Effects of naloxone and morphine on acute hypoxic survival in mice.
OBJECTIVE
To investigate a role of the opiate system during acute hypoxic hypoxia, the effects of naloxone and morphine on hypoxic survival rate were investigated in awake adult mice.


METHODS
Prospective, randomized, animal trial.


METHODS
University research laboratory.


METHODS
Male dd-Y mice (n = 864 in experiment I, n = 144 in experiment II, n = 30 in experiment III).


METHODS
The animals were placed in an airtight plastic chamber into which a continuous flow of 8 L/min 5% oxygen-95% nitrogen was passed.


RESULTS
One and 5 mg/kg naloxone had no significant effect on the survival rate of mice subjected to acute hypoxic hypoxia, whereas 10 mg/kg naloxone decreased the survival rate. On the other hand, 2 and 5 mg/kg morphine was shown to have a protective action against acute hypoxic hypoxia. The protective effects of 5 mg/kg morphine against hypoxia was even antagonized by 5 mg/kg naloxone, which did not itself show any significant effect on the survival rate. The oxygen consumption in the morphine-treated (5 mg/kg) mice was significantly (p < .05) lower (87.0% +/- 4.6%; mean +/- SE) than that in the saline-treated animals.


CONCLUSIONS
The present study suggests that the endogenous opiate system does not play a significant role on the pathophysiology caused by acute hypoxic hypoxia and that the improved survival of the hypoxic animals by morphine is at least partly attributable to its depressant effect on oxygen consumption.
Endoh
H
H
Department of Anesthesiology, Niigata University School of Medicine, Japan.
Taga
K
K
Yamakura
T
T
Sato
K
K
Watanabe
I
I
Fukuda
S
S
Shimoji
K
K
D000701:Analgesics, Opioid / Q000494:pharmacology*; D000704:Analysis of Variance; D000818:Animals; D000860:Hypoxia / Q000378:metabolism*; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000494:pharmacology*; D018847:Opioid Peptides / Q000378:metabolism*; D010101:Oxygen Consumption / Q000187:drug effects; D011446:Prospective Studies; D011897:Random Allocation; D016019:Survival Analysis
D000701:Analgesics, Opioid; D009292:Narcotic Antagonists; D018847:Opioid Peptides; D009270:Naloxone; D009020:Morphine