title: Interaction of colocalized neuropeptides: functional significance in the circadian timing system.
abstract: The suprachiasmatic nucleus (SCN), which appears to act as a circadian clock, contains a subpopulation of local circuit neurons in which vasoactive intestinal peptide (VIP), peptide histidine isoleucine (PHI), and gastrin releasing peptide (GRP) are colocalized. To determine whether VIP, PHI, and GRP interact within the SCN to produce a signal important for circadian control, the behavioral and cellular effects of coadministration of these neuropeptides were investigated. Coadministration of VIP, PHI, and GRP within the SCN mimicked the phase-delaying effects of light on circadian control following in vivo microinjection and activated SCN single units recorded in vitro. These behavioral and cellular effects of coadministration of VIP, PHI, and GRP were significantly greater than administration of VIP, PHI, or GRP alone or coadministration of any 2 of these peptides. These data illustrate a new mechanism whereby multiple, colocalized neuropeptides interact in a functionally significant manner, and indicate that the interaction of VIP, PHI, and GRP may be involved in the regulation of circadian rhythms by the SCN.
authors.affiliation: Department of Biology, Georgia State University, Atlanta 30303.
authors.forename: H E
authors.initials: HE
authors.lastname: Albers
authors.forename: S Y
authors.initials: SY
authors.lastname: Liou
authors.forename: E G
authors.initials: EG
authors.lastname: Stopa
authors.forename: R T
authors.initials: RT
authors.lastname: Zoeller
mesh_terms: D000818:Animals; D001483:Base Sequence; D002940:Circadian Rhythm; D019886:Gastrin-Releasing Peptide; D005768:Gastrointestinal Hormones / Q000502:physiology; D007031:Hypothalamus / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D008969:Molecular Sequence Data; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D015345:Oligonucleotide Probes; D010451:Peptide PHI / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D010455:Peptides / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects; D013493:Suprachiasmatic Nucleus / Q000187:drug effects / Q000502:physiology*; D014660:Vasoactive Intestinal Peptide / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*
chemical_list: D005768:Gastrointestinal Hormones; D015345:Oligonucleotide Probes; D010451:Peptide PHI; D010455:Peptides; D014660:Vasoactive Intestinal Peptide; D019886:Gastrin-Releasing Peptide