A refractory period after brief activation of mammalian skeletal muscle fibres.

A two pulse technique was used to study the decay of mechanical activation in TTX poisoned mouse extensor digitorum longus (EDL) and soleus muscle fibres. A two microelectrode point voltage clamp technique was used with visual endpoint determination of the threshold potential for activation. The excitatory effect of a brief (0.5-2.0 msec) depolarizing pulse decayed quickly and became inhibitory. In EDL fibres the peak inhibition was 0.5-1.0 msec after the termination of the conditioning pulse and decayed within 3.0 msec. Inhibition was less pronounced in soleus fibres and decayed more slowly. It is suggested that inhibition may be responsible for a refractory period in excitation-contraction coupling.