Mechanical response of the frog's rectus to potassium. Effect of various substances

Hrvoje Lorkovi ¹

¹ Institute for Medical Research, Yugoslav Academy of Sciences and Arts Zagreb, Yugoslavia

Veratrine and sodium fluoride potentiate the twitch fiber reaction, as revealed by the changes in the first phase of the frog's rectus potassium contracture. Caffeine potentiates the reaction of both twitch and slow fibers. Sodium thiocyanate and chloroform mainly potentiate the reaction of slow fibers. Glucose, ethyl ether and acetophenone depress the twitch fiber reaction, potentiating, to various degrees, the slow phase. Only in a few cases is the reaction pattern of the muscle affected by changes in exposure time and concentration of these agents. The different actions of the ‘sensitizers to potassium’ are discussed in the light of the present investigations.