Brain Cannabinoid Signaling: Selectivity and Adaptation

69-四氢大麻酚(THC)是大麻的精神活性成分，通过激活中枢神经系统特定区域的大麻素CBL受体(CB1R)而产生多种效应。THC因其精神活性而被广泛使用，可导致成瘾，是止吐、刺激食欲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类药物的治疗性使用。我们先前的研究表明，THC给药后，脑区特异性CB1R脱敏和下调，该受体 神经适应与对体内效应的耐受性有关。建议的研究将阐明特定的信号蛋白，J3-arrestin和6FosB在调节急慢性CB1R信号转导中的作用，通过取消或过度表达蛋白的小鼠模型。CBL-R功能将通过功能神经解剖学和生化药理学进行评估。平行的体内研究将确定CB1R信号的改变是否会转化为行为和生理影响。特定目的1将评估野生型和J3-arrestin-2基因缺失小鼠的CB1R功能和体内效应，以检验J3-arrestin调节急性和慢性CB1R信号、THC介导的体内效应(抗伤害性感觉、运动抑制、嗜睡、低温)和耐受的假设。初步数据显示，CB1R介导的G蛋白活性在 初级J3-arrestin-2缺失小鼠脊髓和CBL R脱敏反应在慢性THC后在13-arrestin-2缺失小鼠中减少。以前的研究表明，慢性THC治疗后2周，CBL R脱敏和下调恢复，因此缺乏稳定性来支持与成瘾相关的持续性变化。特异性目标2假设6FosB是一种稳定的转录因子，参与了THC介导的慢性效应。首先检测6FosB在THC治疗后的区域表达。然后，将在纹状体可诱导过表达或显性负失活6FosB的转基因小鼠中评估CB1R信号和THC的体内效应。初步研究表明，慢性THC治疗后，伏隔核内6FosB表达增加，THC对6FosB高表达小鼠的耐受性减弱，CB1R脱敏。这些研究将阐明调节CBL-R信号和神经适应的细胞和分子机制，并将这些影响转化为体内水平。该项目将确定特定信号蛋白在THC急性和长期激活CB1R的影响中的作用，并与大麻类药物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.