[Cholinoreception in the ambulacral legs of the starfish Asterias rubens].

Muscles of the ambulacral legs of the starfish A. rubens are sensitive to the effect of ACh, reacting to its injection by shortening of the contracture type. Amplitude of the contractile response is directly related to ACh concentration. The highest sensitivity was observed during complete stretching of the leg from the body of the starfish, threshold contractions being recorded in response to 1-10(-8) M. During incomplete stretching of the leg, the sensitivity was found to be lower. Carbocholine sensitivity is higher than acetylcholine one. Proserine increased ACh sensitivity; the increase was very significant (1, 000 times) provided the leg was completely stretched. Atropine and D-tubocurarine decreased muscle sensitivity to ACh, shifting dose effect curves to the right. The data obtained suggest that muscles of the ambulacral leg possess the system ACh-cholinoreceptor, its concentration being the highest at the base of the leg. Cholinoreception is not limited by M- and H-types only.