Retinal GABA(A) receptors participate in the regulation of circadian responses to light.
A role for retinal gamma-aminobutyric acid Type A (GABA(A)) receptors in the regulation of circadian responses to light was examined. Intraocular injections of the GABA(A) antagonist, bicuculline, were performed during the early (Circadian Time [CT] 13.5) and late subjective night (CT 20), followed by a light pulse. Bicuculline significantly decreased the magnitude of phase delays induced by light to 65%, whereas it had no effect on phase advances. To explore the nature of the inhibition elicited by bicuculline, an intensity-response curve was performed. Intraocular injections of bicuculline inhibited phase delays only when induced by high-saturating light illuminances (20 and 100 lux). No effect was observed at light intensities < or = 5 lux. These results suggest that retinal GABA(A) receptors modulate the responsivity of the circadian system to light.
Della Maggiore
V
V
Department of Psychology, University of Toronto, Ontario, Canada.
Ralph
M R
MR
D000818:Animals; D001640:Bicuculline / Q000008:administration & dosage / Q000494:pharmacology; D002940:Circadian Rhythm / Q000187:drug effects; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D018756:GABA Antagonists / Q000008:administration & dosage / Q000494:pharmacology; D058787:GABA-A Receptor Antagonists; D008027:Light; D008297:Male; D008647:Mesocricetus; D009043:Motor Activity / Q000187:drug effects; D010775:Photic Stimulation; D011963:Receptors, GABA-A / Q000502:physiology*; D012160:Retina / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors
D018756:GABA Antagonists; D058787:GABA-A Receptor Antagonists; D011963:Receptors, GABA-A; D001640:Bicuculline