Endocannabinoids and the Control Of Behavior and Cardiovascular Function

早些时候，我们使用两瓶/自由选择范式的小鼠模型首次证明了通过CB1受体作用的内源性大麻素以一种年龄相关的方式促进自愿饮酒(PNAS 100：1393,2003)。这项研究中使用的脑穿透性CB1反向激动剂利莫那班随后被引入用于治疗肥胖症，但由于神经精神副作用，包括焦虑、抑郁和自杀念头，不得不在2008年从药品市场撤出。我的实验室倡导的另一种方法是引入外周受限的CB1反向激动剂，这种药物保留了利莫那班的代谢功效，但在代谢综合征的啮齿动物模型中没有神经行为影响。矛盾的是，这类化合物还被发现可以减少食物摄入量，这是一种中央调节效应。在饮食诱导的肥胖小鼠中，外周阻断CB1可以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逆转其高瘦素血症，从而迅速逆转其瘦素抵抗，从而解决了这一悖论。这让我们想知道，C57BL6小鼠的高酒精偏好是否也可能通过阻断外周CB1而间接影响到CB1激活所促进的另一种中枢功能。一种可能的机制与Ghrelin有关，这是一种胃肽，通过大脑中的Ghrelin受体促进食欲。 去年报告的初步研究结果得到了扩展，研究结果清楚地表明，利莫那班和非脑穿透性CB1反向激动剂JD5037，以及我们自己的几种新型外周CB1拮抗剂，包括MRI-1569和MRI-1891，在使用两瓶自由选择范例显著减少C57BL6小鼠的总酒精摄入量和酒精偏好方面是等效的。此外，阻断CB1可显著降低血浆总生长激素水平和乙酰化生长激素水平。在今年进行的其他实验中，我们发现ghrelin基因敲除和ghrelin Receptor1基因敲除小鼠的酒精偏好和绝对摄入量都较低，外周CB1受体阻断没有造成额外的减少。Ghrelin对血浆Ghrelin的影响和在基因敲除菌株中的发现与Ghrelin参与外周CB1阻断饮酒的影响是一致的。我们还发现，隔膜下迷走神经支配胃取消了外周阻断CB1减少饮酒的效果。这表明迷走神经传入或传出终末上的突触前CB1受体是这些拮抗剂的靶标。正在进行的其他实验是为了区分后两种可能性。

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.