Autoradiography of muscarinic cholinergic receptors in cortical and subcortical brain regions of C57BL/6 and DBA/2 mice.

Mice of the inbred strains C57BL/6 and DBA/2 show strain-dependent behavioural differences which have been correlated with variations in brain cholinergic systems. In the present study, the density of muscarinic cholinergic receptors in both strains of mice was determined by autoradiographic methods using [3H]quinuclidinyl benzilate (QNB) and [3H]pirenzepine as ligands. C57BL/6 mice showed a significantly lower [3H]QNB binding level in the frontal cortex by one third as compared to DBA/2 mice. In the striatum and the cholinergic pontomesencephalic nucleus laterodorsalis tegmenti the [3H]QNB binding was lower in C57BL/6 by 28% and 31%, respectively. The [3H]pirenzepine binding level was found to be significantly higher in C57BL/6 temporal cortex (by 22%). These results are discussed in relation to interstrain differences in cholinergic cell density and in the activity of cholinergic enzymes.