Effect of neonatal handling on serotonin 1A sub-type receptors in the rat hippocampus

Serotonin 1A sub-type receptors play an important role in the etiopathogenesis of depression, which is known to occur more often in females than males. Early experiences can be a predisposing factor for depression; however, the underlying cellular processes remain unknown. In an effort to address such issues, we employed neonatal handling, an experimental model of early experience, which has been previously shown to render females more vulnerable to display enhanced depression-like behavior in response to chronic stress, while it increases the ability of males to cope. In rat pre-pubertal (30 days of age) and adult (90 days) hippocampus, of both males and females, the effect of neonatal handling on serotonin 1A sub-type receptor mRNA and protein levels was determined by in situ hybridization and immunohistochemistry, respectively, while the number of binding sites was determined by in vitro autoradiography using [(3)H]8-hydroxy-2(di-n-propylamino)tetralin as the ligand. Our results revealed a significant sex difference in serotonin 1A sub-type receptor mRNA, protein and binding sites, with females having higher levels than males. Handling resulted in statistically significant decreased numbers of cells positive for serotonin 1A sub-type receptor mRNA or protein, as well as [(3)H]8-hydroxy-2(di-n-propylamino)tetralin binding sites in the area 4 of Ammon's horn and dentate gyrus of both pre-pubertal males and females. In adult animals the number of serotonin 1A sub-type receptor mRNA positive cells was increased as a result of handling in the area 1 of Ammon's horn, area 4 of Ammon's horn and dentate gyrus of males, while it was decreased only in the area 4 of Ammon's horn of females. Furthermore, the number of serotonin sub-type 1A receptor immunopositive cells, as well as [(3)H]8-hydroxy-2(di-n-propylamino)tetralin binding sites was increased in the area 1 of Ammon's horn, area 4 of Ammon's horn and dentate gyrus of handled males, whereas it was decreased in these same brain areas in the handled females. We can thus infer that neonatal handling results in alterations in postsynaptic serotonergic neurotransmission, which may contribute to the sex dimorphic effects of handling as to the vulnerability toward depression-like behavior in response to chronic stressful stimuli.     

Effects of neonatal handling on basal and stress-induced monoamine levels in the male and female rat brain

During periods of high-frequency stimulation the maintenance of synaptic transmission depends on a continued supply of synaptic vesicles. Local recycling in the terminals ensures synaptic vesicle replenishment, but the intermediate steps are still a matter of debate. We analyzed changes in synaptic vesicle pools and endosome-like organelles near the active zone in central nerve terminals during depolarization at the ultrastructural level by electron microscopy. A short, 100 ms, depolarization-induced recruitment of synaptic vesicles was observed from a reserve pool to a recruited pool, within 150 nm of the active zone, and the docked pool at the active zone was increased as well. Prolonged, 15 s or 3 min, depolarization decreased the total amount of synaptic vesicles, which was accompanied by a parallel increase in size and amount of endosome-like organelles. After a period of rest, the number of endosome-like organelles decreased and the amount of synaptic vesicles was restored to control level.The endocytotic nature of part of the endosome-like organelles after 15 s and 3 min depolarization was indicated by their labeling with extracellularly added horseradish peroxidase (HRP). In addition, a small number of synaptic vesicles entrapped HRP under these conditions. After repolarization, the number of HRP-loaded endosome-like structures decreased. Simultaneously, a strong increase in amount of HRP-loaded small vesicles did occur.These results indicate that during sub-second depolarization, synaptic vesicles were rapidly recruited from the reserve pool to replenish the releasable pool, whereas prolonged depolarization (s-min) induced local endocytosis in at least two ways, i.e. either directly as vesicles or via endosome-like organelles from which synaptic vesicles were reformed.     

摘除松果体对大鼠学习记忆及基底前脑胆碱能系统的影响

目的　探讨松果体功能减退对大鼠学习记忆及基底前脑胆碱能系统的影响。方法　选用 3月龄SD大鼠 2 4只 ,随机分为对照组、去松果体组和褪黑素 (MT)组。手术摘除松果体。饲养 1个月后用Morris水迷宫测试学习记忆功能 ,同时用组织化学和免疫组化方法测定海马、前额叶皮质AchE纤维和内侧隔核、斜角带核的ChAT神经元的数量。结果　与对照组比较 ,去松果体组逃避潜伏期明显增加 ,海马、前额叶皮质AchE纤维数量明显减少 ,但内侧隔核、斜角带核的ChAT神经元数量变化不明显。结论　大鼠去松果体可引起大鼠学习记忆能力减弱 ,这可能与基底前脑胆碱能神经元的功能下降有关     

Effect of some phenothiazine and dibenzazepime derivatives on the muscarinic cholinergic system

Laboratory of Pharmacology of the Circulation, Research Institute of Pharmacology, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR M. E. Vartanyan.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol, 113, No. 1, pp. 60–62, January, 1992.     

单侧磨牙缺失对老年学习记忆减退大鼠基底前脑胆碱能系统的影响

目的:探讨单侧缺牙对不同学习记忆能力老年大鼠基底前脑胆碱能系统的影响。方法:用Morris水迷宫筛选出老年记忆减退鼠和老年记忆正常鼠,拔除单侧磨牙后2个月,用免疫组化和组织化学染色观察对其斜角带核垂直支胆碱能神经元和海马CA1区、前额皮质胆碱能纤维密度的影响。结果:斜角带核垂直支ChAT阳性细胞数和海马CA1区、前额皮质AChE阳性纤维密度在老年记忆减退鼠中,拔牙组较对照组(未拔牙)明显下降;海马CA1区AChE阳性纤维密度在老年记忆正常鼠中,拔牙组较对照组明显下降。结论:单侧磨牙缺失可加速老年学习记忆减退鼠基底前脑胆碱能系统的损害。     

Cellular mechanisms underlying the effect of a single exposure to neonatal handling on neurotrophin-3 in the brain of 1-day-old rats

Neurotrophin-3 (NT-3) has an important role in brain development and is thus a good candidate molecule to be involved in the cellular mechanisms mediating the effects of early experiences on the brain. In the present work we employed the model of neonatal handling, which is known to affect the ability of the adult organism to respond to stressful stimuli, and determined its effects on NT-3 levels in the rat hippocampus and cortex 2, 4 and 8 h after handling on postnatal day 1. We also recorded maternal behavior during the 8 h following handling. At both the 4 and 8 h time-points there was an increase in NT-3 positive cells in field 1 of Ammon's horn (CA1 area of the hippocampus) and parietal cortex of the handled animals. In the parietal cortex NT-3 levels increased with time following handling: at 8 h there were more NT-3 positive cells than at 4 h. During the 4 h following the end of handling, handled pups were subject to more maternal licking, indicating that the more intense maternal care could underlie the handling-induced increase in NT-3. In the hippocampus, the handling induced increase in NT-3 was cancelled by inhibition of N-methyl-D-aspartate (NMDA), AMPA/kainate, or GABA-A receptors, as well as L-type voltage-gated Ca(2+) channels. It thus appears that neonatal handling activates these neurotransmitter receptors and channels, leading to increased intracellular Ca(2+) and increased NT-3 expression. NT-3 can then activate downstream effectors and exert its morphogenetic actions and thus imprint the effects of handling on the brain.     

Sexually dimorphic effects of the Lhx7 null mutation on forebrain cholinergic function

It has been reported recently that mice lacking both alleles of the LIM-homeobox gene Lhx7, display dramatically reduced number of forebrain cholinergic neurons. In the present study, we investigated whether the Lhx7 mutation affects male and female mice differently, given the fact that gender differences are consistently observed in forebrain cholinergic function. Our results show that in adult male as well as female Lhx7 homozygous mutants there is a dramatic loss of choline acetyltransferase immunoreactive forebrain neurons, both projection and interneurons. The reduction of forebrain choline acetyltransferase immunoreactive neurons in Lhx7 homozygous mutants is accompanied by a decrease of acetylcholinesterase histochemical staining in all forebrain cholinergic neuron target areas of both male and female homozygous mutants. Furthermore, there was an increase of M1-, but not M2-, muscarinic acetylcholine receptor binding site density in the somatosensory cortex and basal ganglia of only the female homozygous mutant mice. Such an increase can be regarded as a mechanism acting to compensate for the dramatically reduced cholinergic input, raising the possibility that the forebrain cholinergic system in female mice may be more plastic and responsive to situations of limited neurotransmitter availability. Finally, our study provides additional data for the sexual dimorphism of the forebrain cholinergic system, as female mice appear to have a lower density of M1-muscarinic acetylcholine receptors in the striatal areas of the basal ganglia and a higher density of M2-muscarinic acetylcholine receptors, in a number of cortical areas, as well as the striatal areas of the basal ganglia.     

Effects of neonatal testosterone and estrogen on open-field behaviour in rats

On days 1 and 4 after birth male and female rats from the same litter were injected with either testosterone propionate (TP), or estradiol benzoate (EB) or oil. Subjects were tested in the open-field for 2 minutes per day, for 4 successive days at 45 and 85 days of age. Adult females were significantly more active than males in the outer and inner fields, reared more and defecated less. Neonatal TP and EB treatments reduced activity in females, but only EB increased defaecation in females. EB and TP treated females were heavier than controls at 125 days of age but non-significantly so in the case of TP. Gonadal weights in males and females were reduced in EB and TP treatment, as were penile diameter, number of penile papillae and anogenital spacing in EB treated males. Some of these results are consistent with the argument that androgens defeminize or masculinize certain neural mechanisms in the neonate after first being converted to estrogens, but both EB and TP have anomalous effects on males in producing morphological demasculinization.     

Effects of gestational stress and neonatal handling on pain,analgesia, and stress behavior of adult mice

Stressors presented during the late prenatal and early postnatal periods can have long-term effects on offspring behavior, due to the sensitive periods in the formation of brain circuitry associated with early development. This study investigated the long-term effects of prenatal (restraint during the last week of gestation) and postnatal (daily handling for 14 days postnatal) stress, alone and in combination, on adulthood pain behavior, analgesic responses to stress and morphine, and on behavioral indices of stress reactivity. We found that all of the adult responses measured were altered by perinatal manipulations. Nociceptive thresholds were increased by prenatal or by postnatal stress in males and females; application of both stressors in combination negated these effects. Elevations in morphine analgesia were also observed in animals undergoing either perinatal stressor, but not in those who received both stressors. Behavioral and analgesic responses to stress were consistent with previous observations of reduced stress responsiveness following neonatal handling, with some sex-specific findings. Male and female handled subjects exhibited decreases in stress behavior, and both groups of female handled subjects (regardless of prenatal stress [PS] condition) exhibited decreases in stress-induced analgesia (SIA). Males, on the other hand, exhibited decreases in SIA only if they were prenatally stressed (regardless of handling condition). Thus, prenatal and postnatal stressors have differing effects on the neural circuitry underlying pain, pain inhibition, and stress behavior.     

康复新对去卵巢大鼠学习记忆能力和基底前脑胆碱能神经元的影响

目的 探讨康复新对去卵巢大鼠的学习记忆能力的影响及其可能机制.方法 3月龄健康雌性SD大鼠36只,随机分成4组,即假手术组、去卵巢对照组、康复新低剂量组和康复新高剂量组,分别进行干预.8周后用Y迷宫检测大鼠的空间学习记忆能力,用免疫组化染色检测大鼠基底前脑不同区域胆碱能神经元的数目.结果 康复新高剂量组大鼠"学会"所需总训练次数、训练错误次数及记忆检测时错误反应次数与去卵巢对照组比较明显减少(P＜0.05),与假手术组相比差异无统计学意义(P＞0.05);康复新液高、低剂量组大鼠基底前脑内侧隔核(MS)、斜角带核垂直支(vDB)和水平支(hDB)的ChAT阳性神经元数量增多;高剂量组基底前脑各区的ChAT阳性神经元数明显高于去卵巢对照组(P＜0.05),与假手术组相比差异无统计学意义(P＞0.05);而且康复新高剂量组大鼠vDB和hDB的ChAT阳性神经元数明显高于康复新低剂量组(P＜0.05).结论 康复新液可显著改善去卵巢大鼠学习记忆能力,其作用可能是通过增加基底前脑胆碱能神经元的功能实现的;康复新液有望成为防治雌激素撤退引起的神经功能障碍的药物.     

Effects of gonadectomy on immunoreactivity for choline acetyltransferase in the cortex, hippocampus, and basal forebrain of adult male rats

Androgens are known to affect cognitive and mnemonic aspects of spatial processing. The cholinergic system is thought to play an important role in cognition and memory, but little is known about the interaction between androgen and cholinergic neurons. The present study focused on the effects of testosterone on the cholinergic neurons in the anterior cingulate cortex, the posterior parietal cortex, the hippocampus, and the basal forebrain including the medial septum, i.e., regions related to spatial processing. We examined choline acetyltransferase (ChAT) immunoreactivity in three groups of adult male rats: sham-operated (Sham), 28-day gonadectomized (GDX), and 28-day gonadectomized with immediate implantation of testosterone propionate (GDX+TP). Comparison of the Sham and GDX+TP groups demonstrated that the GDX group had significantly decreased cell counts of ChAT-immunoreactive neurons in anterior cingulate cortex layer II/III, posterior parietal cortex layer II/III, and the medial septum, but not in the other basal forebrain subregions examined (the horizontal part of the diagonal band of Broca and the substantia innominata). The GDX group also had significantly reduced hippocampal ChAT-immunoreactive fiber pixel density. The GDX+TP group maintained ChAT-immunoreactive cell counts in the anterior cingulate cortex, posterior parietal cortex, and medial septum equivalent to those in the Sham group. Less than 1% of identified cells showed colocalization of immunoreactivity for ChAT and androgen receptor in the cell bodies of the cortex and basal forebrain.Our observations demonstrate that the presence or absence of testosterone for 4 weeks influenced the cholinergic population region-specifically in the adult rat brain.     

Effects of early weaning on anxiety and prefrontal cortical and hippocampal myelination in male and female Wistar rats

We investigated developmental changes in myelin formation in the prefrontal cortex and the hippocampus, and behavioral effects of early weaning in Wistar rats. Early-weaned rats showed decreased numbers of open-arm entries in an elevated plus-maze in both sexes at 4 weeks old; this effect persisted in males, but ceased in females after this age. Expression of myelin basic protein (MBP) showed both age-dependent increases and sex differences; 4-week-old males exhibited higher MBP levels in the hippocampus, whereas 7-week-old males showed lower MBP levels in the prefrontal cortex compared to females of the same age. There was a tendency for group differences from weaning for the 21.5-kDa isoform in the prefrontal cortex. Although these results suggest that male rats are more vulnerable than females to early-weaning effects on anxiety-related behaviors, further detailed analysis is needed to clarify the functional relationship between myelination and anxiety-related behaviors.     

Stress responses of adolescent male and female rats exposed repeatedly to cat odor stimuli,and long‐term enhancement of adult defensive behaviors

In order to characterize the short‐ and long‐term effects of repeated stressor exposure during adolescence, and to compare the effects of using two sources of cat odor as stressor stimuli, male and female adolescent rats (postnatal day (PND) ～ 38–46) were exposed on five occasions to either a control stimulus, a cloth stimulus containing cat hair/dander, or a section of cat collar previously worn by a cat. Relative to control stimulus exposure, activity was suppressed and defensive behavior enhanced during exposure to either cat odor stimulus (most pervasively in rats exposed to the collar). Only cloth‐exposed rats showed elevated levels of corticosterone (CORT), and only after repeated stressor exposure, but interestingly, rats exposed to the collar stimulus during adolescence continued to show increased behavioral indices of anxiety in adulthood. In this group, the time an individual spent in physical contact with a cagemate during the final adolescent exposure was negatively related to stress‐induced CORT output in adulthood, which suggests that greater use of social support during adolescent stress may facilitate adult behavioral coping, without necessitating increased CORT release. These findings demonstrate that adolescent male and female rats respond defensively to cat odor stimuli across repeated exposures and that exposure to such stressors during adolescence can augment adult anxiety‐like behavior in similar stressful conditions. These findings also suggest a potential role for social behavior during adolescent stressor exposure in mediating long‐term outcomes. © 2012 Wiley Periodicals, Inc. Dev Psychobiol 55: 551–567, 2013     

The ontogeny of exploratory behavior in male and female adolescent rats (Rattus norvegicus)

During adolescence, rats gain independence from their mothers and disperse from the natal burrow, with males typically dispersing further than females. We predicted that, if dispersal patterns are associated with responsiveness to novelty, exploratory behavior in novel environments would increase across adolescence, and males would explore more than females. Alternatively, females might explore more than males, if females are more motivated than males to learn about the immediate environment or if females have poorer spatial abilities than males. Twenty‐five male and 21 female rats were exposed to two novel environments (open field and elevated plus‐maze) during early, mid‐, or late adolescence. Total locomotion and amount of exploration directed towards aversive areas increased across adolescence, even when body weight was included as a covariate. Female adolescents locomoted more and spent more time exploring aversive areas than males. Developmental changes in neural function potentially underlie age and sex differences in exploratory behavior. © 2009 Wiley Periodicals, Inc. Dev Psychobiol 51: 513–520, 2009     

Transplantation of embryonic ventral forebrain neurons to the neocortex of rats with lesions of nucleus basalis magnocellularis--II. Sensorimotor and learning impairments

The cholinergic projection from the nucleus basalis magnocellularis to the neocortex has been implicated in normal memory function and in the dementia of Alzheimer's disease. In order to investigate functions of this cholinergic system of the forebrain, rats with unilateral ibotenic acid lesions of the nucleus basalis magnocellularis have been compared with normal animals and with rats given cortically-placed transplants, either of cholinergic-rich embryonic ventral forebrain cells or of control noncholinergic cells taken from embryonic hippocampus. In the first experiment, lesions of the nucleus basalis magnocellularis led to impairments in step-through passive avoidance and Morris' water-maze tasks, and to locomotor hyperactivity attributable to a reduction in within-trial habituation. The ventral forebrain grafts, but not the noncholinergic hippocampal grafts, significantly ameliorated the deficits of passive avoidance retention, and of water-maze spatial accuracy, but had no effect on the acquisition impairments in either task, nor on the habituation deficit in locomotor activity of the nucleus basalis magnocellularis lesioned rats. In the second experiment, the lesions induced contralateral sensory neglect and ipsilateral turning biases, which were also partially ameliorated by the ventral forebrain grafts. The results support the hypothesis that the basal forebrain-neocortical cholinergic system contributes to certain memory processes, but suggest a more general role for this system in other cortical functions also.     

Pathological and biochemical consequences of acute and chronic neuroinflammation within the basal forebrain cholinergic system of rats

Inflammatory processes may play a critical role in the degeneration of basal forebrain cholinergic cells that underlies some of the cognitive impairments associated with Alzheimer's disease. In the present study, the proinflammagen lipopolysaccharide, from the cell wall of Gram-negative bacteria, was used to produce inflammation within the basal forebrain of rats. The effects of acute, high-dose injections of lipopolysaccharide (2, 20 or 40 microg) upon basal forebrain chemistry and neuronal integrity were compared with the effects of chronic, low-dose lipopolysaccharide infusions (0.18, 0.25, 1.8 or 5.0 microg/h) for either 14, 37, 74 or 112 days. Acute exposure to lipopolysaccharide decreased cortical choline acetyltransferase activity and the number of immunoreactive choline acetyltransferase-positive cells within a small region of the basal forebrain. Regional levels of five different neuropeptides were unchanged by acute, high-dose lipopolysaccharide injections. Chronic lipopolysaccharide infusions produced (i) a time-dependent, but not dose-dependent, decrease in cortical choline acetyltransferase activity that paralleled a decline in the number of choline acetyltransferase- and p75-immunoreactive cells within the basal forebrain, and (ii) a dense distribution of reactive astrocytes and microglia within the basal forebrain. Chronic neuroinflammation might underlie the genesis of some neuropathological changes associated with normal ageing or Alzheimer's disease.     

雌激素对去卵巢大鼠基底前脑胆碱能神经元及一氧化氮合酶阳性神经元的影响

目的　探讨雌激素补充治疗对去卵巢大鼠胆碱能神经元及一氧化氮合酶 (NOS)阳性神经元表达的影响及剂量效应关系。方法　 2 0只去卵巢SD大鼠分成 4个不同剂量组 :0 μg(对照组 )、2 0 μg(0 0 8mg/kg)、5 0 μg(0 2 0mg/kg)、10 0 μg(0 4 0mg/kg)组 ;1周后 ,用乙酰胆碱转移酶 (ChAT)免疫化学方法及尼克酰胺腺嘌呤二核苷酸黄递酶 (NADPH d)组织化学方法研究。结果　NOS阳性神经元在内侧隔核 (MS) ,其数目在各组间无明显差异 (P >0 0 5 )。在斜角带垂直支 (VDB) ,5 0 μg剂量组与对照组相比有明显差异 (P <0 0 5 ) ;ChAT阳性神经元在内侧隔核 (MS) ,其 2 0 μg、5 0 μg剂量组数目出现剂量递增效应 ,与对照组比较有明显差异 (P <0 0 5 ) ,但 10 0 μg剂量组与对照组比较没有明显差异 (P >0 0 5 ) ,同时 5 0 μg与 10 0 μg剂量组比较有明显差异 (P <0 0 5 )。ChAT阳性神经元在斜角带水平支 (HDB) ,各组间均无明显差异 (P >0 0 5 )。结论　雌激素补充治疗能选择性影响基底前脑各亚区NOS和胆碱能神经元 ,并有可能影响学习和记忆能力。     

Transgenerational effects of infantile adversity and enrichment in male and female rats

To discover whether the accumulation of life's experiences, adverse and enriching, inform, and serve the following generation by inheritance we examine whether stress to a weanling female will influence her future offspring, whether prereproductive enrichment to the dam, or postweaning enrichment to the offspring, can reverse the transgenerational effects of stress, and whether, like adversity, enrichment might have transgenerational effects. Female rats were exposed to stressors when they were 27-29 days old. Half of these females and their controls were then raised in an enriched environment from weaning until mating at 60 days to examine whether preproduction enrichment reverses the effects of preproduction stress on offspring. Half of the offspring of each group were raised in an enriched environment after weaning, to see whether it reverses the effects of preproduction stress and buttresses prereproductive enrichment. Behavior was examined in 625 adult offspring in 16 groups covering all permutations of the experimental variables (preproduction weanling stress (PS), preproduction enrichment (PE), offspring enrichment (OE), sex). Exploration, avoidance learning, startle, and social interaction were tested. Results reveal that very early prereproductive experience in females, adverse or enriching, will transgenerationally influence their future offspring, depending on the behavior tested and sex. Our finding that enrichment, whether to the parent or offspring generation, can ameliorate the transgenerational impact of adversity, has novel implications for the malleability of transgenerational inheritance, and its individual, social, and therapeutic impact.