Brain hormones and appetite in fish

1.比目鱼的黑色素浓缩激素(MCH)由17个残基组成，与鲑鱼的MCH在第2位不同。人工合成的MCH的生物活性表现为黑素小体在比目鱼皮肤内的聚集。白底鱼的MCH基因拷贝数明显多于黑底鱼。结果1.禁食组大鼠脑内MCH基因表达水平高于对照组，提示MCH与摄食量有关。本研究克隆了巴氏牙鲨的两个MCH受体(MCH-R)。MCH-R1的表达仅限于大脑，而MCH-R2的转录本在包括大脑在内的几个组织中都被检测到。黑底鱼眼侧皮中MCH-R2的表达高于白底鱼。在金鱼中，脑室注射MCH可减少累积摄食量，而脑室注射MCH抗血清可增加摄食量。禁食组金鱼下丘脑部分MCH免疫反应阳性胞体数目较投喂组显著减少。这些结果表明，MCH可能是金鱼体内的一种厌氧神经肽。我们从巴鳍比目鱼中克隆了三种POMC亚型。POMC-A仅在垂体中表达，而POMC-B和POMC-C在包括垂体在内的多个组织中均有表达。牙鲆脑垂体远侧部和中间部POMC的翻译后加工不同。黑素皮质素受体1和4的表达在巴氏比目鱼的脑、眼球、睾丸和皮肤中观察到。黑素皮质素4受体在肝脏中也有表达，禁食后其表达增加。结果表明，这种受体与能量平衡有关。

1. Melanin-concentrating hormone (MCH) of the barfin flounder is composed of 17 residues, which differs from salmon MCH at a position 2. The biological activity of synthetic MCH was demonstrated by the aggregation of melanosomes in flounder skin after intraperitoneal injection of the peptide. The number of MCH mRNA copies was greater in fish reared with a white background than in those reared with a black background. The MCH gene expression level in the brain was higher in fasted fish than in controls, indicating the association of MCH with food intake.2. We cloned two MCH receptors (MCH-R) from the barfin flounder. The expression of MCH-R1 was confined to the brain, while transcripts of MCH-R2 were detected in several tissues including the brain. The expression of MCH-R2 in eyed-sideskin was higher in fish reared with a black background than with a white background.3. In goldfish, cumulative food intake was decreased by intracerebroventricular injection of MCH, while it was increased by intracerebroventricular injection of MCH antiserum. The number of MCH immunoreactive somata in a part of the goldfish hypothalamus decreased significantly in fasted fish as compared with fed fish. These results indicate that MCH has a potential to function as an anorexigenic neuropeptide in goldfish.4. We cloned three POMC subtypes from the barfin flounder. The expression of POMC-A was confined to the pituitary, while transcripts of POMC-B and-C were detected in several tissues including the pituitary. Posttranslational processing of POMC of the pars distalis and pars intermedia in the barfin flounder pituitary differs from each other.5. Expressions of melanocortin 1 and 4 receptors were observed in the brain, eye-balls, testes, and skin of the barfin flounder. Melanocortin 4 receptor was also expressed in the liver, of which expression was increased by fasting. The results suggest the association of this receptor with energy homeostasis.