Capsaicin suppresses substance P-induced joint inflammation in the rat.
Intra-articular injection of 20 micrograms substance P in rat knee joints results in a pronounced inflammatory response. However, prior intra-articular injection of 1% capsaicin solution (1-5 weeks previously) virtually abolishes this response. This is not a neurotoxic effect of capsaicin on nerve fibres as denervation of the knee produces no alteration of the response to injected substance P. The potent effect of capsaicin on substance P-mediated inflammation cannot be attributed to depletion of mast cells by this treatment as the mast cell degranulator compound 48/80 injected into capsaicin pre-treated knees still gives rise to a marked inflammatory response. Compound 48/80 does not activate nerve fibres to cause release of substance P as it is equally effective in eliciting an inflammatory response in the presence of 100 micrograms of the substance P antagonist D-Pro4, D-Trp7,9,10 SP(4-11) in the synovial cavity. The results suggest that capsaicin may act by depleting substance P receptors in joint tissue.
Lam
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Institute of Physiology, University of Glasgow, U.K.
Ferrell
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WR
D000818:Animals; D001168:Arthritis / Q000139:chemically induced* / Q000503:physiopathology; D002211:Capsaicin / Q000494:pharmacology*; D003714:Denervation; D007270:Injections, Intra-Articular; D007719:Knee Joint / Q000187:drug effects*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D013373:Substance P / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D013583:Synovial Membrane / Q000187:drug effects / Q000503:physiopathology; D003189:p-Methoxy-N-methylphenethylamine / Q000494:pharmacology
D013373:Substance P; D003189:p-Methoxy-N-methylphenethylamine; D002211:Capsaicin