Mechanical activation in dystrophic C57BL mouse muscle.

Stimulus strength-duration curves for contraction threshold have been obtained from normal and dystrophic C57BL mouse muscle fibres using two microelectrode voltage clamp techniques. The threshold membrane potential for activation in dystrophic soleus fibres was further from the resting membrane potential than in normal fibres and was close to the threshold for extensor digitorum longus fibres. When a redistribution if fibre types in dystrophic soleus muscles is taken into account the dystrophic data fell within the normal range of values. It is apparent that the inability of dystrophic C57BL mice to use their hind limbs in the normal way cannot be attributed to a failure of excitation-contraction coupling.