Segmental localisation of the relays mediating crossed inhibition of hindlimb motoneurones from group II afferents in the anaesthetized cat spinal cord.

We have investigated the location of the spinal neurones mediating crossed inhibition from group II afferents. Short latency IPSPs are evoked in hindlimb extensor motoneurones by stimulation of specific contralateral limb nerves at stimuli sufficient to activate group II muscle afferents. Reversible or irreversible interruption of the dorsal columns in the fifth lumbar segment (L5) dramatically attenuated the crossed inhibition. It therefore appears that the central pathway mediating this 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 interneurone is involved.