[Effect of caffeine on tension development of skeletal muscle of mdx mouse]

Among various pharmacological actions of caffeine upon the skeletal muscle, activation of the contractile system by Ca2+ is also influenced by caffeine. So far the effect of caffeine upon the contractile system is not properly studied in pathological muscle specimens. Using the skinned muscle fiber, we compared the effect of caffeine between control and dystrophic (mdx) mouse muscle. In lower Ca2+ (-5 microM), tension generation increased with caffeine. A maximum tension generation in higher Ca2+ (10-30 microM) was suppressed by 30 mM caffeine. In comparison between control and mdx type 2 muscle fiber, tension with caffeine was always more in mdx. On the other hand, modification by 5 mM caffeine was the same between control and mdx type 1 fiber of the soleus muscle. Different responses to caffeine between control and mdx type 2 fiber might be related to prevalent degenerative or regenerative processes. But exact mechanism is not clear yet. Currently, contracture by caffeine or halothane is applied in diagnosis of malignant hyperthermia (MH). Present observations suggested that influence of caffeine on the contractile system constituted one of causes for unspecific results in cases with concurrent neuromuscular diseases.