Cholinergic Neurotransmission

Abstract

Neurotransmitters enable transmission at synapses and from nerve cells to effector organs such as muscles and autonomic effector organs. They are complex: in the case of cholinergic transmission, the system comprises afferent nerves, containing the acetylcholine (ACh), where it is synthesized and stored in vesicles, from which the ACh is released in response to a nerve impulse. At the synapse, neuromuscular junctions and autonomic effector organs, there are specialized receptors, where binding of the neurotransmitter induces a response. There are two main types of receptors: nicotinic receptors, which are ligand-gated ion channels, and muscarinic receptors, which are metabotropic and operate via G proteins. Agonists and antagonists have been identified for each type of receptor and termination of neurotransmission is effected by acetylcholinesterase. Anticholinesterases are substances that antagonize acetylcholinesterase and have important uses as insecticides/acaricides and minor uses in medicine, and certain organophosphates are potentially chemical warfare agents. Cholinergic antagonists have a variety of uses in medicine.