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 measured by laser Doppler flowmetry. Intraplantar injection of interleukin-1 beta (50 pg) significantly enhanced the hyperaemic response to intraplantar capsaicin (0.3 mu g). Pretreatment with a neurotoxic dose of capsaicin reduced the capsaicin-evoked hyperaemia and prevented the facilitatory effect of interleukin-1 beta. Blockade of nitric oxide formation by N-G-nitro-L-arginine methyl ester failed to affect the capsaicin-evoked vasodilatation but abolished its amplification by interleukin-1 beta. These data indicate that the enhancement by interleukin-1 beta of the capsaicin-induced hyperaemia involves thin afferent nerve fibres and depends on nitric oxide as essential intermediate.