[Reciprocal inhibition of human motor neurons at different firing rates].

Abstract

Reciprocal inhibition (RI) has been studied for its effect on repetitive firing of single motoneurons in the extensor carpi ulnaris and soleus muscles of healthy subjects. The peristimulus time histograms (PSTHs) were plotted for different mean firing frequency of motoneurons. Changes in the interspike interval duration were analyzed. It was shown that the "effectiveness" of reciprocal volleys (as it was previously shown for other types of inhibition) depended on the firing rate of a motoneurons. It was found out that RI duration derived from the PSTH, duration of the "effective part" of the interspike interval, rate of the interspike interval lengthening depended on the motoneuron firing frequency. It was also found that the inhibitory effect of the motoneuron firing was pronounced mostly at its low-frequency range. The dependence of "effectiveness" of an inhibitory volley on the moment of its arrival within the interspike interval was analyzed as well.