Calotropis procera latex-induced inflammatory hyperalgesia - effect of bradyzide and morphine.

1 The milky white latex of the plant Calotropis procera induces inflammatory response upon accidental exposure and on local administration that could be effectively ameliorated by antihistaminic and standard anti-inflammatory drugs. 2 The aim of the present study was to evaluate the anti-oedematogenic and analgesic effect of the bradykinin antagonist, bradyzide (BDZ) and the opioidergic analgesic, morphine (Mor) against inflammatory hyperalgesia induced by the dried latex (DL) of C. procera in the rat paw oedema model. 3 An aqueous solution of DL (0.1 ml of 1% solution) was injected into the sub-plantar surface of the rat paw and the paw volume was measured at different time intervals. The inhibitory effect of bradyzide and morphine on oedema formation and hyperalgesic response was compared with that of cyproheptadine (CPH), a potent inhibitor of DL-induced oedema formation. 4 The hyperalgesic response was evaluated by the dorsal flexion pain test, compression test and by observing motility, stair-climbing ability, and the grooming behaviour of the rats. 5 The effect of these drugs was also evaluated against DL-induced writhings in the mouse model. 6 Both bradyzide and morphine inhibited DL-induced oedema formation by 30-40% and CPH was more effective in this regard (81% inhibition). The antihyperalgesic effect of both the drugs was more pronounced than that of CPH. Both bradyzide and morphine markedly inhibited the grooming behaviour and the effect of morphine could be reversed by pretreatment with naloxone. 7 Thus, our study shows that DL-induced oedema formation is effectively inhibited by antihistaminic/antiserotonergic drug and associated hyperalgesia by analgesic drugs.