Pharmacological characterisation of a neurotoxin from the venom of Boiga dendrophila (Mangrove catsnake)

In this study, we have pharmacologically characterised boigatoxin-A, a three finger toxin isolated from the venom of the colubrid, Boiga dendrophila (Mangrove catsnake). In the chick biventer cervicis nerve-muscle preparation boigatoxin-A (1 μM) displayed poorly reversible postsynaptic blockade as evidenced by the inhibition of indirect (0.1 Hz, 0.2 ms, supramaximal V) twitches and responses to exogenous acetylcholine (1 mM) and carbachol (20 μM). Boigatoxin-A (0.3-0.5 μM) caused a concentration-dependent depression of the maximum response of cumulative concentration response curves to CCh (0.6-80 μM). Boigatoxin-A (1 μM) induced readily reversible inhibition of electrically evoked (0.2 Hz, 0.3 ms, 70-100 V) twitches of the prostatic segment of the rat vas deferens. This inhibition was not significantly attenuated by 8-phenyltheophylline (20 μM) or idazoxan (1 μM). Boigatoxin-A (1 μM) did not affect α,β-mATP (10 μM) or noradrenaline (25 μM) responses in unstimulated epididymal segments of the rat vas deferens. Our data suggests that this toxin has weak postsynaptic neurotoxicity in skeletal muscle and also prejunctional neurotoxic activity in the smooth muscle of the rat vas deferens to inhibit the release of neurotransmitter(s), but not via prejunctional purinergic or adrenergic receptors. This is the first report of such activity for a toxin isolated from snake venom and reinforces the largely untapped potential of colubrid venoms.