[Dopamine effect on ionic conduction and adenyl cyclase activity in the central nervous system of the pond snail]

The mode of dopamine action (DA) was investigated both on identified neurons (growth hormone producing cells--GHC) and on the membrane fraction of the CNS tissue homogenate. Adenylate cyclase activity (ACA) in the Lymnaea membrane depended on the GTP, stimulated and inhibited by different well known mediators, dopamine action being one of them. DA produced a stimulatory and inhibitory action on ACA. Direction of the DA action depended on the GTP concentration: at lower concentration of the GTP DA was a stimulator of ACA, at higher--an inhibitor. It is shown that inhibitory influence of DA on ACA was prevented by treatment of the membrane of the catalytic subunit of the protein kinase A (cPKA). It is particularly noticeable that inhibitory influence of cPKA-dependent phosphorylation reduced the inhibitory action of ALF4-, a G-protein activator. Effect of DA application on the GHC induced appearance of inward and outward currents through the neuronal membrane.