Ans. is 'c' i.e., Dopamine o Dopamine acts on dopamine (D1 & D2) and adrenergic (a1 + a2 + b1) receptors, with no action on b2 receptorso Dobutamine is a relatively selective b1 agonist. Though it acts on both a and b receptors, the only prominent action of clinically employed doses is its b1 action, i.e. an increase in force of cardiac contraction and output, without a significant change in HR., BP and Peripheral resistance.