Viperidae snake venoms block nicotinic acetylcholine receptors and voltage-gated Ca super(2+) channels in identified neurons of fresh-water snail Lymnaea stagnalis

Snake venoms contain a vast array of toxic polypeptide components interacting with a variety of cell targets. Thus, Elapidae snake venoms contain alpha -neurotoxins with very high affinity for nicotinic acetylcholine receptors (nAChRs) and a few toxins able to suppress the activity of Ca super(2+) and K super(+) channels. Experimental evidence for the presence of nAChR antagonists and voltage-gated ionic channel blockers in venoms of Viperidae snakes is very scarce. In this study, effects of crude venoms of seven snake species (Vipera nikolskii, Echis multisquamatus, Gloydius saxatilis, Bitis arietans, Vipera renardi, Vipera lebetina, and Naja kaouthia) on nAChRs and voltage-gated Ca super(2+) channels were studied for the first time. The experiments were carried out on isolated identified neurons of the fresh-water mollusc Lymnaea stagnalis using voltage-clamp and intracellular perfusion techniques. All Viperidae snake venoms under study blocked nAChRs and voltage-gated Ca super(2+) channels. The potency of these venoms against nAChRs was significantly lower in comparison with N. kaouthia venom which is rich of alpha -neurotoxins; however, the extent of Ca super(2+) channel block by venoms of Viperidae snakes and N. kaouthia was similar. The data obtained suggest that Viperidae snake venoms tested in this study contain peptides with affinity both for nAChRs and for voltage-gated Ca super(2+) channels.