THERMOREGULATORY EFFECT OF INTRACEREBRAL INJECTIONS OF NEUROPEPTIDE-Y IN RATS AT DIFFERENT ENVIRONMENTAL TEMPERATURES

1. In order to characterize the thermoregulatory actions of brain neuropeptide Y (NPY), the effects of intra-third ventricular (I3V) injection of NPY on temperatures of colon (T-co), brown adipose tissue (T-BAT) and tail skin (T-s) were observed at ambient temperatures (T-a) of 19 and 8 degrees C. 2. The injection NPY in a dose of 8 mcg/100 wt evoked a fall of T-co by about 2 degrees C in both neutral and cold environments. NPY (4 and 8 mcg/100 g body wt) induced dose-dependent T-co falls in rats at thermoneutral environment. The thermolytic reactions induced by I3V administration of NPY were associated with a fall in T-BAT but no changes in I-s were observed. 3. The results suggest that NPY may mediate hypothermic response in neutral and cold environments mainly by its effects on the brown adipose tissues in the rat.