noun, plural: cholinergic agents
Acetylcholine is a chemical found in vertebrate neurons that carries information across the synaptic cleft, the space between two nerve cells. It is the neurotransmitter used by parasympathetic nervous system to send messages. A synapse or a receptor that uses acetylcholine as a neurotransmitter is described as cholinergic. Drugs that act physiologically like acetylcholine is referred to as cholinergic drugs or cholinergic agents.
Cholinergic agents may be classified based on their activity. They can be "indirect-acting" or "direct-acting". Those that are capable of mimicking the behavior of acetylcholine, i.e. stimulating the acetylcholine receptors such as nicotinic or muscarinic receptors, are the direct-acting cholinergic agents. Examples include bethanechol, carbachol, methacholine, arecoline, nicotine, muscarine, and pilocarpine.
Cholinergic agents that act indirectly, i.e. by inhibiting cholinesterase, thereby promoting the release of acetylcholine, are the indirect-acting cholinergic agents. These agents are capable of producing, altering, or releasing acetylcholine, especially from parasympathetic nerve endings. Examples of cholinergic agents that act as reversible cholinersterase inhibitors are donepezil, neostigmine, tacrine, pyridostigmine. Irreversible cholinesterase inhibitors include malthion, isoflurophate, and echothiphate. Cholinergic agents that promote the release of acetylcholine are cisapride, droperidol, domperidone, and risperidone.