Agonist antagonist combination acting on the same receptor is ?

Ans. is 'a' i.e., Isoprenaline and propranolol Receptor antagonists (Pharmalogical antagonists) Receptor antagonists are those drugs that blocks the action of agonist by acting on same receptors. Example: Isoprenalineis b1 and b2 receptor agonist while propranolol has antagonistic action on b1 and b2 receptors. Note : Physiological antagonists Physiological antagonists are those that produce opposite action by acting on different receptors. Example Histamine causes bronchoconstriction H1receptors and this action is antagonized by adrenaline which causes bronchodilodation through b1 receptors Leukotrienes cause bronchoconstriction cystinyl leukotriene receptors and this action is antagonised by salbutamol which causes bronchodilatation through b2 receptors.