Journal of Applied Physiology, Vol 68, Issue 4 1376-1385, Copyright © 1990 by American Physiological Society
Effect of naloxone on spectral shifts of the diaphragm EMG during inspiratory loading
J. J. Petrozzino, A. T. Scardella, J. K. Li, N. Krawciw, N. H. Edelman and T. V. Santiago
Department of Medicine, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, New Brunswick 08903-0019.
Shifts in the power spectrum of the diaphragm EMG to lower frequencies may
occur in the presence of fatiguing inspiratory flow-resistive loads (IRL).
However, such a shift of the centroid frequency (fc) could follow a
reduction in central output through a differential reduction in
end-inspiratory high-frequency power (HFP). In unanesthetized goats, we
tested the hypothesis that activation of the endogenous opioid system by
IRL would differentially reduce central respiratory output, causing a
reduction in fc. IRL was imposed for 180 min after which naloxone (0.1
mg/kg, NLX) was given. fc was computed from the power spectral density
estimated by the Welch method. IRL reduced fc from 148.0 +/- 9.8 (SE) Hz at
base line to 141.1 +/- 8.9 Hz or to 95.5 +/- 1.3% of base line by 180 min
(both P less than 0.05). NLX increased fc to 148.9 +/- 9.9 Hz or to 100.6
+/- 1.1% of base line (both P less than 0.05). The decline in fc during IRL
was found to be the result of a reduction in HFP, predominantly toward the
end of inspiration. The reversibility of this fc shift with NLX suggests a
central mechanism consequent to elaboration of endogenous opioids and not a
peripheral (muscular) event consequent to muscle fatigue.
