Clegg Deborah J, Air Ellen L, Woods Stephen C, Seeley Randy J
Department of Psychiatry, University of Cincinnati Medical Center, PO Box 670559 Cincinnati, OH 45267-0559, USA.
Endocrinology. 2002 Aug;143(8):2995-3000. doi: 10.1210/endo.143.8.8977.
Melanin-concentrating hormone (MCH) and orexin-A are orexigenic peptidergic neurotransmitters produced primarily in the lateral hypothalamus. Because two other hypothalamic peptides, neuropeptide Y and agouti-related peptide, increase food intake by a mechanism that depends on activation of opioid receptors, we assessed whether MCH or orexin-A also elicits food intake via opioid receptor activation. A dose of naloxone (0.3 mg/kg, ip) that had no effect on its own reduced the acute orexigenic effect of third ventricular (i3vt) orexin-A (3 ng/rat). However, this same dose of naloxone had no effect on i3vt MCH (5 microg/rat)-induced hyperphagia. Because the opioid system has also been linked to food selection, we investigated whether MCH or orexin-A alters food choice when rats have simultaneous access to two diets differing in the relative amounts of fat and carbohydrate. Whereas i3vt MCH stimulated intake of both diets and did not alter food choice, i3vt orexin-A stimulated intake of only the high fat diet. These data indicate that despite several similarities between MCH and orexin-A, these two lateral hypothalamic area peptides stimulate food intake by recruiting different neural circuits and exert different effects on food choice.
促黑素（MCH）和食欲素A是主要在下丘脑外侧产生的促食欲肽能神经递质。由于另外两种下丘脑肽，即神经肽Y和刺鼠相关肽，通过一种依赖阿片受体激活的机制增加食物摄入量，因此我们评估了MCH或食欲素A是否也通过阿片受体激活引发食物摄入。一剂纳洛酮（0.3毫克/千克，腹腔注射）本身无作用，但可降低第三脑室注射（i3vt）食欲素A（3纳克/只大鼠）的急性促食欲作用。然而，相同剂量的纳洛酮对i3vt注射MCH（5微克/只大鼠）诱导的摄食过多无作用。由于阿片系统也与食物选择有关，因此我们研究了在大鼠可同时获取脂肪和碳水化合物相对含量不同的两种食物时，MCH或食欲素A是否会改变食物选择。虽然i3vt注射MCH刺激了两种食物的摄入量且未改变食物选择，但i3vt注射食欲素A仅刺激了高脂肪食物的摄入量。这些数据表明，尽管MCH和食欲素A之间存在一些相似之处，但这两种下丘脑外侧区肽通过募集不同的神经回路来刺激食物摄入，并对食物选择产生不同影响。
