Effect of a single dose of ethanol on developing peripheral nerve of chick embryos

Fetal Alcohol syndrome (FAS) is a condition occurring in some children of mothers who have consumed alcohol during pregnancy. It is characterized by physical and mental growth retardation, craniofacial anomalies and derangements of numerous body systems. A particular distressing feature of FAS is affection of the nervous system, which manifest as motor and sensory derangements and neurobehavioral deficits. However, no specific changes in the brain and spinal cord that could conclusively explain these neuronal defects have been reported. The aim of this study was to investigate the effects of a single high dose of ethanol exposure during early gestation on the peripheral nerve, with a view to understanding the neuronal disorders appearing in FAS. A chick model of FAS was used and embryos were exposed to 5%, 10% and 15% ethanol immediately after hatching. The effects on general growth and development and on the peripheral nerve of ethanol-exposed embryos were examined following the full period of gestation. There was a significant reduction in crown-rump length, head circumference and body weight in ethanol-exposed chicks as compared with appropriate control groups. The degree of growth retardation among the different alcohol exposed groups was dose dependent and significant prenatal embryo mortality was seen in those exposed to 15% ethanol. In embryos that survived the exposure to 15% ethanol, features of myelin degeneration were observed in the peripheral nerve in the majority of cases. No features of myelin degeneration were observed in embryos exposed to 5% and 10% ethanol or in the control groups. This study demonstrates the direct toxic effects of a single high dose of ethanol on developing embryos in general and the peripheral nerves in particular. Accordingly the pathological changes observed in peripheral nerves could account for some of the neurobehavioral deficits observed in FAS.