The Role of l -Dopa in the Nervous System of Sea Anemones: A Putative Inhibitory Transmitter in Tentacles

l-Dopa evokes transitory inhibition of spontaneous contractions of tentacle longitudinal muscles in sea anemones. It also modulates spontaneous contractions of the sphincter muscle in isolated preparations and whole animals. 2. Extracellular recordings from the tentacles of Calliactis parasitica show that l-Dopa evokes bursts of electrical events apparently associated with a local nerve net. 3. We propose that l-Dopa be added to the growing list of putative transmitter substances in sea anemones, its action being to coordinate local inhibition of spontaneous tentacle contractions.