PHARMACOLOGICAL ACTIONS OF THE VENOM OF THE INDIAN CATFISH (PLOTOSUS-CANIUS HAMILTON)

The venom of the common Indian catfish P. canius Hamilton (locally cal led 'Kanmagur') was examined for its pharmacodynamic activity. The LD5 0 of the venom in mice was found to be 3.9 mg/kg (ip). At lower doses, the venom produced a positive inotropic effect on toad and rabbit hea rts, while at higher doses it produced cardiac arrest. In the isolated guineapig auricle, the venom increased the rate and amplitude of cont raction. The venom increased rat blood pressure-an action antagonised by alpha-adrenergic blocker (phenoxybenzamine). It reduced the rate an d amplitude of rat and guineapig respiration leading to respiratory ar rest and death. The venom did not alter the cutaneous capillary permea bility of guineapig but produced vasoconstrictor effect on rat hindqua rter perfusion. It induced contractions in several smooth muscle prepa rations viz., ileum and colon of guineapig, fundus, uterus and ileum o f rat. On isolated guineapig ileum, the venom produced contraction whi ch was not antagonised by atropine and mepyramine, but was partially a ntagonised by methysergide associated with a residual contraction whic h was abolished by SC 19220, a prostaglandin receptor blocker. The ven om produced irreversible blockade of electrically induced twitch respo nse on isolated rat phrenic nerve diaphragm and chick biventer cervici s preparation. Haemolysis was not produced by the venom on mice, guine apig and human RBC (washed).