Differential modulation of short and long latency sensory responses in the SI cortex by IL-6

The effects of topical application of interleukin-6 (IL-6) on the short and long latency evoked unit responses of the neurones in the primary somatosensory (SI) cortex were determined quantitatively in anaesthetized rats. IL-6 (0.01, 0.1, 1.0 units) significantly suppressed (-15.13 +/- 3.4%) short latency afferent sensory responses, while it induced profound facilitation (+464.74 +/- 132.7%) of long latency responses in a dose-dependent manner. IL-6-induced afferent modulations fully recovered by 60 min after drug administration. In control experiments, saline solution containing 0.2% bovine serum albumin, used as a vehicle, did not affect afferent sensory transmission. Implications of these results are discussed with reference to the different somatosensory functions of short and long latency response components in the SI cortex.