Brain Cannabinoid Signaling: Selectivity and Adaptation

69-大麻的精神活性成分四氢大麻酚（THC）通过激活特定CNS区域中的大麻素CB 1受体（CB 1 R）产生多种作用。THC因其精神活性而被广泛使用，这可能导致成瘾，并且是止吐，食欲刺激和抗痉挛药物的主要成分。长期使用THC会产生耐受性和依赖性，这可能会导致成瘾并限制大麻素的治疗用途。我们先前的研究揭示了THC给药后脑区域特异性CB 1 R脱敏和下调，并且该受体 神经适应与对体内效应的耐受性有关。拟议的研究将阐明特定的信号传导蛋白，J3-arrestin和6 FosB在急性和慢性CB 1 R信号传导的调节中的作用，使用废除或过表达的蛋白质的小鼠模型。将通过功能神经解剖学和生化药理学评估CBIR功能。平行的体内研究将确定改变的CB 1 R信号传导是否转化为行为和生理效应。具体目标1将在野生型和J3-抑制蛋白-2缺失小鼠中评估CB 1 R功能和体内效应，以检验J3-抑制蛋白调节急性和慢性CB 1 R信号传导、THC介导的体内效应（抗伤害感受、运动抑制、僵住症、体温过低）和耐受性的假设。初步数据显示，CB 1 R介导的G蛋白活性在 在13-抑制蛋白-2缺失小鼠中，慢性THC后的未处理的13-抑制蛋白-2缺失小鼠脊髓和CB 1 R脱敏减少。之前的研究表明，CBl R脱敏和下调在长期THC治疗后2周内恢复，因此缺乏稳定性来支撑与成瘾相关的持续变化。具体目标2假设，6 FosB，一个稳定的转录因子，参与慢性THC介导的影响。首先检查THC处理后6 FosB的区域表达。然后在纹状体中具有6 FosB的诱导性过表达或显性负失活的转基因小鼠中评估CB 1 R信号传导和THC的体内作用。初步研究表明，在慢性THC治疗后，6 FosB在丘脑核中增加，并且向6 FosB过表达的小鼠施用THC显示小鼠的耐受性减弱和CB 1 R脱敏。这些研究将阐明调节CB 1 R信号传导和神经适应的细胞和分子机制，并将这些作用转化为体内水平。该项目将确定特定信号蛋白在THC急性和长期CB 1 R激活作用中的作用，并与大麻素治疗和药物滥用有关。

69-tetrahydrocannabinol (THC), the psychoactive component of marijuana, produces a variety of effects by activating cannaibinoid CBl receptors (CB1R) in specific CNS regions. THC is widely used illicitly for its psychoactive properties, which can lead to addiction, and is the primary component of antiemetic, appetite stimulating and anti-spasticity medications. Chronic THC use produces tolerance and dependence, which might contribute to addiction and limit the therapeutic use of cannabinoids. Our previous studies revealed brain region-specific CB1R desensitization and downregulation after THC administration, and this receptor neuroadaptation was associated with tolerance to in vivo effects. The proposed studies will elucidate the role of specific signaling proteins, J3-arrestin and 6FosB in regulation of acute and chronic CB1R signaling using mouse models with abrogated or overexpressed proteins. CBl R function will be assessed by functional neuroanatomy and biochemical pharmacology. Parallel in vivo studies will determine whether altered CB1R signaling translates into behavioral and physiological effects. Specific Aim 1 will assess CB1R function and in vivo effects in wild-type and J3-arrestin-2 null mice to test the hypothesis that J3-arrestin regulates acute and chronic CB1R signaling, THC-mediated in vivo effects (antinociception, locomotor inhibition, catalepsy, hypothermia) and tolerance. Preliminary data show that CB1R-mediated G-protein activity is increased in na'ive J3-arrestin-2 null mouse spinal cord and CBl R desensitization following chronic THC is reduced in 13-arrestin-2 null mice. Previous studies showed that CBl R desensitization and down regulation recover by 2 weeks following chronic THC treatment and therefore lack the stability to underlie persistent changes associated with addiction. Specific Aim 2 hypothesizes that 6FosB, a stable transcription factor, is involved in chronic THC-mediated effects. The regional expression of 6FosB after THC treatment will first be examined. Then CB1R signaling and THC in vivo effects will be assessed in transgenic mice with inducible overexpression or dominant negative inactivation of 6FosB in the striatum. Preliminary studies show increased 6FosB in nucleus accumbens following chronic THC treatment, and administration of THC to 6FosB overexpressing mice revealed attenuated tolerance and CB1R desensitization in mice. These studies will elucidate cellular and molecular mechanisms that regulate CBl R signaling and neuroadaptation and translate these effects to the in vivo level. This project will determine roles of specific signaling proteins in the effects of acute and long-term CB1R activation by THC and are relevant to cannabinoid therapeutics and drug abuse.