Modulation of respiratory rhythm in vitro: role of gi/o-protein
mediated mechanisms.
Johnson, Stephen M., Jeffrey C. Smith, and Jack L. Feldman.
Systems Neurobiology Laboratory, Department of Physiological
Science, University of California at Los Angeles, Box 951527, Los
Angeles, California 90095-1527
APStracts 3:0051A, 1996.
Slice preparations from neonatal rat medulla that generate respiratory
rhythm in vitro were used to test for Gi/o-protein mediated
mechanisms affecting breathing rhythm in mammals. The frequency of
inspiratory motor discharge recorded from hypoglossal (XII) nerve
roots decreased with bath-application of [gamma]-aminobutryic acid
(GABA) and norepinephrine (NE) as well as agonists specific for
GABAB, [alpha]2-adrenergic, and [mu]-opioid receptors; 5
-hydroxytryptamine (5HT) had little effect on frequency.
Microinjection of these specific agonists into the
preB[diaeresis]otzinger Complex (preB[diaeresis]otC), the site of
respiratory rhythm generation in vitro, also decreased frequency. In
contrast, substance P (SP) increased frequency when bath-applied or
microinjected into the preB[diaeresis]otC. To test for involvement of
Gi/o proteins, pertussis toxin (PTX) was injected into the CSF of
newborn rats and slices from these animals were tested 48 hr later
for block of drug effects on rhythm. In PTX-treated slices, the
frequency decrease due to GABAB, [mu]-opioid, and [alpha]2-adrenergic
receptor activation was attenuated (P
Received 22 May 1995; accepted in final form 9 January 1996.
APS Manuscript Number A533-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 25 January 96