Amygdala Modulation of Adolescent Alcohol Effects on Pain

摘要 青少年时期的酒精会在大脑中产生永久性的适应不良变化。青少年饮酒者 据报道，成年后疼痛障碍的患病率更高，功能磁共振成像显示 与不饮酒的人相比，杏仁核的激活更大。杏仁核，更具体地说是中央核 杏仁核(CEA)是疼痛相关脑谷氨酸传递过程中处理疼痛的关键脑区 地区。CEA对酒精很敏感，但根据接触时间的不同，结果会有所不同。 在成年啮齿动物模型中，慢性酒精通过上调N-甲基-D-天冬氨酸(NMDAR)增加CEA活性 亚单位和AMPAR介导的兴奋性传递导致疼痛处理的增加。这些影响是 暂时性的，因为NMDAR亚单位表达和谷氨酸传递的变化在1-2周内恢复正常 在暴露之后。在青少年酒精暴露模型中，NMDAR亚单位和谷氨酸增加 延长的杏仁核中的信号一直持续到成年期，这表明青少年酒精的影响更大 坚持不懈。黑素皮质素系统和神经特异性黑素皮质素4受体(MC4R)高度表达 并调节谷氨酸能传递。MC4R突触后增加AMPAR，调制 NMDAR功能，并增加其他疼痛相关区域的谷氨酸信号。黑素皮质素在脑内的信号转导 杏仁核调节疼痛相关行为，CEA内MC4R拮抗逆转酒精诱导 成年大鼠的痛觉过敏。成人饮酒会降低MC4R的表达，但青少年饮酒会降低MC4R的表达 成年期增加MC4R的表达。黑素皮质素系统如何调节谷氨酸在脑内的传递 CEA，青少年酒精对CEA谷氨酸和黑素皮质素系统的纵向影响，以及如何 黑素皮质素系统对疼痛的纵向调节作用尚未得到解决。使用老鼠模型， 我们将测试青少年酒精暴露对CEA中黑素皮质素和谷氨酸能信号的影响， 慢性MC4R拮抗作用在此期间对细胞效应的影响，我们将测试MC4R拮抗作用 在成年期对青少年间歇性乙醇(AIE)蒸气模型引起的痛敏进行研究。男性和 雌性Wistar大鼠将在出生后28天至56天期间接受酒精蒸气，其中一组接受 在此期间，慢性MC4R通过脑室内的微泵拮抗。我们将使用西方印迹 AIE(PND)后急性检测AMPAR和NMDAR亚基及黑素皮质素系统蛋白表达 56)和成年期(PND 86)。我们将使用切片电生理学来测量谷氨酸能传递 青春期和成年期CEA的表达，以及MC4R药物对其的调节作用。最后，我们将测试效果 成年期CEA和鼻腔MC4R拮抗作用对伤害性感受的影响。我们的假设是AIE 在CEA中产生持续增加的黑素皮质素和谷氨酸能信号，介导AIE- 诱导痛敏，青春期慢性MC4R阻断逆转AIE诱导的细胞 成年后使用MC4R拮抗剂将挽救AIE诱导的痛觉过敏。

Abstract Alcohol during the adolescent period produces permanent maladaptive changes in the brain. Adolescent drinkers report greater prevalence of pain disorders in adulthood, and functional magnetic resonance imaging has shown greater amygdala activation compared to non-drinkers. The amygdala, and more specifically the central nucleus of the amygdala (CeA) is a key brain region in pain processing by glutamate transmission from pain-related brain regions. The CeA is sensitive to alcohol, however there are divergent results depending on timing of exposure. In adult rodent models, chronic alcohol increases CeA activity by upregulating N-methyl-D-Aspartate (NMDAR) subunits and AMPAR mediated excitatory transmission leading to increased pain processing. These effects are transient, as changes in NMDAR subunit expression and glutamate transmission normalize within 1-2 weeks following exposure. In an adolescent alcohol exposure model, increases in NMDAR subunit and glutamate signaling lasts into adulthood in the extended amygdala, suggesting adolescent alcohol effects are more persistent. The melanocortin system and neural specific melanocortin 4 receptor (MC4R) are highly expressed in the CeA and regulate glutamatergic transmission. MC4R increases AMPAR post-synaptically, modulates NMDAR function, and increases glutamate signaling in other pain-related regions. Melanocortin signaling in the amygdala modulates pain-related behaviors as intra-CeA MC4R antagonism reverses alcohol-induced hyperalgesia in adult rats. Adult alcohol exposure decreases MC4R expression, but adolescent alcohol exposure increases MC4R expression in adulthood. How the melanocortin system modulates glutamate transmission in the CeA, the longitudinal effects of adolescent alcohol on CeA glutamate and melanocortin systems, and how the melanocortin system modulates pain processing longitudinally have yet to be addressed. Using a rat model, we will test the effect of adolescent alcohol exposure on melanocortin and glutamatergic signaling in CeA, the effect of chronic MC4R antagonism on cellular effects during this period, and we will test MC4R antagonism during adulthood on hyperalgesia induced by an adolescent intermittent ethanol (AIE) vapor model. Male and female Wistar rats will receive alcohol vapor from postnatal day (PND) 28 to PND 56, with one cohort receiving chronic MC4R antagonism via intracerebroventricular minipumps during this period. We will use Western blots to measure AMPAR and NMDAR subunits, and melanocortin system protein expression acutely after AIE (PND 56) and during adulthood (PND 86). We will use slice electrophysiology to measure glutamatergic transmission in the CeA during adolescence and adulthood, and its modulation by MC4R drugs. Finally, we will test the effects of intra-CeA and intranasal MC4R antagonism on nociception in adulthood. Our hypothesis is that AIE produces lasting increases in melanocortin and glutamatergic signaling in the CeA that mediates AIE- induced hyperalgesia, that chronic MC4R blockade during adolescence reverses AIE-induced cellular effects, and that MC4R antagonism in adulthood will rescue AIE-induced hyperalgesia.