title: Gastrin-releasing peptide mediates light-like resetting of the suprachiasmatic nucleus circadian pacemaker through cAMP response element-binding protein and Per1 activation.
abstract: Circadian rhythmicity in the primary mammalian circadian pacemaker, the suprachiasmatic nucleus (SCN) of the hypothalamus, is maintained by transcriptional and translational feedback loops among circadian clock genes. Photic resetting of the SCN pacemaker involves induction of the clock genes Period1 (Per1) and Period2 (Per2) and communication among distinct cell populations. Gastrin-releasing peptide (GRP) is localized to the SCN ventral retinorecipient zone, from where it may communicate photic resetting signals within the SCN network. Here, we tested the putative role of GRP as an intra-SCN light signal at the behavioral and cellular levels, and we also tested whether GRP actions are dependent on activation of the cAMP response element-binding protein (CREB) pathway and Per1. In vivo microinjections of GRP to the SCN regions of Per1::green fluorescent protein (GFP) mice during the late night induced Per1::GFP throughout the SCN, including a limited population of arginine vasopressin-immunoreactive (AVP-IR) neurons. Blocking spike-mediated communication with tetrodotoxin did not disrupt overall Per1::GFP induction but did reduce induction within AVP-IR neurons. In vitro GRP application resulted in persistent increases in the spike frequency of Per1::GFP-induced neurons. Blocking endogenous Per1 with antisense oligodeoxynucleotides inhibited GRP-induced increases in spike frequency. Furthermore, inhibition of CREB-mediated gene activation with decoy oligonucleotides blocked GRP-induced phase shifts of PER2::luciferase rhythms in SCN slices. Altogether, these results indicate that GRP communicates phase resetting signals within the SCN network via both spike-dependent and spike-independent mechanisms, and that activation of the CREB pathway and Per1 are key steps in mediating downstream events in GRP resetting of SCN neurons.
authors.affiliation: Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235, USA.
authors.forename: Karen L
authors.initials: KL
authors.lastname: Gamble
authors.forename: Gregg C
authors.initials: GC
authors.lastname: Allen
authors.forename: Tongrong
authors.initials: T
authors.lastname: Zhou
authors.forename: Douglas G
authors.initials: DG
authors.lastname: McMahon
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D000704:Analysis of Variance; D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D001127:Arginine Vasopressin / Q000378:metabolism; D001522:Behavior, Animal; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002940:Circadian Rhythm / Q000187:drug effects / Q000502:physiology*; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D019886:Gastrin-Releasing Peptide / Q000378:metabolism / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000502:physiology* / Q000528:radiation effects; D049452:Green Fluorescent Proteins / Q000235:genetics; D066298:In Vitro Techniques; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D056950:Period Circadian Proteins; D010775:Photic Stimulation / Q000379:methods; D013493:Suprachiasmatic Nucleus / Q000187:drug effects* / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology; D013997:Time Factors; D015533:Transcriptional Activation; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism
chemical_list: D000779:Anesthetics, Local; D018797:Cell Cycle Proteins; D017362:Cyclic AMP Response Element-Binding Protein; D009687:Nuclear Proteins; C539023:Per1 protein, mouse; D056950:Period Circadian Proteins; D001127:Arginine Vasopressin; D049452:Green Fluorescent Proteins; D014660:Vasoactive Intestinal Peptide; D013779:Tetrodotoxin; D019886:Gastrin-Releasing Peptide