MDL-12330A INHIBITS THE NONNEURONAL ADENYLYL-CYCLASE FROM THE FRESH-WATER SNAIL PLANORBARIUS-CORNEUS, BUT THE NEURONAL ENZYME IS ACTIVATED BY THIS COMPOUND

cyclopentyl)azacyclotridecan-2-imine-hydrochloride (MDL 12330A), consi dered an inhibitor of adenylyl cyclase, has been tested on the enzyme activity of neuronal and non-neuronal tissues from the freshwater snai l Planorbarius corneus. The drug dose-dependently activates the basal as well as agonist-stimulated adenylyl cyclase in the ganglionic prepa rations, while it exerts an inhibitory effect on the enzyme present in the non-nervous tissues examined, SQ 22536 and forskolin, respectivel y an inhibitor and activator of adenylyl cyclase, behave as generally reported both in central and peripheral tissues of the snail. This is, to our knowledge, the first report of a stimulatory action of MDL 123 30A on an adenylyl cyclase system.