Retinoic acid prevents alteration of neuronal morphology and locomotion of zebrafish embryos induced by ethanol exposure during gastrulation

• Author / Creator

  Ferdous, Jannatul

• Ethanol (EtOH) exposure during development has been shown to lead to deficits in fine and gross motor control. In this study I used zebrafish embryos in the gastrulation stage to determine the developmental effects of a brief, 5-hour exposure to EtOH. I treated fertilized zebrafish eggs from 5.25 hours post fertilization (hpf) to 10.75 hpf, with 10 mM, 50 mM, 100 mM EtOH or 150 mM EtOH. Embryos were removed from the EtOH wash at the end of gastrulation and were allowed to develop. They were then examined for general animal morphology, the c-start reflex behavior, Mauthner cell morphology and motor neuron morphology in 2-day old embryos. EtOH treated animals exhibited a minor but significant increase in gross morphological deformities compared with untreated fish. Locomotor studies showed that EtOH treatment resulted in an increase in the average angular velocity of the tail bend during the escape response, and an increase in the peak speed of the tail. Furthermore, there was a marked increase in abnormally directed escape behaviors, with treated embryos showing greater incidences of c-starts in inappropriate directions. Immunolabelling of the Mauthner cells, which are born during gastrulation, showed them to be significantly smaller in fish treated with 100 mM EtOH and 150 mM EtOH compared with untreated animals. Immunolabelling of primary motor neurons using the anti-znp1antibody, showed no significant effect on axonal branching of primary motor neurons, whereas secondary motor axons possessed a greater number of branches in ethanol treated fish compared with controls. Together these findings indicate that ethanol exposure during gastrulation leads to alterations in behavior and neuronal morphology.
  The vitamin A derivative, RA, has been shown to prevent FASD in a number of preparations. Therefore, I determined whether co-treatment of alcohol and retinoic acid could prevent the effects of alcohol exposure during gastrulation. I exposed zebrafish embryos to either ethanol (150 mM) alone, retinoic acid (10-9 M) alone, or a combination of retinoic acid (10-9 M) plus ethanol (150 mM) for 5 hours from 5 hpf to 10.75 hpf (gastrulation). Ethanol treatment during gastrulation altered a range of features in embryonic zebrafish. Importantly, I found that co-treatment with retinoic acid prevented all of the effects of ethanol including survival, body length, M-cell morphology and escape response movements. Treatment with RA alone had no significant effect on any of these parameters. Together these findings show that ethanol exposure during the brief period of gastrulation has a significant effect on neuronal morphology, and that this can be prevented with retinoic acid co-treatment.

• Subjects / Keywords

  • Development
  • Retinoic Acid
  • FASD
  • Ethanol
  • Zebrafish
  • Fetal Alcohol Spectrum Disorder

• Graduation date

  Fall 2018

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R32F7K70S

• License

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