Rapid cooling contracture in frog striated muscles treated with chlorpromazine and haloperidol.

Rapid cooling contracture (RCC) was observed in frog toe muscles pretreated with caffeine, chlorpromazine (CPZ), or haloperidol (HPD). During rapid cooling contracture in the presence of caffeine (caffeine-RCC) tension developed to more than 0.8 of the maximum tetanic tension (P0). CPZ inhibited twitch but induced rapid cooling contracture (CPZ-RCC) between 50 and 150 microM; the tension saturated at the level of 0.75 P0 at 100 microM. HPD also inhibited twitch and induced rapid cooling contracture (HPD-RCC) at concentrations greater than 25 microM; the maximum tension was 0.25 P0. In the presence of dantrolene (10 microM), the tension during CPZ-RCC was reduced by 40%. Procaine (0.25%) reduced the CPZ-RCC tension by as much as 60%. These results suggest that CPZ and HPD induced rapid cooling contracture by reducing Ca2+-accumulation in sarcoplasmic reticulum.