Zebrafish embryos exposed to alcohol undergo abnormal development of motor neurons and muscle fibers

Children with Fetal Alcohol Spectrum Disorder have significantly delayed motor skills, and deficiencies in reflex development. The reasons underlying these motor deficits are not fully understood. The purpose of this thesis was to investigate the effect of embryonic exposure to ethanol (EtOH) on motor neuron and muscle fiber morphology and physiology in zebrafish. We observed that EtOH-exposed fish took longer to hatch and exhibited fewer swimming bouts in response to touch. Immunolabelling of motor neurons indicated that EtOH-exposed fish had significantly higher rates of motor neuron axon defects. Examination of muscle fiber morphology revealed that EtOH exposure resulted in significantly smaller muscle fibers. Miniature endplate current (mEPC) recordings from muscle fibers revealed that event amplitudes, rise times, half widths, frequencies and decay times were affected by EtOH exposure. These findings indicate that motor neurons and muscle fibers of zebrafish are affected by embryonic EtOH exposure, which may be related to deficits in locomotion.