Snake Venom Neurotoxins: Pharmacological Classification

Abstract

Neurotoxic proteins isolated from various snake venoms, because of their high affinity for a particular target site are used extensively as pharmacological tools to gain insights into the function of the nervous system. The potency of these molecules lies in their affinities towards the biomolecules involved in the functioning of neuromuscular transmission. Neuromuscular and pathophysiological effects of neurotoxic proteins result from their interaction with various microcompartments based on their similarities in mass and conformation to the types of amino acids and disulfide bridges in the normal ligands. Snake venom toxins can be broadly classified depending on whether their site of action is at the skeletal neuromuscular junction, or at sites other than the skeletal neuromuscular junction. Skeletal neuromuscular junction‐specific neurotoxins include the following: postsynaptic toxins, presynaptic toxins, presynaptic toxins with musculotropic or myonecrotic actions, presynaptic and postsynaptic, presynaptic and postsynaptic toxins with musculotropic or myonecrotic actions, myotoxic and antiAChE neurotoxins, etc. Snake venom neurotoxins with affinities selective to the sites other than the skeletal NMJ were categorised as non‐skeletal neuromuscular junction snake venom neurotoxins and they include toxins with affinity for muscarinic and neuronal receptors; toxins with affinity for K⁺ and Ca^{2 +} ion channels, toxins with affinity for enzymes and muscle elements, centrally‐acting neurotoxins, peptide neurotoxin and miscellaneous neurotoxins. There is an additional miscellaneous class of snake venom neurotoxins that includes weak neurotoxin, muscarinic toxin‐like proteins and vipoxin. The toxic mechanisms of well‐studied snake venom neurotoxins and their sites of action underlying neurotoxicity are discussed in this review, and they form the basis for classification of snake venom neurotoxins.

Keywords: :

• Presynaptic
• Postsynaptic
• Snake venom neurotoxins
• Skeletal neuromuscular junction
• Toxin
• Vipoxin

Acknowledgments

The author wishes to acknowledge the scholarship (PDF) during sabbatical period at Dept. of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, USA, with Prof. Anthony T. Tu, (Oct.97–May 98), and Prof. B.G.Shivananda, Principal, Al Ameen College of Pharmacy, Bangalore for supporting the visitor's exchange program.