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
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