Nicotinic binding sites in rat and mouse brain: comparison of acetylcholine, nicotine, and alpha-bungarotoxin.

The properties of the binding sites for radiolabeled acetylcholine (measured in the presence of atropine), nicotine, and alpha-bungarotoxin were compared in brain tissue prepared from both rat and mouse. These three binding sites were tested for the following properties: affinity and density of ligand binding, effects of competitive inhibitors, regional distribution, effects of treatment with dithiothreitol and the reversal of these effects by treatment with 5,5'-dithiobis(2-nitrobenzoic acid), thermal lability, effects of protease treatment, and response to chronic administration of nicotine in vivo. The binding sites for acetylcholine and nicotine were affected identically for all measurements, whereas the binding site for alpha-bungarotoxin was affected in a manner different from that for the other two ligands. Although the regional distribution of nicotine and acetylcholine binding differed between rat and mouse brain, other properties of this binding site were very similar between the two species. The results are consistent with the proposal that acetylcholine and nicotine bind to the same sites in both rat and mouse brain, whereas alpha-bungarotoxin binds to different sites.