title: Phase delays to light and gastrin-releasing peptide require the protein kinase A pathway.
abstract: Daily photic resetting of the circadian system relies on the transmission of light information from the retina to retinorecipient cells within the ventrolateral suprachiasmatic nucleus (SCN) core, and subsequent activation of rhythmic clock cells in the dorsolateral region. Some neurochemicals such as gastrin-releasing peptide (GRP) mimic the phase shifting effects of light and induce Ca(2+)-dependent gene expression in the SCN. Activation of the cAMP-response element binding protein (CREB) is necessary for Ca(2+)-dependent transcription to occur and accompanies behavioral phase shifting; however, several biochemical cascades are involved in this phenomenon. One pathway that has been implicated in photic responses involves protein kinase A (PKA). It is not known if this pathway participates in mediating phase shifts to GRP. Here we show that preventing PKA activation attenuates both light- and GRP-induced phase shifts in locomotor behavior, but only during the early-subjective night. This finding demonstrates that activation of PKA is an important component in the photic signaling pathway and may mediate GRP output signaling from the SCN core to the shell; however, this effect appears to be temporally dependent.
authors.affiliation: Department of Psychiatry, Dalhousie University, 5909 Veterans Memorial Lane, Abbie J. Lane Bldg, QEII Health Sciences Centre, Halifax, Nova Scotia, B3H 2E2, Canada; Department of Medicine, Division of Geriatric Medicine, 1421-5955 Veterans Memorial Lane, Veterans Memorial Bldg, Capital District Health Authority, Halifax, Nova Scotia, B3H 2E1, Canada; Department of Psychology and Neuroscience, Dalhousie University, Life Sciences Centre, P.O. Box 1500, Halifax, Nova Scotia, B3H 4R2, Canada.
authors.forename: Roxanne
authors.initials: R
authors.lastname: Sterniczuk
authors.affiliation: Department of Psychology, University of Calgary, 2500 University Dr. NW, Calgary, AB, T2N 1N4, Canada.
authors.forename: Glenn R
authors.initials: GR
authors.lastname: Yamakawa
authors.affiliation: Department of Psychology, University of Calgary, 2500 University Dr. NW, Calgary, AB, T2N 1N4, Canada.
authors.forename: Tara
authors.initials: T
authors.lastname: Pomeroy
authors.affiliation: Department of Psychology, University of Calgary, 2500 University Dr. NW, Calgary, AB, T2N 1N4, Canada; Hotchkiss Brain Institute, University of Calgary, 3330 Hospital Dr. NW, Calgary, AB, T2N 4N1, Canada; Department of Physiology and Pharmacology, University of Calgary, 3330 Hospital Dr. NW, Calgary, AB, T2N 4N1, Canada. Electronic address: antlem@ucalgary.ca.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Antle
mesh_terms: D000818:Animals; D002940:Circadian Rhythm / Q000187:drug effects / Q000502:physiology*; D006224:Cricetinae; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology*; D019886:Gastrin-Releasing Peptide / Q000494:pharmacology / Q000502:physiology*; D008297:Male; D008647:Mesocricetus; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D010775:Photic Stimulation / Q000379:methods*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013493:Suprachiasmatic Nucleus / Q000187:drug effects / Q000502:physiology; D013997:Time Factors
chemical_list: D019886:Gastrin-Releasing Peptide; D017868:Cyclic AMP-Dependent Protein Kinases
keywords: Gastrin-releasing peptide; KT5720; Light; Neuropeptide; Photic phase shifting; Suprachiasmatic nucleus