Canadian Medical Guide > Chemicals and Drugs > Peripheral Nervous System Agents > Autonomic Agents Terms and Definitions

Autonomic Agents

Medical Definition:	Agents affecting the function of, or mimicking the actions of, the autonomic nervous system and thereby having an effect on such processes as respiration, circulation, digestion, body temperature regulation, certain endocrine gland secretions, etc.
Guide Notes:	GEN: avoid; prefer specifics; consider also AUTONOMIC NERVOUS SYTEM /drug eff

Autonomic Agents Categories.

	Bronchoconstrictor Agents - Agents causing the narrowing of the lumen of a bronchus or bronchiole.
	Bronchodilator Agents - Agents that cause an increase in the expansion of a bronchus or bronchial tubes.
	Ganglionic Blockers - Agents having as their major action the interruption of neural transmission at nicotinic receptors on postganglionic autonomic neurons. Because their actions are so broad, including blocking of sympathetic and parasympathetic systems, their therapeutic use has been largely supplanted by more specific drugs. They may still be used in the control of blood pressure in patients with acute dissecting aortic aneurysm and for the induction of hypotension in surgery.
	Ganglionic Stimulants - Agents that mimic neural transmission by stimulation of the nicotinic receptors on postganglionic autonomic neurons. Drugs that indirectly augment ganglionic transmission by increasing the release or slowing the breakdown of acetylcholine or by non-nicotinic effects on postganglionic neurons are not included here nor are the nonspecific cholinergic agonists.
	Miotics - Agents causing contraction of the pupil of the eye. Because the size of the pupil is under the antagonistic control of the sympathetic and parasympathetic systems, drugs affecting either system can cause miosis. Drugs that mimic or potentiate the parasympathetic input to the circular constrictor muscle and drugs that inhibit sympathetic input to the radial dilator muscle tend to contract the pupils. Some sources use the term miotics only for the parasympathomimetics but any drug used to induce miosis is included here.
	Mydriatics - Agents that dilate the pupil. They may be either sympathomimetics or parasympatholytics. The latter cause cycloplegia or paralysis of accommodation at high doses and may precipitate glaucoma. Mydriatics are used in eye diseases and to facilitate eye examination.
	Parasympatholytics - Agents that inhibit the actions of the parasympathetic nervous system. The major group of drugs used therapeutically for this purpose is the MUSCARINIC ANTAGONISTS.
	Parasympathomimetics - Drugs that mimic the effects of parasympathetic nervous system activity. Included here are drugs that directly stimulate muscarinic receptors and drugs that potentiate cholinergic activity, usually by slowing the breakdown of acetylcholine (CHOLINESTERASE INHIBITORS). Drugs that stimulate both sympathetic and parasympathetic postganglionic neurons (GANGLIONIC STIMULANTS) are not included here.
	Sympatholytics - Drugs that inhibit the actions of the sympathetic nervous system by any mechanism. The most common of these are the ADRENERGIC ANTAGONISTS and drugs that deplete norepinephrine or reduce the release of transmitters from adrenergic postganglionic terminals (see ADRENERGIC AGENTS). Drugs that act in the central nervous system to reduce sympathetic activity (e.g., centrally acting alpha-2 adrenergic agonists, see ADRENERGIC ALPHA-AGONISTS) are included here.
	Sympathomimetics - Drugs that mimic the effects of stimulating postganglionic adrenergic sympathetic nerves. Included here are drugs that directly stimulate adrenergic receptors and drugs that act indirectly by provoking the release of adrenergic transmitters.

Autonomic Agents Medical Definitions and Terms

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