title: Circadian control during the day and night: Role of neuropeptide Y Y5 receptors in the suprachiasmatic nucleus.
abstract: Circadian rhythms are reset by light during the night or by nonphotic stimuli during the day. Neuropeptide Y (NPY), which appears to mediate at least some nonphotic phase shifts by its actions in the suprachiasmatic nucleus (SCN), induces phase advances during the day and inhibits light-induced phase advances during the night. In this study, we used a highly selective Y5-like agonist to test whether activation of NPY Y5 receptors is sufficient to mimic NPY during the day and late night in Syrian hamsters. We also tested whether NPY in the early night reduces light-induced phase delays in a dose-dependent manner. Microinjection of a selective Y5 receptor agonist, (Ala(31), Aib(32))-NPY, into the SCN significantly inhibited light-induced phase advances during the late night, but did not induce phase advances during the day. In addition, concentrations of NPY ranging from 0.23 to 23 mM did not attenuate light-induced phase delays in the early night. These results suggest that activation of Y5-like receptors is sufficient to inhibit light-induced phase advances during the late night but is not sufficient to induce phase advances during the day. Furthermore, this study provided no evidence that NPY can inhibit light-induced phase shifts early in the night.
authors.affiliation: Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235, USA.
authors.forename: Karen L
authors.initials: KL
authors.lastname: Gamble
authors.forename: J Christopher
authors.initials: JC
authors.lastname: Ehlen
authors.forename: H Elliott
authors.initials: HE
authors.lastname: Albers
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D002940:Circadian Rhythm / Q000187:drug effects / Q000502:physiology*; D006224:Cricetinae; D003624:Darkness; D004305:Dose-Response Relationship, Drug; D008027:Light; D008297:Male; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D009478:Neuropeptide Y / Q000494:pharmacology; D017476:Receptors, Neuropeptide Y / Q000037:antagonists & inhibitors / Q000502:physiology*; D013493:Suprachiasmatic Nucleus / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects
chemical_list: D009478:Neuropeptide Y; D017476:Receptors, Neuropeptide Y; C100568:neuropeptide Y5 receptor