The endogenous catecholamines epinephrine and norepinephrine have profound effects on smooth muscle activity, cardiac function, carbohydrate and fat metabolism, hormone secretion, neurotransmitter release, and central nervous system actions. These activities are mediated by GPCRs belonging to two subfamilies, the α- and β -adrenergic receptors (Bylund et al., 1994). The β -adrenergic receptors, primarily the β2 subtype, mediate relaxation of smooth muscle in many tissues, and β 2-selective agonists are the preferred drugs for stimulating bronchodilation in the treatment of asthma and chronic obstructive pulmonary disease (Sears and Lotvall, 2005). Activation of the β-adrenergic receptors, primarily the β1 subtype and to a lesser extent the β2 subtype, acutely increases heart rate, cardiac output, and cardiac automaticity, and chronically increases cardiac myocyte apoptosis. As a result, β -adrenergic receptor antagonists (β blockers) are effective in the treatment of congestive heart failure and arrhythmia (Feldman et al., 2005). Chemicon's β2 adrenoceptor membrane preparations are crude membrane preparations made from our proprietary stable recombinant cell lines to ensure high-level of GPCR surface expression; thus, they are ideal HTS tools for screening of antagonists of β2 adrenoceptor interactions with (-)Iodocyanopindolol (ICYP). The membrane preparations exhibit a Kd of 0.51 nM for [125I]-(-)ICYP. With 5 µg/well β2 Adrenoceptor Membrane Prep and 0.5 nM [125I]-(-)ICYP, a greater than 40-fold signal-to-background ratio was obtained.