Ventilatory long-term facilitation in unanesthetized rats.
Olson, E. B., Jr. , C. J. Bohne, M. R. Dwinell, A. Podolsky, E. H. Vidruk, D. D. Fuller, F.
L. Powell, and G. S. Mitchel.
1The John Rankin Laboratory of Pulmonary Medicine, Department of Preventive
Medicine, University of Wisconsin School of Medicine, Madison 53705«hyphen»2368;
2Department of Comparative Biosciences, School of Veterinary Medicine, University of
Wisconsin, Madison, Wisconsin 53706«hyphen»1102; and 3Division of Physiology,
Department of Medicine, and White Mountain Research Station, University of California,
San Diego, La Jolla, California 92093«hyphen»0623
APStracts 8:0249A, 2001.
We tested the hypothesis that unanesthetized rats exhibit ventilatory long-term facilitation
(LTF) after intermittent, but not continuous, hypoxia. Minute ventilation (ve) and carbon
dioxide production (vco2) were measured in unanesthetized, unrestrained male Sprague-
Dawley rats via barometric plethysmography before, during, and after exposure to
continuous or intermittent hypoxia. Hypoxia was either isocapnic [inspired O2 fraction
(«fio2») = 0.08-0.09 and inspired CO2 fraction («fico2») = 0.04] or poikilocapnic («fio2»
= 0.11 and «fico2» = 0.00). Sixty minutes after intermittent hypoxia, «ve» or
«ve»/«vco2» was significantly greater than baseline in both isocapnic and poikilocapnic
conditions. In contrast, 60 min after continuous hypoxia, «ve» and «ve»/«vco2» were not
significantly different from baseline values. These data demonstrate ventilatory LTF after
intermittent hypoxia in unanesthetized rats. Ventilatory LTF appeared similar in its
magnitude (after accounting for CO2 feedback), time course, and dependence on
intermittent hypoxia to phrenic LTF previously observed in anesthetized, vagotomized,
paralyzed rats.
Received 20 February 2001; accepted in final form 13 April 2001
APS Manuscript Number A165-1.
Article publication pending J Appl Physiol
ISSN 1080-4757 Copyright 2001 The American Physiological Society.
Published in APStracts on 18 June 2001