premise: Muscarinic acetylcholine receptors are recognized as mAChRs.
hypothesis: Muscarinic acetylcholine receptors , or mAChRs , are acetylcholine receptors that form G protein-receptor complexes in the cell membranes of certain neurons and other cells . Their counterparts are nicotinic acetylcholine receptors ( nAChRs ) , receptor ion channels that are also important in the autonomic nervous system .