title: Acute, subacute and chronic effects of central neuropeptide Y on energy balance in rats.
abstract: Central neuropeptide Y (NPY) injection has been reported to cause hyperphagia and in some cases also hypometabolism or hypothermia. Chronic central administration induced a moderate rise of short duration in body weight, without consistent metabolic/thermal changes. In the present studies the acute and subsequent subacute ingestive and metabolic/thermal changes were studied following intracerebroventricular (i.c.v.) injections of NPY in cold-adapted and non-adapted rats, or the corresponding chronic changes following i.c.v. NPY infusion. Besides confirming basic earlier data, we demonstrated novel findings: a temporal relationship for the orexigenic and metabolic/thermal effects, and differences of coordination in acute/subacute/chronic phases or states. The acute phase (30-60 min after injection) was anabolic: coordinated hyperphagia and hypometabolism/hypothermia. NPY evoked a hypothermia by suppressing any (hyper)metabolism in excess of basal metabolic rate, without enhancing heat loss. Thus, acute hypothermia was observed in sub-thermoneutral but not thermoneutral environments. The subsequent subacute catabolic phase exhibited opposite effects: slight increase in metabolic rate, rise in body temperature, reaching a plateau within 3-4 h after injection -- this was maintained for at least 24 h; meanwhile the food intake decreased and the normal daily weight gain stopped. This rebound is only indirectly related to NPY. Chronic (7-day long) i.c.v. NPY infusion induced an anabolic phase for 2-3 days, followed by a catabolic phase and fever, despite continued infusion. In cold-adaptation environment the primary metabolic effect of the infusion induced a moderate hypothermia with lower daytime nadirs and nocturnal peaks of the circadian temperature rhythm, while at near-thermoneutral environments in non-adapted rats the infusion attenuated only the nocturnal temperature rise by suppressing night-time hypermetabolism. Further finding is that in cold-adapted animals, the early feeding effect of NPY-infusion was enhanced, whereas the early hypothermic effect in cold was limited by interference with competing thermoregulatory mechanisms.
authors.affiliation: Department of Pathophysiology, Faculty of Medicine, University of Pécs, 12 Szigeti ut, Pecs H-7624, Hungary. miklos.szekely@aok.pte.hu
authors.forename: M
authors.initials: M
authors.lastname: Székely
authors.forename: E
authors.initials: E
authors.lastname: Pétervári
authors.forename: E
authors.initials: E
authors.lastname: Pákai
authors.forename: Z
authors.initials: Z
authors.lastname: Hummel
authors.forename: Z
authors.initials: Z
authors.lastname: Szelényi
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D001481:Basal Metabolism / Q000187:drug effects; D001831:Body Temperature / Q000187:drug effects; D001833:Body Temperature Regulation; D001835:Body Weight / Q000187:drug effects; D003080:Cold Temperature; D004435:Eating / Q000187:drug effects; D004734:Energy Metabolism / Q000187:drug effects*; D005260:Female; D007276:Injections, Intraventricular; D007700:Kinetics; D009478:Neuropeptide Y / Q000008:administration & dosage*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D009478:Neuropeptide Y