Volume 50: 327-331, 2001

SHORT COMMUNICATION


Ventilatory Response to Sustained Hypoxia in Carotid Body Denervated Rats

H. MAXOVÁ, M. VÍZEK

Institute of Pathological Physiology, Second Faculty of Medicine, Charles University, and Center for Experimental Cardiovascular Research, Prague, Czech Republic

Received June 1, 2000
Accepted November 1, 2000


Summary
Hypoxia stimulates ventilation, but when it is sustained, a decline in the ventilatory response is seen. The mechanism responsible for this decline lies within the CNS, but still remains unknown. In this study, we attempted to elucidate the possible role of hypoxia-induced depression of respiratory neurons by comparing the ventilatory response to hypoxia in intact rats and those with denervated carotid bodies. A whole-body plethysmograph was used to measure tidal volume, frequency of breathing and minute ventilation (VE) in awake and anesthetized intact rats and rats after carotid body denervation during exposure to hypoxia (FIO2 0.1). Fifteen-minute hypoxia induced an initial increase of VE in intact rats (to 248 % of control ventilation in awake and to 227 % in anesthetized rats) followed by a consistent decline (to 207 % and 196 % of control VE, respectively). Rats with denervated carotid bodies responded with a smaller increase in VE (to 134 % in awake and 114 % in anesthetized animals), but without a secondary decline (145 % and 129 % of control VE in the 15th min of hypoxia). These results suggest that afferentation from the carotid bodies and/or the substantial increase in ventilation are crucial for the biphasicity of the ventilatory response to sustained hypoxia and that a central hypoxic depression cannot fully explain the secondary decline in VE.


Key words
Ventilatory response · Sustained hypoxia · Carotid body denervation · Rats

Reprint requests
H. Maxová, Institute of Pathological Physiology, Second Faculty of Medicine, Charles University, Plzeňská 221, Prague 5, CZ-150 00, Czech Republic, fax 420 2 5721 0995

PHYSIOLOGICAL RESEARCH
© 2001 by the Institute of Physiology, Czech Academy of Sciences

ISSN 0862 - 8408

Issue 3