First Advisor

Deborah Lutterschmidt

Date of Award

2016

Document Type

Thesis

Degree Name

Bachelor of Science (B.S.) in Biology and University Honors

Department

Biology

Subjects

Developmental neurobiology -- Research, Glucocorticoids -- Physiological effect, Prenatal influences, Red-sided garter snake

DOI

10.15760/honors.330

Abstract

Little is currently known about normal brain development and the growth of new nerve cells, known as neurogenesis, in most species, let alone how exposure to prenatal stress affects these processes. Using red-sided garter snakes as our animal model, we have a unique opportunity to study the impact of exposure to elevated maternal glucocorticoids, commonly known as "stress hormones", on brain development. This species is viviparous, with a proto-placental structure through which developing fetuses receive nutrients from the dam. Adult snakes also exhibit high rates of seasonal changes in neurogenesis. We captured mated female snakes and treated one-third of them with subcutaneous glucocorticoid hormone implants, one-third with subcutaneous metyrapone, a glucocorticoid synthesis inhibitor, and one-third with a subcutaneous blank control capsule. At ~14 weeks following birth, we injected the neonates with BrdU, a thymidine analog that is incorporated into the DNA of newly-formed cells. We euthanized the neonates at ~15 weeks of age. Immunohistochemistry for BrdU was followed by manually counting the number of stained neurons and statistical analyses to determine differences in neurogenesis between groups. The metyrapone-treated group had significantly reduced brain cell proliferation compared to the control group (P=0.024). While the difference was not statistically significant (P=0.058), the corticosterone group also had reduced brain cell proliferation compared to the control group. These findings suggest that animals whose glucocorticoid levels are disrupted by environmental factors (i.e. heavy predation threat or compromised habitat) produce offspring with compromised brain development.

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Persistent Identifier

http://archives.pdx.edu/ds/psu/18012

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