[Effects of dantrolene sodium on some types of visceral muscles (author's transl)]

Twitch contraction height of the outer layer of esophagus was reduced by 5 X 10(-6) g/ml of dantrolene to 7% of the height observed before the application. High-K induced contracture of this preparation and of cremaster muscle were also depressed to 14% and to 18% of the control, respectively. When dantrolene (25 X 10(-6) g/ml) was applied during the contracture induced by 9.7 X 10(-4) g/ml of caffeine, a complete relaxation was observed. Dantrolene had no effect either on the evoked twitch contraction of the smooth muscle of vas deferens or on spontaneous contractions of the taenia coli. High-K induced contracture of these smooth muscles was not affected by dantrolene. Electron micrograph showed that the outer layer of esophagus and cremaster muscle were composed of striated muscle cells in which the sarcoplasmic reticulum, transverse tubulus, and triadic junctions were well developed. In smooth muscle preparations, although sarcoplasmic reticula were observed, neither transverse tubula nor triadic junctions comparable to those in the striated muscle were evident. These morphological differences may explain differences in the action of the drug.