SOMATOSENSORY-EVOKED POTENTIALS - INHIBIT ORY INTERACTIONS OF CUTANEOUS AND OR PROPRIOCEPTIVE AFFERENCES AT THE CORTICAL LEVEL AND THEIR GABAERGIC DETERMINISM IN THE BABOON/

Double stimulations induce deep and long-lasting inhibition (0-300 ms) of the P16-N30 components of somatosensory potentials (SEP) evoked by sciatic or sural nerve stimulation. This inhibition is evidenced on b oth SI and MI cortical areas, demonstrating similar course and duratio n, whatever the source (right or left limb) and/or the modality (exter o- or proprioceptive) of conditioning and testing afferences. The dept h of this inhibition depends on the relative amplitude of the conditio ning to testing SEP. After muscle injection of a subconvulsive dose of bicuculline, tSEPs are facilitated when individually elicited. When d ouble stimulations are used, the inhibition of the SEP test is sharply reduced (with a 30-ms interstimulus delay). However, disinhibition of the conditioned SEP does not depend on separate individual SEP facili tations. Cortical GABAergic type a circuits are likely to be involved in inhibition of the conditioned SEP. This inhibition would be a non-i nvasive image of inhibitions that preserve the specificities of sensor y messages in primary areas.