A comparison of the regional ontogenesis of nicotine- and muscarine-like binding sites in mouse brain

Abstract

The postnatal development of the cholinergic neurotransmitter system was studied in the cortex, hippocampus, midbrain and cerebellum of 3-, 7-, 12-, 17- and 30-day-old NMRI mice. The concentration of muscarine-like binding sites determined with [3H]quinuclidinyl benzilate as a ligand increased progressively with age. A similar developmental pattern was found for the activity of a presynaptic marker, choline acetyltransferase (ChAT). When expressed as a percentage of the values for 30-day-old mice, however, the muscarine-like receptors were parallel but preceding the development of ChAT in all the brain regions studied. The concentration of nicotine-like binding sites studied with [3H]α-bungaro-toxin as a ligand gradually increased with age in the cortex, hippocampus and midbrain, with a peak between days 7 and 12, followed by a decrease towards day 30. With [3H]tubocurarine as a ligand, on the other hand, the concentration of nicotine-like binding sites was in general high at 3 days and gradually decreased with age, suggesting that different subpopulations of nicotine-like receptors might be determined when the two ligands are used.