beta2 - Adrenergic Receptors (NE)

Activation of adenylyl cyclase by agonists that bind to beta2-adrenergic receptors.
Binding to beta2-adrenoceptors stimulates adenylyl cyclase by activating the stimulatory G protein, Gs, which leads to the dissociation of its alpha subunit charged with GTP. This alpha subunit directly activates adenylyl cyclase, resulting in an increased rate of synthesis of cAMP. These catalytic units also phosphorylate the cAMP response element binding protein (CREB), which modifies gene expression.
beta2-adrenergic receptors cause relaxation or dilation of smooth muscle in the following organs:

• Eye: ciliary muscle relaxation (mydriasis - dilation)
• Eye: ciliary epithelium (beta-2 mediated increased aqueous humor production).
• Eye: NOTE: stimulation of alpha-2 receptors (also found in ciliary epithelium) causes decrease in aqueous humor production
• Arterioles: (coronary, skeletal muscle, pulmonary, abdominal, and renal) dilation
• Lungs: tracheal and bronchial smooth muscle dilation
• Stomach and Intestine: decrease motility
• Bladder: detrusor muscle relaxation
• Sex Organs, Female: relaxation.

Adapted from Figure 9-2: StatRef Online Library: Basic and Clinical Pharmacology 8th ed. (2001)
by Michael Bolger, 8/26/01
Copyright(c) 2001 The McGraw Hill Companies, Inc. All rights reserved