Different levels of acetylcholinesterase and choline acetyltransferase activities in C57Bl/6 and DBA/2 mice are not accompanied with different density of cortical acetylcholinesterase reactive fibers.

Mice of the inbred strains C57B1/6 and DBA/2 show strain-dependent behavioural differences which have been correlated with variations in the organization of brain cholinergic systems. The aim of our study was to analyse the extent of cholinergic interstrain differences in circumscript brain regions of C57B1/6 and DBA/2 mice. The biochemical determination of choline acetyltransferase and acetylcholinesterase in cortical areas, basal forebrain and striatum showed significantly lower enzyme activities in most of the regions of C57B1/6 mice. The deficit was most pronounced in the basal forebrain/diagonal band, in the piriform cortex, and striatum. The density of acetylcholinesterase-stained cortical fibres did not reflect the biochemical interstrain differences. This may be due to a different enzyme content in the nerve fibers of the two mice strains. The previous findings are discussed in terms of brain cholinergic disorders in which the extent of damage but also the proportions of regional deficits may influence the pattern of behavioural dysfunctions.