SEGMENTAL LOCALIZATION OF THE RELAYS MEDIATING CROSSED INHIBITION OF HINDLIMB MOTONEURONS FROM GROUP-II AFFERENTS IN THE ANESTHETIZED CAT SPINAL-CORD

We have investigated the location of the spinal neurones mediating cro ssed inhibition from group II afferents. Short latency IPSPs are evoke d in hindlimb extensor motoneurones by stimulation of specific contral ateral limb nerves at stimuli sufficient to activate group II muscle a fferents. Reversible or irreversible interruption of the dorsal column s in the fifth lumbar segment (L5) dramatically attenuated the crossed inhibition. It therefore appears that the central pathway mediating t his crossed inhibition involves an interneuronal relay located in the L5 segment or further rostrally. As a consequence of this anatomy, the short central latency of the crossed IPSPs suggests that a single int erneurone is involved.