Guanfacine enhances cardiac acetylcholine release with little effect on norepinephrine release in anesthetized rabbits.

An α2A-adrenergic agonist guanfacine improves autonomic imbalance in attention-deficit hyperactivity disorder, suggesting that it may be useful to correct autonomic imbalance in chronic heart failure (CHF) patients. To investigate the effects of guanfacine on cardiac autonomic nerve activities, a microdialysis technique was applied to anesthetized rabbit heart. Acetylcholine (ACh) and norepinephrine (NE) concentrations in atrial dialysates were measured as indices of cardiac autonomic nerve activities. Guanfacine at a dose of 100 μg/kg significantly decreased heart rate and increased dialysate ACh concentration without decreasing sympathetic NE release. Guanfacine may be useful for vagal activation therapy in CHF patients.