Neurochemical control of tissue resistance in piglets.
Martin, Richard J., Ismail A. Dreshaj, Martha J. Miller, Musa A.
Haxhiu.
Rainbow Babies & Childrens Hospital, Department of Pediatrics,
11100 Euclid Avenue, Cleveland, OH 44106
APStracts 2:0182A, 1995.
Lung resistance may be influenced by chemoreceptor activity and
modulated by inspiratory neural output, however, it is unknown
whether the contractile elements of lung tissue participate in these
changes during early development. In anesthetized, paralyzed, open
-chested piglets, we measured phrenic ENG, lung resistance (RL), and
tissue resistance utilizing alveolar capsules in order to partition
the hypercapnic and hypoxic responses of RL into tissue (Rti) and
airway (Raw) components. Inhalation of 7% CO2 significantly increased
RL (7.4 + .5 to 11.3 + .6 cm H2O/L/sec), Rti (5.2 + .5 to 6.9 + .5)
and Raw (2.2 + 0.2 to 4.4 + .4). Inhalation of 12% O2 caused more
modest increases in RL, Rti and Raw. Oscillations in tracheal and
alveolar pressures appeared in synchrony with phrenic activity in
response to both chemoreceptor stimuli. Cholinergic blockade
eliminated these oscillations and significantly reduced the
hypercapnic and hypoxic responses of RL, Rti and Raw. These data
demonstrate for the first time that hypercapnia and hypoxia elicit a
cholinergically mediated increase in tissue resistance which, just
like the airway component of RL, is modulated by inspiratory neural
output, and is present during early development. Such coordination in
neural function throughout the respiratory system may serve to
optimize gas exchange during early postnatal life.
Received 12 September 1994; accepted in final form 24 April 1995.
APS Manuscript Number A956-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 9 May 1995.