Opiate withdrawal in the fetal rat: A behavioral profile

Offspring of women exposed to opiate drugs such as heroin and methadone dur ing pregnancy have a high incidence of morbidity and mortality. Infants als o show opiate withdrawal. In this study, we examined the behavioral effects of precipitated withdrawal in morphine-dependent fetal rats at gestational day (GD) 20. The dam was implanted on GD 14 with a pellet containing 75.0 mg of morphine. On GD 20, the dam underwent chemoyelotomy at L1/L2. The ute rine horns were externalized and four subject fetuses were selected for beh avioral observation, two from each uterine horn. The fetus was then injecte d subcutaneously with either saline or naltrexone (1.0 mg/kg) and the behav iors of the fetus recorded every 15 sec for 20 min. The results show that n altrexone injected fetuses that had been chronically exposed to morphine de monstrated increased limb and mouth movements, face wiping, and body curls, and spent less time quiet as compared with control fetuses. These results indicate that a morphine withdrawal-like syndrome occurs in the fetal rat. (C) 2000 Elsevier Science Inc.