Effects of Eserine and Neostigmine on the Interaction of Alpha-Bungarotoxin with 'Aplysia' Acetylcholine Receptors.
ARMED FORCES RADIOBIOLOGY RESEARCH INST BETHESDA MD
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Binding of 125 I a-bungarotoxin to acetylcholine receptors of a ganglionic homogenate of the marine mollusc Aplysia is blocked by the anticholinesterases eserine and neostigmine. Eserine and neostigmine also block toxin binding to a solubilized receptor preparation. Unlike their relative potency in blocking toxin binding, neostigmine is a more potent inhibitor of Aplysia acetylcholinesterase than is eserine. alpha-Bungarotoxin does not affect esterase activity or interfere with the ability of eserine to block the esterase. The response to acetylcholine recorded through intracellular microelectrodes is blocked by alpha-bungarotoxin. Neither eserine nor neostigmine blocks the acetylcholine response, but rather prolongs and increases it as expected from their effects on the esterase. Eserine blocks the alpha-bungarotoxin inhibition of the physiologic acetylcholine response. These results indicate that eserine and neostigmine block the binding of alpha-bungarotoxin by interacting with a site which is different from both the esterase and the cholinergic sites of the acetylcholine receptor. These experiments provide further information on the mechanisms of action of specific components of snake venoms.