Muscarinic and nicotinic cholinergic agonists: structural analogies and discrepancies

Acetylcholine, the first identified neurotransmitter acts on both types of cholinergic receptors. Both rigid and flexible derivatives of acetylcholine could either be selective muscarinic or selective nicotinic agonists while some compounds show activity at both receptor subclasses. Earlier structure-activity considerations are revisited. Ligand and receptor based calculations have been applied in the hope to identify characteristic geometrical and steric requirements for the activity on the receptor subtypes. Results are treated critically and applied cautiously for predicting selective structural requirements by the cholinergic receptor subclasses.