PHYSIOLOGICAL AND BEHAVIORAL EVIDENCE THAT CHEMICALS IN THE ENVIRONMENT INFLUENCE DEVELOPMENT OF THE ZEBRAFISH OLFACTORY SYSTEM

Olfactory imprinting is the process of producing life-long changes through neural modification that is independent of associative learning. Here, I provide data to demonstrate that olfactory imprinting in zebrafish leads to neurobiological and behavioral changes. I treated zebrafish with an amino acid (AA) or a bile acid (BA) mixture from 4 days post-fertilization (dpf) to 40 dpf. Behavior studies showed that fish treated with odorants for 40 days exhibited preferential responses to treated odorants, which was different from the controls. These behavioral changes were retained 3 months after the odor treatment was ceased. Whole-mount immunohistochemistry was conducted using antibodies for parvalbumin (PV) and OTX. We discovered that treated fish had increased PV and OTX expression in the olfactory epithelium (OE) at 7 dpf and increased PV expression in the olfactory bulb (OB) at 12 dpf. Detailed analysis indicated that increased PV expression was observed in the OE apical region of treated groups while OTX was increased in both the apical and basal regions of the OE. In three regions of the OB analyzed, BA treated fish showed a doubling in PV expression in all regions while doubling was in two regions in AA treated fish. Increased OTX expression was in the three regions of AA treated fish but not in BA treated fish. These data demonstrate that exposure to AA or BA during zebrafish development leads to long-lasting physiological and behavioral changes. The report also includes a study of embryonic zebrafish treated with SP600125 (anthrapyrazolone), an inhibitor of the c-Jun N-terminal kinase (JNK) signaling pathway. Zebrafish embryos were treated with 1.25 μM, 5 μM, or 12.5 μM of SP600125 from 18 to 48 hours post-fertilization (hpf) followed by evaluation at 120 hpf. Zebrafish treated at 1.25 μM were not affected developmentally while embryos treated at xv 5 μM and higher displayed numerous morphological defects including edemas, eye malformations and reduction in olfactory organ size. Overall, it was observed that treatment at 5 μM, SP600125 caused severe developmental defects and that these defects worsened with increasing concentrations. Taken together, these data indicate that the environment has a profound influence on zebrafish development.PH.D in Biology, December 201