Augmented blood pressure variability following continuous infusion of noradrenaline in rats

Objective: Augmented blood pressure (BP) variability has been shown to be associated with cardiovascular diseases. Activity of the sympathetic nervous system is an important determinant factor of the 24-h profile of BP variability, although it is unknown whether persistent adrenergic activation causes augmented BP variability or not. Here we report that continuous infusion of noradrenalin augments 24-h BP variability in rats. Methods: Nine-week-old male Wistar rats were continuously infused with subcutaneous 30 mu g/h noradrenalin, 150 mu g/h of the alpha 1-adrenergic agonist phenylephrine, or 30 mu g/h of the beta-agonist isoproterenol, for 14 days. Noradrenalin-infused rats were also administered either oral 5 mg/day prazosin or 50 mg/day atenolol during the infusion period. BP variability was evaluated before and after 7 and 14 days of the infusion, using a coefficient of variation of BP recorded every 15 min under an unrestrained condition via an abdominal aortic catheter by a radiotelemetry system. Results: Continuous infusion of noradrenalin significantly increased 24-h BP variability at 7 and 14 days, slightly elevating BP levels, while this increase in BP variability was partially attenuated by prazosin, but not by atenolol. Continuous infusion of phenylephrine augmented BP variability, but isoproterenol had no effect on the variability. Conclusion: Continuous infusion of noradrenalin augmented 24-h BP variability partly through an alpha 1-adrenergic receptor-mediated mechanism in rats, suggesting that the noradrenalin-infused rat is an animal model of augmented BP variability induced by persistent adrenergic activation.