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an agent that blocks the transmission of excitation from cholinergic nerve fibers; an antagonist of the mediator acetylcholine. Cholinolytics belong to different groups of chemical compounds. The action of cholinolytics is caused primarily by competition with acetylcholine to bind m-choline receptors or to stably depolarize excitable postsynaptic membranes.
A distinction is made between m- and n-cholinolytics. M-cholinolytics comprise the alkaloids of belladonna—atropine and scopolamine—and platyphylline, as well as structurally similar synthetic substances such as homatropine and the tertiary and quaternary ammonium compounds aprophen and metacin. By blocking the m-choline receptors of the body’s organs, these agents dilate the pupils, cause accommodation paralysis, raise intraocular pressure, inhibit the secretion of saliva, perspiration, and fluids from the gastric and intestinal glands, accelerate the heart rate, and relax the smooth muscles of the bronchi and stomach. They are used to treat renal, hepatic, and intestinal colic and gastric and duodenal ulcers, to dilate the pupils, and to relieve bronchospasm.
Ganglion-blocking n-cholinolytics affect the choline receptors of the sympathetic and parasympathetic ganglia, and curariform agents affect the skeletal muscles. Some cholinolytics are able to cross the blood-brain barrier, affect both the bioelectrical activity of the brain and higher nervous activity, and relieve tremor and convulsions caused by nicotine and anticholinesterases. These cholinolytics, called central m- and n-cholinolytics, include benactyzine and adiphenine hydrochloride and act as tranquilizers, intensifying the effect of soporifics, narcotics, and analgesics. They are used in anesthesiology, neuropathology, and psychiatry and in the treatment of ulcers, colitis, and bronchial asthma, owing to their peripheral cholinolytic and spasmolytic effect. Certain drugs used to treat parkinsonism, spastic paralysis, and hyperkinesia, including Artane, tropacine, and orphenadrine, are also classified as central cholinolytics.
REFERENCESMashkovskii, M. D. Lekarstvennye sredstva, 7th ed., part 1. Moscow, 1972.
The Pharmacological Basis of Therapeutics, 5th ed. London, 1975.
IU. P. VEDERNIKOV