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Role of endogenous opiates in hypoxic ventilatory response in the newborn primate.

The effects of opiate receptor antagonism by naltrexone hydrochloride on the biphasic hypoxic ventilatory response in the infant Macaca nemestrina have been investigated. Minute ventilation, tidal volume, and respiratory frequency were measured in six animals from timed gestations before and during inhalation of a hypoxic gas mixture. All studies were completed in non-rapid-eye-movement sleep. Arterial blood gases were obtained during each stimulus period. All animals demonstrated the typical biphasic ventilatory response to acute moderate-severe hypoxemia. After the administration of naltrexone hydrochloride to block opiate receptors, the animals still manifested a biphasic hypoxic response that was no different than that noted prior to drug administration. Naltrexone hydrochloride had no effect on room air resting ventilation in any of the animals. Our data suggest that endogenous opiates play no physiological role in the acute ventilatory response to moderate-severe hypoxia in the newborn subhuman primate.