Rhythmic variation in gamma-aminobutyric acid(A)-receptor subunit composition in the circadian system and median eminence of Syrian hamsters

Temporal changes in the level of expression of gamma -aminobutyric acid (GA BA)(A) receptor subunits alpha2, alpha5, beta1 and beta3 were characterized by Western blot analysis in the hamster suprachiasmatic nuclei, retina and median eminence. A nocturnal maximum in the level of GABA(A) receptor beta 1 subunit at midday and midnight (12:00 and 00.00 h) was found in the supra chiasmatic nucleus (SCN), the retina and the median eminence of Syrian hams ters. alpha2 and beta3 subunit levels peaked during the day in the median e minence. Finally, retinal alpha5 levels were maximal during the night. beta 1 temporal changes in the SCN and median eminence, as well as alpha2 variat ions in the median eminence were maintained under constant dark conditions, suggesting an endogenous control, while the other variations were only obs erved under light-dark cycle conditions. (C) 2001 Elsevier Science B.V. All rights reserved.