Although the anticholinesterase (anti-ChE) agents have only limited applica- tions in therapy, and from the viewpoint of practical significance they are more appropriately classified as toxic compounds or insecticides than as drugs, in their capacity of pharmacological tools they have few equals. The concept of neuro- humoral transmission was originally established largely from experiments in which physostigmine, or eserine, was employed to protect acetylcholine (ACh), the trans- mitter of the cholinergic nerves, from rapid hydrolytic destruction by acetyl- cholinesterase (AChE) and other...