title: Phase shifting of circadian rhythms and depression of neuronal activity in the rat suprachiasmatic nucleus by neuropeptide Y: mediation by different receptor subtypes.
abstract: Neuropeptide Y (NPY) has been implicated in the phase shifting of circadian rhythms in the hypothalamic suprachiasmatic nucleus (SCN). Using long-term, multiple-neuron recordings, we examined the direct effects and phase-shifting properties of NPY application in rat SCN slices in vitro (n = 453). Application of NPY and peptide YY to SCN slices at circadian time (CT) 7.5-8.5 produced concentration-dependent, reversible inhibition of cell firing and a subsequent significant phase advance. Several lines of evidence indicated that these two effects of NPY were mediated by different receptors. NPY-induced inhibition and phase shifting had different concentration-response relationships and very different phase-response relationships. NPY-induced phase advances, but not inhibition, were blocked by the GABAA antagonist bicuculline, suggesting that NPY-mediated modulation of GABA may be an underlying mechanism whereby NPY phase shifts the circadian clock. Application of the Y2 receptor agonists NPY 13-36 and (Cys2,8-aminooctanoic acid5,24,D-Cys27)-NPY advanced the peak of the circadian rhythm but did not inhibit cell firing. The Y1 and Y5 agonist [Leu31,Pro34]-NPY evoked a substantial inhibition of discharge but did not generate a phase shift. NPY-induced inhibition was not blocked by the specific Y1 antagonist BIBP-3226; the antagonist also had no effect on the timing of the peak of the circadian rhythm. Application of the Y5 agonist [D-Trp32]-NPY produced only direct neuronal inhibition. These are the first data to indicate that at least two functional populations of NPY receptors exist in the SCN, distinguishable on the basis of pharmacology, each mediating a different physiological response to NPY application.
authors.affiliation: Neuroscience Drug Discovery, Bristol-Myers Squibb Pharmaceutical Research Institute, Wallingford, Connecticut 06492, USA.
authors.forename: V K
authors.initials: VK
authors.lastname: Gribkoff
authors.forename: R L
authors.initials: RL
authors.lastname: Pieschl
authors.forename: T A
authors.initials: TA
authors.lastname: Wisialowski
authors.forename: A N
authors.initials: AN
authors.lastname: van den Pol
authors.forename: F D
authors.initials: FD
authors.lastname: Yocca
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D014151:Anti-Anxiety Agents / Q000494:pharmacology; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D001640:Bicuculline / Q000494:pharmacology; D002940:Circadian Rhythm / Q000187:drug effects / Q000502:physiology*; D004594:Electrophysiology; D018756:GABA Antagonists / Q000494:pharmacology; D058787:GABA-A Receptor Antagonists; D008297:Male; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D009478:Neuropeptide Y / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000494:pharmacology / Q000502:physiology*; D010446:Peptide Fragments / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D017476:Receptors, Neuropeptide Y / Q000819:agonists / Q000502:physiology; D013493:Suprachiasmatic Nucleus / Q000737:chemistry* / Q000187:drug effects / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000502:physiology
chemical_list: D014151:Anti-Anxiety Agents; C092926:BIBP 3226; D018756:GABA Antagonists; D058787:GABA-A Receptor Antagonists; D009478:Neuropeptide Y; D010446:Peptide Fragments; D017476:Receptors, Neuropeptide Y; C062924:neuropeptide Y (13-36); C062259:neuropeptide Y, Leu(31)-Pro(34)-; C086545:neuropeptide Y, Trp(32)-; D005680:gamma-Aminobutyric Acid; D001120:Arginine; D001640:Bicuculline