RAP1A and Myocardial fibrosis: Scientific studies have found that the cAMP and Rap1 signaling pathways are interconnectable, and their signaling and possible mechanisms associated with myocardial fibrosis in heart failure are described below (Fig. 8): During the development of heart failure, there is a significant decrease in β1-AR on the cell membrane of cardiac fibroblasts [23–25], which affects the dissociation of the Gsα to which it is coupled, resulting in a significant decrease in the amount of AC6, the effector protein of Gsα, on the cell membrane [26].