FETAL BREATHING IS NOT INHIBITED BY ETHANOL EXPOSURE DURING PROLONGEDREDUCED UTERINE BLOOD-FLOW

When prolonged hypoxemia is induced in fetal sheep by reducing uterine blood flow, fetal breathing movements (FBM) return to normal incidenc e after their initial decrease. Ethanol also inhibits FBM. These exper iments were designed to determine the role of fetal oxygenation status in affecting ethanol-induced inhibition of FBM. A 1-h maternal infusi on of 1 g ethanol/kg maternal body weight was given to animals followi ng 20 h of reduced uterine blood flow (RUBF; n = 9), as well as to nor moxemic (n = 9) fetal sheep, and the effect on FBM, electrocortical ac tivity (ECoG), and electroocular activity (EOG) was determined. In nor moxemic fetuses, the incidence of FBM decreased from 26.1 +/- 5.5% to 2.8 +/- 1.6% (p < 0.05) with ethanol, subsequently returning to baseli ne values over 6 h, but there was no effect of ethanol on FBM incidenc e 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 no rmoxemic fetuses, but there was no change in RUBF fetuses. We conclude that the adaptive mechanism(s) invoked by fetal sheep during prolonge d RUBF abolishes its ability to respond behaviourally to ethanol.