Allosteric drugs acting at muscarinic acetylcholine receptors.

The binding properties of muscarinic acetylcholine receptors are affected by various drugs acting at a second (allosteric) binding site, usually (but not always) at supratherapeutic concentrations. Allosteric drugs acting at GABA receptors present advantages over competitive drugs; this explains the interest raised by allosteric effects on muscarinic receptors. A theoretical and practicable definition of allosteric drugs acting at muscarinic receptors will be given in this work, together with a summary of recent data concerning the number, position, and structural requirements of their binding sites.