Date of Award

4-2016

Degree Name

Doctor of Philosophy

Department

Biological Sciences

First Advisor

Dr. Christine A. Byrd-Jacobs

Second Advisor

Dr. John M. Spitsbergen

Third Advisor

Dr. Wendy S. Beane

Fourth Advisor

Dr. Christopher A. Pearl

Abstract

The adult zebrafish olfactory system, with its persistent neuronal turnover and abundant regenerative capacity, is an excellent model system for studies of adult brain plasticity. Reversible deafferentation, achieved by repeated intranasal irrigation with detergent, reduces bulbar innervation and affects bulb structure and function, while cessation of treatment permits reinnervation and recovery of bulb volume. Alterations in cell genesis may account for this phenomenon. This study focuses on adult neurogenesis in the zebrafish olfactory system following reversible deafferentation and direct olfactory bulb injury.

Potential alterations in cell proliferation, differentiation, migration, and survival in the olfactory bulb following single and repeated intranasal irrigation with detergent and reafferentation were examined. Chronic deafferentation and reafferentation cause a bilateral increase in the number of new cells migrating into the bulbs. Both influence the survival of new cells, while reafferentation alters differentiation causing a reduction in the number of new cells becoming neurons.

Since the telencephalic ventricular zone is the source of adult-formed cells it was examined following bulbar damage from intranasal irrigation with detergent, cautery ablation of the olfactory organ, and direct injury. Chemical and cautery ablation cause an immediate bilateral increase in ventricular zone proliferation, with cautery ablation causing a significantly greater response. Unlike deafferentation, direct injury to the bulb causes a unilateral increase in new cells in the ventricular zone side ipsilateral to the injured bulb. One week recovery following detergent deafferentation results in a bilateral reduction in proliferating cells, likely the result of increased migration away from the ventricular zone and into the bulbs. Thus, ventricular zone proliferation is influenced by type, extent, and severity of injury.

Also investigated was a potential immune response following direct bulb injury. Direct bulb injury results in an acute immune response by microglia, enhanced by an apparent immigration of leukocytes. The immune response resolves quickly without indications of chronic inflammation. These findings are similar to that reported in other zebrafish brain regions.

This study provides novel information regarding the plasticity of adult neurogenesis in the olfactory bulb and ventricular zone following bulbar damage and begins to elucidate the role of the immune system in this process

Access Setting

Dissertation-Campus Only

Restricted to Campus until

4-15-2026

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