Role of the Peripheral Arterial Chemoreceptors in the Integrated Cardiovascular Response to Systematic Hypoxia
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University of Lagos
Experiments were performed on healthy male and female mongrel dogs, anaesthetized with a sodium pentobarbitone. The animals were either allowed to breathe spontaneously or were artificially ventilated using a mechanical respirator. Systematic hypoxia was induced by allowing animals to breathe a hypoxia gas mixture containing 7% 02 in 93% nitrogen. Vascularly isolated carotid chemoreceptor areas were perfused at constant perfusion pressure through an extracorporeal circuit assembly with hypoxic blood or arterial blood obtained from an artificial membrane lung. The role of carotid chemoreceptor was assessed by perfusing the carotid bifurcation areas with arterial or normoxic blood, while the animal still breathe the hypoxic gas mixture. The role of aortic chemoreceptor was assessed by comparing cardiovascular responses to systemic hypoxia before and after bilateral mid-cervical vagotomy, since afferents from aortic and carotid chemoreceptor during systemic hypoxia was assessed by perfusing the carotid chemoreceptor with arterial blood in animals that were vagotomised. Cardiovascular variables measured included blood pressure (BP) hear rate (HR), left ventricular pressure (LVP), MAXIMUM RATE OF RISE of left ventricular pressure (LVdp/dt max) and femoral artery perfusion pressure (FAPP). The control values of these variables were determined and compared with the values during systemic hypoxia; systemic hypoxia with carotid withdrawal; systemic hypoxia with aortic withdrawal by vagotomy; and with systemic hypoxia with both carotid and aortic withdrawal.
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Peripheral Arterial , Chemoreceptors , Systemic Hypoxia , Cardiovascular
Egbengu, E.P. ( 1987). Role of the Peripheral Arterial Chemoreceptors in the Integrated Cardiovascular Response to Systematic Hypoxia. Thesis Submitted in Fulfillment of the Requirements for the Degree Doctor of Philosophy (ph.D) in Physiology of the University of Lagos.