Date Thesis Awarded
Bachelors of Science (BS)
Paul D. Heideman
Eric L. Bradley
While neuroendocrine variation is presumed to be important for brain function and natural selection, very little is known about wild-source heritable variation. Within wild populations of rodents living in temperate zones, some individuals respond strongly to changes in environmental conditions, such as photoperiod, while others do not. Changes in photoperiod are assessed by changes in the duration of melatonin secretion. Melatonin affects many physiological processes, such as the stimulation or inhibition of reproduction, changes in body weight and food intake, and changes in immune function. Immune cells can respond to melatonin with circadian and seasonal changes in function. In this honors thesis, I tested whether differences in neuroendocrine signaling pathways that regulate reproduction are related to differences in immune function in both long-day and short-day photoperiods. For experimental subjects, I used two lines of wild-source Peromyscus leucopus that had previously undergone artificial selection for either strong reproductive response to short-day photoperiod or no response. I measured the amount of inflammation in response to a delayed-type hypersensitivity reaction on one of the pinnae of each mouse to measure immune function. In the Run 1, mice in the short-day photoperiod had significantly enhanced delayed-type hypersensitivity responses relative to mice in long-day photoperiod. In the data from Run 1, mice from the non-responsive line in short-day photoperiod had significantly enhanced delayed-type hypersensitivity responses relative to mice from the responsive line. In the combined data from Runs 1 and 2, the effect of line on inflammation from the delayed-type hypersensitivity test was marginally insignificant. Previous studies indicate that the selection lines vary in seasonal reproductive phenotype and also have differences in neuroendocrine signaling pathways that regulate reproduction. My data indicate that the selection lines may also differ in the strength of immune response to a challenge, suggesting that the wild source population contains biologically significant heritable variation in this aspect of immune function.
Kaugars, Katherine E., "Heritable Variation in Responsiveness to Photoperiod, Reproduction, and Immune Function in a Population of Peromyscus leucopus" (2013). Undergraduate Honors Theses. Paper 639.
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