The effect of capsaicin and conventional analgesics in two models of monoarthritis in the rat.
Systemic administration of capsaicin has been shown to be antinociceptive in a number of acute nociceptive models. We present here two models of prolonged hyperalgesia in the rat induced by intra-articular injection of uric acid or Freund's complete adjuvant into the knee. The time course of hyperalgesia lasts up to 48 h with uric acid and 5 to 10 days with Freund's adjuvant. The hyperalgesia was maximal in both models after 18 h. At this time, the weight tolerated by the injected leg was reduced by 70-80% in the Freund's-treated and 50-60% in the uric-treated animals, compared to the uninjected leg. The hyperalgesia was reversed in both models by indomethacin and ibuprofen (1-100 mg kg-1 s.c.), paracetamol (50-500 mg kg-1 s.c.) and morphine (2-16 mg kg-1 s.c.) in a dose-dependent manner. The morphine reversal was blocked by coadministration with naloxone (2.5 mg kg-1 s.c.). Capsaicin (3-9 mg kg-1 s.c.) also reversed the hyperalgesia in both models.
Davis
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A
Sandoz Institute for Medical Research, London, UK.
Perkins
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MN
D000818:Animals; D001169:Arthritis, Experimental / Q000188:drug therapy*; D002211:Capsaicin / Q000494:pharmacology*; D004195:Disease Models, Animal; D004737:Enflurane / Q000494:pharmacology*; D005260:Female; D005620:Freund's Adjuvant; D006930:Hyperalgesia / Q000188:drug therapy; D051381:Rats; D017207:Rats, Sprague-Dawley; D014527:Uric Acid
D014527:Uric Acid; D005620:Freund's Adjuvant; D004737:Enflurane; D002211:Capsaicin