[Effects of the tone of arterial vessels on the antiorthostatic response of hemodynamics].

Contribution of the original angiotensin-2 controlled arterial tone to the shifts in systolic and diastolic arterial pressure (AP) was assessed in unconscious rats during tail-suspension. With this technique, values of original mean AP were elevated from 80-110 to 111-140 mm Hg. In the head-down position, rise in the tone was concurrent to a twofold increase in the number of "uncompensated" responses and a similar decrease in the number of test-resistant responses. The original arterial tone high, maximum decline of diastolic pressure was significantly less pronounced. Recovery of both systolic and diastolic arterial pressures was more dynamic against the background of high original tone. Magnitude of the diastolic AP variation dominated over that of systolic AP. These results are being analyzed in comparison with the data about orthostatic compensatory reactions.