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Endogenous opioid effects on abdominal muscle activity during inspiratory loading
A T Scardella1, J J Petrozzino, M Mandel
1Department of Medicine, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, New Brunswick 08903-0019.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|September 1, 1990
Summary
Endogenous opioid signaling depresses abdominal muscle responses during inspiratory flow-resistive loading. Naloxone administration reversed this effect, increasing external oblique muscle activity and improving breathing mechanics in goats.
Area of Science:
- Respiratory Physiology
- Neuroscience
- Pharmacology
Background:
- Previous studies suggested naloxone (NLX) increases tidal volume during inspiratory flow-resistive loading (IRL) possibly via abdominal muscles.
- Endogenous opioid systems are implicated in modulating respiratory muscle activity.
Purpose of the Study:
- To test the hypothesis that endogenous opioids depress abdominal muscle response to IRL.
- To investigate the role of opioid signaling in respiratory compensation during inspiratory loading.
Main Methods:
- Seven unanesthetized goats were subjected to 3 hours of IRL (50 cmH2O.l-1.s).
- Measurements included tidal volume (VT), arterial blood gases, diaphragm (EMGdi), external oblique (EMGeo), transversus abdominis (EMGta), and external intercostal (EMGei) muscle activity.
- Naloxone (NLX) or saline was administered post-loading.
Main Results:
- IRL decreased VT and initially increased EMGdi, but EMGdi did not sustain the increase.
- External oblique muscle (EMGeo) activity initially increased then significantly decreased during prolonged IRL.
- NLX administration significantly increased EMGeo activity (91%) but only minimally increased EMGdi (15%).
Conclusions:
- Endogenous opioid elaboration actively depresses the abdominal muscle response during sustained IRL.
- Naloxone reverses this opioid-mediated depression, highlighting its role in ventilatory control during respiratory loading.