The
venom of the common Indian
catfish P. canius Hamilton (locally called 'Kanmagur') was examined for its pharmacodynamic activity. The
LD50 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 hearts, while at higher doses it produced
cardiac arrest. In the isolated
guinea pig auricle, the
venom increased the rate and amplitude of contraction. The
venom increased
rat blood pressure--an action antagonised by alpha-
adrenergic blocker (
phenoxybenzamine). It reduced the rate and amplitude of
rat and
guinea pig respiration leading to respiratory arrest and
death. The
venom did not alter the cutaneous
capillary permeability of
guinea pig but produced
vasoconstrictor effect on
rat hindquarter
perfusion. It induced contractions in several
smooth muscle preparations viz.,
ileum and
colon of
guinea pig, fundus,
uterus and
ileum of
rat. On isolated
guinea pig ileum, the
venom produced contraction which was not antagonised by
atropine and
mepyramine, but was partially antagonised by
methysergide associated with a residual contraction which was abolished by SC 19220, a
prostaglandin receptor blocker. The
venom produced irreversible blockade of electrically induced twitch response on isolated
rat phrenic nerve diaphragm and chick biventer cervicis preparation.
Haemolysis was not produced by the
venom on
mice,
guinea pig and
human RBC (washed).