The effect of temperature on the effects of the phospholipase A₂ neurotoxins β-bungarotoxin and taipoxin at the neuromuscular junction

Snake venom neurotoxins with phospholipase A₂ affect the neuromuscular junction with three distinct phases. There is a transient decrease in twitch height, followed by a facilitatory phase and finally a progressive blockade. It has been suggested that the initial phase is a direct consequence of the binding of the toxins to nerve terminals. This study was designed to determine whether the initial phase is present under conditions that would reduce the enzyme activity of the toxins. At 27 °C, β-bungarotoxin and taipoxin exhibited all three phases, i.e. 5-6 min after exposure to the preparation, twitch height was significantly reduced (P