Glucocorticoid-endocannabinoid interactions in the amygdala

描述（由申请人提供）：创伤后应激障碍（PTSD）是由创伤性生活事件引发的，其特征是以情境诱发的闪回和反复噩梦的形式反复检索创伤记忆。杏仁核是一个重要的大脑结构，参与情感记忆的形成和消失。糖皮质激素，作为一般应激反应的一部分分泌的类固醇激素，以及内源性大麻素，与大脑中CB1受体结合的脂质分子，已被证明对恐惧条件反射的巩固和消除很重要。糖皮质激素和内源性大麻素都通过基底外侧杏仁核复合体（BLA）的作用增强恐惧记忆的形成和消除。患有创伤后应激障碍的患者通常表现出低循环水平的皮质类固醇，特别是在皮质醇昼夜分泌节奏的最低点，皮质类固醇治疗可以改善创伤后应激障碍症状的主观测量。最近的一项研究表明，糖皮质激素对条件恐惧消退的促进作用依赖于BLA中CB1受体的激活，将BLA中糖皮质激素和内源性大麻素在条件恐惧消退中的作用联系起来。当前的研究旨在确定糖皮质激素和内源性大麻素对BLA恐惧调节作用的细胞机制。我们将验证糖皮质激素触发BLA GABA突触内源性大麻素合成和逆行释放的假设，从而抑制BLA神经元的突触抑制性输入。该提案的具体目的是：1)使用液相色谱-质谱法对糖皮质激素诱导的BLA和CeA中内源性大麻素合成的快速增加进行生化测试；2)利用全细胞膜片钳记录急性离体杏仁核切片，从电生理上确定糖皮质激素是否通过激活膜受体和内源性大麻素逆行释放来诱导GABA突触输入到BLA神经元的快速抑制。糖皮质激素、矿化皮质激素和大麻素受体的药理学和遗传学操作以及细胞内信号通路将被用来表征糖皮质激素和内源性大麻素在BLA中的新型分子相互作用。BLA中的内源性大麻素和糖皮质激素在恐惧条件反射的巩固和消退中的重要性，以及恐惧条件反射与PTSD记忆加工的相关性，表明本研究的结果将为PTSD等压力相关疾病的药物治疗提供重要的见解和可能的目标。

DESCRIPTION (provided by applicant): Post-traumatic stress disorder (PTSD) is triggered by a traumatic life event and is characterized by the recurrent retrieval of the traumatic memory in the form of context-induced flashbacks and recurrent nightmares. The amygdala is a critical brain structure involved in both the formation and the extinction of emotional memories. Glucocorticoids, steroid hormones secreted as part of the general stress response, and endocannabinoids, lipid molecules that bind to CB1 receptors in the brain, have been shown to be important for the consolidation and extinction of fear conditioning. Both glucocorticoids and endocannabinoids enhance fear memory formation and extinction via actions within the basolateral amygdaloid complex (BLA). Patients suffering from PTSD typically show low circulating levels of corticosteroids, particularly at the nadir of the diurnal cortisol secretory rhythm, and corticosteroid treatment causes improvement in subjective measures of PTSD symptoms. A recent study showed that the glucocorticoid facilitation of conditioned fear extinction is dependent on CB1 receptor activation in the BLA, linking the actions of glucocorticoids and endocannabinoids in the BLA in conditioned fear extinction. The current study is designed to determine the cellular mechanisms that link glucocorticoid and endocannabinoid effects on fear conditioning in the BLA. We will test the hypothesis that glucocorticoids trigger endocannabinoid synthesis and retrograde release at GABA synapses in the BLA, leading to the suppression of synaptic inhibitory input to BLA neurons. The specific aims of the proposal are: 1) to test biochemically for a rapid glucocorticoid-induced increase in endocannabinoid synthesis in the BLA and CeA using a liquid chromatography-mass spectrometry approach; and 2) to determine electrophysiologically whether glucocorticoids induce a rapid suppression of GABA synaptic inputs to BLA neurons via activation of a membrane receptor and the retrograde release of endocannabinoids using whole-cell patch clamp recordings in acute in vitro slices of amygdala. Pharmacological and genetic manipulations of glucocorticoid, mineralocorticoid and cannabinoid receptors and intracellular signaling pathways will be employed to characterize the novel molecular interactions between glucocorticoids and endocannabinoids in the BLA. The importance of endocannabinoids and glucocorticoids in the BLA in the consolidation and extinction of fear conditioning, and the relevance of fear conditioning to memory processing in PTSD, suggests that the outcome of this study will provide important insight into, and possible targets for, pharmacological treatment of stress-related disorders such as PTSD. PUBLIC HEALTH RELEVANCE: The proposed research on glucocorticoid-endocannabinoid interactions in the amygdala will provide critical insight into the basic biological mechanisms responsible for emotional memory formation and retention/extinction. The better understanding of emotional memory mechanisms gained from these studies will enhance our ability and improve the tools available to address increasingly prevalent and devastating mental illnesses brought on by stress and trauma, including posttraumatic stress disorder, anxiety disorders and phobias. The link between corticosteroids and endogenous cannabinoids is relevant not only to the basic biology of emotional memory formation, but also to the interaction between illicit drug use and anxiety disorders, as increased drug abuse in certain emotionally disturbed populations may be the result of compensation for a deficit in endogenous psychoactive chemicals involved in the generation of positive emotions.