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

Activation of γ-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 t...

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Bibliographic Details
Published in:Journal of biological rhythms 2008-02, Vol.23 (1), p.16-25
Main Authors: Ehlen, J. Christopher, Novak, Colleen M, Karom, Mary C, Gamble, Karen L, Albers, H. Elliott
Format: Article
Language:English
Subjects:
Activation
Circadian rhythm
Circadian rhythms
GABA
Gene expression
Genetic aspects
Hypotheses
Light
Messenger RNA
Muscimol
Night
Period protein
Physiological aspects
Receptor mechanisms
Receptors
Suprachiasmatic nucleus
γ-Aminobutyric acid A receptors
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Summary:Activation of γ-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 GABAA receptor interact by altering the expression of Period 1 and/or Period 2 mRNA in the SCN is tested. The GABAA 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 GABAA 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.
ISSN:0748-7304
1552-4531
DOI:10.1177/0748730407310785