Circadian rhythm in the Ca2+‐inhibitable adenylyl cyclase activity of the rat striatum

Abstract

In the present study, we demonstrate that the Ca²⁺‐inhibitable adenylyl cyclase (AC) activity in the striatum exhibits a daily oscillation with a peak occurring around 10:00 h. A circadian fluctuation of the AC activity evoked by an A2a adenosine‐selective agonist was also observed. Intrastriatal injection of an A2a‐selective adenosine agonist or antagonist during the interval in which the Ca²⁺‐inhibitable AC activity was at its peak resulted in a more significant alteration of locomotor activity than those observed at a later interval. The marked circadian variation in the Ca²⁺‐inhibitable AC activity in the striatum appears to cause a circadian fluctuation in the action of at least one neuromodulator.