EFFECT OF SEROTONIN AND NEUROPEPTIDES ON ADENYLATE-CYCLASE OF THE CENTRAL-NERVOUS-SYSTEM AND PERIPHERAL ORGANS OF THE FRESH-WATER SNAIL PLANORBARIUS-CORNEUS

The effect of serotonin, FMRFamide and the small cardioactive peptide B (SCPB) on adenylate cyclase activity of the central nervous system a nd some peripheral organs of the freshwater snail Planor-barius corneu s was investigated. The amine and the cardioactive peptide stimulated the enzyme, although with different potencies, in all tissues studied and, when tested in combination, an additive activation was obtained. FMRFamide induced differential effects in the various targets : marked stimulation of adenylate cyclase, additive to that provoked by seroto nin or SCPB, in salivary glands; inhibition of the enzyme, both alone and in combination with the other neuromediators, in the nervous tissu e; whereas no influence was found in adenylate cyclase activity in the buccal mass. In the last of these tissues, the peptide might act thro ugh an intracellular second messenger other than cyclic AMP. The respo nsiveness of adenylate cyclase to these neuromediators in all the cent ral ganglia suggested that they can exert an important role as neurotr ansmitters and/or neuromodulators in the central nervous system of the snail. Moreover, in the Light of the differential sensitivity of aden ylate cyclase in the salivary glands and buccal mass, we suggest that serotonin, FMRFamide and SCPB modulate the feeding behaviour of P. cor neus in a complex way. (C) 1996 Elsevier Science Ltd.