GROUP IA NONRECIPROCAL INHIBITION FROM WRIST EXTENSOR TO FLEXOR MOTONEURONS IN HUMANS

Interneurones mediating disynaptic inhibition from extensor to flexor carpi radialis muscles were characterized by pharmacological stimulati on of Renshaw cells. It is, indeed, known that only Ia interneurones a re blocked by recurrent inhibition. Renshaw cell potentiation, induced by intravenous administration of 2 g levo-acetylcarnitine, blocked Ia reciprocal inhibition from triceps to biceps muscles but not disynapt ic inhibition from extensor to flexor carpi radialis muscles. It is co ncluded that the interneurones mediating this latter inhibition are no t Ia interneurones. This kind of inhibition could be an example of a I a non-reciprocal inhibitory pathway.