Temperature dependence of electro-mechanical coupling in crayfish muscle fibers

Summary In single fibers of crayfish muscle the membrane was clamped to definite potentials for periods of 10 ms to 10 s. Contraction of the fiber was measured isometrically. The influence of temperature on the relations between contraction and amplitude as well as duration of depolarization was determined.Upon cooling the preparation from 20 to 10°C maximum force of contraction decreased with a Q₁₀ of 3, while the rate of rise of contraction was reduced even more. Relaxation was more slowed by cooling than contraction. The Q₁₀ of the delay of relaxation relative to repolarization and of the rate of relaxation were in the range of 3–10. The results suggest that cooling decreases the amplitude of the active state and slows its rise and decay. Only one of the measured parameters had a low Q₁₀ of 1.2, namely the period of continued increase of rate of rise of contraction after repolarization. A state of excitation of an internal membrane system continued after repolarization of the surface membrane could explain this finding.This work was supported by the Deutsche Forschungsgemeinschaft.