CIRCADIAN-RHYTHM IN THE CA2-INHIBITABLE ADENYLYL-CYCLASE ACTIVITY OF THE RAT STRIATUM()

In the present study, we demonstrate that the Ca2+-inhibitable adenyly l cyclase (AC) activity in the striatum exhibits a daily oscillation w ith a peak occurring around 10:00 h. A circadian fluctuation of the AC activity evoked by an A2a adenosine-selective agonist was also observ ed. Intrastriatal injection of an A2a-selective adenosine agonist or a ntagonist during the interval in which the Ca2+-inhibitable AC activit y was at its peak resulted in a more significant alteration of locomot or activity than those observed at a later interval. The marked circad ian variation in the Ca2+-inhibitable AC activity in the striatum appe ars to cause a circadian fluctuation in the action of at least one neu romodulator.