AJP - Regulatory, Integrative and Comparative Physiology, Vol 259, Issue 1 139-R146, Copyright © 1990 by American Physiological Society
Control of interbreath interval in the African lungfish
A. I. Pack, R. J. Galante and A. P. Fishman
Department of Medicine, Hospital of the University of Pennsylvania, Philadelphia 19104-4283.
We have performed studies to examine the effect of variations in
intrapulmonary pressure on the interval between lung breaths in the African
lungfish. Studies were performed in two different preparations. In the
first we produced changes in lung pressure using a controlled-infusion
pump. Increases in intrapulmonary pressure prolonged the interval between
lung breaths. At a pressure of 2.5 cmH2O the average interval was 2.6 +/-
1.8 min (mean +/- SD); at 5.0 cmH2O, 8.1 +/- 3.5 min; and at 7.5 cmH2O,
16.2 +/- 3.8 min. Inflations of the lung early in the interbreath interval
had less of an effect on its duration than inflations later in the
interval. In the second preparation we used a system in which gas flowed
continuously through both lungs. Intrapulmonary pressure was varied by
changing outlet pressure and O2 concentration by changing the composition
of the gas mixture. This allowed separate control of both O2 concentration
and intrapulmonary pressure. At a fixed O2 concentration intrapulmonary
pressure increased the duration of the interval between lung breaths. At a
fixed pressure, reductions in O2 concentration shortened the interval.
There was no significant interactive effect of O2 and pressure. Lung
inflation did not alter the frequency of gill ventilation. These results
imply that a reflex highly similar to the Hering-Breuer
expiratory-promoting reflex was already present in the African lungfish.
