Document Detail

Phrenic motoneuron firing rates before, during, and after prolonged inspiratory resistive loading.
MedLine Citation:
PMID:  9292463     Owner:  NLM     Status:  MEDLINE    
Phrenic motoneuron firing rates during brief inspiratory resistive loading (IRL) are high, and nearly all the motoneurons are recruited. Diaphragmatic fatigue has been difficult to demonstrate during IRL. Furthermore, evidence from studies in limb muscles has shown variable motoneuron responses to prolonged high-intensity loads. We studied phrenic motoneuron firing rates before, during, and after prolonged IRL in anesthetized rabbits. Of 117 phrenic axons, only 2 axons were not recruited; 41 axons were silent during unloaded breathing but were recruited at higher loads. Silent axons showed a more rapid increase in firing rate as the load increased. Phrenic motoneuron firing rates increased throughout the period of loading, whereas airway pressure swings did not. After prolonged IRL, higher motoneuron firing rates were needed during brief loads to produce the same airway pressure. No evidence of a decline in motoneuron firing rates was seen at any point. We conclude that the respiratory muscles can be shown to demonstrate physiological responses consistent with fatigue during prolonged IRL, and activation rates are high and remain so throughout this prolonged loading.
J D Road; A M Cairns
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  83     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  1997 Sep 
Date Detail:
Created Date:  1997-10-14     Completed Date:  1997-10-14     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  776-83     Citation Subset:  IM    
Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada V5Z 3J5.
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MeSH Terms
Action Potentials / physiology
Airway Resistance / physiology*
Axons / physiology
Carbon Dioxide / metabolism
Motor Neurons / physiology*
Oxygen Consumption / physiology
Phrenic Nerve / cytology,  physiology*
Recruitment, Neurophysiological / physiology
Reg. No./Substance:
124-38-9/Carbon Dioxide

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