[Comparative characteristics of depolarization (potassium) and acetylcholine contracture of Lampetra fluviatilis lamprey phasic muscle].

Acetylcholine (Ach) contractures of thin bundle from m. longitudinal linguae of the lamprey differs by several parameters from depolarization (potassium) contracture, although Ach similar to K ions totally depolarizes the surface membrane of muscle fibers. Maximum tension of Ach contracture is 30--100% higher than that of K contracture, maximum of both contractures being observed at the same membrane potential level (approximately -10mV). The rate of rise of Ach contracture is 10 times higher, whereas the latent period is 3 times shorter as compared with the same parameters of K contracture. At higher Ach concentrations (10(-5)--10(-4) g/ml) the latent period of contracture is shorter than that of depolarization.