Many snake toxins affect the release of acetylcholine at the neuromuscular junction. The phospholipase toxins, which include β-bungarotoxin, crotoxin, notexin, and taipoxin, cause an irreversible block of acetylcholine release after a period in which release is augmented. The dendrotoxins from African mamba snakes do not block, release or affect spontaneous release of acetylcholine, but only facilitate release in response to nerve action potentials. The dendrotoxins and at least some of the phospholipase toxins block certain K+ currents in neurons. As a consequence, both types of toxins can facilitate the evoked release of acetylcholine from mammalian motor nerves. The toxins also act on central neurons following intracerebroventricular injection. They can be radiolabeled and shown to bind to specific high affinity sites on neuronal membranes. Consequently, the toxins are used to probe the distribution of K+ channels in the central nervous system and to isolate putative K+ channel proteins. This chapter explains the methods used to study the effects of such toxins on neuromuscular transmission and on the excitability of motor nerve endings.
|Name||Methods in Neurosciences|
- potassium channel-blocking toxins
- snake venom
- neuromuscular transmission