Mouse strain-specific changes in nicotinic receptor expression with age

The onset and severity of age-related loss of neuronal nicotinic acetylcholine receptor (nAChR) expression in the mammalian hippocampus can vary considerably between individuals. We have examined the expression of four nAChR subunits (nAChR alpha4, nAChR alpha5, nAChR alpha7 and nAChR beta4) in the dorsal hippocampus of adult (12-14 months) and aged (24-28 month) animals from two-mouse strains (CBA/J and C57BL/6). The expression of nAChR alpha4 was selectively diminished with age in both strains, and there was a significant loss of nAChR alpha7 in CA1 of aged CBA/J, but not C57BL/6. There was no change in nAChR alpha5 expression with age whereas nAChR beta4 preferentially diminished in the C57BL/6 CA1 region and remained the same or slightly increased in the aged CBA/J. Coincident with the loss of neuronal nAChR alpha4 in the CBA/J strain was a significant age-related increase of nAChR alpha4 staining of astrocytes, most notably in the stratum radiatum. These results suggest that mouse strains of different genetic backgrounds undergo dissimilar age-related changes in the expression of nAChRs.