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Ventilatory long-term facilitation in unanesthetized rats.
E B Olson1, C J Bohne, M R Dwinell
1The John Rankin Laboratory of Pulmonary Medicine, Department of Preventive Medicine, University of Wisconsin School of Medicine, Madison, 53705-2368, USA. ebolson@facstaff.wisc.edu
Journal of Applied Physiology (Bethesda, Md. : 1985)
|July 18, 2001
Summary
Unanesthetized rats show sustained breathing increases (ventilatory long-term facilitation) after intermittent hypoxia, but not continuous hypoxia. This breathing response is similar to findings in anesthetized animals.
Area of Science:
- Physiology
- Respiratory Control
- Neuroscience
Background:
- Ventilatory long-term facilitation (LTF) is a sustained increase in breathing.
- LTF has been observed in anesthetized animals but its occurrence in unanesthetized models is less understood.
Purpose of the Study:
- To investigate if unanesthetized rats exhibit ventilatory LTF following intermittent or continuous hypoxia.
- To compare ventilatory LTF in unanesthetized rats with previous findings in anesthetized models.
Main Methods:
- Minute ventilation (VE) and carbon dioxide production (VCO2) were measured in unanesthetized rats using barometric plethysmography.
- Rats were exposed to either intermittent or continuous isocapnic or poikilocapnic hypoxia.
- Breathing parameters were assessed before, during, and 60 minutes after hypoxic exposure.
Main Results:
- Intermittent hypoxia, both isocapnic and poikilocapnic, induced a significant increase in VE and VE/VCO2 compared to baseline.
- Continuous hypoxia did not result in significant changes in VE or VE/VCO2 60 minutes post-exposure.
- The magnitude and time course of ventilatory LTF in unanesthetized rats were comparable to phrenic LTF in anesthetized rats.
Conclusions:
- Unanesthetized rats demonstrate ventilatory long-term facilitation (LTF) after intermittent hypoxia.
- The findings suggest that ventilatory LTF can occur in awake, unrestrained conditions and is dependent on the pattern of hypoxic exposure.