Effect of morphine on fetal electrocortical activity and breathing movements in fetal sheep.

Morphine (1 mg/kg) given to the lamb fetus near term induces a significant increase in low-voltage high-frequency (LVHF) electrical activity in the brain. This pattern of the electrocorticogram (ECOG) is associated with simultaneous continuous fetal breathing movements of greater amplitude than control. Naloxone prevents and reverses these morphine-induced changes. The observed phenomena suggest that opiate receptors may play a stimulant role in the control of fetal LVHF ECOG and fetal breathing movements.