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Non-equivalency of inactivation and denervation in altering characteristics of muscle fibre type in rat soleus muscle

Zhu Peihong, Li Ruhong

Shanghai Institute of Physiology, Academia Sinica. Shanghai, China

Abstract

The fast-twitch muscle extensor digitorum longus (EDL) and the slow-twitch muscle (SOL) of the rat were completely inactivated by chronically blocking the sciatic nerve with tetrodotoxin. The inactivation-induced changes in the contractile properties, M-ATPase histochemical staining and Z-band width of these muscles were examined, and compared with those produced by denervation. Results show that the inactivated EDL is similar to the denervated one, i.e. having slower contraction, normal fibre type proportion and Z-band-width. But, in SOL several differences were noted. In contrast to the slowing contraction due to denervation, the inactivated SOL gets faster. In comparison to normal SOL, the number of type II fibres becomes doubled in the inactivated SOL, whereas denervation has no significant effect on the fibre type proportion. Several possibilities were discussed with regard to the non-equivalency of TTX inactivation and denervation in altering characteristics of the SOL fibre type.

Key words: Inactivation;Denervation;Fast-twitch muscle;Alow-twitch muscle

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Citing This Article：

Zhu Peihong, Li Ruhong. Non-equivalency of inactivation and denervation in altering characteristics of muscle fibre type in rat soleus muscle. Acta Physiol Sin 1986; 38 (3): (in Chinese with English abstract).