Pinillos M L, De Pedro N, Alonso-Gómez A L, Alonso-Bedate M, Delgado M J
Departamento de Biología Animal II (Fisiología Animal), Facultad de Biología, Universidad Complutense, 28040, Madrid, Spain.
Physiol Behav. 2001 Apr;72(5):629-34. doi: 10.1016/s0031-9384(00)00399-1.
Feeding regulation by monoamines, neuropeptides and certain hormones has been studied in fish, but a possible role of melatonin is unknown. The purpose of the present study was to investigate the effects of melatonin on food intake in goldfish. Fishes were housed in 12L:12D and injected with different doses of either melatonin or 2-iodomelatonin. Two routes of administration, intracerebroventricular and intraperitoneal injections, and two times of the daily photocycle, midday and midnight, were tested. Food intake was measured at 2, 5 and 8 h postinjection. Melatonin and its analog, 2-iodomelatonin intracerebroventricularly injected had no effect on food intake at any time. However, intraperitoneal injections of both indoleamines significantly reduced food intake at different postinjection times. The inhibitory effect of melatonin was blocked by intraperitoneal administration of its antagonist, luzindole. These results demonstrate the in vivo efficiency of luzindole as melatonin antagonist, and thus provide a useful experimental tool to investigate melatonin functions. In conclusion, both melatonin and its agonist 2-iodomelatonin administered peripherally, inhibit food intake in goldfish, and this inhibitory effect appears to be mediated via luzindole-sensitive melatonin receptors. Our results strongly suggest that melatonin is involved in the peripheral satiety mechanisms in goldfish.
单胺、神经肽和某些激素对鱼类摄食调节的研究已有不少，但褪黑素的潜在作用尚不清楚。本研究旨在探究褪黑素对金鱼食物摄入量的影响。将金鱼饲养在12小时光照：12小时黑暗的环境中，并注射不同剂量的褪黑素或2-碘褪黑素。测试了两种给药途径，即脑室内注射和腹腔注射，以及每日光周期的两个时间点，中午和午夜。在注射后2小时、5小时和8小时测量食物摄入量。脑室内注射褪黑素及其类似物2-碘褪黑素在任何时候对食物摄入量均无影响。然而，腹腔注射这两种吲哚胺在注射后的不同时间均显著降低了食物摄入量。褪黑素的拮抗剂鲁辛朵腹腔给药可阻断其抑制作用。这些结果证明了鲁辛朵作为褪黑素拮抗剂在体内的有效性，从而为研究褪黑素功能提供了一种有用的实验工具。总之，外周给予褪黑素及其激动剂2-碘褪黑素均会抑制金鱼的食物摄入量，且这种抑制作用似乎是通过对鲁辛朵敏感的褪黑素受体介导的。我们的结果强烈表明，褪黑素参与了金鱼外周的饱腹感机制。
