Oral Administration of Morphine Delays Neural Plate Development in Rat Embryos

Previous studies have shown that morphine administration could inhibit neural tube development in rat embryos and produce behavioral defects in human and animals. In the present study, the effects of maternal morphine consumption on embryonic neural plate development in Wistar rats were investigated. Twenty-four female Wistar rats (250 – 300 g) were crossed with males. After pregnancy, the treatment group received 0.1 mg/mL of morphine in drinking water daily (14 mL water/100 g of body weight for each rat), while the control group received tap water. Eight days and 12 hours after the onset of pregnancy, the animals were anesthetized by chloroform and the embryos were taken out surgically. Lengths of embryos were determined by a caliper. Embryos were fixed in formalin 10% and tissue was processed, sectioned, and stained with hematoxylin and eosin. The sections were examined for neural plate development by a light microscope and Motic software. Embryonic length in the treatment group was significantly decreased compared to the control group. Neural plate was observed in the control group. Development of neural plate and other embryonic layers (ectoderm, mesoderm, and endoderm) were delayed in the treatment group. In the treatment group, ectoderm layer was poorly developed in embryos exposed to morphine. Morphine consumption during pregnancy could cause a delay in the development of the neural plate as well as embryonic layers, especially the ectoderm.