The role of pulmonary stretch receptor feedback in the control of
episodic breathing in the bullfrog.
Kinkead, Richard, and William K. Milsom.
Department of Zoology, University of British Columbia, 6270
University Blvd., Vancouver, British Columbia, Canada, V6T 1Z4
APStracts 3:0302R, 1996.
This study compared the "fictive" breathing patterns of
decerebrate, paralysed, unidirectionally ventilated bullfrogs in
which pulmonary stretch receptor feedback was either absent
(bilateral vagotomy), maintained constant at different levels (tonic)
or oscillated with each fictive breath (phasic) under different
levels of hypoxic or CO2-related respiratory drive. Tonic and phasic
PSR feedback had identical effects on the fictive breathing pattern;
decreasing PSR feedback increased the peak integrated trigeminal ENG
and decreased breathing frequency. The effects of bilateral vagotomy
and lung deflation to 0 cm H2O on breathing pattern were identical.
While hypoxia (FO2 = 0.06) had no significant effect on fictive
breathing, ventilating frogs with increasing CO2 levels (FCO2 range:
0.00 to 0.03) increased the number of breaths in each fictive
breathing episode and this effect was potentiated by PSR feedback.
Whenever respiratory drive was increased, regardless of the method
(increase in PSR feedback or chemoreceptor drive), occasional single
breaths were replaced by breathing episodes indicating that the
mechanisms responsible for the clustering of the breaths and the
onset/termination of breathing episodes are not dependent on either
input alone.
Received 8 August 1995; accepted in final form 27 July 1996.
APS Manuscript Number R501-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 August 1996