<prompt> Which of the following effects of adrenaline would be blocked by phentolamine but NOT by propanolol?Cardiac stimulationRelaxation of bronchial smooth muscleRelaxation of the uterusContraction of the radial smooth muscle in the iris  <response>: Phentolamine is an a blocker whereas propranolol is a b blocker. So, phentolamine will block those actions which are mediated by a receptors .i.e. contraction of radial smooth muscle in the iris. 