Journal of Applied Physiology, Vol 64, Issue 3 966-971, Copyright © 1988 by American Physiological Society
Hypoxia does not increase CSF or plasma beta-endorphin activity
A. Freedman, A. T. Scardella, N. H. Edelman and T. V. Santiago
Department of Medicine, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, New Brunswick 08903-0019.
The ability of moderate (30-50 Torr arterial PO2) and severe (less than 30
Torr arterial PO2) hypoxia to generate endogenous opioids that modulate
ventilation was studied in unanesthetized goats. Ventilation and its
components, arterial blood gas tensions and pH, and plasma and
cerebrospinal fluid (CSF) beta-endorphin activity were measured before and
after 4 h of sustained moderate or severe hypoxia. Ventilation, as
expected, increased with hypoxia. There were no significant changes in
either plasma or CSF beta-endorphin activity after sustained hypoxia. To
rule out elaboration of endogenous opioids other than beta-endorphin after
hypoxia, naloxone or saline was administered to five of the seven goats
exposed to 4 h of severe hypoxia, and their ventilatory responses were
compared for 30 additional min of hypoxic breathing. No significant
differences in ventilation occurred in the two treatment groups during this
time period. We conclude that, unlike increases in airway resistance,
moderate and severe hypoxia do not cause the elaboration of endogenous
opioids that modify respiratory output in unanesthetized adult goats. The
apparent ability of hypoxia to cause elaboration of endogenous opioids in
the neonate may represent a maturational phenomenon.
