Document Detail


Chronic hypercapnia resets CO2 sensitivity of avian intrapulmonary chemoreceptors.
MedLine Citation:
PMID:  9950907     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Avian intrapulmonary chemoreceptors (IPC) are vagal sensory neurons that participate in the control of breathing. IPC action potential frequency is inversely proportional to PCO2, but it is unclear whether low PCO2 or high pH is the immediate stimulus for signal transduction in IPC. To address this question, comparisons were made between single cell neural responses of 34 IPC recorded in 6 anesthetized ducks (Anas platyrhynchos) acclimatized 12 days to 7.5% inspired CO2 and 22 IPC recorded in 9 normal anesthetized ducks. We hypothesized that if respiratory-linked pH changes determine IPC activity, action potential frequency as a function of inspiratory PCO2 (PICO2) should be greater after acclimatization due to metabolic acid-base compensation and higher pH. Conversely, if PCO2 alone determines IPC discharge, action potential frequency vs. PCO2 should be unchanged by acclimatization. Results indicate that after acclimatization ventilation was depressed at 28 and 42 Torr PICO2 (P < 0.05) and mean plasma pH at 40 Torr PCO2 increased from 7.38 +/- 0. 03 to 7.56 +/- 0.02 (P < 0.05), indicating significant metabolic acid-base compensation and HCO-3 retention. Mean IPC discharge rate was elevated by CO2 acclimatization at all PCO2 studied. In acclimatized vs. normal animals, regression analysis of IPC discharge as a function of lnPCO2 showed increased mean intercepts of 81.1 +/- 4.0 vs. 48.4 +/- 3.6 impulses/s (P < 0.05) and increased mean slopes of -19.0 +/- 1.0 vs. -12.0 +/- 1.1 impulses. s-1. lnPCO2-1 (P < 0.05). Results indicate that IPC response to CO2 is mediated by H+ from CO2 hydration and not by CO2 directly.
Authors:
D E Bebout; S C Hempleman
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The American journal of physiology     Volume:  276     ISSN:  0002-9513     ISO Abbreviation:  Am. J. Physiol.     Publication Date:  1999 Feb 
Date Detail:
Created Date:  1999-03-30     Completed Date:  1999-03-30     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0370511     Medline TA:  Am J Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  R317-22     Citation Subset:  IM; S    
Affiliation:
Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona 86011-5640, USA.
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MeSH Terms
Descriptor/Qualifier:
Adaptation, Physiological
Animals
Blood Physiological Phenomena
Carbon Dioxide / metabolism*
Chemoreceptor Cells / physiology*
Chronic Disease
Ducks / physiology*
Electrophysiology
Female
Hydrogen-Ion Concentration
Hypercapnia / metabolism,  physiopathology*
Lung / innervation*,  metabolism*
Male
Partial Pressure
Receptors, Cell Surface
Respiration
Grant Support
ID/Acronym/Agency:
HL-07212/HL/NHLBI NIH HHS; HL-17731/HL/NHLBI NIH HHS
Chemical
Reg. No./Substance:
0/Receptors, Cell Surface; 124-38-9/Carbon Dioxide

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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