Studies on the Myoneural Physiology of Echinodermata. v. the Lantern Retractor Muscle of Parechinus: Responses to Drugs.

Although it has been known for many years that certain muscles of echinoderms are responsive to acetylcholine (ACh) (Bacq, 1935, i937> 1939; de Buy 1936; Iriye & Dille, 1940; Sawaya, 1951; Prosser & Judson, 1952; Ambache & Sawaya, 1953; Florey & McLennan, 1959) further studies on the pharmacology of these muscles have mostly been limited in scope. We have recently developed a preparation of the lantern retractor muscle of the echinoid Parechinus angulosus Mortensen. Such preparations may show spontaneous activity and are sensitive to stimulation by light (Boltt & Ewer, 1963). The response to light typically consists of a 'quick' contraction followed, if the duration of illumination exceeds about 8 sec, by a slower 'delayed' contraction. Very prolonged illumination releases rhythmic activity. There is also evidence that light may stimulate some type of inhibitory system in this preparation. In the hope of gaining a closer insight into its workings, we have examined the responses of the preparation to a number of different pharmacological agents. Although the results obtained do not in fact help towards a greater understanding of events, they appeared to be of sufficient interest to warrant publication.