Aryldiazonium salts as photoaffinity labels of the nicotinic acetylcholine receptor PCP binding site

Several aryldiazonium salts are described as irreversible blockers of the phencyclidine binding site of the nicotinic cholinergic receptor. A partial hydrophobic character increases the affinity of these salts for the phencyclidine binding site. Photoaffinity labelling with a tritiated diazonium salt in the presence of either carbamylcholine or alpha-bungarotoxin leads to incorporation of radioactivity into the 4 subunits of the receptor. Among these diazonium salts, an imidazole derivative is unique in that the photoinduced irreversible blocking in only effective when the receptor is in a desensitised state.