CB2 Cannabinoid Receptors and Cocaine Action: Studies with Conditional Knock Outs

 描述(由申请人提供)：物质使用障碍(SUD)是一种毁灭性的精神病理学，没有FDA批准的药物治疗。CB2大麻素受体(CB2R)是药物干预的一个有希望的靶点。先前的研究表明，CB2R激动剂可减少可卡因的静脉自我给药(SA)，并抑制可卡因诱导的过度运动。由于CB2R激动剂几乎没有明显的行为效应，它们代表着治疗SUD的一条很有前途的新途径。不幸的是，他们的研究缺乏良好的实验工具，阻碍了进一步揭示CB2R信号治疗肥厚症的潜在可能性的进展。我们最近开发了一种转基因小鼠，其中CB2R表达与EGFP表达偶联，CB2R基因是“牙线状”的，因此可以有条件地缺失(CB2Rtg)。这种小鼠模型允许增强检测，并允许有条件地删除CB2R。暴露在可卡因中伴随着小胶质细胞的激活，小胶质细胞激活减少与寻求可卡因的减少有关。小胶质细胞表达CB2R，小胶质细胞激活后CB2R表达增加。小胶质细胞CB2R促进神经保护表型，包括抑制促炎细胞因子的释放。最近的研究还表明，CB2R在DA神经元中表达，并具有抑制DA释放的作用。我们将用这一提议中的实验验证两个假设：慢性可卡因暴露增加小胶质细胞CB2R的表达，CB2R激动剂通过小胶质细胞和DA神经元CB2R作用于减少可卡因SA。我们将通过两个目标来检验这些假设。在第一个目标中，我们将利用CB2Rtg的EGFP报告功能来确定可卡因对CB2R表达的影响。在第二个目标中，我们将利用CB2Rtg的丛生功能来特异性地删除小胶质细胞和DA神经元中的CB2R；然后应用消减方法来探索CB2R激动剂降低运动活性和可卡因SA的细胞作用部位。这些研究的成功完成将影响对可卡因对神经炎症和CB2R表达的影响的理解，以及CB2R通过澄清参与CB2R激动剂抑制作用的细胞类型在调节可卡因摄入量中的作用(S)。我们还将建立有条件的CB2R/-小鼠品系，以进一步研究Cb2R/-小鼠 这是大脑功能中非常有趣的受体。因此，这些研究将影响可卡因对大脑影响的机制研究，并为脑内CB2R的研究提供重要的新工具。

 DESCRIPTION (provided by applicant): Substance use disorder (SUD) is a devastating psychopathology that is without FDA-approved drug therapies. One promising target for pharmacological intervention are CB2 cannabinoid receptors (CB2R). Previous studies have demonstrated that CB2R agonists reduce intravenous self-administration (SA) of cocaine and inhibit cocaine-induced hyperlocomotion. Since CB2R agonists have very few overt behavioral effects, they represent a promising new avenue for the treatment of SUD. Unfortunately, a lack of good experimental tools for their study inhibits further progress in uncovering the potential fo manipulation of CB2R signaling to treat SUDs. We have recently developed a transgenic mouse in which CB2R expression is coupled to eGFP expression and the CB2R gene is "floxed", thus can be conditionally deleted (CB2Rtg). This mouse model allows for enhanced detection and enables conditional deletion of the CB2R. Exposure to cocaine is accompanied by microglial activation and reduced microglial activation is associated with reduced cocaine seeking. Microglia express CB2R, which is increased upon microglial activation. Microglial CB2R promote a neuroprotective phenotype, including suppressed release of pro-inflammatory cytokines. Recent studies also demonstrate that CB2R are expressed in DA neurons and function to inhibit DA release. We will test two hypotheses with the experiments in this proposal: that chronic cocaine exposure increases expression of microglial CB2R and that CB2R agonists act via microglial and DA neuronal CB2R to reduce cocaine SA. We will test these hypotheses with two aims. In aim one, we will use the eGFP reporter feature of the CB2Rtg to determine the effects of cocaine on CB2R expression. In aim two, we will use the floxed feature of the CB2Rtg to specifically delete CB2R from microglia and DA neurons; then apply a subtraction approach to explore the cellular site of action of CB2R agonists to reduce locomotor activity and cocaine SA. Successful completion of these studies will impact understanding of the effects of cocaine on neuroinflammation and CB2R expression; and the roles of CB2R in regulating cocaine intake through clarification of the cell types(s) that are involved in the inhibitory actions of CB2R agonists. We will also establish conditional CB2R-/- mouse lines for further studies of the role of this very interesting receptor in brain function. Thus, these studies will impact mechanistic examination of cocaine effects on the brain and provide important new tools for the study of the CB2R in the brain.