Cardiovascular response to emotional stress and spontaneous blood pressure variability in genetically hypertensive rats of the Lyon strain.

1. Intra-aortic blood pressure (BP) was continuously recorded in freely moving genetically hypertensive (LH), normotensive (LN) and low BP (LL) rats of the Lyon strains under basal conditions and during aversive stimulation (a jet of air for 20 min). Rats were studied when 5 and 14 weeks old. 2. The 24 h standard deviation (i.e., variability) of diastolic BP was significantly greater in LH rats of both ages than in LN and LL control rats. 3. In response to the stressor, LH rats showed larger increases in BP than age-matched controls. 4. The BP variability was related to the BP responses to stress in the whole series of rats. 5. It is concluded that the spontaneous BP variability and the BP responses to an experimental stressor rely upon a common regulatory mechanism in rats and that an increased lability of diastolic BP is a primary characteristic of Lyon hypertensive rats.