CIRCADIAN RHYTHMICITY IN THE GABAERGIC SYSTEM IN THE SUPRACHIASMATIC NUCLEI OF THE RAT

The participation of GABAergic mechanisms in the regulation of circadi an rhythmicity by the suprachiasmatic nuclei (SCN) has been suggested from different lines of evidence. Little is known, however, whether GA BA synthesis, release, uptake or content within the SCN may show a cir cadian pattern. The present results show that the activity of the GABA ergic system within the SCN region of the rat exhibits circadian rhyth micity, which is manifested by correlative changes of the GABA content and the glutamic acid decarboxylase activity under the light/dark cyc le, and by changes in the GABA content in animals kept under constant darkness.