This Article Full Text (PDF) References Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via Google Scholar Citing Articles via Scopus Google Scholar Articles by Ehlen, J. C. Articles by Albers, H. E. Search for Related Content PubMed PubMed Citation Articles by Ehlen, J. C. Articles by Albers, H. E. Pubmed/NCBI databases Compound via MeSH Substance via MeSH Hazardous Substances DB MUSCIMOL Social Bookmarking                   What's this?

Interactions of GABA_A Receptor Activation and Light on Period mRNA Expression in the Suprachiasmatic Nucleus

Department of Biology, Georgia State University, Atlanta, GA, jehlen{at}msm.edu

Colleen M. Novak

Mayo Clinic, Endocrine Research Unit, Saint Mary's Hospital, Rochester, MN

Mary C. Karom

Department of Biology, Georgia State University, Atlanta, GA

Karen L. Gamble

Vanderbilt University, Department of Biological Sciences, Nashville, TN

H. Elliott Albers

Department of Biology, Georgia State University, Atlanta, GA, Department of Psychology, Center for Behavioral Neuroscience, Georgia State University, Atlanta, GA

Activation of -aminobutyric acid (GABA)_A receptors in the suprachiasmatic nucleus (SCN) resets the circadian clock during the day and inhibits the ability of light to reset the clock at night. Light in turn acts during the day to inhibit the phase-resetting effects of GABA. Some evidence suggests that Period mRNA changes in the SCN are responsible for these interactions between light and GABA. Here, the hypothesis that light and the GABA_A receptor interact by altering the expression of Period 1 and/or Period 2 mRNA in the SCN is tested. The GABA_A agonist muscimol was injected near the SCN just prior to a light pulse, during the mid-subjective day and the early and late subjective night. Changes in Period 1 and Period 2 mRNA were measured in the SCN by in situ hybridization. Light-induced Period 1 mRNA was inhibited by GABA_A receptor activation in the early and late subjective night, while Period 2 mRNA was only inhibited during the late night. During the subjective day, light had no effect on the ability of muscimol to suppress Period 1 mRNA hybridization signal. Thus, light and GABA _A receptor activation inhibit each other's ability to induce behavioral phase shifts throughout the subjective day and night. However, only in the late night are these behavioral effects correlated with changes in Period gene expression. Together, our data support the hypothesis that the interacting effects of light and GABA are the result of the opposing actions of these stimuli on Period mRNA, but only during the subjective night.

Key Words: circadian rhythm • GABAA receptor • light • Period genes • nonphotic • phase shift

Journal of Biological Rhythms, Vol. 23, No. 1, 16-25 (2008)
DOI: 10.1177/0748730407310785


CiteULike    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?