Thyrotropin releasing hormone (trh) stimulates perinatal rat
respiration in vitro.
Greer, John J., Zaidoon Al-Zubaidy & Jo Ellen Carter.
Division of Neuroscience, Department of Physiology, University of
Alberta Perinatal Research Centre, University of Alberta, Edmonton,
Alberta T6G 2S2
APStracts 3:0173R, 1996.
In the present study, we test whether TRH stimulates respiratory
frequency in perinatal rats by acting at regions of the medulla
responsible for respiratory rhythmogenesis, the pre
-B[diaeresis]otzinger complex. We also test whether TRH stimulates
respiration in the fetal rat at a time shortly after the inception of
respiratory rhythmogenesis (E17-18). Two in vitro experimental models
were utilized: the isolated brain stem-spinal cord preparation from
fetal (E17-E18) and neonatal rats (P0-2) and the medullary slice
preparation isolated from neonatal rats (P1-P2). Bath application of
TRH caused a dose-dependent, reversible increase (maximum increase
nearly equal to 60%) in the frequency of respiratory rhythmic neural
discharge generated by brainstem-spinal cord (EC50 nearly equal to 9
nM) and medullary slice (EC50 nearly equal to 2.5 nM) neonatal rat
preparations. Pressure injection of TRH unilaterally into the region
of the pre-B[diaeresis]otzinger complex of the neonatal medullary
slice caused an 28% increase in the frequency of respiratory
discharge. Application of TRH to the medium bathing fetal rat
brainstem-spinal cord preparations caused approximately a three-fold
increase in respiratory discharge frequency. We conclude that TRH
stimulates respiratory discharge frequency from the time near
inception of respiratory motor discharge and acts directly at the
pre-B[diaeresis]otzinger complex.
Received 8 May 1995; accepted in final form 25 April 1996.
APS Manuscript Number R274-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 8 May 96