Pharmacological study of arterial blood variability in an experiment on awake animals

The purpose of the present investigation was ю evaluate the effects of the representatives of two classes of antihypertensive drills central acting agents and those affecting the rennin-angiotensin system on blood pressure (BP) variability in awake rats. Experiments were carried out on normotensive male Wistar rats, spontaneously-hypertensive rats (SHR), and non-inbred albino rats with induced renal hypertension. In the experiments. HI' and intersystolic interval were recorded and arterial baroreceptor reflex was tested. Mean BP variability appeared as undulating fluctuations with a variable amplitude (from 5 to 15 mm Hg) and a duration of 5 to several tens of cardiac cycles. The observed BP fluctuations had no well-defined periodic shape. They did not affect mean BP and stable-unstable BP transition was not attended by mean pressure changes. In hypertensive rats, BP and its variability were higher and the baroreceptor reflex was less than in normotensive rats. Captopril and aprovel in used doses produced an antihypertensive effect; they did not affect HP variability. In hypertensive animals, captopril-induced reductions in BP were followed by a decrease in its variability whereas approve was responsible lor an increase in BP variability. Clonidine and rilmenidine lowered mean BP and its variability in all experiments.