[Excitability cycle of the soleus motor nucleus during synergistic conditioning in man].

Electrical stimulation of medial or lateral gastrocnemius nerve modulates the H reflex of the soleus muscle in a well defined sequence of inhibitory and facilitatory phases the amplitude of which depends on the strength of the conditioning stimulus. This method of investigation of the soleus monosynaptic reflex pathway avoids the disadvantages of homonymous conditioning. Discussion of our results points to the roles of Ib and Renshaw cells inhibitions in the early phases of the recovery cycle, and to the roles of reafferents, disinhibition of Renshaw cells, presynaptic inhibition and muscarinic discharge of Renshaw cells for the late phases.