Effect of caffeine on capsaicin induced hyperalgesia in mice

Caffeine is the most widely consumed behaviorally active substance in the world. In the past several pharmaceutical companies used caffeine along with other drugs to get analgesic effect. The present research work was undertaken to investigate the effect of interaction of caffeine and capsaicin on animal model of hyperalgesia in mice. To meet these objectives, effect of drugs was studied using tail immersion test, an animal model of thermal hyperalgesia and tail withdrawal test in mice, an animal model of cold hyperalgesia. The efficacy of three active principles alone and in combination of indomethacin, caffeine and prochlorperazine in reverting hyperalgesia was studied. Indomethacin 0.3 mg/ kg, i.p., caffeine 0.1 & 0.3 mg/ kg, i.p. and prochlorperazine 0.1 mg/ kg as well as combination reverted morphine withdrawal induced hyperalgesia. Initial application of capsaicin was found to be algesic leading to noxious stimulation in peripheral nervous system, which may cause allodynia and hyperalgesia. Thus this mechanism is also being studied in this study. Since most of the centrally acting analgesics act by way of their effect on dopaminergic mechanism and modifying calcium release, further studies on hyperalgesic activity were carried out using caffeine, capsaicin, amlodipine, haloperidol in the tail immersion (hot water of 55°C) and the tail withdrawal test (cold ethanol -14°C).