Behavior of long-term dantrolene sodium-treated rat skeletal muscles. Histochemical and electromechanical aspects

Histochemical and electrochemical studies were carried out on skeletal rat muscles treated with dantrolene sodium (DS) for 60 days. Histochemical experiments revealed a conversion from fast twitch (type II) to slow twitch (type I) fibers for soleus (S), gastrocnemius (GM),a dn extensor digitorum longus (EDL) muscles. However, a significant decrease of muscle contractility was not observed in these chronically treated rat muscles in opposition to both those directly exposed in vitro as the muscles obtained from only 1-h DS-treated animals.