Strain-dependent variations in the number of forebrain cholinergic neurons.

The morphological organization of putatively cholinergic neurons was studied in the forebrain of two inbred mouse strains (C57BL/6 and DBA/2) by means of acetylcholinesterase pharmacohistochemistry. In both strains, putatively cholinergic perikarya were seen in the caudato-putamen, medial septum, diagonal band, and basal nucleus of Meynert: in all these regions, their distribution was similar in both strains, but their density was significantly higher (from 20 to 32%) in DBA/2 mice. The present data demonstrate the existence of genetically determined differences in the organization of forebrain cholinergic systems.