI:C to pregnant mice produced offspring that exhibited multiple schizophrenia-related behavioral deficits in adulthood. Here, we characterized the effect of maternal inflammation during fetal brain development on adult limbic morphology and expression of GABAA-receptors. The PolyI:C treatment did not induce morphological abnormalities but resulted in a significant increase in GABAA receptor subunit alpha2 immunoreactivity (IR) in the ventral dentate gyrus and basolateral amygdala in adult treated compared to control subjects. Correlative analyses between the a2 subunit IR in the ventral dentate gyrus and the performance in the prepulse inhibition paradigm revealed a significant correlation in controls that was however absent in the pathological condition. These results suggest that prenatal immune activation-induced disturbances of early brain development result in profound alterations in the limbic expression of GABAA receptors that may underlie the schizophrenia-related behavioral deficits in the adult mice.     

The expression of non-clustered protocadherins in adult rat hippocampal formation and the connecting brain regions

Non-clustered protocadherins (PCDHs) are calcium-dependent adhesion molecules which have attracted attention for their possible roles in the neuronal circuit formation during development and their implications in the neurological disorders such as autism and mental retardation. Previously, we found that a subset of the non-clustered PCDHs exhibited circuit-dependent expression patterns in thalamo-cortical connections in early postnatal rat brain, but such patterns disappeared in adulthood. In this study, we identified that the non-clustered PCDHs showed differential expression patterns along the septotemporal axis in the subregions of adult hippocampus and dentate gyrus with topographical preferences. The expressions of PCDH1, PCDH9, PCDH10 and PCDH20 showed septal preferences, whereas the expressions of PCDH8, PCDH11, PCDH17 and PCDH19 showed temporal preferences, suggesting that they play roles in the formation/maintenance of intrahippocampal circuits. PCDHs also exhibited the region-specific expression patterns in the areas connected to hippocampal formation such as entorhinal cortex, lateral septum, and basolateral amygdaloid complex. Furthermore, the expression levels of three PCDHs (PCDH8, PCDH19 and PCDH20) were regulated by the electroconvulsive shock stimulation of the brain in the adult hippocampus and dentate gyrus. These results suggest that non-clustered PCDHs are involved in the maintenance and plasticity of adult hippocampal circuitry.     

肝性脑病大鼠海马齿状回神经元形态及一氧化氮合酶表达的变化

目的:观察肝性脑病模型组大鼠海马齿状回内神经元的变化及一氧化氮合酶(NOS)的表达,探讨海马神经元的形态学改变及一氧化氮(NO)在肝硬化和肝性脑病发病机制中的作用。方法:先对50只雄性大鼠进行Morris水迷宫测试,之后将动物分为正常对照组和实验模型组。9周后建立CCL4肝性脑病模型,分别取两组大鼠肝、海马组织进行HE染色、Nissl染色及NADPH-d染色。结果:(1)肉眼下可见模型组肝脏普遍呈坏死性肝硬化;(2)HE模型组血氨浓度明显高于正常对照组(P<0.05);(3)Nissl染色结果显示实验组大鼠海马神经元数目减少、染色较浅,胞浆内Nissl体减少或消失;(4)NADPH-d染色结果显示实验组可见粗大轴突着色,树突联系广泛;对照组则少有粗大轴突着色,树突间联系不如实验组广泛。实验组一氧化氮合酶(NOS)阳性神经元染色较对照组深,为紫蓝或深蓝色,且阳性神经元的数目较多。结论:(1)血氨增高是肝性脑病发病机制之一;(2)肝性脑病时海马受到损伤,并且一氧化氮(NO)可能介导了神经元的损伤。     

Chronic corticosterone administration down-regulates metabotropic glutamate receptor 5 protein expression in the rat hippocampus

Several lines of evidence suggest a dysfunctional glutamate system in major depressive disorder (MDD). Recently, we reported reduced levels of metabotropic glutamate receptor subtype 5 (mGluR5) in postmortem brains in MDD, however the neurobiological mechanisms that induce these abnormalities are unclear. In the present study, we examined the effect of chronic corticosterone (CORT) administration on the expression of mGluR5 protein and mRNA in the rat frontal cortex and hippocampus. Rats were injected with CORT (40 mg/kg s.c.) or vehicled once daily for 21 days. The expression of mGluR5 protein and mRNA was assessed by Western blotting and quantitative real-time PCR (qPCR). In addition, mGluR1 protein was measured in the same animals. The results revealed that while there was a significant reduction (−27%, P=0.0006) in mGluR5 protein expression in the hippocampus from CORT treated rats, mRNA levels were unchanged. Also unchanged were mGluR5 mRNA and protein levels in the frontal cortex and mGluR1 protein levels in both brain regions. Our findings provide the first evidence that chronic CORT exposure regulates the expression of mGluR5 and are in line with previous postmortem and imaging studies showing reduced mGluR5 in MDD. Our findings suggest that elevated levels of glucocorticoids may contribute to impairments in glutamate neurotransmission in MDD.     

Coexistence of neuropeptide Y and somatostatin in rat and human cortical and rat hypothalamic neurons

The distribution and coexistence of neuropeptide Y (NPY) and somatostatin (SOM) were evaluated in rat and human cerebral cortex and in the rat hypothalamic arcuate nucleus (n) using double immunofluorescent staining in which primary antisera were raised in different species. The results of the study indicate extensive coexistence of NPY and SOM in both rat and human cortex but only occasional coexistence in the rat arcuate n.     

Activation of p42 mitogen-activated protein kinase by arachidonic acid and trans-1-amino-cyclopentyl-1,3-dicarboxylate impacts on long-term potentiation in the dentate gyrus in the rat: analysis of age-related changes

Maintenance of long-term potentiation in perforant path–granule cell synapses is associated with an increase in glutamate release, which we have suggested relies on an interaction between arachidonic acid and the metabotropic glutamate receptor agonist, trans-1-amino-cyclopentyl-1,3-dicarboxylate (ACPD). Evidence suggests that this interaction is dependent on stimulation of tyrosine kinase, which phosphorylates and activates phospholipase Cγ. In this study, we demonstrate that arachidonic acid and ACPD stimulate tyrosine phosphorylation of a protein of about 40,000 mol. wt and further analysis, using a specific antibody, suggested that this may be extracellular signal-regulated kinase, one member of the family of mitogen-activated protein kinases. Activity of extracellular signal-regulated kinase was increased by arachidonic acid and ACPD in vitro, but it was also increased by induction of long-term potentiation in perforant path–granule cell synapses. A role for extracellular signal-regulated kinase in long-term potentiation was supported by the observation that expression of long-term potentiation, as well as the associated increases in endogenous glutamate release and extracellular signal-regulated kinase activation, were inhibited by pretreatment with the mitogen-activated protein kinase inhibitor, PD98059, while PD98059 pretreatment inhibited the interaction between arachidonic acid and ACPD on glutamate release. An age-related decrease in extracellular signal-regulated kinase activity was observed in the dentate gyrus, and there was no evidence of increased extracellular signal-regulated kinase activity or endogenous glutamate release in tissue prepared from aged rats in which long-term potentiation was compromised.

The evidence is consistent with the view that increased activation of extracellular signal-regulated kinase plays a role in long-term potentiation, and that activation of this kinase relies on the interaction between arachidonic acid and ACPD.     

Inhibitor of vascular endothelial growth factor receptor tyrosine kinase attenuates cellular proliferation and differentiation to mature neurons in the hippocampal dentate gyrus after transient forebrain ischemia in the adult rat

Neurogenesis in the adult hippocampal dentate gyrus is promoted by transient forebrain ischemia. The mechanism responsible for this ischemia-induced neurogenesis, however, remains to be determined. It has been suggested that there may be a close relationship between neurogenesis and the expression of vascular endothelial growth factor, an angiogenic factor. The purpose of the present study was to examine the relationship between vascular endothelial growth factor and cell proliferation in the dentate gyrus after transient forebrain ischemia. The mRNA expression of vascular endothelial growth factor was increased in the dentate gyrus on day 1 after ischemia. Immunohistochemical analysis on day 9 after ischemia, when a significant increase in cell proliferation was seen, showed that the cerebral vessel space in the subgranular zone of the dentate gyrus had not been affected by the ischemia. Neither were the vascular densities on days 1 and 3 after ischemia altered compared with those of non-operated naïve control rats. Furthermore, the distance from the center of the proliferative cells to the nearest cerebral vessel of ischemic rats was comparable to that of the sham-operated rats. We demonstrated that transient forebrain ischemia-induced cell proliferation and differentiation to mature neurons in the hippocampal dentate gyrus was attenuated by the i.c.v. administration of a vascular endothelial growth factor receptor tyrosine kinase inhibitor. These results suggest that vascular endothelial growth factor receptor at the early period of reperfusion may contribute to neurogenesis rather than to angiogenesis in the hippocampal dentate gyrus.     

复方丹参对脑缺血再灌注后大鼠海马和齿状回神经细胞凋亡及Bcl-2 mRNA表达的影响

目的:探讨中药复方丹参对大鼠脑缺血再灌注后海马和齿状回神经细胞凋亡及Bcl-2 mRNA表达的影响。方法:采用大脑中动脉内栓线法建立大鼠大脑中动脉缺血再灌注模型,应用原位细胞凋亡检测和原位杂交技术检测大鼠海马和齿状回神经细胞凋亡和Bcl-2 mRNA的表达并做图像分析。结果:与假手术对照组比较,缺血再灌注组凋亡神经细胞主要位于缺血侧海马CA1、CA3区,齿状回凋亡细胞较少。3个区神经细胞Bcl-2mRNA的表达在缺血再灌注2 h后升高,随时间的延长逐渐增强。复方丹参组神经细胞Bcl-2 mRNA的表达明显强于缺血再灌组,而凋亡神经细胞数明显较低。结论:复方丹参可通过上调神经细胞Bcl-2 mRNA的表达,抑制神经细胞凋亡,从而减轻缺血再灌注对大鼠海马和齿状回的损伤。     

Ultrastructural distribution of glycinergic and GABAergic neurons and axon terminals in the rat dorsal cochlear nucleus,with emphasis on granule cell areas

A knowledge of neurotransmitters in the neurons of the rat cochlear nuclear complex is of importance in understanding the function of auditory circuits. Using post-embedding ultrastructural immunogold labelling, the distribution of glycinergic and GABAergic neurons and axonal terminals has been studied in the molecular, fusiform and polymorphic layers of the rat dorsal cochlear nucleus (DCN). This technique is not limited by the penetration of antibodies into the nervous tissue as in pre-embedding methods, and allows a fine neurochemical mapping of the nervous tissue. Numerous glycinergic and GABAergic axon terminals contain pleomorphic and flat synaptic vesicles, and are present in all layers (1, 2, 3) of the dorsal cochlear nucleus. Glycine and GABA-negative large terminals (mossy fibres) are mainly seen in granule cell areas of layer 2 (fusiform layer). Mossy fibres contact the dendrites of GABA- and glycine-negative granule cells and of the few unipolar brush cells (excitatory neurons). The least common cells in the granule cell areas are GABAergic and glycinergic Golgi-stellate neurons. In unipolar brush cells, aggregations of vesicles seem to be the origin of their characteristic ringlet-bodies. Golgi-stellate cells send their inhibitory terminals to the dendrites of granule and unipolar brush cells, occasionally directly to mossy fibres. Small or (less frequently) large GABAergic terminals contact the soma or the main dendrite of unipolar brush cells. The circuit of a hypothetical functional unit of neurons in the DCN is proposed. The inputs from auditory tonotopic or non-auditory non-tonotopic mossy fibres eventually reach pyramidal cells through axons from the granule cells or unipolar brush cells. Pyramidal cells convey an excitatory signal from the DCN to higher mesencephalic nuclei for further elaboration of the acoustic signal.     

跑步对早期APP/PS1转基因阿尔茨海默病小鼠海马CA1区和齿状回神经元数量的影响

目的:应用体视学方法定量研究跑步对早期APP/PS1转基因阿尔茨海默病(AD)小鼠海马CA1和齿状回区域内神经元的影响。方法:将6月龄雄性APP/PS1转基因AD小鼠,随机分为跑步组和未跑步对照组。用Morris水迷宫检测2组小鼠的空间学习记忆能力,然后用体视学方法定量研究海马CA1和齿状回区域的体积和神经元的数量。结果:与对照组相比,跑步组AD小鼠Morris水迷宫的逃避潜伏期明显缩短,平台所在象限时间百分比和穿越平台次数均显著增加。体视学研究显示,跑步组AD小鼠海马CA1和齿状回的体积分别比对照组显著增大42.8%和27.3%,并且跑步组AD小鼠海马CA1和齿状回区域内的神经元数量分别比对照组显著增加61.8%和62.2%。结论:跑步能延缓早期AD小鼠空间学习记忆能力的下降;并且可降低AD小鼠海马CA1和齿状回区域内神经元的死亡。     

Effect of naloxone-precipitated morphine withdrawal on c-fos expression in rat corticotropin-releasing hormone neurons in the paraventricular hypothalamus and extended amygdala

Morphine withdrawal is characterized by physical symptoms and a negative affective state. The 41 amino acid polypeptide corticotropin-releasing hormone (CRH) is hypothesized to mediate, in part, both the negative affective state and the physical withdrawal syndrome. Here, by means of dual-immunohistochemical methodology, we examined the co-expression of the c-Fos protein and CRH following naloxone-precipitated morphine withdrawal. Rats were treated with slow-release morphine 50 mg/kg (subcutaneous, s.c.) or vehicle every 48 h for 5 days, then withdrawn with naloxone 5 mg/kg (s.c.) or saline 48 h after the final morphine injection. Two hours after withdrawal rats were perfused transcardially and their brains were removed and processed for immunohistochemistry. We found that naloxone-precipitated withdrawal of morphine-dependent rats increased c-Fos immunoreactivity (IR) in CRH positive neurons in the paraventricular hypothalamus. Withdrawal of morphine-dependent rats also increased c-Fos-IR in the central amygdala and bed nucleus of the stria terminalis, however these were in CRH negative neurons.     

Coexistence of glutamate decarboxylase and somatostatin immunoreactivity in cultured hippocampal neurons of the rat

The immunoperoxidase-antiperoxidase method (PAP) was combined with immunofluorescence for simultaneous localization of glutamate decarboxylase (GAD)-and somatostatin-like immunoreactivity in rat hippocampal neurons growing in dissociated cell culture. A subpopulation of GAD-immunoreactive neurons additionally exhibited somatostatin-like immunostaining. GAD-negative somatostatin-positive cells could not be observed. It is discussed whether the cultured somatostatin-containing GAD neurons correspond to a certain subclass of basket cells as they occur in situ.     

Glutamatergic receptor expression changes in the Alzheimer's disease hippocampus and entorhinal cortex

Alzheimer''s Disease (AD) is the leading form of dementia worldwide. Currently, the pathological mechanisms underlying AD are not well understood. Although the glutamatergic system is extensively implicated in its pathophysiology, there is a gap in knowledge regarding the expression of glutamate receptors in the AD brain. This study aimed to characterize the expression of specific glutamate receptor subunits in post‐mortem human brain tissue using immunohistochemistry and confocal microscopy. Free‐floating immunohistochemistry and confocal laser scanning microscopy were used to quantify the density of glutamate receptor subunits GluA2, GluN1, and GluN2A in specific cell layers of the hippocampal sub‐regions, subiculum, entorhinal cortex, and superior temporal gyrus. Quantification of GluA2 expression in human post‐mortem hippocampus revealed a significant increase in the stratum (str.) moleculare of the dentate gyrus (DG) in AD compared with control. Increased GluN1 receptor expression was found in the str. moleculare and hilus of the DG, str. oriens of the CA2 and CA3, str. pyramidale of the CA2, and str. radiatum of the CA1, CA2, and CA3 subregions and the entorhinal cortex. GluN2A expression was significantly increased in AD compared with control in the str. oriens, str. pyramidale, and str. radiatum of the CA1 subregion. These findings indicate that the expression of glutamatergic receptor subunits shows brain region‐specific changes in AD, suggesting possible pathological receptor functioning. These results provide evidence of specific glutamatergic receptor subunit changes in the AD hippocampus and entorhinal cortex, indicating the requirement for further research to elucidate the pathophysiological mechanisms it entails, and further highlight the potential of glutamatergic receptor subunits as therapeutic targets.     

Pubertal exposure to anabolic androgenic steroids increases spine densities on neurons in the limbic system of male rats

Human studies show that the number of teenagers abusing anabolic androgenic steroids (AAS) is increasing. During adolescence, brain development is altered by androgen exposure, which suggests that AAS may potentially alter central nervous system (CNS) development. The goal of the present study was to determine whether pubertal AAS exposure increased dendritic spine densities on neurons within the medial amygdala and the dorsal hippocampus. Pubertal gonadally intact male rats received the AAS testosterone propionate (5 mg/kg) or vehicle for 5 days/week for 4 weeks. To determine the long-term implications of pubertal AAS use, another set of males received the same AAS treatment and was then withdrawn from AAS exposure for 4 weeks. Results showed that pubertal AAS exposure significantly increased spine densities on neurons in the anterior medial amygdala, posterodorsal medial amygdala, and the cornu ammonis region 1 (CA1) of the hippocampus compared with gonadally intact control males. Spine densities returned to control levels within the anterior medial amygdala and the posterodorsal medial amygdala 4 weeks after withdrawal. However, spine densities remained significantly elevated after AAS withdrawal in the CA1 region of the hippocampus, suggesting that pubertal AAS exposure may have a long-lasting impact on CA1 hippocampal neuroanatomy. Since pubertal AAS exposure increased spine densities and most excitatory synapses in the CNS occur on dendritic spines, AAS may increase neuronal excitation. It is proposed that this increase in excitation may underlie the behavioral responses seen in pubertal AAS-treated male rats.     

Restricted access to food, but not sucrose, saccharine, or salt, synchronizes the expression of Period2 protein in the limbic forebrain

Restricted feeding schedules (RF) in which daily access to food is limited to a few hours each day can entrain the rhythms of expression of circadian clock genes in the brain and periphery in rodents. The critical factors mediating the effect of RF on rhythms of clock gene expression are unknown. Previously, we demonstrated that daytime RF shifts the phase of expression of the clock protein, Period2 (PER2) in the oval nucleus of the bed nucleus of the stria terminalis in rats kept on a 12-h light/dark cycle, and restored the rhythm of PER2 expression in rats housed in constant light. We now report that RF also modifies the rhythms of PER2 expression in the central and basolateral nuclei of the amygdala and in the dentate gyrus, such that all three areas become synchronized, peaking 12 h after the time of food presentation. Daily limited access to sucrose or saccharine in freely fed rats or scheduled access to saline in sodium-deprived rats had no effect on these PER2 rhythms. Thus, it would appear that the rhythms of PER2 in limbic forebrain structures are sensitive to signals that arise from the alleviation of a negative metabolic state associated with scheduled feeding and that access to rewarding substances in the absence of food deprivation or metabolic challenges, per se, is not sufficient to alter the rhythms of PER2 expression in these regions.