Gs Salbutamol is of course an agonist at beta 2 adrenoceptors, which in bronchial smooth muscle, are coupled to Gs. Gs stimulates adenylate cyclase resulting in increased production of cAMP. In turn, cAMP activates protein kinase A Activation of protein kinase A results in relaxation of bronchial smooth muscle. The mechanism behind this relaxation is not fully delineated, but involves a) negative modulation of myosin light chain kinase and b) reduction in intracellular calcium levels.