Kuhlmann, Jurgen and Okonjo, K. O. and Maelicke, Alfred
Desensitization is a property of the cholinergic binding region of the
nicotinic acetylcholine receptor, not of the receptor-integral ion channel.
The reversible acctylchollne esternse inhibitor (-}.physostiilmine (¢serine) is th© prolotypc of a new class of nie~tinlc ucetylcholinc receptor
(nAChR) activating liga,ds: it induces cation fluxes into nAChR.rich membrane vesicl~s from 7~r#eda marmoeata cle~:tric tissue even under condl.
lions of antalionist blocked :tcctylcholin~ binding sil~s (Okonjo, Kuhlm~mn. Maelicke. Neuron, in press). This su~tlest's that escrine exerts it~ than.
nel.activating proi'~rty via binding sites at the nAChR separate from those of tile natural transmitter. We now report thllt eserine e'-m activate
the channel wen when the receptor has t~en preincub~ttcd (des©nsitiz©d) with elevated concentrations of acetylcholi~e, Titus the confornudional
state Of the receptor corresponding to de~nsitixation is confined to the transmitter bindinB rclli0n, leaving the ch=tr'4nel fully activatable ,- albeit
only from other than the tr~msmitter bindin~ site(s),
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