Regional [(3)H]acetylcholine and [(3)H]nicotine binding in developing mouse brain

The postnatal development of nicotine-like binding sites in the cortex, hippocampus, midbrain and cerebellum of 3-, 7-, 12-, 17- and 30-day-old mice was studied. Two different nicotinic cholinergic ligands, namely [(3)H]acetylcholine ([(3)H]ACh) and [(3)H]nicotine ([(3)H]NIC) were used to detect the nicotine-like binding sites in in vitro binding assays. The postnatal development of the binding sites of [(3)H]NIC increased gradually with age in all brain regions studied. The [(3)H]ACh binding, on the other hand, showed a marked peak on day 12 in the cerebellum and midbrain but did not change notably with age in the hippocampus and cortex, except for a slight temporary increase in the cortex on day 7. The time-course for the appearance of nicotinic binding sites as observed with [(3)H]ACh was found to be rather similar to that earlier described for [(3)H]alpha-bungarotoxin binding sites, whereas that for [(3)H]NIC differed from that described for other nicotinic ligands.