PT - JOURNAL ARTICLE AU - DAVID O. CARPENTER AU - LLOYD A. GREENE AU - WILLIAM SHAIN AU - ZVI VOGEL TI - Effects of Eserine and Neostigmine on the Interaction of α-Bungarotoxin with <em>Aplysia</em> Acetylcholine Receptors DP - 1976 Nov 01 TA - Molecular Pharmacology PG - 999--1006 VI - 12 IP - 6 4099 - http://molpharm.aspetjournals.org/content/12/6/999.short 4100 - http://molpharm.aspetjournals.org/content/12/6/999.full SO - Mol Pharmacol1976 Nov 01; 12 AB - Binding of [125I]α-bungarotoxin to acetylcholine receptors of ganglionic homogenate of the marine mollusc Aplysia is blocked by the anticholinesterases eserine (I50 = 4 µM) and neostigmine (I50 = 0.2 mM). The classical acetylcholine antagonist d-tubocurarine blocks with an I50 of 2 µM. Eserine (I50 = 3.2 µM) and neostigmine (I50 &gt; 1 mM) also block toxin binding to a solubilized receptor preparation. In contrast to their relative potency in blocking toxin binding, neostigmine is a more potent inhibitor of Aplysia acetylcholinesterase (I50 = 14 nM) than is eserine (I50 = 250 nM). α-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 α-bungarotoxin. Neither eserine nor neostigmine blocks the acetylcholine response; rather, they prolong and increase it, as expected from their effects on the esterase. Eserine (0.1 mM) blocks the α-bungarotoxin inhibition of the physiological acetylcholine response. These results indicate that eserine and neostigmine block the binding of α-bungarotoxin by interacting with a site which is different from both the esterase and the cholinergic sites of the acetylcholine receptor.