The anthozoan neuropeptide Antho-RWamide I modulates Ca2+ current in sea anemone myoepithelial cells.

The anthozoan neuropeptide Antho-RWamide I (< Glu-Ser-Leu-Arg-Trp-NH2) excites contraction of endodermal muscles in sea anemones. Single electrode voltage clamp recordings from semi-intact preparations of endodermal myoepithelial cells reveal that Antho-RWamide I increases an inward Ca2+ current. Evidence for the involvement of a Ca2+ current in contraction was supported by the observation that Cd2+ abolished spontaneous contractions and reduced inward current. Contractions and inward currents induced by Antho-RWamide I were not, however, completely abolished in the presence of Cd2+. We conclude that Antho-RWamide, a putative neurotransmitter at sea anemone smooth muscle, acts by opening, either directly or indirectly, Ca2+ channels in the muscle membrane.