The sea snake Enhydrina schistosa is major neurotoxin, enhydrotoxin-and produced irreversible neuromuscular blockade of single twitch responses to indirect electrical stimulation. The tetanic stimulation elicited sustained tetanus during the neuromuscular blockade. The sustained tetanus was transformed to an exaggerated twitch response, following treatment of enhydrotoxin-a plus monovalent sea snake antivenin and washout when the mammalian neuromuscular preparation completely restored to normal twitch responses to single indirect electrical stimulation.
The exaggerated twitch response as a facilitatory post tetanic potentiation (fPTP) is discovered as an expression of the presynaptic nicotinic stimulatory autoreceptor at the mammalian neuromuscular junction. The observation of fPTP as a presynaptic nicotinic stimulatory autoreceptor was analogous to the experiments of tetanic fade induced by d-tubocurarine on mammalian neuromuscular junction subjected to high frequency stimulation.
Key Words: Exaggerated twitch response, facilitatory post tetanic potentiation, presynaptic nicotinic stimulatory auto receptor.