β-adrenergic receptors couple with G protein alpha-s subtype (Wenzel-Seifert K et al, 2002), increasing cAMP activity resulting in heart muscle contraction, smooth muscle relaxation and glycogenolysis. There are three β subtypes in humans; β1 found mainly in the heart and kidneys (Frielle et al. 1987), β2 found mainly in the lungs, vascular smooth muscle and skeletal muscle (Kobilka et al. 1987) and β3 found mainly in fat cells (Emorine et al. 1989). The catecholamines adrenaline (ADR) and noradrenaline (NaAd) are natural endogenous ligands that bind to β-adrenergic receptors and cause general physiological changes (increases in heart rate, blood pressure and glucose levels) that prepare the body for physical activity ('fight-or-flight response') (Tank & Lee Wong 2015).