Glucocorticoid-endocannabinoid interactions in the amygdala

描述(申请人提供)：创伤后应激障碍(PTSD)是由创伤性生活事件触发的，其特征是以情境诱导的闪回和反复出现的噩梦的形式重现创伤性记忆。杏仁核是一个关键的大脑结构，参与情绪记忆的形成和消亡。糖皮质激素，作为一般应激反应的一部分而分泌的类固醇激素，以及内源性大麻素，是与大脑中CB1受体结合的脂分子，已被证明对巩固和消除恐惧条件反射非常重要。糖皮质激素和内源性大麻素都通过在杏仁基底外侧复合体(BLA)内的作用来增强恐惧记忆的形成和消退。患有创伤后应激障碍的患者通常表现出低水平的皮质类固醇激素，特别是在皮质醇分泌节律的最低点，皮质类固醇治疗可以改善创伤后应激障碍症状的主观指标。最近的一项研究表明，糖皮质激素对条件性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性恐惧消退中的作用联系起来。目前的研究旨在确定BLA中糖皮质激素和内源性大麻素对恐惧条件反射的影响的细胞机制。我们将验证糖皮质激素触发内源性大麻素的合成和BLA中GABA突触的逆行释放，导致对BLA神经元的突触抑制输入的假设。该建议的具体目的是：1)使用液-质联用的方法，以生化方法测试糖皮质激素诱导的BLA和CEA内源性大麻素合成的快速增加；以及2)使用全细胞膜片钳记录，在急性体外杏仁核脑片上，确定糖皮质激素是否通过激活膜受体和逆行释放内源性大麻素，诱导快速抑制GABA突触输入到BLA神经元。糖皮质激素、盐皮质激素和大麻素受体的药理和遗传操作以及细胞内信号通路将被用来表征BLA中糖皮质激素和内源性大麻素之间的新的分子相互作用。BLA中内源性大麻素和糖皮质激素在恐惧条件作用的巩固和消退中的重要性，以及恐惧条件作用与创伤后应激障碍记忆处理的相关性，表明这项研究的结果将为创伤后应激相关疾病(如创伤后应激障碍)的药物治疗提供重要的洞察和可能的靶点。 公共卫生相关性：拟议中的杏仁核内糖皮质激素-内源性大麻激素相互作用的研究将为情绪记忆形成和保持/消亡的基本生物学机制提供关键的见解。从这些研究中获得的对情绪记忆机制的更好理解将增强我们的能力，并改进可用的工具，以应对由压力和创伤带来的日益普遍和破坏性的精神疾病，包括创伤后应激障碍、焦虑症和恐惧症。皮质类固醇和内源性大麻素之间的联系不仅与情绪记忆形成的基本生物学有关，而且与非法药物使用和焦虑症之间的相互作用有关，因为某些情绪障碍人群中药物滥用的增加可能是对参与产生积极情绪的内源性精神活性化学物质不足的补偿。

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.