Cardiovascular effects of nebivolol in spontaneously hypertensive rats persist after treatment withdrawal.

OBJECTIVES: We observed previously that nebivolol treatment for 2 months reduced cardiovascular lesions in spontaneously hypertensive rats (SHR). Therefore, we investigated whether this beneficial effect is increased with a longer treatment, and its persistence after withdrawal.
METHODS: Male SHR were treated with 8 mg/kg per day of nebivolol (N-SHR) for 6 months. A separate group was also given identical treatment but they were then monitored for a further 3 months after drug withdrawal. SHR and Wistar-Kyoto rats (WKY) receiving vehicle were used as controls. Systolic blood pressure and heart rate were measured using the tail-cuff method. Left ventricular weight/body weight ratio was calculated as the hypertrophy index. Cardiac and vascular fibrosis was evaluated on sections stained with sirious red. Vascular reactivity was evaluated on aortic rings through acetylcholine and sodium nitroprusside responses. The effect of treatment on vascular structure was assessed by lumen diameter, wall thickness and medial cross-sectional area determination.
RESULTS: Blood pressure was reduced in N-SHR. After withdrawal it increased progressively, without reaching the values of the hypertensive controls. Cardiac hypertrophy and collagen content both in heart and aorta were significantly reduced, and these changes persisted after nebivolol suppression. Acetylcholine-induced relaxant response was improved by nebivolol and maintained after withdrawal. Medial thickness and cross-sectional area were significantly reduced in both conductance and resistance arteries, and these effects persisted after withdrawal.
CONCLUSION: The nebivolol antihypertensive effect was accompanied by an important reduction of hypertrophy and collagen deposition in both vascular and left ventricle tissue, which was maintained after a long period of therapy withdrawal.