RESPONSES TO NEUROPEPTIDE-Y IN ADULT HAMSTER SUPRACHIASMATIC NUCLEUS NEURONS IN-VITRO

We investigated the effects of neuropeptide Y and related analogues on the extracellularly recorded spontaneous firing rate activity of adul t Syrian hamster suprachiasmatic nucleus neurones in vitro. Sixty-seve n neurones were tested with neuropeptide Y: 45% were suppressed, 4% we n activated, and the remaining 51% were unresponsive. These responses were not blocked by the GABA receptor antagonist bicuculline, indicati ng that neuropeptide Y-evoked responses did not appear to be dependent on GABA(A) receptor activation. We tested the effects of the neuropep tide Y Y, receptor agonist [Leu(31), Pro(31)]neuropeptide Y and the ne uropeptide Y Y-2 receptor agonist neuropeptide Y-(13-36) on nine cells suppressed by neuropeptide Y in order to determine the receptor subty pe(s) mediating the effects of neuropeptide Y. Four of nine cells were suppressed by [Leu(31), Pro(31)]neuropeptide Y only, one of nine was suppressed by neuropeptide Y-(13-36) only, two of nine were suppressed by both compounds, while the remaining two cells did not respond to e ither compound. These data suggest that neuropeptide Y can modulate su prachiasmatic nucleus function directly, without recruitment of GABA, interneurones. Further, our results indicate that neuropeptide Y may a ct on more than one receptor subtype within the adult hamster suprachi asmatic nucleus. (C) 1998 Elsevier Science B.V.