Age-related protective role of parasympathetic nervous system against hypercalcaemia-induced ventricular arrhythmias in the rat

Time of appearance of extrasystoles, ventricular fibrillation, and cardiac arrest were monitored in urethane-anaesthetized rats of different ages following CaCl2 infusion. Ca++ required to produce ventricular arrhythmias was significantly higher in younger than in older animals. Bilateral vagotomy or atropine treatment significantly reduced Ca++ requirements for production of arrhythmias in younger but not in older animals. These findings support the hypothesis of vagally mediated age-related antagonism toward Ca++-induced ventricular arrhythmias. This suggests that young subjects are less prone to develop ventricular rhythm disturbances as a result of hypercalcaemic states.