This thesis describes several state-of-the-art challenge methods to study the cholinergic system in humans by measuring the effects of compounds that selectively act upon muscarinic or... Show moreThis thesis describes several state-of-the-art challenge methods to study the cholinergic system in humans by measuring the effects of compounds that selectively act upon muscarinic or nicotinic acetylcholine receptors. The thesis reveals part of the complexity of the cholinergic system, its changes related to aging, its relationship with cognitive function and performance, and its role in inflammation. Additionally, the methodology described in the thesis provides controlled circumstances using repeated measurement of drug concentrations and effects during a pharmacologic cholinergic challenge that can be used in drug development of new compounds with cholinergic activity. Show less