A 24-year-old woman, who was diagnosed recently with pheochromocytoma, presents to the ER with high blood pressure. Treatment with phentolamine is initiated. Heart rate monitoring shows tachycardia because of this treatment. What is the etiology of tachycardia following phentolamine administration? A-Blockade of cholinergic receptors B-Blockade of alpha1 adrenergic receptors C-Blockade of alpha2 adrenergic receptors D-Blockade of beta-adrenergic receptors E- Stimulation of adrenal gland to release epinephrine Answer
