NITRIC-OXIDE MEDIATES THE AMPLIFICATION BY INTERLEUKIN-1-BETA OF NEUROGENIC VASODILATATION IN THE RAT SKIN

Blood flow in the plantar hindpaw skin of anaesthetized rats was measu red by laser Doppler flowmetry. Intraplantar injection of interleukin- 1 beta (50 pg) significantly enhanced the hyperaemic response to intra plantar capsaicin (0.3 mu g). Pretreatment with a neurotoxic dose of c apsaicin reduced the capsaicin-evoked hyperaemia and prevented the fac ilitatory effect of interleukin-1 beta. Blockade of nitric oxide forma tion by N-G-nitro-L-arginine methyl ester failed to affect the capsaic in-evoked vasodilatation but abolished its amplification by interleuki n-1 beta. These data indicate that the enhancement by interleukin-1 be ta of the capsaicin-induced hyperaemia involves thin afferent nerve fi bres and depends on nitric oxide as essential intermediate.