Evidence for the presynaptic location of adenylate cyclase and the cyclic AMP-stimulated protein kinase which is bound to synaptic membranes.

By comparison of activities measured with either intact or ruptured synaptosomes it was found that half of the cerebral adenylate cyclase is presynaptic while all the membranes bound, cyclic AMP-stimulated protein kinase activity appears to be presynaptic with the cyclic AMP receptor facing inward.