2nd messenger in vagal bradycardia ?

Ans. is 'a' i.e., cAMP Muscarinic receptors (cholinergic receptors) in hea are M2 type. These are responsible for vagus mediated bradycardia. M2 mediated actions are through cAMP. TYPES OF RECEPTORS Drug action on receptors is a two step process ? Step 1 - Binding of drug to receptors that leads to conformational change in receptors (in case of agonist) or prevention of conformational change by competing with agonist (in case of antagonist). Step 2 - This conformational change induces changes in systems within the cell through a series of intermediate steps (transduction) that in turn brings about the response to the drug.