Rat Amygdala Research Articles

Chronic stress leads to persistent and contrasting stellate neuron dendritic hypertrophy in the amygdala of male and female rats, an effect not found in the hippocampus

In males, chronic stress enhances dendritic complexity in the amygdala, a region important in emotion regulation. An amygdalar subregion, the basolateral amygdala (BLA), is influenced by the hippocampus and prefrontal cortex to coordinate emotional learning and memory. This study quantified changes in dendritic complexity of BLA stellate neurons ten days after an unpredictable chronic stressor ended in both male and female rats. In addition, dendritic complexity of hippocampal neurons in male rats was assessed at a similar timepoint. Following Golgi processing, stressed male and female rats showed enhanced BLA dendritic complexity; increased arborization occurred near the soma in males and distally in females. As the brain was sampled ten days after chronic stress ended, BLA dendritic hypertrophy persisted in both sexes after the stressor had ended. For the hippocampus, CA3 dendritic complexity was similar for control and stressed males when assessed eight days after stress ended, suggesting that any stress-induced changes had resolved. These results show persistent enhancement of BLA dendritic arborization in both sexes following chronic stress, reveal sex differences in how BLA hypertrophy manifests, and suggest a putative neurobiological substrate by which chronic stress may create a vulnerable phenotype for emotional dysfunction.

The long-term effects of maternal deprivation on the number and size of inhibitory interneurons in the rat amygdala and nucleus accumbens.

There is an increasing evidence supporting the hypothesis that traumatic experiences during early developmental periods might be associated with psychopathology later in life. Maternal deprivation (MD) in rodents has been proposed as an animal model for certain aspects of neuropsychiatric disorders. To determine whether early-life stress leads to changes in GABAergic, inhibitory interneurons in the limbic system structures, specifically the amygdala and nucleus accumbens, 9-day-old Wistar rats were exposed to a 24 h MD. On postnatal day 60 (P60), the rats were sacrificed for morphometric analysis and their brains were compared to the control group. Results show that MD affect GABAergic interneurons, leading to the decrease in density and size of the calcium-binding proteins parvalbumin-, calbindin-, and calretinin-expressing interneurons in the amygdala and nucleus accumbens. This study indicates that early stress in life leads to changes in the number and morphology of the GABAergic, inhibitory interneurons in the amygdala and nucleus accumbens, most probably due to the loss of neurons during postnatal development and it further contributes to understanding the effects of maternal deprivation on brain development.

Sex Differences in Addictive Behavior of Adult Rats: Effects of Prenatal Alcohol Exposure

Alcohol experienced during gestation is associated with the development of neurodevelopmental and neuropsychiatric dysfunctions, as well as addictive behavior in the offspring. However, the biological basis of these effects remains poorly understood. Taking into account that the extrahypothalamic corticotropin-releasing factor (CRF) system plays an important role in regulation of the negative emotional state produced by alcohol abuse and withdrawal, the present study was aimed at investigating: 1) the effect of prenatal alcohol exposure (PA) on voluntary alcohol drinking (free choice 24 hours/day) or intermittent (“drinking in the dark”) regimen in adult Wistar rats; 2) differences in the basal gene expression levels of CRF and CRF-R1 in amygdala of adult PA and control rats; and 3) the effect of voluntary alcohol drinking on the above mRNA levels. PA males displayed a significantly greater voluntary alcohol intake than control males as observed by both drinking paradigms. 24 hours after the first withdrawal episode, PA males demonstrated a higher level of anxiety in the light-dark box test. No differences were found between PA and control females. Basal amygdalar CRF and CRFR1 mRNA levels did not differ between PA and control rats of both sexes. No difference was observed in the amygdalar CRF and CRFR1 mRNA levels after alcohol drinking in PA and control males. Conversely, the CRF mRNA levels in amygdala of PA female rats decreased under the action of alcohol consumption, compared to control female rats. The results show that the PA effect on future alcohol-related behavior is sex-specific, but do not support the hypothesis that changes in CRF and CRFR1 mRNA levels in amygdala may be responsible for high alcohol intake in males.

Cocaine Exposure Increases Excitatory Synaptic Transmission and Intrinsic Excitability in the Basolateral Amygdala in Male and Female Rats and across the Estrous Cycle

Introduction: Sex and ovarian hormones influence cocaine seeking and relapse vulnerability, but less is known regarding the cellular and synaptic mechanisms contributing to these behavioral sex differences. One factor thought to influence cue-induced seeking behavior following withdrawal is cocaine-induced changes in the spontaneous activity of pyramidal neurons in the basolateral amygdala (BLA). However, the mechanisms underlying these changes, including potential sex or estrous cycle effects, are unknown. Methods: Ex vivo whole-cell patch clamp electrophysiology was conducted to investigate the effects of cocaine exposure, sex, and estrous cycle fluctuations on two properties that can influence spontaneous activity of BLA pyramidal neurons: (1) frequency and amplitude of spontaneous excitatory postsynaptic currents (sEPSCs) and (2) intrinsic excitability. Recordings of BLA pyramidal neurons were conducted in adult male and female rats and across the estrous cycle following 2–4 weeks of withdrawal from extended-access cocaine self-administration (6 h/day for 10 days) or drug-naïve conditions. Results: In both sexes, cocaine exposure increased the frequency, but not amplitude, of sEPSCs and neuronal intrinsic excitability. Across the estrous cycle, sEPSC frequency and intrinsic excitability were significantly elevated only in cocaine-exposed females in the estrus stage of the cycle, a stage when cocaine-seeking behavior is known to be enhanced. Conclusions: Here, we identify potential mechanisms underlying cocaine-induced alterations in the spontaneous activity of BLA pyramidal neurons in both sexes along with changes in these properties across the estrous cycle.

CB1R chronic intermittent pharmacological activation facilitates amphetamine seeking and self-administration and changes in CB1R/CRFR1 expression in the amygdala and nucleus accumbens in rats

Patterns of drug ingestion may have a dissimilar impact on the brain, and therefore also the development of drug addiction. One pattern is binge intoxication that refers to the ingestion of a high amount of drug on a single occasion followed by an abstinence period of variable duration. In this study, our goal was to contrast the effect of continuous low amounts with intermittent higher amounts of Arachidonyl-chloro-ethylamide (ACEA), a CB1R agonist, on amphetamine seeking and ingestion, and describe the effects on the expression of CB1R and CRFR1 in the central nucleus of the amygdala (CeA) and in the nucleus accumbens shell (NAcS). Adult male Wistar rats were treated with a daily administration of vehicle or 20 μg of ACEA, or four days of vehicle followed by 100 μg of ACEA on the fifth day, for a total of 30 days. Upon completion of this treatment, the CB1R and CRFR1 expression in the CeA and NAcS was evaluated by immunofluorescence. Additional groups of rats were evaluated for their anxiety levels (elevated plus maze, EPM), amphetamine (AMPH) self-administration (ASA) and breakpoint (A-BP), as well as AMPH-induced conditioned place preference (A-CPP). Results indicated that ACEA induced changes in the CB1R and CRFR1 expression in both the NAcS and CeA. An increase in anxiety-like behavior, ASA, A-BP and A-CPP was also observed. Since the intermittent administration of 100 μg of ACEA induced the most evident changes in most of the parameters studied, we concluded that binge-like ingestion of drugs induces changes in the brain that may make the subject more vulnerable to developing drug addiction.

Administration of the glutamate-modulating drug, riluzole, after stress prevents its delayed effects on the amygdala in male rats.

Extracellular glutamate levels are elevated across brain regions immediately after stress. Despite sharing common features in their genesis, the patterns of stress-induced plasticity that eventually take shape are strikingly different between these brain areas. While stress causes structural and functional deficits in the hippocampus, it has the opposite effect on the amygdala. Riluzole, an FDA-approved drug known to modulate glutamate release and facilitate glutamate clearance, prevents stress-induced deficits in the hippocampus. But whether the same drug is also effective in countering the opposite effects of stress in the amygdala remains unexplored. We addressed this question by using a rat model wherein even a single 2-h acute immobilization stress causes a delayed expression of anxiety-like behavior, 10 days later, alongside stronger excitatory synaptic connectivity in the basolateral amygdala (BLA). This temporal profile-several days separating the acute stressor and its delayed impact-allowed us to test if these effects can be prevented by administering riluzole in drinking water after acute stress. Poststress riluzole not only prevented the delayed increase in anxiety-like behavior on the elevated plus maze but also blocked the increase in spine density on BLA neurons 10 days later. Further, stress-induced increase in the frequency of miniature excitatory postsynaptic currents recorded in BLA slices, 10 days later, was also blocked by the same poststress riluzole administration. Together, these findings underscore the importance of therapeutic strategies, aimed at glutamate uptake and modulation, in correcting the delayed behavioral, physiological, and morphological effects of stress on the amygdala.

The effect of prolonged emotional and pain stress on the expression of the <i>bdnf</i> gene in the brain of rats with contrast excitability of the nervous system

BACKGROUND: The neurotrophic factor BDNF performs important functions in synaptic plasticity and functional activity of neurons, involve in the stress response and the pathogenesis of post-stress disorders. The specificity of post-stress changes in the bdnf mRNA level due to genetically determined features of excitability of the nervous system has not been studied.
 AIM: To study the level of bdnf mRNA in the prefrontal cortex, hippocampus and amygdala of rats of two strains with contrasting excitability of the nervous system in normal condition and at different times after prolonged emotional and painful stress exposure (after 24 hours, 7, 24, 60 days).
 MATERIALS AND METHODS: The study was carried out on adult male rats of two strains with a different level of excitability of the nervous system (HT high threshold and LT low threshold of excitability). As a model of chronic stress, a long-term emotional and painful exposure according to Hecht was used. The bdnf mRNA level was determined using quantitative real-time PCR. Changes in the level of bdnf mRNA in the prefrontal cortex, hippocampus and amygdala of control and experimental groups of rats of two strains were studied at different time points (24 hours, 7, 24 days, 2 months) after prolonged emotional and painful stress exposure.
 RESULTS: It was found that in highly excitable LT rats, a decrease in the expression of the bdnf gene in the prefrontal cortex occurs 24 hours and persists up to 7 days after exposure, in the hippocampus 2 months after exposure. In rats of the low-excitable HT strain, the decrease in bdnf mRNA was not detected.
 CONCLUSIONS: In highly excitable LT rats, prolonged emotional and painful stress causes a decrease in the expression of the bdnf gene in the prefrontal cortex and hippocampus. In low-excitable rats of the HT strain, no significant decrease in the mRNA level of this neurotrophin was found in any of the studied brain regions. The possible association of this specificity of changes in the level of bdnf mRNA with a greater severity of post-stress anxiety-like behavior disorders in highly excitable rats compared with low-excitable ones is discussed.

The passive avoidance task ameliorate the toxic effects of bisphenol A on dopamine D1 receptor density in hippocampus, amygdala, and cerebellum of male rats.

Dopamine D1 receptor seems to play a role in mediating plasticity. Therefore, the present study aimed to investigate the effects of passive avoidance tasks postexposed to BPA on dopamine D1 receptor density in the hippocampus, amygdala, and cerebellum of male rats. Thirty-five male Sprague-Dawley rats weighing 220.300g, in standard light-dark 12 h light/12 h dark were used in the present study; water and food were ad libitum. Animals were divided into six groups. Administration of BPA 5 and 50 mg/kg/day were gavaged for 15 days. Learning and memory assessment were done by a shuttle box after 15 days of BPA administration. The density of the dopamine D1 receptor was investigated using an immunohistochemistry (IH) procedure. For determining the color difference in IH sections, Image Analyzer software was used. The data were analyzed by one-way ANOVA followed by Tukey's as a post hoc test. The data showed that BPA in both doses could significantly increase the density of dopamine D1 receptors in the hippocampus, amygdala, and cerebellum of male rats; learning in rats postexposed to BPA improves dopamine D1 receptor density significantly in three brain structures. According to the results, passive avoidance learning and memory can improve the density of dopamine D1 receptors in the hippocampus, amygdala, and cerebellum of male rats.

Neuronal and astrocytic protein degradation are critical for fear memory formation.

Strong evidence has implicated proteasome-mediated protein degradation in the memory consolidation process. However, due to the use of pharmacological approaches, the cell type specificity of this remains unknown. Here, we used neuron-specific and novel astrocyte-specific CRISPR-dCas9-KRAB-MECP2 plasmids to inhibit protein degradation in a cell type-specific manner in the amygdala of male rats. We found that while inhibition of neuronal, but not astrocytic, protein degradation impaired performance during the training session, both resulted in impaired contextual fear memory retention. Together, these data provide the first evidence of a cell type-specific role for protein degradation in the memory consolidation process.

Allopregnanolone-mediated GABAA-Rα4 function in amygdala and hippocampus of PMDD liver qi-invasion syndrome model rats.

Premenstrual dysphoric disorder (PMDD) is a common mental health challenge among women of reproductive age. Allopregnanolone (3α, 5α-THP; ALLO) mediated functional alterations of GABAA receptors (GABAA-R) are involved in PMDD pathogenesis, however, the specific mechanism remains unknown. Therefore, we investigated the role of ALLO mediated GABAA-Rα4 in the pathophysiology of PMDD. We determined whether the pathogenesis of PMDD is associated with ALLO mediated GABAA-Rα4 expression changes in different brain regions. Rat models of PMDD liver-qi invasion syndrome (PMDD-LIS) were established via the resident intruder paradigm. Behavioral changes of rats were assessed by aggressive behavior tests, EPM and OFT. The levels of progesterone and ALLO in serum as well as brain areas were determined by ELISA. Variations in GABAA-Rα4 levels in brain regions were assessed by immunofluorescence and RT-PCR. Medicated serum was used to interfere with rat hippocampal neurons, and changes in Cl- current were recorded through electrophysiology. Premenstrual anxiety and irritability of PMDD-LIS patients can be simulated in PMDD-LIS rat models. Exogenous ALLO significantly improved the anxiety behaviors of PMDD-LIS rats. Changes in ALLO among different brain regions varied. GABAA-Rα4 expressions were low in the amygdala and abnormally high in the hippocampus, however, ALLO alleviated these deviations. Whole-cell patch clamp recording technique showed a weaker Cl- current intensity of PMDD-LIS rats, reduced neuroinhibitory functions and increased Cl- current intensity in the ALLO group drug serum intervention and enhanced emotional inhibition function. We established that ALLO regulation of the GABAA-Rα4 subunit in the amygdala and hippocampus is involved in PMDD-LIS pathogenesis.

Hesperidin Exerts Anxiolytic-like Effects in Rats with Streptozotocin- Induced Diabetes via PKA/CREB Signaling.

The mechanisms underlying synaptic injury and anxiety-like behavioral changes caused by diabetes and the strategies to reverse these changes are not well understood. This study examined the neuroprotective effects of hesperidin on anxiety-like behaviors in diabetic rats and investigated the underlying mechanisms from the perspective of the PKA/CREB pathway. Rats with streptozotocin-induced diabetes were treated orally with hesperidin (50 and 150 mg/kg) for 10 weeks. The elevated plus maze (EPM), hole board test (HBT), and marbleburying test (MBT) were used to assess anxiety-like behaviors. We further examined the effects of hesperidin on the PKA/CREB pathway in vivo and in vitro. The results show that supplementation with hesperidin exerted anxiolytic effects on the diabetic rats, as evidenced by increased percentages of open arm entries and time spent in the open arms in the EPM; decreased numbers of hole visits in the HBT; decreased numbers of marbles buried; and increased expression of PKA, CREB, BDNF, and synaptic proteins in the amygdala and hippocampus of diabetic rats. Hesperidin was found to reverse the imbalance in the PKA/CREB/BDNF pathway. In vitro, we found that the PKA inhibitor H89 reversed the protective effects of hesperidin against cell injury and reversed the HG-induced expression of PKA, pCREB/CREB, and BDNF. Our results demonstrated that hesperidin could ameliorate the anxiety-like behaviors of diabetic rats and that activating the PKA/CREB/BDNF pathway contributed to the beneficial effects. This study may provide important insights into the mechanisms underlying anxiety-like behaviors in diabetes and identify new therapeutic targets for clinical treatment.

Efficacy of suspended moxibustion stimulating Shenshu (BL23) and Guanyuan (CV4) on the amygdala-HPA axis in rats with kidney-deficiency symptom pattern induced by hydrocortisone.

To investigated the effects of suspended moxibustion stimulating Shenshu (BL23) and Guanyuan (CV4) acupoints on the amygdala and HPA axis in our rat model and elucidated the possible molecular mechanisms of moxibustion on kidney- deficiency symptom pattern (KYDS). Sixty male Sprague Dawley rats were randomly divided into a control group ( 12) and an experimental group ( 48). Rats in the experimental group were given intramuscular injections of hydrocortisone to establish a KYDS model. The 48 rats successfully modeled were then randomly divided into a model group (model, 12), a carbenoxolone intraperitoneal injection group (CBX, 12), a moxibustion group (moxi, 12), and a moxi + CBX group ( 12). In the moxi, the Shenshu (BL23) and Guanyuan (CV 4) acupoints were treated with moxibustion for 14 d. After treatment, measures were taken of serum levels of corticosterone (CORT), adrenocorticotropic hormone (ACTH), and corticotropin-releasing hormone (CRH). The expression of mineralocorticoid receptors (MRs), glucocorticoid receptors (GRs), 11beta-hydroxysteroid dehydrogenase type 1 (11β-HSD1), CRH, and ACTH in the rats' amygdala, hypothalamus, or pituitary (as appropriate) was detected. Data were analyzed using one-way analysis of variance. Compared with those of the control group, the serum levels of CRH, ACTH, and CORT; the mRNA and protein expressions of MR, GR, and 11β-HSD1 in the amygdala; the mRNA and protein expressions of 11β-HSD1 in the hypothalamus; the CRH mRNA expression in the amygdala and hypothalamus; and the ACTH mRNA expression in the pituitary of the rats in the model group were all significantly decreased (0.05 or 0.01). After treatment with moxibustion, all the aforementioned observation indices except for 11β-HSD1 mRNA expression were ameliorated compared with those in the model group (0.05 or 0.01). Suspended moxibustion can effectively improve the serum levels of ACTH, CRH, and CORT and can up-regulate the mRNA and protein expressions of MR, GR, 11β-HSD1, CRH, and ACTH in the amygdala and hypothalamus of KYDS rats. This may be one of the molecular mechanisms with which moxibustion alleviates KYDS.

Impact of Mephedrone on Fear Memory in Adolescent Rats: Involvement of Matrix Metalloproteinase-9 (MMP-9) and N-Methyl-D-aspartate (NMDA) Receptor.

Treatment of Post-Traumatic Stress Disorder (PTSD) is complicated by the presence of drug use disorder comorbidity. Here, we examine whether conditioned fear (PTSD model) modifies the rewarding effect of mephedrone and if repeated mephedrone injections have impact on trauma-related behaviors (fear sensitization, extinction, and recall of the fear reaction). We also analyzed whether these trauma-induced changes were associated with exacerbation in metalloproteinase-9 (MMP-9) and the GluN2A and GluN2B subunits of N-methyl-D-aspartate (NMDA) glutamate receptor expression in such brain structures as the hippocampus and basolateral amygdala. Male adolescent rats underwent trauma exposure (1.5 mA footshock), followed 7 days later by a conditioned place preference training with mephedrone. Next, the post-conditioning test was performed. Fear sensitization, conditioned fear, anxiety-like behavior, extinction acquisition and relapse were then assessed to evaluate behavioral changes. MMP-9, GluN2A and GluN2B were subsequently measured. Trauma-exposed rats subjected to mephedrone treatment acquired a strong place preference and exhibited impairment in fear extinction and reinstatement. Mephedrone had no effect on trauma-induced MMP-9 level in the basolateral amygdala, but decreased it in the hippocampus. GluN2B expression was decreased in the hippocampus, but increased in the basolateral amygdala of mephedrone-treated stressed rats. These data suggest that the modification of the hippocampus and basolateral amygdala due to mephedrone use can induce fear memory impairment and drug seeking behavior in adolescent male rats.

Interleukin-1β and TNF-α are elevated in the amygdala of adult rats prenatally exposed to ethanol.

Affective disorders, including anxiety and depression, developed in adult offspring of the mothers who consumed alcohol during pregnancy could be associated with an imbalance in neuroimmune factors in the amygdala (corpus amygdaloideum) resulted in impaired emotional stimulus processing. The aim of this study was to compare the content of cytokines TNF-α, IL-1α, IL-1β, IL-10, and IL-17 in the amygdala of adult female rats exposed to alcohol in utero and control rats. Cytokine levels were evaluated using a multiplex immunoassay system; mRNA expression was investigated using a real-time reverse transcription-polymerase chain reaction (RT-qPCR) assay. Prenatal alcohol exposure led to the increase in the content of TNF-α and IL-1β without significant changes in the mRNA expression level. Our data suggest that ethanol exposure to the fetus during pregnancy can result in long-term alterations in the content of the key neuroinflammatory factors in the amygdala, which in turn can be a risk factor for affective disorders in the adulthood.

Acute Wheel-Running Increases Markers of Stress and Aversion-Related Signaling in the Basolateral Amygdala of Male Rats

Physical activity (PA) is a non-invasive, cost-effective means of reducing chronic disease. Most US citizens fail to meet PA guidelines, and individuals experiencing chronic stress are less likely to be physically active. To better understand the barriers to maintaining active lifestyles, we sought to determine the extent to which short- versus long-term PA increases stress- and aversion-related markers in wild-type (WT) and low voluntary running (LVR) rats, a unique genetic model of low physical activity motivation. Here, we tested the effects of 1 and 4 weeks of voluntary wheel-running on physiological, behavioral, and molecular measures of stress and Hypothalamic Pituitary Adrenal (HPA)-axis responsiveness (corticosterone levels, adrenal wet weights, and fecal boli counts). We further determined measures of aversion-related signaling (kappa opioid receptor, dynorphin, and corticotropin releasing hormone mRNA expression) in the basolateral amygdala (BLA), a brain region well characterized for its role in anxiety and aversion. Compared to sedentary values, 1, but not 4 weeks of voluntary wheel-running increased adrenal wet weights and plasma corticosterone levels, suggesting that HPA responsiveness normalizes following long-term PA. BLA mRNA expression of prodynorphin (Pdyn) was significantly elevated in WT and LVR rats following 1 week of wheel-running compared to sedentary levels, suggesting that aversion-related signaling is elevated following short- but not long-term wheel-running. In all, it appears that the stress effects of acute PA may increase molecular markers associated with aversion in the BLA, and that LVR rats may be more sensitive to these effects, providing a potential neural mechanism for their low PA motivation.

The changes of serotonin-modulating anticonsolidation protein and dihydropyrimidinase-related protein 2 in the amygdala and blood of depressive rats

Nowadays, depression is referred to psychiatric disease and is widely spread throughout the world. The pathogenesis of depression in humans is characterized by significant disturbances of serotonin turnover and its downregulation in brain structures. The objective of the present study was the definition of the levels of serotonin-modulating anticonsolidation protein (SMAP) and dihydropyrimidinase-related protein 2 (DRP2) in the brain amygdala, platelets, and to anti-SMAP natural autoantibodies in the depression Wistar rats of both sexes. A depression state in the rats was formed in the dominant model and its successful formation was confirmed in the forced swimming test by the decreased timeframe of active swimming. Through the application of an indirect ELISA test in the depressive male and female rats, a downregulation of SMAP and DRP2 in the amygdala, an upregulation of SMAP in the platelets of depressive male rats, a noticeable downregulation of DRP2 in the platelets of depressive female rats, and a sharp downregulation of anti-SMAP natural autoantibodies in the serum of depressive male rats were observed.

Prenatal Hypoxia-Induced Adverse Reaction to Mild Stress is Associated with Depressive-Like Changes in the Glucocorticoid System of Rats.

The effects of prenatal hypoxia on neurodevelopment are predominantly associated with impaired maternal glucocorticoid stimulation of the fetus, which is "imprinted" in altered sensitivity of glucocorticoid reception in brain structures of offspring and can affect brain plasticity during lifespan. This study aimed to investigate response of the brain glucocorticoid system to mild stress (MS) in adult rats that survived prenatal severe hypoxia (PSH) on embryonic days 14-16. In response to MS the control (but not PSH) rats demonstrate increased corticosterone levels, a decrease in exploratory activity and increased anxiety. In the raphe nuclei of adult PSH rats the expression of glucocorticoid receptors (GR) is increased without changes in serotonin levels in comparison with the control. MS induces a decrease in GR expression accompanied by up-regulation of tryptophan hydroxylase 2 (tph2) and down-regulation of monoamine oxidase A (maoa) transcription in the raphe nuclei of both control and PSH groups. PSH also causes significant deviations in GR expression and GR-dependent transcription in the hippocampus, the medial prefrontal cortex, but not in the amygdala of rats. However, in response to MS, PSH rats demonstrate mild changes in their activity, while in control animals the MS-induced activity of the glucocorticoid system in these brain structures is similar to intact PSH animals. Impaired activity of the glucocorticoid system in the extrahypothalamic brain structures of PSH rats is accompanied by increase in the hypothalamic corticotropin-releasing hormone (CRH) levels in comparison with the control regardless of MS. Synthesis of proopiomelanocortin (POMC) and release of adrenocorticotropic hormone (ACTH) into the blood are decreased in response to MS in the pituitary of control rats, which demonstrates a negative glucocorticoid feedback mechanism. Meanwhile, in the pituitary of PSH rats reduced POMC levels were found regardless of MS. Thus, prenatal hypoxia causes depression-like patterns in the brain glucocorticoid system with adverse reaction to mild stressors.

Long-lasting BDNF signaling alterations in the amygdala of adolescent female rats exposed to the activity-based anorexia model.

Introduction: Anorexia nervosa (AN) is a severe psychiatric disorder characterized by a pathological fear of gaining weight, excessive physical exercise, and emotional instability. Since the amygdala is a key region for emotion processing and BDNF has been shown to play a critical role in this process, we hypothesized that alteration in the amygdalar BDNF system might underline vulnerability traits typical of AN patients. Methods: To this end, adolescent female rats have been exposed to the Activity-Based Anorexia (ABA) protocol, characterized by the combination of caloric restriction and intense physical exercise. Results: The induction of the anorexic phenotype caused hyperactivity and body weight loss in ABA animals. These changes were paralleled by amygdalar hyperactivation, as measured by the up-regulation of cfos mRNA levels. In the acute phase of the pathology, we observed reduced Bdnf exon IX, exon IV, and exon VI gene expression, while mBDNF protein levels were enhanced, an increase that was, instead, uncoupled from its downstream signaling as the phosphorylation of TrkB, Akt, and S6 in ABA rats were reduced. Despite the body weight recovery observed 7 days later, the BDNF-mediated signaling was still downregulated at this time point. Discussion: Our findings indicate that the BDNF system is downregulated in the amygdala of adolescent female rats under these experimental conditions, which mimic the anorexic phenotype in humans, pointing to such dysregulation as a potential contributor to the altered emotional processing observed in AN patients. In addition, since the modulation of BDNF levels is observed in other psychiatric conditions, the persistent AN-induced changes of the BDNF system in the amygdala might contribute to explaining the onset of comorbid psychiatric disorders that persist in patients even beyond recovery from AN.

Inhibiting silence information regulator 2 and glutaminase in the amygdala can improve social behavior in autistic rats.

To investigate the underlying molecular mechanisms by which silence information regulator (SIRT) 2 and glutaminase (GLS) in the amygdala regulate social behaviors in autistic rats. Rat models of autism were established by maternal sodium valproic acid (VPA) exposure in wild-type rats and SIRT2-knockout ( SIRT2 -/-) rats. Glutamate (Glu) content, brain weight, and expression levels of SIRT2, GLS proteins and apoptosis-associated proteins in rat amygdala at different developmental stages were examined, and the social behaviors of VPA rats were assessed by a three-chamber test. Then, lentiviral overexpression or interference vectors of GLS were injected into the amygdala of VPA rats. Brain weight, Glu content and expression level of GLS protein were measured, and the social behaviors assessed. Brain weight, amygdala Glu content and the levels of SIRT2, GLS protein and pro-apoptotic protein caspase-3 in the amygdala were increased in VPA rats, while the level of anti-apoptotic protein Bcl-2 was decreased (all P<0.01). Compared with the wild-type rats, SIRT2 -/- rats displayed decreased expression of SIRT2 and GLS proteins in the amygdala, reduced Glu content, and improved social dysfunction (all P<0.01). Overexpression of GLS increased brain weight and Glu content, and aggravated social dysfunction in VPA rats (all P<0.01). Knockdown of GLS decreased brain weight and Glu content, and improved social dysfunction in VPA rats (all P<0.01). The glutamate circulatory system in the amygdala of VPA induced autistic rats is abnormal. This is associated with the upregulation of SIRT2 expression and its induced increase of GLS production; knocking out SIRT2 gene or inhibiting the expression of GLS is helpful in maintaining the balanced glutamate cycle and in improving the social behavior disorder of rats.

EphrinA4 mimetic peptide impairs fear conditioning memory reconsolidation in lateral amygdala

Fear memory may undergo a process after memory reactivation called reconsolidation. To examine the roles of ephrinA4 in fear memory reconsolidation an inhibitory ephrinA4 mimetic peptide (pep-ephrinA4), that targets the EphA binding site and inhibits EphA activation, was used. Pep-ephrinA4 was microinjected into the lateral amygdala (LA) of fear-conditioned rats 24 h after training and 30 min before tone CS memory retrieval. Memory retrieval was unaffected by pep-ephrinA4. However, the animals were impaired in fear memory tested 1 h or 24 h afterward when compared to controls. Fear-conditioned animals injected with pep-ephrinA4 into LA immediately after long-term memory retrieval were unaffected when tested 24 h afterward. Microinjection into LA of a peptide originated from an ephrinA4 site that does not interact with EphA did not affect fear memory reconsolidation. Rats that were administrated with pep-ephrinA4 systemically 24 h after fear conditioning and 30 min before CS memory retrieval were impaired in long-term fear conditioning memory tested 24 h afterward when compared to the control peptide. These results show that ephrinA4 binding sites are needed for long-term fear memory reconsolidation in LA and may serve as a target for the treatment of fear-related disorders by blocking reconsolidation.