Which of the following effects of adrenaline would be blocked by phentolamine but NOT by propanolol?
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.
Cardiac stimulation
Relaxation of bronchial smooth muscle
Relaxation of the uterus
Contraction of the radial smooth muscle in the iris
Sympathetic System