1697 ROLE OF ENDOGENOUS OPIATES IN CO₂ SENSITIVITY IN THE NEWBORN PRIMATE

Abstract

Recent reports indicate that naloxone will shorten the duration of primary apnea following asphyxia (Ped.Res. 14:357, 1980) and prevent the secondary depression of ventilation during hypoxia in the newborn rabbit (Ped.Res.14:643, 1980). Previous authors have shown the CO₂ sensitivity in the newborn increases with postnatal maturation (J.A.P. 41:41, 1976; J.A.P. 48:347, 1980). To determine whether endorphins depress CO₂ sensitivity in the immediate newborn period, five newborn M. nemestrina were studied on day 2-3 and again on day 19-21. V_E/Kg and PO.2 were measured in duplicate trials in tracheotomized animals during steady state hyperoxia (FiO₂=1.0), then again at 5-7 minutes of hyperoxic hypercapnia (FiO₂=0.96, FiCO₂=0.04). Naltrexone was given IV at a dose of 0.1 mg/kg and the trials were repeated.

Values are mean ± S.E.M. Statistical analysis by paried t test. These results suggest that endogenous opiates do not influence the hyperoxic hypercapnic response in the newborn subhuman primate and confirm recent reports in adult humans (Am.Rev.Resp. Dis.121:1045,1980).

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