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Left ventricular inotropic and peripheral vasomotor responses from independent changes in pressure in the carotid sinuses and cerebral arteries in anaesthetized dogs
Author(s) -
Hainsworth R.,
Karim F.
Publication year - 1973
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1973.sp010077
Subject(s) - medicine , peripheral , vasomotor , cardiology , inotrope , cerebral arteries , carotid arteries , anesthesia
1. The pressure perfusing the isolated carotid sinuses and the pressure perfusing the cerebral circulation were changed independently, and the resulting inotropic responses in the left ventricle and peripheral vasomotor responses were determined. 2. Inotropic responses were assessed by measuring changes in the maximum rate of change of left ventricular pressure (d P /d t max) with heart rate and mean aortic pressure held constant. Vascular resistance changes were usually assessed by perfusing the descending thoracic aorta at constant flow and measuring changes in perfusion pressure. 3. Decreases in carotid sinus pressure over the baroreceptor sensitivity range resulted in a 45% increase in d P /d t max and a 59% increase in vascular resistance. 4. Unless arterial oxygen tension was abnormally low, lowering cerebral perfusion pressure to 50 mm Hg resulted in little or no inotropic and vasomotor responses. In the presence of hypoxaemia ( P a,O2 < 60 mm Hg), lowering cerebral perfusion pressure to below about 80 mm Hg resulted in marked responses. 5. These experiments suggest that, unless arterial oxygen tension is abnormally low, the carotid sinus reflex and not cerebral hypotension is important in the control of the inotropic state of the heart and of vasomotor activity. With hypoxaemia, responses from cerebral hypotension may also be important.