Hypothermia and feeding induced simultaneously in rats by perfusion of neuropeptide Y in preoptic area

Abstract

Changes in the body temperature (Tbo) of the unrestrained rat as well as the hyperphagic-like ingestion of food were simultaneously determined during the sustained elevation of neuropeptide Y1-36 (NPY) within the anterior hypothalamic preoptic area (AH/POA). A single guide tube was implanted stereotaxically in each rat for repeated perfusions by means of push-pull cannulae of either the CSF solvent vehicle or NPY. Following postoperative recovery, each site in the AH/POA was perfused for 6.0 min at a rate of 20 microliters/min over four successive intervals at a concentration of 100 ng/1.0 microliters or 250 ng/1.0 microliters, with an interval of 6.0 min intervening between perfusions. During repeated perfusions of NPY in the fully sated and normothermic rat, concentration-dependent eating, or a hypothermia or both responses occurred simultaneously. Mean cumulative intakes of food over 3.0 h were 12.1 +/- 1.4 and 21.5 +/- 2.7 g following the 100 and 250 ng concentrations of NPY, respectively. The mean maximal declines in Tbo were -0.92 +/- 0.21 and -1.1 +/- 0.28 degrees C, respectively after the lower and higher concentrations of the peptide. Push-pull perfusions of artificial CSF control vehicle at homologous anatomical sites in the AH/POA were without effect on feeding or the Tbo of the rats. These results demonstrate that repeated and sustained elevation of NPY in the AH/POA can cause a perturbation of the neuronal mechanisms underlying the normal "set-point" for body temperature as well as satiety.(ABSTRACT TRUNCATED AT 250 WORDS)