Figure 5. Sympathetic neurons decrease cardiomyocyte size via β‐adrenergic signalling .

A, treatment of co‐cultured cardiomyocytes with propranolol (2 μm) resulted in an increase in average cardiomyocyte cell size, while treatment of myocte‐only cultures with isoproterenol (10 μm) resulted in a decrease in cell size (n = 3). B, β₁‐ and β₂‐receptors in co‐cultures were blocked with bisoprolol (left) and ICI‐118,551 (right), respectively. There was no effect of bisoprolol on cardiomyocyte size, but when β₂‐receptors were blocked with ICI‐118,551 there was a significant increase in cell size (n = 3). C, when cholinergic signalling was blocked with the cholinergic antagonist scopolamine (10 μm) in co‐cultures, there was no effect on size of cardiomyocytes. Stimulating cholinergic signalling in myocyte‐only cultures with the cholinergic agonist muscarine (2.5 μm) also had no statistically significant effect. (n = 3; *P < 0.05 vs. co‐culture control; ^# P < 0.05 vs. myocyte‐only control.)