The morphogenesis of myeloschisis in the rat

Pregnant Sprague-Dawley rats were utilized in this study. They were separated into two groups. In the control group, a single intragastric dose of distilled water was given on the 11th day of gestation. In the test group, a single intragastric dose of ethylenethiourea (ETU), 240 mg/kg was given on the same day of gestation. Embryos were recovered 12, 24, 36, and 48 hours after ETU and distilled water administration, and were prepared for scanning electron microscopy and light microscopy. The posterior neuropore of rat fetuses in the control group closed completely on gestation day 12.5. However, the closure of posterior neuropore in ETU-induced fetuses is shown to have been disrupted 12 hours after ETU administration. Marked neural tissue overgrowth in the posterior neuropore resulted in neural fold eversion and finally produced a picture of lumbosacral myeloschisis on day 13 of gestation. Our observation implies that myeloschisis is induced by non-closure of the neural fold, not by reopening after its proper closure.