Recovery of the Kinetic and Tonic Components in M-wave after Repetitive Stimulation

抄録

1) Electric stimuli were given to the ulnar nerve at the elbow in men and the responses (M-waves) were picked up by bipolar surface electrodes placed above the M. abductor digiti V. 2) The kinetic component of the M-wave has a lower threshold than the tonic component in the strength- duration curve. 3) With paired stimulation, both the kinetic and tonic components were noticed on the second response even at a stimulus interval of 2 msec. 4) Similar responses were obtained successively by the repetitive stimulation of less than 20 per sec. At the rate of 30 per sec, the tonic activity was abolished in the fourth or fifth and in the subsequent responses. 5) A test stimulus was applied 10 msec after 10 conditioning shocks. When the rate of conditioning stimulus was more than 10 per sec, the tonic component was abolished and the ‘pure’ kinetic responses were obtained. Full recovery of the tonic component requires 200 and 300 msec after 10 impulses at the rate of 10 and 50 per sec, respectively. The inhibition of kinetic component was observed after conditioning at 200 per sec and the full recovery occurred within 100 msec. 6) It is suggested that during repetitive stimulation the transmitter available for immediate release is exhausted faster in the tonic motor nerve terminals than in the kinetic nerve terminals, probably due to a slower mobilization or larger quantal liberations of transmitter.