Effects of serotonin, dopamine and prostaglandin E(2) on adenylate cyclase activity and cyclic AMP levels in different ganglia of the freshwater snail Planorbis corneus L.

The effects of different neuroactive agents on cyclic AMP level of selected ganglia of Planorbis corneus were studied. Serotonin, dopamine and prostaglandin E(2) were capable of increasing significantly cyclic AMP synthesis in all the preparations. When such substances were tested in pairs, supra-additive effects were always observed. In high Ca(2+)-high Mg(2+) solutions dopamine action was blocked, meanwhile serotonin and prostaglandin E(2) were still effective in stimulating cyclic AMP synthesis. In the same experimental condition the supra-additive increases of the nucleotide level by drug combinations disappeared. Serotonin, but not dopamine, significantly stimulated adenylate cyclase activity in all the preparations, while prostaglandin E(2) was effective only in the Viscero-Parietal Complex. The presence of the adenylate cyclase activity in the nervous tissue of Planaorbis was substained by histochemical studies. These results demonstrating that in the nervous system of Planorbis cyclic AMP level is affected by neurotransmitters and neuromodulators, might support the idea of the crucial role of the cyclic nuclotide in the modulation of synaptic transmission.