The b-adrenoceptors can be divided into b1, b2, b3 and b4-adrenoceptors defined in terms of agonist potencies, b2-adrenoceptors displayed a higher selectivity for nor-adrenaline than for adrenaline. B2-receptors are mainly postsynaptic and are located on a number of tissues including blood vessels, bronchi, GIT, skeletal muscle, liver and mast cell. Activation results in vasodilatation, bronchodilation, relaxation of the GIT, glycogenolysis in the liver, tremor in skeletal muscle and inhibition of histamine release from mast cells. Transduction is via G-proteins coupled to the intracellular second messenger adenylate cyclase. B-receptors are positively coupled to adenylate cyclase via activation of Gs G-protein, however activation of the b2-adrenoceptors results in stimulation and inhibition of adenylate cyclase. The b2-receptor selective agonists are widely used in the treatment of asthma and other related bronchospastic conditions. They are commonly used in the treatment of angina pectoris, cardiac arrhythmia and for the long-term treatment of patients who survive myocardial infarction. B-receptor antagonists have also been used as anti-hypertensive for a number of years. Beta-blockers have also proven useful in the treatment of conditions such as migraine, anxiety disorders, hyperthyroidism, alcohol withdrawal and when applied topically are useful in the treatment of glaucoma and ocular hypertension.
Intended for research use only. Not for use in human, therapeutic, or diagnostic applications.