HYPOTHERMIA AND FEEDING INDUCED SIMULTANEOUSLY IN RATS BY PERFUSION OF NEUROPEPTIDE-Y IN PREOPTIC AREA

Changes in the body temperature (T(bo)) of the unrestrained rats 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-mu-l/min over four successive intervals at a concentration of 100 ng/1.0-mu-l or 250 ng/1.0-mu-l, 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 T(bo) 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 T(bo) 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 "setpoint" for body temperature as well as satiety. Further, as long as the level of NPY in the hypothalamus is chronically elevated over time, a shift in T(bo) or persistent eating occurs either simultaneously or independently depending upon the population of neurons affected. It is thus envisaged that NPY plays an integrative role metabolically within neurons of the AH/POA in the control of energy metabolism coupled with caloric intake.