Ghrelin, a novel growth hormone (GH)-releasing peptide with an acylated side chain, is the endogenous ligand for the GH secretagogue receptor. Intracerebroventricular (ICV) injection of ghrelin stimulates GH secretion and feeding of rats, but ghrelin inhibited feeding of neonatal chicks. It was also confirmed that ghrelin induced sleep-like behavior later than 30 minutes post-administration in neonatal chicks. However, exciting behavior was observed in a short period (less than 30 min) in previous reports. Thus, we further investigated the behavioral changes in neonatal chicks by ICV administration of ghrelin within a short period. Chicks were divided into two groups and administered ICV saline or 2 fig of ghrelin and the numbers of step and vocalization were monitored. Just after behavioral test, the amount of monoamines of chick hypothalamus was determined by high performance liquid chromatography. Central ghrelin enhanced the numbersof step and kept the numbers of vocalization, but no significant difference in the amount of monoamines was detected. In conclusion, central ghrelin activates chick behavior in a short period without modification of hypothalamic monoamine contents.
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