Sex differences in hippocampal response to endocannabinoids after exposure to severe stress

Women are more vulnerable to stress‐related mental disorders than men and the naturally occurring fluctuation in estrogen that occur across the estrus cycle can dramatically influence the pathophysiology observed following traumatic events. It has been demonstrated that the endocannabinoid (eCB) system could represent a therapeutic target for the treatment of post‐traumatic stress disorder (PTSD) in males. The current study aimed to examine the effects of exposure to a traumatic event and acute enhancement of eCB signaling on hippocampal‐dependent learning and plasticity in male and female rats. Males and females were exposed to the single prolonged stress (SPS) model of PTSD (restraint, forced swim, and sedation) followed by acute administration of the fatty acid amide hydrolase (FAAH) inhibitor URB597 (0.3 mg/kg). Females were in diestrus during SPS exposure. SPS exposure impaired extinction and hippocampal plasticity tested a week later in males and females. Sex differences were observed in the effects of URB597 on hippocampal plasticity of SPS‐exposed rats. Also, URB597 normalized the SPS‐induced upregulation in CB1 receptor levels in the amygdala, prefrontal cortex (PFC), and hippocampus in males. In females, URB597 normalized the SPS‐induced up regulation in CB1 receptors in the amygdala and PFC, but not hippocampus. Our findings support the eCB system as a therapeutic target for the treatment of disorders associated to inefficient fear coping in males and females. There are differences in the hippocampal response of males and females to the enhancement of eCB signaling after intense stress suggesting sex differences in treatment efficacy. © 2016 Wiley Periodicals, Inc.     

创伤后应激障碍发生自杀的研究进展

随着近年来对创伤后应激障碍（PTSD）的关注越来越多,目前认为PTSD患者自杀率远远高于普通人群,因此,早期识别自杀并干预将具有重大的医学和社会意义。现从PTSD发生自杀的流行病学、影响因素、生物学机制及干预几个方面进行综述。     

Single prolonged stress: toward an animal model of posttraumatic stress disorder

Although selective serotonin reuptake inhibitors (SSRIs) are reported to be effective in decreasing posttraumatic stress disorder (PTSD) symptoms, a subgroup of PTSD patients remain chronically symptomatic and maintain conditioned fear responses to traumatic stimuli. In this context, the establishment of an appropriate animal model of PTSD is necessary to promote better understanding of the mechanisms of the disorder and to facilitate the development of more effective therapeutic alternatives to SSRIs. Although no single widely accepted animal model of PTSD has been established to date, the single prolonged stress (SPS) animal model has been partially validated as a model for PTSD. SPS rats mimic the pathophysiological abnormalities and behavioral characteristics of PTSD, such as enhanced anxiety‐like behavior and glucocorticoid negative feedback, and they exhibit the expected therapeutic response to paroxetine on enhanced fear memory. In addition, SPS rats exhibit enhanced freezing in response to contextual fear conditioning, and impaired extinction of fear memory, which is alleviated by D ‐cycloserine. The enhanced consolidation and impaired extinction of fear memory found in SPS rats suggests that this model has additional value because recent studies of PTSD indicate that memory abnormalities are a central feature. In this study, we summarize the behavioral and pathophysiological PTSD‐like symptoms in SPS, focusing on memory abnormalities, and evaluate the validity of SPS as an animal model of PTSD. Depression and Anxiety, 2009. © 2009 Wiley‐Liss, Inc.     

Alterations in the hippocampal glycinergic system in an animal model of posttraumatic stress disorder

Previous studies have demonstrated that rats subjected to single prolonged stress (SPS) exhibit posttraumatic stress disorder (PTSD)-like symptoms, such as enhanced contextual fear in response to trauma-related and trauma-unrelated events. Furthermore, we previously reported that upregulation of hippocampal glycine transporter 1 (GlyT-1) mRNA after context exposure could be the initial mechanism underlying impaired fear extinction in SPS rats. To clarify the involvement of the hippocampal glycinergic system in impaired fear extinction in SPS rats, we measured the time course of changes in the duration of freezing and the hippocampal levels of Gly-T1 mRNA using contextual fear conditioning (FC) and extinction training. We also used in vivo microdialysis to measure the concentration of extracellular glycine in the hippocampus during the time interval between FC and the first context exposure. SPS rats exhibited increased and sustained contextual fear responses. The enhanced contextual fear response in SPS rats was associated with a sustained increase in hippocampal levels of Gly-T1 mRNA after FC relative to sham rats, and by a decrease in the extracellular glycine concentration. GlyT-1 mRNA levels in rats that underwent repeated extinction training were significantly lower than in rats that did not undergo extinction training. These findings indicate that reduced activity of the hippocampal glycinergic system could be closely involved in impaired fear extinction in SPS rats, suggesting that activation of the glycinergic system by d-cycloserine or GlyT-1 inhibitors may ameliorate the impairment of fear extinction.     

Enhancement of acoustic prepulse inhibition by contextual fear conditioning in mice is maintained even after contextual fear extinction

Prepulse inhibition (PPI) of the acoustic startle response is one of the few and major paradigms for investigating sensorimotor gating systems in humans and rodents in a similar fashion. PPI deficits are observed not only in patients with schizophrenia, but also in patients with anxiety disorders. Previous studies have shown that PPI in rats can be enhanced by auditory fear conditioning. In this study, we evaluated the effects of contextual fear conditioning (FC) for six times a day and fear extinction (FE) for seven days on PPI in mice. C57BL/6J mice (male, 8–12 weeks) were divided into three groups; no-FC (control), FC and FC + FE. We measured PPI at the following three time points, (1) baseline before FC, (2) after FC, and (3) after FE. The results showed that PPI was increased after FC. Moreover, the enhanced PPI following FC was observed even after FE with decreased freezing behaviors. These results suggested contextual fear conditioning could enhance acoustic PPI, and that contextual fear extinction could decrease freezing behaviors, but not acoustic PPI.     

创伤后应激障碍合并酒精使用障碍的访谈与治疗

本文目的是通过报道病例诊疗全过程,呈现创伤后应激障碍(PTSD)合并酒精使用障碍的临床诊疗思路及治疗方案。咨客,男性,55岁。12岁时目睹母亲自杀的全过程,随后出现恐惧、孤独、失眠、回避谈论创伤相关话题、反复出现与创伤相关的梦境、易激惹、疼痛及酗酒等一系列情绪、认知、躯体及行为改变,并持续至今。社会功能明显受损,近1年和妻子离婚后症状加重而前来咨询。经过本次咨询,被诊断为PTSD合并酒精使用障碍。建议采用生物-心理-社会的综合干预方法,鼓励咨客进行规律运动,使用选择性5-羟色胺和去甲肾上腺素再摄取抑制剂(SNRI)及第二代抗精神病药物改善情绪、缓解疼痛;心理治疗方面,推荐延迟暴露疗法和认知调整;社会资源方面,在症状缓解后,鼓励咨客积极寻找工作,创造挽回其前妻的可能性。     

Time-dependent inhibition of hippocampal LTP in vitro following contextual fear conditioning in the rat

The effects of contextual fear‐learning on hippocampal synaptic excitability were investigated by means of high frequency tetanic stimulation (HFS) in rat brain slices (hippocampal CA1 region), prepared at different intervals (immediately, 24 h or 7 days) after a one‐trial contextual fear conditioning paradigm session. In the latter, rats that had previously received aversive electrical footshocks in the experimental apparatus exhibited freezing (the conditioned response) when placed again in the same apparatus (retrieval test). It was shown that contextual fear‐learning affects the hippocampal synaptic response. In fact, the HFS produced a decrease in the amplitude of short‐term (STP) and long‐term potentiation (LTP) when compared to control ‘naïve’ subject values. This decrease in STP amplitude could be observed only in slices prepared immediately after the training session. A decrease in the amplitude of long‐term but not short‐term potentiation was also observed at 24 h. At 7 days, no decreases in amplitude were observed. These modifications may be thought of as specifically associated with the learning process as they were not recorded in brain preparations from ‘shock‐only’ rats (i.e. those that received the same number of aversive stimuli of equal intensity as the conditioned group but with the shocks compressed temporally so that the shocked subjects could not associate nociceptive stimulation and surroundings – no conditioned freezing during retention testing). In ‘exploration’ preparations (brain slices from rats having only freely explored the experimental apparatus without receiving any adverse stimulation) a decrease in LTP amplitude was recorded only immediately after the training session, and STP was never modified. The synaptic response modifications do not appear to be due to presynaptic events, as they are not associated with paired‐pulse facilitation curve (PPF) modifications. The present results show that contextual fear conditioning and exploration of a novel environment (i) reduce the ability to induce synaptic plasticity; (ii) differentially influence STP and LTP and that (iii) the persistence of synaptic modifications depends on an animal's prior experience.     

Alteration of synaptic transmission in the hippocampal‐mPFC pathway during extinction trials of context‐dependent fear memory in juvenile rat stress models

The medial prefrontal cortex (mPFC) has been proposed to be essential for extinction of fear memory, but its neural mechanism has been poorly understood. The present study examined whether synaptic transmission in the hippocampal‐mPFC pathway is related to extinction of context‐dependent fear memory in freely moving rats using electrophysiological approaches combined with behavioral analysis. Population spike amplitude in the mPFC was decreased during the first extinction trial by exposure to contextual fear conditioning. This synaptic inhibition was reversed by repeated extinction trials, accompanied by decreases in fear‐related freezing behavior. These results suggest that alteration of synaptic transmission in the hippocampal‐mPFC pathway is associated with the extinction processes of context‐dependent fear memory. Further experiments were performed to elucidate whether early postnatal stress alters the synaptic response in the mPFC during extinction trials using a juvenile stress model, based on our previous findings that early postnatal stress affects the behavioral response to emotional stress. Adult rats that previously were exposed to five footshocks (FS) (shock intensity, 0.5 mA; intershock interval, 28 seconds; shock duration, 2 seconds) at postnatal day 21 to 25 (week 3; 3W‐FS) exhibited impaired reversal of both inhibitory synaptic transmission and freezing behavior induced by repeated extinction trials. The neuronal and behavioral deficits observed in the 3W‐FS group were prevented by pretreatment with the serotonin_1A receptor agonist tandospirone (1 mg/kg, i.p.). These results indicate the possiblity that aversive stress exposure during the third postnatal week impaired extinction processes of context‐dependent fear memory. The deficits in extinction observed in the 3W‐FS group might be attributable to dysfunction of hippocampal‐mPFC neural circuits involving 5‐HT_1A receptor mechanisms. Synapse 63:805–813, 2009. © 2009 Wiley‐Liss, Inc.     

Cotinine enhances the extinction of contextual fear memory and reduces anxiety after fear conditioning

Posttraumatic stress disorder (PTSD) is an anxiety disorder triggered by traumatic events. Symptoms include anxiety, depression and deficits in fear memory extinction (FE). PTSD patients show a higher prevalence of cigarette smoking than the general population. The present study investigated the effects of cotinine, a tobacco-derived compound, over anxiety and contextual fear memory after fear conditioning (FC) in mice, a model for inducing PTSD-like symptoms. Two-month-old C57BL/6J mice were separated into three experimental groups. These groups were used to investigate the effect of pretreatment with cotinine on contextual fear memory and posttreatment on extinction and stability or retrievability of the fear memory. Also, changes induced by cotinine on the expression of extracellular signal-regulated kinase (ERK)1/2 were assessed after extinction in the hippocampus. An increase in anxiety and corticosterone levels were found after fear conditioning. Cotinine did not affect corticosterone levels but enhanced the extinction of contextual fear, decreased anxiety and the stability and/or retrievability of contextual fear memory. Cotinine-treated mice showed higher levels of the active forms of ERK1/2 than vehicle-treated mice after FC. This evidence suggests that cotinine is a potential new pharmacological treatment to reduce symptoms in individuals with PTSD.     

Noradrenergic enhancement of reconsolidation in the amygdala impairs extinction of conditioned fear in rats--a possible mechanism for the persistence of traumatic memories in PTSD

Background: Posttraumatic stress disorder (PTSD) is associated with enhanced noradrenergic activity. Animal and human studies demonstrate that noradrenergic stimulation augments consolidation of fear learning. Retrieval of well‐established memories by presenting a learned fear cue triggers reconsolidation processes during which memories may be updated, weakened, or strengthened. We previously reported that noradrenergic blockade in the rat amygdala impairs reconsolidation of fear memories. Here we investigated the effects of noradrenergic enhancement on reconsolidation of learned fear. Methods: Using auditory fear conditioning in rats, we tested the effects of postretrieval intraamygdala infusion of the β‐adrenergic receptor agonist isoproterenol or the antagonist propranolol on conditioned fear in the amygdala. Results: A single intraamygdala infusion of isoproterenol following a retrieval of a well‐consolidated memory enhanced fear memory elicited by the learned fear stimulus and impaired extinction of this memory 48 hr later. Intraamygdala infusion of the β‐adrenergic receptor antagonist propranolol following a consecutive retrieval trial blocked the enhancing effects of isoproterenol on fear memory. Conclusions: Postretrieval β‐adrenergic stimulation in the amygdala enhances reconsolidation of fear memories, making them resistant to extinction. Noradrenergic augmentation during retrieval of fear memories may thus contribute to persistence and severity of traumatic memories. Reconsolidation may be a useful tool in understanding the pathology of PTSD and may thus help in developing new and in modifying existing treatments of traumatic memories. Depression and Anxiety 28:186–193, 2011. © 2011 Wiley‐Liss, Inc.     

单一连续应激对大鼠行为学和海马Bcl-2、Bax表达的影响

目的 检测单一连续应激(single prolonged stress,SPS)对大鼠行为学和海马神经细胞Bax、Bcl-2表达的影响.方法 将Wistar大鼠分为对照组和应激组.应激组给予SPS应激,采用旷场实验、拒俘反应实验、Morries水迷宫实验等观察大鼠情感行为改变,采用化学发光法测定血清皮质醇浓度,应用免疫组织化学方法检测海马神经元Bcl-2、Bax的表达.结果 对照组水迷宫实验逃避潜伏期为5.632s±1.065s,应激组为20.762s±3.236s(t=9.932,P＜0.01);对照组血清皮质醇浓度为1.25 μg/dl ±0.12μg/dl,应激组为0.58μg/dl±0.09μg/dl(t=7.340,P＜0.01).应激组海马Bcl-2、Bax表达升高,Bcl-2/Bax上调.结论 SPS应激能使大鼠表现出创伤后应激障碍行为,使海马神经细胞Bcl-2/Bax上凋,这可能与创伤后应激障碍发病机制有关.     

创伤后应激障碍大鼠海马中脑源性生长因子的表达变化

目的研究创伤后应激障碍(PTSD)大鼠血浆、海马CA_1区和齿状回神经元内脑源性生长因子(BDNF)的变化。方法用单一连续刺激(SPS)方法刺激大鼠产生PTSD模型,另进行强迫游泳(FS)刺激作为对照,ELISA检测不同时间(正常、刺激后2 h、12 h、1 d、7 d以及7 d后再次给予强迫游泳后2 h)大鼠血浆BDNF;取SPS后2 h、7 d、SPS+再次游泳后2 h和FS+再次游泳后2 h鼠脑组织,正常脑组织为对照,免疫组织化学技术观察大鼠海马神经元内BDNF的表达,以及采用荧光实时定量PCR法检测大鼠海马神经元内的BDNF-mRNA相对表达。结果大鼠经SPS刺激后2 h时血浆BDNF明显高于正常,7 d时与正常大鼠无明显差异,SPS+再游泳-2 h时明显高于各时间段及FS+再游泳后2 h;大鼠海马CA1区、齿状回内BDNF的表达以及海马内BDNF-mRNA相对表达也出现相似的改变。结论 PTSD大鼠血浆中BDNF浓度变化与海马内BDNF表达相关,BDNF的改变影响PTSD大鼠对创伤刺激的恐惧记忆形成、巩固和再摄取。     

Facilitation of fear extinction by the 5‐HT1A receptor agonist tandospirone: Possible involvement of dopaminergic modulation

Fear extinction‐based exposure treatment is an important component of psychotherapy for anxiety disorders such as posttraumatic stress disorder (PTSD). Recent studies have focused on pharmacological approaches combined with exposure therapy to augment extinction. In this study, we elucidated the therapeutic potential of the serotonin 1A (5‐HT_1A) receptor agonist tandospirone compared with the effects of the N‐methyl‐D ‐aspartate partial agonist D ‐cycloserine (DCS), focusing on the possible involvement of dopaminergic mechanisms. We used a rat model of juvenile stress [aversive footshock (FS)] exposure during the third postnatal week (3wFS). The 3wFS group exhibited extinction deficit reflected in sustained fear‐related behavior and synaptic dysfunction in the hippocampal CA1 field and medial prefrontal cortex (mPFC), which are responsible for extinction processes. Tandospirone administration (5 mg/kg, i.p.) before and after the extinction trials ameliorated both the behavioral deficit and synaptic dysfunction, i.e., synaptic efficacy in the CA1 field and mPFC associated with extinction training and retrieval, respectively, was potentiated in the tandospirone‐treated 3wFS group. Extracellular dopamine release in the mPFC was increased by extinction retrieval in the non‐FS control group. This facilitation was not observed in the 3wFS group; however, tandospirone treatment increased cortical dopamine levels after extinction retrieval. DCS (15 mg/kg, i.p.) also ameliorated the extinction deficit in the 3wFS group, but impaired extinction in the non‐FS control group. These results suggest that tandospirone has therapeutic potential for enhancing synaptic efficacy associated with extinction processes by involving dopaminergic mechanisms. Pharmacological agents that target cortical dopaminergic systems may provide new insights into the development of therapeutic treatments of anxiety disorders, including PTSD. © Synapse, 2013. © 2012 Wiley Periodicals, Inc.     

玉树地震后罹患创伤后应激障碍、焦虑症和抑郁症调查

目的:调查玉树地震后不同人群创伤后应激障碍(PTSD)、焦虑症、抑郁症的发生情况。方法:抽取震后灾区人群、其非灾区的亲属人群、灾区救援人群及非灾区人群为对象,每一人群进行随机分成两组,第1组每周进行1次集体心理干预;第2组每周进行3次集体心理干预。采用PTSD检查量表平民版(PCL-C)、焦虑自评量表(SAS)、抑郁自评量表(SDS)对不同人群在3个月、6个月进行问卷调查。结果:各人群在干预3个月和6个月均检出PTSD、焦虑症、抑郁症。各人群中第2组干预6个月时PTSD、焦虑症、抑郁症检出率明显低于干预3个月时(P均0.05)。结论:震后不同人群均存有PTSD、焦虑症、抑郁症发生;随着时间推移及积极干预可明显降低其发生。     

NMDA receptor antagonism in the basolateral but not central amygdala blocks the extinction of Pavlovian fear conditioning in rats

Glutamate receptors in the basolateral complex of the amygdala (BLA) are essential for the acquisition, expression and extinction of Pavlovian fear conditioning in rats. Recent work has revealed that glutamate receptors in the central nucleus of the amygdala (CEA) are also involved in the acquisition of conditional fear, but it is not known whether they play a role in fear extinction. Here we examine this issue by infusing glutamate receptor antagonists into the BLA or CEA prior to the extinction of fear to an auditory conditioned stimulus (CS) in rats. Infusion of the α‐amino‐3‐hydroxyl‐5‐methyl‐4‐isoxazole‐propionate (AMPA) receptor antagonist, 2,3‐dihydroxy‐6‐nitro‐7‐sulfamoyl‐benzo[f]quinoxaline‐2,3‐dione (NBQX), into either the CEA or BLA impaired the expression of conditioned freezing to the auditory CS, but did not impair the formation of a long‐term extinction memory to that CS. In contrast, infusion of the N‐methyl‐d ‐aspartate (NMDA) receptor antagonist, d,l ‐2‐amino‐5‐phosphonopentanoic acid (APV), into the amygdala, spared the expression of fear to the CS during extinction training, but impaired the acquisition of a long‐term extinction memory. Importantly, only APV infusions into the BLA impaired extinction memory. These results reveal that AMPA and NMDA receptors within the amygdala make dissociable contributions to the expression and extinction of conditioned fear, respectively. Moreover, they indicate that NMDA receptor‐dependent processes involved in extinction learning are localized to the BLA. Together with previous work, these results reveal that NMDA receptors in the CEA have a selective role acquisition of fear memory.     

Cholinergic neuronal lesions in the medial septum and vertical limb of the diagonal bands of Broca induce contextual fear memory generalization and impair acquisition of fear extinction

Previous research has shown that the ventral medial prefrontal cortex (vmPFC) and hippocampus (Hipp) are critical for extinction memory. Basal forebrain (BF) cholinergic input to the vmPFC and Hipp is critical for neural function in these substrates, which suggests BF cholinergic neurons may be critical for extinction memory. In order to test this hypothesis, we applied cholinergic lesions to different regions of the BF and observed the effects these lesions had on extinction memory. Complete BF cholinergic lesions induced contextual fear memory generalization, and this generalized fear was resistant to extinction. Animals with complete BF cholinergic lesions could not acquire cued fear extinction. Restricted cholinergic lesions in the medial septum and vertical diagonal bands of Broca (MS/vDBB) mimicked the effects that BF cholinergic lesions had on contextual fear memory generalization and acquisition of fear extinction. Cholinergic lesions in the horizontal diagonal band of Broca and nucleus basalis (hDBB/NBM) induced a small deficit in extinction of generalized contextual fear memory with no accompanying deficits in cued fear extinction. The results of this study reveal that MS/vDBB cholinergic neurons are critical for inhibition and extinction of generalized contextual fear memory, and via this process, may be critical for acquisition of cued fear extinction. Further studies delineating neural circuits and mechanisms through which MS/vDBB cholinergic neurons facilitate these emotional memory processes are needed. © 2015 Wiley Periodicals, Inc.