Date

4-30-2024

Document Type

Thesis

Abstract

Circadian disruptions are quite detrimental to one’s health- leading to many different diseases. The suprachiasmatic nuclei (SCN) (center of regulation of the circadian clock) can perceive light from the retina, allowing the SCN to register cues such as light to aid in regulating the biological clock. Due to this connection constant light is a common disruption, which can cause increased hyperactivity, anxiety, and altered circadian rhythm in mice. This study’s purpose is to determine how two rhodopsin lacking blind sub-strains of C3H mice respond to constant light regarding their behavior, physiology, and their circadian clock, as well as investigating any differences between the C3H sub-strains. Thirty-two C3H male and thirty-two female mice were purchased. Sixteen mice of each sex were from Charles River Laboratory (HeN) and sixteen mice of each sex were also from Jackson Laboratory (HeJ), and half of each sub-strain was housed in constant light and 12:12 light dark cycle. After eight weeks behavioral tests were done: open field and light dark box assay. Tissue samples of the SCN and frontal lobe were collected to analyze levels of ACTH, corticosterone, and BDNF. All mice in LD entrained to the 12:12 LD cycle, and all mice in LL exhibited a lengthened period. However, the HeN mice had a longer period and stronger power than the HeJ mice. There were no cycle differences regarding: weight gain, food intake, BDNF, ACTH, corticosterone, or anxiolytic behavior, indicating that constant light does not elicit the detrimental effects found in seeing mice. HeN mice also had increased weight gain, food intake, and were overall more anxious than HeJ mice. These strain differences could be attributed to a missense point mutation in the Tlr4 gene, which affects the immune system and can impact the biological clock, and possibly the HPA axis. In conclusion, both sub-strains of C3H seem to be immune to the negative effects of constant light, however there are a multitude of strain differences that could be due to a genetic difference and should be explored further.

Department

Biological Sciences

Thesis Comittee

Dr. Joseph Seggio, Thesis Advisor
Dr. Kenneth Adams, Committee Member
Dr. Michael Carson, Committee Member

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