NEUROPEPTIDE-Y PHASE-SHIFTS CIRCADIAN-RHYTHMS IN-VIVO VIA A Y-2 RECEPTOR

NEUROPEPTIDE Y (NPY) injected into the suprachiasmatic region 6 h befo re the onset of locomotor activity produces phase advances in circadia n rhythms. The present study investigated whether the phase advances p roduced by NPY in Syrian hamsters are mediated by a Y-1- or Y-2-like N PY receptor by comparing the phase advancing effects of the Y-1 agonis t, [Leu(31),Pro(34)]NPY, and the Y-2 agonist, NPY(3-36), following the ir injection into the suprachiasmatic region. Microinjection of the Y- 2 agonist produced phase advances that were significantly greater than those produced by the microinjection of the Y-1 agonist. These data s upport the hypothesis that the phase advancing effects of NPY in the s uprachiasmatic region are mediated by a Y-2-like NPY receptor, similar to results found in vitro.