The interaction of clonidine and nitric oxide on feeding behavior in the chicken.

Central administration of alpha 2-receptor agonists stimulate food intake in mammalian and avian species. Recently we reported that inhibition of nitric oxide (NO) synthase (NOS) decreased food intake in chickens. In the present study, we investigated whether the increased eating induced by clonidine (Clon), an alpha 2-receptor agonist, is attenuated by NOS inhibition. In the first experiment, four levels (0, 9.4, 18.8 or 37.5 nmol/10 microliters) of Clon were administered into the right lateral ventricle of chickens, and food intake was monitored. Clon increased 30 min-food intake in a dose-dependent manner. In a co-administration study of L-NG-nitro-arginine methyl ester HCl (LNNA), a NOS inhibitor, and Clon, LNNA (0, 1.5, 3.0 or 5.9 mumol) attenuated food intake induced by Clon (37.5 nmol) in a dose-dependent manner. Our results suggest the possibility that NO interacts with adrenergic neurons in the central nervous system to modulate feeding behavior in the chicken.