Revealing the Precise Role of Calretinin Neurons in Epilepsy: We Are on the Way / 神经科学通报·英文版

Epilepsy is a common neurological disorder characterized by hyperexcitability in the brain. Its pathogenesis is classically associated with an imbalance of excitatory and inhibitory neurons. Calretinin (CR) is one of the three major types of calcium-binding proteins present in inhibitory GABAergic neurons. The functions of CR and its role in neural excitability are still unknown. Recent data suggest that CR neurons have diverse neurotransmitters, morphologies, distributions, and functions in different brain regions across various species. Notably, CR neurons in the hippocampus, amygdala, neocortex, and thalamus are extremely susceptible to excitotoxicity in the epileptic brain, but the causal relationship is unknown. In this review, we focus on the heterogeneous functions of CR neurons in different brain regions and their relationship with neural excitability and epilepsy. Importantly, we provide perspectives on future investigations of the role of CR neurons in epilepsy.

Inhibiting silence information regulator 2 and glutaminase in the amygdala can improve social behavior in autistic rats / 浙江大学学报·医学版

OBJECTIVE@#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.@*METHODS@#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.@*RESULTS@#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).@*CONCLUSIONS@#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.

Effects of Chronic Restraint Stress on Apoptosis of Amygdala Cells in Rats / 法医学杂志

OBJECTIVES@#To explore the damage effects of chronic restraint stress (CRS) on amygdala cells through the rat CRS model.@*METHODS@#The rat CRS model was established, and the changes in body weight and adrenal mass in control group and CRS group were monitored at 1 d, 7 d, 14 d and 21 d. The behavior changes were evaluated by the percentage of retention time of open arms and open arm entries using the elevated plus maze (EPM). ELISA was used to detect the concentrations of rat's corticotropin releasing hormone (CRH), adrenocorticotropic hormone (ACTH) and cortisol. The changes of expression of glucocorticoid receptor (GR) and glial fibrillary acidic protein (GFAP) in amygdala were determined by immunohistochemistry and Western blotting. Ultrastructure changes of glial cell were observed by transmission electron microscopy. The apoptosis rate of amygdala was measured by flow cytometry.@*RESULTS@#Compared with the control group at the same time points, body weight of CRS 1 d, 7 d, 14 d and 21 d groups increased slowly, but adrenal mass increased significantly; the serum level of CRH, cortisol and ACTH increased significantly at 7 d, 14 d and 21 d respectively; the expression of GR in amygdala was increased while that of GFAP was decreased; EPM test suggested that the percentage of retention time of open arms and open arm entries decreased significantly after 14 d. The CRS group showed different degrees of glial cell damage in amygdala, and the apoptosis rate of glial cell was significantly increased in 21 d group.@*CONCLUSIONS@#This study successfully established a CRS model in rats, and anxiety-like behavioral changes in model rats may be caused by apoptosis of amygdala astrocytes.

Temporomandibular inflammation mobilizes parvalbumin and FosB/deltaFosB neurons of amygdala and dorsal raphe

Pathophysiological mechanisms involved in orofacial pain and their relationship with emotional disorders have emerged as an important research area for multidisciplinary studies. In particular, temporomandibular disorders (TMD) have been evaluated clinically from both physiological and psychological perspectives. We hypothesized that an altered neuronal activity occurs in the amygdala and the dorsal raphe nucleus (DR), encephalic regions involved in the modulation of painful and emotional information. Adult male Wistar rats were used in an experimental complete Freund's adjuvant (CFA)-induced temporomandibular joint (TMJ) inflammation model. CFA was applied for 1 or 10 days, and the animals were euthanized for brain samples dissection for FosB/ΔFosB and parvalbumin (PV) immunostaining. Our results were consistent in showing that the amygdala and DR were activated in the persistent inflammatory phase (10 days) and that the expression of PV+ interneurons in the amygdala was decreased. In contrast, in the DR, the expression of PV+ interneurons was increased in persistent states of CFA-induced TMJ inflammation. Moreover, at 10 days of inflammation, there was an increased co-localization of PV+ and FosB/ΔFosB+ neurons in the basolateral and central nucleus of the amygdala. Different nuclei of the amygdala, as well as portions of the DR, were activated in the persistent phase (10 days) of TMJ inflammation. In conclusion, altered activity of the amygdala and DR was detected during persistent inflammatory nociception in the temporomandibular joint. These regions may be essential for both sensory and affective dimensions of orofacial pain.

Effect of Heroin on DLG4 Expression in Hippocampus, Amygdala and Frontal Cortex of Rats / 法医学杂志

OBJECTIVE@#To observe the expression of discs large homolog 4 (DLG4) protein in hippocampus, amygdala and frontal cortex of rats and evaluate postsynaptic density in heroin dependence.@*METHODS@#The rat heroin dependent model was established by increasing intraperitoneal injection of heroin. DLG4 proteins in hippocampus, amygdala and frontal cortex of heroin dependent 9, 18, 36 days rats were detected with immunohistochemical staining and compared with that in the control group.@*RESULTS@#DLG4 proteins in hippocampus, amygdala and frontal cortex were gradually reduced with extension of heroin dependent time.@*CONCLUSION@#Heroin dependence can affect postsynaptic density of hippocampus, amygdala and frontal cortex. The changes become more apparent with extension of heroin dependence time.

Ketamine alters behavior and decreases BDNF levels in the rat brain as a function of time after drug administration

Objective: To evaluate behavioral changes and brain-derived neurotrophic factor (BDNF) levels in rats subjected to ketamine administration (25 mg/kg) for 7 days. Method: Behavioral evaluation was undertaken at 1 and 6 hours after the last injection. Results: We observed hyperlocomotion 1 hour after the last injection and a decrease in locomotion after 6 hours. Immobility time was decreased and climbing time was increased 6 hours after the last injection. BDNF levels were decreased in the prefrontal cortex and amygdala when rats were killed 6 hours after the last injection, compared to the saline group and to rats killed 1 hour after the last injection. BDNF levels in the striatum were decreased in rats killed 6 hours after the last ketamine injection, and BDNF levels in the hippocampus were decreased in the groups that were killed 1 and 6 hours after the last injection. Conclusion: These results suggest that the effects of ketamine on behavior and BDNF levels are related to the time at which they were evaluated after administration of the drug. .

Induction of Zenk protein expression within the nucleus taeniae of the amygdala of pigeons following tone and shock stimulation

In this study, we evaluated the expression of the Zenk protein within the nucleus taeniae of the pigeon’s amygdala (TnA) after training in a classical aversive conditioning, in order to improve our understanding of its functional role in birds. Thirty-two 18-month-old adult male pigeons (Columba livia), weighing on average 350 g, were trained under different conditions: with tone-shock associations (experimental group; EG); with shock-alone presentations (shock group; SG); with tone-alone presentations (tone group; TG); with exposure to the training chamber without stimulation (context group; CG), and with daily handling (naive group; NG). The number of immunoreactive nuclei was counted in the whole TnA region and is reported as density of Zenk-positive nuclei. This density of Zenk-positive cells in the TnA was significantly greater for the EG, SG and TG than for the CG and NG (P < 0.05). The data indicate an expression of Zenk in the TnA that was driven by experience, supporting the role of this brain area as a critical element for neural processing of aversive stimuli as well as meaningful novel stimuli.

The Expression of Corticotropin-Releasing Factor in the Central Nucleus of the Amygdala, Induced by Colorectal Distension, is Attenuated by General Anesthesia

Corticotrophin-releasing factor (CRF), a key regulator of the hypothalamic-pituitary axis, is expressed in the central nucleus of the amygdala (CeA) and its expression is upregulated in stress-related disorders. We investigated here the effect of noxious colorectal distension (CRD) on the expression of CRF in the CeA of conscious and unconscious rats. Adult male rats with or without general anesthesia were exposed to visceral pain induced by CRD for 5 min; this procedure was repeated 3 times with 1 min resting after each distension. The rats were sacrificed and sections of the CeA were immunostained for CRF as an indicator for anxiety response, and for phosphorylated extracellular signal-regulated kinase (p-ERK) as a marker for pain-specific activation of neurons; sections of lumbosacral spinal cord were immunostained for c-Fos as a marker for activation of spinal neurons. CRD elicited a significant increase in the expression of CRF and p-ERK in the CeA and of c-Fos in the spinal cord. General anesthesia attenuated the increase in CRF and p-ERK in the CeA, but did not affect the expression of spinal c-Fos. These results suggest that conscious recognition of pain at higher brain centers is an important determinant of CRF expression in the CeA.

Changes in the biogenic amine content of the prefrontal cortex, amygdala, dorsal hippocampus, and nucleus accumbens of rats submitted to single and repeated sessions of the elevated plus-maze test

It has been demonstrated that exposure to a variety of stressful experiences enhances fearful reactions when behavior is tested in current animal models of anxiety. Until now, no study has examined the neurochemical changes during the test and retest sessions of rats submitted to the elevated plus maze (EPM). The present study uses a new approach (HPLC) by looking at the changes in dopamine and serotonin levels in the prefrontal cortex, amygdala, dorsal hippocampus, and nucleus accumbens in animals upon single or double exposure to the EPM (one-trial tolerance). The study involved two experiments: i) saline or midazolam (0.5 mg/kg) before the first trial, and ii) saline or midazolam before the second trial. For the biochemical analysis a control group injected with saline and not tested in the EPM was included. Stressful stimuli in the EPM were able to elicit one-trial tolerance to midazolam on re-exposure (61.01 percent). Significant decreases in serotonin contents occurred in the prefrontal cortex (38.74 percent), amygdala (78.96 percent), dorsal hippocampus (70.33 percent), and nucleus accumbens (73.58 percent) of the animals tested in the EPM (P < 0.05 in all cases in relation to controls not exposed to the EPM). A significant decrease in dopamine content was also observed in the amygdala (54.74 percent, P < 0.05). These changes were maintained across trials. There was no change in the turnover rates of these monoamines. We suggest that exposure to the EPM causes reduced monoaminergic neurotransmission activity in limbic structures, which appears to underlie the "one-trial tolerance" phenomenon.

Noise induced nocturnal cortisol secretion and tolerable overhead flights.

Mainly dependent on level and dynamic increase sound produces over-shooting excitations which activate subcortical processing centers (e.g. the amygdala, functioning as fear conditioning center) besides cortical areas (e. g. arousing annoyance, awakenings) as well. In addition there exist very close central nervous connections between subcortical parts of the auditory system (e.g. amygdala) showing typical plasticity effects (sensitization) and the hypothalmic-pituitary-adrenal (HPA)-axis. Using that causal chain noise induce cortisol excretion even below the awakening threshold. Thus repeated noise events (e.g. overflights during night time) may lead to accumulation of the cortisol level in blood. This can happen because its time-constant of exponential decrease is about 50 to 10 times larger than that one for adrenaline and noradrenaline. This fact and the unusual large permeability of cortisol through the cell membranes opens a wide field of connections between stress-dependent cortisol production and the disturbance of a large number of other endocrine processes, especially as a result of long-term stress activation by environmental influences such as environmental noise. Based upon a physiological model calculating the cortisol accumulation starting at a nightly threshold of physiological over-proportional reactions around Lmax = 53 dB(A) the number of tolerable noise events (over-flights in a nightly time range) can be estimated for given indoor peak sound pressure levels, keeping the cortisol increase within the normal range. Examples of results for 8 hours in the night are for instance number and level combinations (NAL-values) of 13 events with 53 dB(A) indoor peak level or 6 events with 70 dB(A) indoor peak level respectively.

In Vivo Microdialysis Measures of Extracellular Norepinephrine in the Rat Amygdala during Sleep-wakefulness

Norepinephrine (NE)-containing locus ceruleus (LC) has been known to participate in the regulation of the sleep-wake cycle according to the differential firing rate. The aim of this study was to know the change of extracellular NE level in the rat amygdala, which are reciprocally connected with LC, during sleep-wake-fulness. Extracellular NE levels in the rat amygdala were inrestigated during different stages of the sleep-waking cycle using in vivo microdialysis and polygraphic recording. Dialysates were collected every 5 min and correlated with the results of polygraphic recording. The content of NE was measured by high-performance liquid chromatography with electrochemical detection. NE level was the highest in active waking (AW) and, when compared to AW, NE level was progressively lower in quiet waking (QW; 86%), quiet sleep (QS; 72%), and active sleep (AS or REM sleep; 61%). This result suggests that the rat amygdala also participates in the regulation of the sleep-wake cycle according to the differential NE release.

D-Fenfluramine selectively releases 5-HT from dorsal raphe terminals

The aim of this study was to investigate whether D-fenfluramine (FEN) releases 5-hydroxytryptamine (5-HT) selectively from dorsal raphe (DR) terminais. Male Wistar rats, 180-200 g, were implanted with microdialysis probes in the amygdala (Am; N = 5) and dorsal hippocampus (DH; N = 6) and 5-HT levels were measured by electrochemical detection. Under basal conditions, 5-HT levels were approximately 50 and 230 fmol per 30 min sample, in the Am and DH, respectively. FEN (1O mg/kg, ip) produced a 3-4-fold increase in 5HT relesse in the Am, but not in the DH. Since the Am is mainly innervated by DR fibers while the DH receives 5-HT input chiefly from the median raphe (MR), the present results support the view that FEN selectively releases 5-HT from DR terminals.