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Heart rate changes evoked by hypoxia in the anaesthetized, artificially ventilated cat
Author(s) -
O'Donnell CP,
Bower EA
Publication year - 1992
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/expphysiol.1992.sp003587
Subject(s) - heart rate , cats , atropine , medicine , anesthesia , carotid sinus , blood pressure , hypoxia (environmental) , chloralose , vagotomy , cardiology , chemistry , organic chemistry , oxygen
Reflex changes in heart rate evoked by hypoxia were investigated in cats anesthetized with chloralose and ventilated by positive pressure during administration of vecuronium or gallamine. In five cats receiving vecuronium and with aortic pressure stabilized, systemic hypoxia (arterial O2 pressure (Pa, O2) 34.9 mmHg) reduced heart rate by 55.8 +/− 7.5 beats min‐1 (mean +/− S.E.M.). After administration of atropine, hypoxia (Pa, O2 32.1 mmHg) increased heart rate by 28.2 +/− 3.4 beats min‐1. After subsequent bilateral ablation of carotid sinus and vagus nerves, hypoxia (Pa, O2 31.9 mmHg) increased heart rate by 7.1 +/− 1.8 beats min‐1. The cardiac accelerator response to hypoxia was further examined in groups of cats treated with gallamine and atropine. In four vagotomized cats, local perfusion of both carotid sinuses with hypoxic blood (Pa, O2 37.7 mmHg) increased heart rate by 15.5 +/− 2.3 beats min‐1. In the same cats, systemic hypoxia (Pa, O2 38.3 mmHg) increased heart rate by 16.4 +/− 2.3 beats min‐1. The heart rate increment in cats which had undergone either bilateral adrenalectomy or cardiac sympathectomy was similar to the increment in unoperated cats. The increment was significantly less in cats which had both adrenal glands and cardiac sympathetic nerves ablated. It is concluded that stimulation of the carotid bodies in the cat excites both parasympathetic and sympathetic cardiac nerves simultaneously.