Selective reduction in type I adenylyl cyclase after microsphere embolism in rat brain

Alterations of adenylyl cyclase (AC) subtypes after cerebral ischemia remain unclear. The purpose of the present study was to characterize alterations in AC after sustained cerebral ischemia. Sustained cerebral ischemia was induced by injection of 900 microspheres into the right (ipsilateral) internal carotid artery of rats. Microsphere embolism (ME) decreased the Ca(2+)/calmodulin-sensitive AC activity in the ipsilateral hippocampus examined up to 7 days after the embolism, whereas basal and 5'-guanylyl imidodiphosphate-sensitive AC activities were not altered. An immunoreactivity of type I adenylyl cyclase (AC-I) was decreased in the ipsilateral hippocampus during these periods, whereas type V/VI AC and VIII AC immunoreactivities were not altered. These results suggest that a selective reduction in the AC-I level and activity is induced by ME, which may lead to dysfunction of AC signal transduction.