Saturday, October 31, 2009

Pharmacology of the Peripheral Nervous System (PNS)

reference: merk manual of medical info.

Types of receptors

Body’s natural agonist

Resulting action

Drugs that target the receptor


Alpha 1

Epinephrine & norepinephrine

Fight or flight reactions; constriction of the blood vessels in the skin, digestive tract and urinary tract, breakdown of glucose in the liver (releasing energy, a decrease in the activity of stomach & intestine & contraction of smooth muscle in the genital & urinary organs.

Agonist: methoxamine, phenylephrine.

Antagonist: doxazosin, prazosin, tamsulosin & terazosin

Alpha 2

Epinephrine & norepinephrine

A decrease in insulin secretion, in the clumping of platelets, in the constriction of the blood vessels in the skin & intestine and in the release of norepinephrine from nerves.

Agonist: clonidine.

Antagonist: yohimbine

Beta 1

Epinephrine &norepinephrine

An increase in heart rate, in the force of heart contraction & in secretion of rennin ( a hormone in controlling blood pressure)

Agonist: dobutamine, isoproterenol.

Antagonist: beta- blockers (used to treat beta blockers and hypertension) atenolol, metaprolol.

Beta 2

Epinephrine &norepinephrine

Dilatation of smooth muscle in the blood vessels, airways, digestive tract, breakdown of glycogen in skeletal muscle (releasing glucose energy).

Agonist: albuterol, isoetharine and terbetaline.

Antagonist: propanolol




A decrease in heart rate and the force of the heart’s contraction, constriction of airways, dilatation of blood vessel throughout the body and an increase in activity of the stomach, intestines, bladder & salivary, lacrimal & sweat gland

Agonist: bethanechol & carbachol

Antagonist: atropine, ipratropium & scopolamine



Contraction of skeletal muscle

Agonist: not commonly used

Antagonist: attacurium, pancuronium, tubocurarine

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