Pharmacological responses of the dorsal longitudinal muscle of Sabellastarte magnifica

1. 1. Strips of dorsal longitudinal muscle of Sabellastarte magnifica exhibit apparently anomalous responses to drugs. Thus, acetylcholine causes either a contraction or a relaxation, or both. 2. 2. d -Tubocurarine fails to block the stimulating action of acetylcholine; moreover, the acetylcholine-induced contractions are larger in curarized strips. 3. 3. Nicotine exerts a combination of relaxing and stimulating effects; the former being blocked by d -tubocurarine. 4. 4. Adrenaline causes a slow and sustained contraction. 5. 5. 5-Hydroxytryptamne elicits a relaxation, but potentiates the acetylcholine-induced contractions. 6. 6. To explain these observations it is proposed that this muscle is made of different types of cells with different physiological and pharmacological properties.