Short-term cardiovascular responses to a step decrease in peripheral conductance in humans.
A step decrease in total peripheral conductance (TPC) was introduced in 10 healthy volunteers by rapid inflation to suprasystolic pressure of bilateral thigh cuffs. This provoked a sudden statistically significant increase in mean arterial blood pressure (MAP) of 5 mmHg during supine rest and of 8 mmHg during moderate supine exercise by the quadriceps muscles. Central venous pressure was not changed by cuff inflation. The increase in MAP was blunted by a rapid but transient decrease in both heart rate (HR) and cardiac stroke volume. At rest, a gradual increase in TPC, starting after 4 s, nearly fully restored MAP to its original value at 10 s. During exercise, MAP was halfway corrected at 10 s but then started to increase again, probably as a result of an ischaemic muscle pressor response. After cholinergic blockade by atropine, the immediate HR response was eliminated, but HR decreased gradually after a delay of 3 s. The time development of the slow increase in TPC was not changed by atropine. In conclusion, the regulatory correction of a sudden increase in arterial pressure in supine unanesthetized healthy humans is achieved through an immediate transient parasympathetic bradycardia during the first few seconds and a more gradual sympathetic peripheral vasodilation after 4 s. After cholinergic blockade, a slow presumably sympathetic HR response was observed.
Toska
K
K
Department of Physiology, University of Oslo, Norway.
Eriksen
M
M
Walløe
L
L
D000328:Adult; D001285:Atropine / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D002320:Cardiovascular Physiological Phenomena; D002319:Cardiovascular System / Q000187:drug effects; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D010276:Parasympatholytics / Q000494:pharmacology; D013997:Time Factors; D014655:Vascular Resistance / Q000502:physiology*
D010276:Parasympatholytics; D001285:Atropine