CONTRACTILE PROPERTIES OF STRIATED-MUSCLE FIBERS OF ESOPHAGEAL MUSCLE IN COMPARISON TO SKELETAL-MUSCLES OF RAT

  • 1 January 1978
    • journal article
    • research article
    • Vol. 37  (2) , 335-346
Abstract
The contractile properties of the striated esophageal rat muscle were studied in vitro at 35.degree. C and 25.degree. C. They were compared with those of the slow-twitch soleus muscle and the fast-twitch extensor digitorum longus (EDL) muscle. The contraction time of the esophageal muscle is 30 msec (.+-. 2.5 msec SE) at 35.degree. C. It is small but significantly longer than those of the soleus muscle. It is remarkable that the twitch-tetanus ratio of the esophageal muscle fibers is approximately 2 .times. that of the skeletal muscles. Immediately after a tetanic stimulation the amplitude of a single twitch of the fast EDL is increased (posttetanic potentiation); in the slow soleus muscle it is unchanged or decreased. The muscle fibers of the esophagus exhibit a post-tetanic-potentiation, but this is smaller than in EDL. A decrease of the temperature of the bathing solution causes in preparations of the fast EDL a higher tension developed by a single twitch (cold potentiation). This is not detectable in preparations of the slow soleus muscle. The esophageal muscle shows also a remarkable cold potentiation, but it is smaller than in EDL. An increase of the extracellular K+-concentration evokes a short-lasting contracture in the rat muscles. The mechanical thresholds of the esophageal muscle fibers are clearly higher than those of the soleus muscle but lower than those of the EDL. The striated esophageal muscle fibers of the rat in spite of their low speed of contraction show some properties of muscle fibers of the fast twitch type.

This publication has 2 references indexed in Scilit: