Neuropeptide-Y: a possible mediator of prolactin-induced feeding and regulator of energy balance in the ring dove (Streptopelia risoria)

Abstract

Although neuropeptide-Y (NPY) has been widely reported to be a potent stimulator of feeding activity and regulator of energy homeostasis, most of the supportive evidence for such effects has been gathered in mammalian species. This study characterized the orexigenic potency of NPY in an avian species, the ring dove, and measured changes in hypothalamic NPY-immunoreactive (NPY-ir) cell numbers in response to energy state fluctuations or intracranial administration of the potent orexigenic hormone prolactin. Food intake was significantly elevated in male doves at 1 h after intracerebroventricular (i.c.v.) injection of 0.25 and 0.5 microg NPY but not after injection of a higher dose (1.0 microg). In time course studies, food intake was increased at 1 h after i.c.v. injection of 0.5 microg NPY but was not elevated at 2, 3, or 4 h. The number of NPY-ir cell bodies in the infundibular region of the dove hypothalamus increased two to four-fold following acute food deprivation, chronic food restriction, or repeated i.c.v. injections of prolactin. No additive effects were observed when food restriction and prolactin treatment were combined. These findings suggest that NPY is involved in energy homeostasis in doves and are consistent with the hypothesis that prolactin-induced hyperphagia is mediated in part by NPY.