[Coordination between locomotor and respiratory rhythms in the great ramshorn snail Planorbarius corneus: transmitter-dependent modifications].

In a reduced preparation of Planorbarius corneus consisting of the CNS and mantle complex, both the dopamine precursor L-DOPA and the serotonin precursor 5-HTP have been found to be able to induce and maintain rhythmic pneumostome (PN) movements phase-coupled to fictive cyclic locomotion in a neurotransmitter-specific manner. After the transection of pedal commissures, pharmacologically induced PN movements were coordinated with the locomotor activity rhythm generated by the left pedal ganglion, as in Lymnaea regardless of spatial inversion of its CNS. Nevertheless, in Planorbarius during the 5-HTP-induced fictive muscular locomotion, the PN was never opened, but cuddled up to the mantle at the same phase of the locomotor cycle corresponding to close down the PN in Lymnaea.