Synaptic potentials recorded from sea anemone muscle cells in situ

Three pulse types, A,B, and C, can be recorded from column ring preparations of the sea anemone Calliactis parasitica (Couch). Lucifer Yellow injection confirmed that the recording sites are intracellular in endodermal myoepithelial cells. Type C pulses are spontaneously active depolarizing pulses, arising from a resting potential of around -60mV, and are usually < 5 mV in amplitude. When the cells were voltage-clamped these pulses reversed at around 0 mV membrane potential; therefore, we conclude that they are synaptic potentials. In some cells an increase in frequency of type C pulses accompanied contraction of the circular muscle field. Inward currents in these myoepithelial cells are carried by Ca2+, and although Na(+)-free solutions did not affect inward currents they did eliminate type C pulses, i.e., these synaptic potentials may result from activity of Na(+)-dependent nerve cells.