CHOLINERGIC DRUG

any of various drugs that inhibit, enhance, or mimic the action of the neurotransmitter acetylcholine within the body. Acetylcholine is the primary transmitter of nerve impulses within the parasympathetic nervous system-i.e., that part of the autonomic nervous system that consists chiefly of cholinergic fibres and which helps contract smooth muscles, dilate blood vessels, increase secretions, and slow the heart rate. Some cholinergic drugs, such as muscarine, pilocarpine, and arecoline, mimic the activity of acetylcholine in stimulating the parasympathetic nervous system. These drugs have few therapeutic uses, though one of them, nicotine, is widely used as a stimulant. Other cholinergic drugs, such as atropine and scopolamine, inhibit the action of acetylcholine and thus suppress all the actions of the parasympathetic nervous system. These drugs help dry up such bodily secretions as saliva and mucus and relax smooth-muscle walls. They are used therapeutically to relieve spasms of the smooth-muscle walls of the intestines, to relieve bronchial spasms, to diminish salivation and bronchial secretions during anesthesia, and to dilate the pupil during ophthalmological procedures. See also anticholinesterase.