The use of a modified [3H]4-DAMP radioligand binding assay with increased selectivity for muscarinic M3 receptor shows that cortical CHRM3 levels are not altered in mood disorders

Abstract

[3H]4-DAMP is a radioligand that has been used to quantify levels of the muscarinic receptor CHRM3 protein in situ. However, in addition to high affinity binding to CHRM3, [3H]4-DAMP binds with low affinity to CHRM1 confounding the potential to discriminate between changes in these two muscarinic receptors. We have developed a [3H]4-DAMP binding assay, optimised for measuring CHRM3 protein levels in the cortex, with minimal selectivity towards CHRM1. The selectivity of our assay towards CHRM3 was confirmed using recombinant receptor-expressing, cell lysate preparations. [3H]4-DAMP binding levels were similar between wildtype and CHRM1 knockout mice, confirming that the amount of [3H]4-DAMP b..