Use of Antibodies in the Research on Muscarinic Receptor Subtypes

Antibodies can be a powerful tool to detect receptor expression at the protein level. Their main advantage is the potential of good spatial resolution in immunohistochemistry, whereas their main limitation is that they yield less quantitative results as compared to radioligand binding. However, most available antibodies against muscarinic acetylcholine receptor subtypes have shown poor target selectivity when tested stringently, e.g., often yielded similar staining patterns in wild-type and knock-out animals or cells transfected with the target as compared to a closely related receptor subtype. On the other hand, a small number of antibodies have been validated to some degree for selectivity for a muscarinic receptor subtype. Protocols for their use in immunohistochemistry are discussed. However, it remains a key learning that each investigator should carefully establish whether the intended antibody is indeed selective for the target under investigation under the assay conditions being applied.