Comparison of [3H]nicotine and [3H]acetylcholine binding in mouse brain: regional distribution.

In a continuing study of nicotine binding sites, we determined the relative amount of nicotine binding and acetylcholine binding in various brain regions of C57/BL and of DBA mice. Although midbrain showed the highest and cerebellum the lowest binding for both [3H]nicotine and [3H]acetylcholine, the ratio of nicotine to acetylcholine binding showed a three-fold regional variation. Acetylcholine inhibition of [3H]nicotine binding indicated that a portion of nicotine binding was not inhibited by acetylcholine. These results indicate important differences between the binding of (+/-)-[3H]nicotine and that of [3H]acetylcholine.