Vibration-induced inhibition of the early components of the tibial nerve somatosensory evoked potential is mediated at a spinal synapse

Objectives: To investigate whether afferent-induced suppression of cortical somatosensory evoked potentials (SEPs) occurs at a spinal site along the t ransmission route of afferent signals from the tibial nerve to the primary somatosensory cortex. Methods: Evoked potentials were recorded at 4 points (sciatic nerve, L5, C1 , and cortex) along the path of transmission following electrical stimulati on of the tibial nerve in halothane-anesthetized cats. The amplitudes of ev oked potentials sampled during vibration of quadriceps were compared to evo ked potentials sampled without the vibration. Results: The spinal SEP recorded at C1 and the cortical SEP were both subst antially reduced by patellar tendon vibration. The L5 spinal SEP and the sc iatic nerve potential were unaffected. Vibration of quadriceps did not infl uence the latency of the evoked potentials. Conclusions: These results indicate that efferent-induced suppression of th e initial complex of the SEP can be mediated at a spinal synapse. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.