Neuromuscular Transmission in a Sea Anemone

Abstract

1. Brief electrical potentials can be recorded from a suction electrode over the marginal sphincter or over a tentacle of the anemone Calliactis polypus following appropriate stimulation of the anemone. These potentials are thought to be muscle action potentials because they precede contraction by about 12 msec. (29-31° C.) and their size is smoothly graded with the size of the contraction. 2. The tentacles and sphincter are activated by a through-conducting system in the oral disk and column. As with other anemones studied, two stimuli are required to evoke sphincter contraction. The maximum interval between an effective pair of stimuli is about 600 msec, and the sphincter potential and contraction increase with decreasing intervals to a minimum interval (as short as 15 msec.) below which there is no response to the second shock. Tentacles behave similarly except that they often produce small potentials and sometimes tiny contractions to single stimuli. 3. During repetitive stimulation the muscle potentials facilitate and the individual contractions both facilitate and sum. The tentacle musculature becomes maximally active earlier in a stimulus burst than does the sphincter.