Prenatal morphine exposure induces age-related changes in seizure susceptibility in male rats

The purpose of this study was to investigate the effects of prenatal exposure to morphine (5-10 mg/kg on days 11-18 of gestation) on flurothyl seizure susceptibility in adult and developing male rats. In adult rats, prenatal morphine exposure increased the threshold to clonic seizures but not to tonic-clonic seizures. The effects of prenatal morphine exposure on clonic seizures were age dependent. At postnatal day (PND) 15, prenatal drug exposure did not alter the seizure threshold. At PND 25, there was a reduction in the threshold but by PND 38, the clonic seizure threshold was increased and this increase persisted into adulthood. Prenatal exposure to morphine did not alter the tonic-clonic seizure threshold in any age group of intact male rats. A group of male rats prenatally exposed to morphine was gonadectomized in adulthood. In gonadectomized rats both clonic and tonic-clonic thresholds were increased. These results suggest that exposure to morphine during mid to late gestation induces age-dependent alterations in the susceptibility to clonic but not tonic-clonic seizures. In adult male rats the threshold to tonic-clonic seizures is influenced by prior gonadectomy in adulthood.