Pharmacological characterization of the rat's paw oedema induced by Echis coloratus Venom
2003
Al-Asmari, A.K. (Armed Forces Hospital, Riyadh (Saudi Arabia). Research Centre)
The present study was conducted to investigate the inflammatory response induced by Echis coloratus venom (ECLV) in the rat hind-paw by measuring paw oedema. Non-heated ECLV (50 mug paw-1) caused a marked paw oedema (plateau) accompanied by intense haemorrhage whereas heated venom (97 degree centigrade, 30 s; 3.125-75 mug paw-1) produced a dose and time- dependent non-haemorrhagic oedema. The response with heated ECLV was maximal within 15 min, disappearing over 24 h. Heated ECLV (50 mug paw-1) was optimized to test the effect of various drugs on oedema induced by the ECLV. The results showed that cyproheptadine (H1 and H3) receptor antagonist highly (P less than 0.001) reduced venom-induced rat paw oedema and was moderately (P less than 0.01) reduced by dexamethasone. A proteinase inhibitor (aprotinin), cyclooxygenase inhibitor (indomethacin) and histamine (H1) receptor antagonist (chlorpheniramine) produced a low but significant inhibition of oedema formation. The commercially available antivenom was found to be ineffective when administered intravenously, whereas its local administration partially reduced rat paw oedema induced by ECLV, but was not statistically significant. The present study concluded that ECLV alone induced oedema and the expected principal mediators of this inflammatory response were serotonin, histamine, cyclo- oxygenase and other prostaglandins (PGs) and cytokines. Finally the polyspecific antivenom given intravenously could not prevent the oedema forming effect in rats.
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