研究小组在新一期美国《国家科学院院刊》（PNAS）上报告说，他们以老鼠为实验对象发现，服用可卡因后，在大脑控制产生快感的“愉快中枢”内，一种黑色素聚集激素（MCH）对多巴胺具有调节作用，从而使大脑产生对可卡因的上瘾响应。
多巴胺是一种神经递质，对中枢神经系统的正常工作至关重要。大脑产生愉快感时，就会释放多巴胺。此前研究曾发现，有毒瘾者大脑中“愉快中枢”区域的多巴胺水平明显高于常人。
新研究发现，成瘾过程中，MCH和多巴胺的水平同时升高。如果阻断实验鼠大脑内MCH的活动，就可以抑制机体对可卡因的渴望，实验鼠表现出的可卡因瘾性明显减小。
研究人员说，这表明在大脑产生愉快感及成瘾过程中，MCH是多巴胺的一个关键调控者。他们认为，如果以MCH为目标，有望寻找到戒除可卡因瘾性的新疗法，甚至有可能找到戒除尼古丁上瘾等针对其他物质瘾性的新疗法。（生物谷Bioon.com）
生物谷推荐原始出处：
PNAS April 2, 2009, doi: 10.1073/pnas.0811331106
The melanin-concentrating hormone system modulates cocaine reward
Shinjae Chunga,b, F. Woodward Hopfc, Hiroshi Nagasakid, Chun-Ying Lia, James D. Belluzzia, Antonello Boncic and Olivier Civellia,b,1
Drug addiction is mediated by complex neuronal processes that converge on the shell of the nucleus accumbens (NAcSh). The NAcSh receives inputs from the lateral hypothalamus (LH), where self-stimulation can be induced. Melanin-concentrating hormone (MCH) is produced mainly in the LH, and its receptor (MCH1R) is highly expressed in the NAcSh. We found that, in the NAcSh, MCH1R is coexpressed with dopamine receptors (D1R and D2R), and that MCH increases spike firing when both D1R and D2R are activated. Also, injecting MCH potentiates cocaine-induced hyperactivity in mice. Mice lacking MCH1R exhibit decreased cocaine-induced conditioned place preference, as well as cocaine sensitization. Using a specific MCH1R antagonist, we further show that acute blockade of the MCH system not only reduces cocaine self-administration, but also attenuates cue- and cocaine-induced reinstatement. Thus, the MCH system has an important modulatory role in cocaine reward and reinforcement by potentiating the dopaminergic system in the NAcSh, which may provide a new rationale for treating cocaine addiction.
source: 生物谷
