Further evidence for Renshaw inhibition in man. A combined electrophysiological and pharmacological approach

Experiments involving the acute administration of a central cholinergic substance (L-acetylcarnitine) were performed on 6 healthy subjects to obtain additional evidence that the electrophysiological method developed by Bussel and Pierrot-Deseilligny in 1977 does actually assess recurrent inhibition in man. In all the subjects, the drug further decreased the amplitude of a test H reflex (H') following a conditioning H reflex (H1). The amount of this supplementary inhibition was found to be related to the size of H1 reflex. Experimental evidence is also presented that H' reflex supplementary depression is not contaminated by homonymous Ib effects. It is concluded that the method effectively tests the excitability of Renshaw cells in man.