Detection of Non-neuronal Acetylcholine

The biological role of acetylcholine and the cholinergic system has been revisited within the last decades. Acetylcholine and the pivotal components of the cholinergic system (high-affinity choline uptake, choline acetyltransferase, and its end product acetylcholine, muscarinic and nicotinic receptors, cholinesterases) are expressed by more or less all mammalian cells, i.e., cells not innervated by neurons at all. Moreover, acetylcholine and cholinergic binding sites have been described in plants. Acetylcholine is even detected in bacteria and algae and thus represents an extremely old signaling molecule on the evolutionary time scale. The following chapter summarizes the detection of acetylcholine beyond neurons with particular emphasis on the presence of acetylcholine in so-called primitive organisms. Finally, an overview is given about the detection in mammalian non-neuronal cells. The existence of the non-neuronal cholinergic system has identified an important new target to illuminate the pathophysiological background of acute and chronic inflammatory diseases as well as heart diseases and cancer.