PRENATAL MORPHINE TREATMENT AND THE DEVELOPMENT OF THE STRIATUM

To study the hypothesis that prenatal exposure to opiates alters rates of mitosis, neuronal migration and/or cell survival in the developing striatum, we injected pregnant rats twice daily with morphine from E5 through term. At either E14 or E19, the rats were injected with bromodeoxyuridine (BrdU) to label permanently neurons undergoing final mitosis. Embryos were obtained at E14, E16, E19 or the day of birth (PO). Brains were processed for immunocytochemical detection of BrdU. The prenatal treatment with morphine did not appear to alter mitotic rates at either E14 or E19. However, the number of labeled cells detected on PO was decreased in the ventrolateral caudate-putamen and in the nucleus accumbens by morphine treatment. These results suggest that prenatal exposure to morphine disrupts neuronal migration and/or cell survival. In the anlage of the nucleus accumbens labeled with BrdU at E19, small bits of labeled nuclear material were found in the morphine-treated E19 embryos, suggesting increased apoptosis.