Extracellular norepinephrine in the medial hypothalamus increases during feeding in chicks: a microdialysis study

Norepinephrinergic function in the medial hypothalamus is important for the regulation of feeding behavior in chicks as well as in rats. This study wa s conducted to clarify the variation of extracellular norepinephrine (NE) i n the medial hypothalamus, including the paraventricular nucleus (PVN) and the ventromedial hypothalamic nucleus (VMN), during feeding behavior of lay er-type chicks. To measure extracellular NE and 4-hydroxy-3-methoxyphenylgl ycol (MHPG), a major metabolite of NE, we used microdialysis and high-press ure liquid chromatography (HPLC) with electrochemical detection. After the collection of baseline samples, food-deprived animals were allowed access t o the food for 3 h. Extracellular NE significantly increased during the fir st hour of access to food, and then returned to baseline levels. MHPG also increased during the feeding, but its increase continued throughout the rem ainder of the experiment. This study suggests that the variation of NE in t he medial hypothalamus may be involved in the control of feeding in layer-t ype chicks. (C) 2000 Elsevier Science Inc. All rights reserved.