Fetal breathing is not inhibited by ethanol exposure during prolonged reduced uterine blood flow

Abstract

When prolonged hypoxemia is induced in fetal sheep by reducing uterine blood flow, fetal breathing movements (FBM) return to normal incidence after their initial decrease. Ethanol also inhibits FBM. These experiments were designed to determine the role of fetal oxygenation status in affecting ethanol-induced inhibition of FBM. A 1-h maternal infusion of 1 g ethanol/kg maternal body weight was given to animals following 20 h of reduced uterine blood flow (RUBF; n = 9), as well as to normoxemic (n = 9) fetal sheep, and the effect on FBM, electrocortical activity (ECoG), and electroocular activity (EOG) was determined. In normoxemic fetuses, the incidence of FBM decreased from 26.1 +/- 5.5% to 2.8 +/- 1.6% (p < 0.05) with ethanol, subsequently returning to baseline values over 6 h, but there was no effect of ethanol on FBM incidence in RUBF fetuses (32.8 +/- 9.1%). Ethanol increased the incidence of intermediate ECoG from 16.6 +/- 2.9% to 49.0 +/- 9.8% (p < 0.01) in normoxemic fetuses, but there was no change in RUBF fetuses. We conclude that the adaptive mechanism(s) invoked by fetal sheep during prolonged RUBF abolishes its ability to respond behaviourally to ethanol.