Estrogen differentially alters NMDA- and kainate-induced seizures in prenatally morphine- and saline-exposed adult female rats.

The purpose of the present study was to investigate the effects of prenatal exposure to morphine on seizure susceptibility in adult female rats. Adult female rats, exposed to saline or morphine on prenatal days 11-18, were ovariectomized (OVX) and some were injected 48 h prior to seizure testing with estradiol benzoate (EB). To assess the latency to onset of stereotypy and seizures, females received systemic injections of N-methyl-D-aspartate (NMDA; 150, 175, 200 mg/kg) or kainic acid (KA; 10 or 15 mg/kg). Prenatal morphine exposure increased the latency to onset of wet-dog-shakes (WDS) in both OVX and OVX, EB-injected females after the higher dose of KA. However, prenatal morphine exposure increased the latency to onset of stereotypy only in OVX, EB-injected females after the highest dose of NMDA. Prenatal morphine exposure also increased the latency to onset of seizures after the lower dose of KA, but did not change the latency to onset of NMDA-induced seizures. Additionally, an EB injection increased the latency to onset of seizures in both saline- and morphine-exposed females after the lowest dose of NMDA, but decreased the latency to onset of seizures after the lower dose of KA. Thus, the present study demonstrates that prenatal morphine exposure has different effects on the estrogen regulation of the onset of seizures and stereotypy induced by NMDA or KA in adult, OVX female rats.