Pharmacology Which of the following effects of adrenaline would be blocked by phentolamine but NOT by propanolol? A Cardiac stimulation B Relaxation of bronchial smooth muscle C Relaxation of the uterus D Contraction of the radial smooth muscle in the iris 💡 Explanation Which of the following effects of adrenaline would be blocked by phentolamine but NOT by propanolol? ✓ Correct Answer: D. Contraction of the radial smooth muscle in the iris