Endocannabinoids and the Control Of Behavior and Cardiovascular Function

我们先前已经首次证明，内源性大麻素通过CB 1受体起作用，以年龄依赖性方式促进自愿饮酒，使用两瓶/自由选择范例的小鼠模型（PNAS 100：1393，2003）。本研究中使用的脑渗透剂CB 1反向激动剂利莫那班随后被引入作为肥胖症的治疗，但由于神经精神副作用，包括焦虑，抑郁和自杀意念，不得不在2008年从制药市场撤出。另一种方法，由我的实验室倡导，是引入外周限制性CB 1反向激动剂，保留利莫那班的代谢疗效，但没有其在代谢综合征的啮齿动物模型中的神经行为影响。巧合的是，这些化合物也被发现减少食物摄入，这是一种中枢介导的作用。这一矛盾通过以下证明得到解决：在饮食诱导的肥胖小鼠中，外周CB 1阻断通过逆转其高瘦素血症（通过抑制脂肪组织中瘦素的产生和增加肾脏中瘦素的清除）来迅速逆转其瘦素抵抗。这让我们想知道C57 B16小鼠的高度酒精偏好，另一个由CB 1激活促进的中枢功能，是否也可能通过外周CB 1的阻断而间接受到影响。一个可能的机制涉及生长激素释放肽，一种胃肽，通过大脑中的生长激素释放肽受体促进食欲。 去年报道的初步研究结果已经得到了扩展，研究结果清楚地表明，利莫那班和非脑渗透性CB 1反向激动剂JD 5037，以及我们自己的几种新型外周CB 1拮抗剂，包括MRI-1569和MRI-1891，在显著降低C57 BL 6小鼠的总酒精摄入量以及乙醇偏好方面是等效的，使用两瓶，自由选择范式此外，CB 1阻断显着降低血浆中的总以及乙酰化生长激素释放肽的水平。在今年进行的其他实验中，我们发现ghrelin基因敲除和ghrelin受体1基因敲除小鼠的酒精偏好和绝对摄入量都较低，外周CB 1受体阻断剂没有引起额外的减少。对血浆ghrelin的影响和在敲除菌株中的发现与ghrelin参与外周CB 1阻断对饮酒的影响是一致的。我们还发现，膈下胃迷走神经去神经消除了外周CB 1阻滞减少饮酒的功效。这表明，突触前CB 1受体的传出或传入迷走神经末梢是这些拮抗剂的目标。正在进行的其他实验将区分后两种可能性。

We have earlier demonstrated for the first time that endocannabinoids acting via CB1 receptors promote voluntary alcohol drinking in an age-dependent manner, using a mouse model of two bottle/free choice paradigm(PNAS 100:1393, 2003). The brain-penetrant CB1 inverse agonist rimonabant used in this study was subsequently introduced as a treatment of obesity, but had to be wihdrawn from the pharmaceutical market in 2008, due to neuropsychiatric side effects, including anxiety, depression and suicidal ideation. An alternative approach, championed by my laboratory, was the introduction of peripherally restricted CB1 inverse agonists that retained the metabolic efficacy of rimonabant but were devoid of its neurobehavioral effects in rodent models of the metabolic syndrome. Paradoxically, such compounds were also found to reduce food intake, a centrally mediated effect. This paradox was resolved by the demonstration that peripheral CB1 blockade in diet-induced obese mice rapidly reversed their leptin resistance by reversing their hyperleptinemia, via inhibiting leptin production in adipose tissue and increasing leptin clearance in the kidney. This made us to wonder whether the high alcohol preference of C57Bl6 mice, another central function promoted by CB1 activation, may also be affected indirectly through blockade of CB1 in the periphery. A possible mechanism involves ghrelin, a gastric peptide that promotes appetite via ghrelin receptors in the brain. The preliminary findings reported last year have been extended and the findings clearly indicate that rimonabant and the non brain-penetrant CB1 inverse agonists, JD5037, as well as several of our own novel peripheral CB1 antagonists including MRI-1569 and MRI-1891, were equieffective in markedly reducing total alcohol intake as well as ethanol preference in C57BL6 mice, using a two bottle, free choice paradigm. Furthermore, CB1 blockade significantly reduced plasma levels of total as well as acetylated ghrelin. In additional experiments conducted this year, we found that both alcohol preference and absolute intake are lower in ghrelin knockout and ghrelin receptor1 knockout mice, with no additional reduction caused by peripheral CB1 receptor blockade. The effects on plasma ghrelin and the finding in the knockout strains are compatible with ghrelin involvement in the effects of peripheral CB1 blockade on alcohol drinking. We also found that subdiaphragmatic vagal denervation of the stomach abolished the efficacy of peripheral CB1 blockade to reduce drinking. This suggests that presynaptic CB1 receptors on either efferent or afferent vagal terminals are the targets of these antagonists. Additional experiments in progress are to distinguish between these latter two possibilities.