Feeding increases 5-hydroxytryptamine and norepinephrine within the hypothalamus of chicks

It is thought that hypothalamic 5-hydroxytryptamine (5HT) and norepinephrin e (NE) are involved in the regulation of feeding in chicks. The present stu dy was conducted to elucidate changes in the levels of extracellular 5HT an d NE in the hypothalamus during feeding of chicks. In order to measure 5HT, NE and 4-hydroxy-3-methoxyphenylglycol (MHPG), which is a major metabolite of NE, we used brain microdialysis and high-pressure liquid chromatography with an electrochemical detector. After collecting samples to determine th e basal levels of 5HT, NE and MHPG, food-deprived birds were given access t o food. 5HT levels in the medial hypothalamus (MH) and lateral hypothalamus (LH) increased during the first 30 min of feeding, and then returned to ba sal levels. NE and MHPG in the LH increased during feeding, and remained el evated throughout the experiment. This study supports an idea that hypothal amic monoamines in the chick brain are involved in the regulation of feedin g. (C) 2001 Elsevier Science Inc. All rights reserved.