Transformation of ultrastructural type of fast-twitch muscle fibres after cross-innervation by tetrodotoxin-blocked slow muscle nerve.
It is shown in rats that cross-innervation of the fast-twitch muscle extensor digitorum longus (EDL) by the nerve of the slow-twitch muscle soleus (SOL) can cause a complete transformation of the Z-band width from the fast to the slow muscle fibre type within two weeks and that it can still induce such a transformation, though usually less completely, even when impulse activity is excluded by chronical tetrodotoxin (TTX) block of the nerve. This provides a piece of clear-cut evidence for the presence of some activity-independent trophic factor in the neural determination of skeletal muscle fibre type.
D000818:Animals; D008854:Microscopy, Electron; D009119:Muscle Contraction / Q000187:drug effects*; D009132:Muscles / Q000187:drug effects / Q000294:innervation / Q000648:ultrastructure*; D051381:Rats; D012584:Sciatic Nerve / Q000187:drug effects / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology*
D013779:Tetrodotoxin