Blood pressure variability and baroreflex sensitivity are not different in spontaneously hypertensive rats and stroke-prone spontaneously hypertensive rats

Aim: To demonstrate and compare hemodynamic phenotypes of blood pressure (BP), blood pressure variability (BPV) and baroreflex sensitivity (BRS) in genetic hypertensive rats. Methods: BP was recorded continuously in conscious, freely moving rats using a computerized technique. BPV was expressed as the standarddeviation of beat-to-beat BP values during a 1-h period. BRS was determined by measuring the heart period prolongation in response to the elevation in BP pro-duced by an intravenous injection of phenylephrine. Results: Body weight and heart period were not different between spontaneously hypertensive rats (SHR) and stroke-prone spontaneously hypertensive rats (SHR-SP) at the age of 15 weeks. The BP level was markedly higher in SHR-SP than SHR, whereas there were no significant differences in BPV and BRS. Quantitatively, systolic, diastolic and mean BP were significantly elevated by 36.9%, 42.9% and 39.5%, respectively, in SHR-SP compared with SHR (P<0.01). However, their variabilities were elevated only by 14.0%, 0.4% and 10.1%, respectively, without statistical signifi-cance (P>0.05). Conclusion: BPV and BRS were not changed in parallel with the BP alterations in SHR and SHR-SP.