Abstract
Aging is associated with a progressive decrease in appetite and food intake. Orexin-A, NPY (neuropeptide Y), and ghrelin, which are appetite-stimulating peptides, are known to play a critical role in food intake. In this study, the stimulatory effect of intracerebroventricular administration of these peptides on food intake was compared among young (4-month-old), adult (11-month-old) and old (24-27-month-old) male Wistar rats. A stainless steel cannula was implanted stereotactically into the left lateral ventricle. After a 7-day recovery period, different doses of orexin-A (0 to 3 nmol), NPY and ghrelin (0 to 1 nmol) were injected into the left lateral ventricle without anesthesia. Food consumption was measured at 1, 2, and 4 hr after injection. We also examined the plasma levels of acylated and desacyl ghrelin in young and old rats by ELISA. Intracerebroventricular administration of orexin-A and NPY stimulated food intake in young and adult rats, but, no effects were observed at any dose in old rats. Ghrelin increased food intake in a dose-dependent manner in all groups and the effect of ghrelin was reduced with advancing age. Either acylated or desacyl plasma ghrelin level did not differ between young and old rats significantly. In conclusion, the result that the orexigenic effect of these peptides, orexin-A, NPY and ghrelin were diminished in old rats could be responsible for the age-related decrease in food intake. [J Physiol Sci. 2006;56 Suppl:S220]
