Date of Thesis

5-4-2017

Thesis Type

Masters Thesis

Degree Type

Master of Science

Department

Biology

First Advisor

Mark Haussmann

Second Advisor

Jennifer Rice Stevenson

Third Advisor

Christopher Martine

Abstract

Chronic stressors, such as chronic isolation in social mammals, can elevate glucocorticoids (CORT), which may affect cellular aging mechanisms such as increasing levels of oxidative stress and shortening telomere lengths. Prairie voles (Microtus ochrogaster) are a useful model species to study chronic isolation due to their social and pair-bonding behaviors. Recent work in prairie voles suggests that oxytocin and social support may mitigate some of the negative consequences of social isolation, possibly by reducing CORT levels. We investigated the influences of isolation, oxytocin or social support on stress physiology, behavior, and cellular aging. Voles were divided into six groups: isolated (I), paired (P), isolated (IV) and paired (PV) with daily vehicle injections, and isolated (IO) and paired (PO) with daily oxytocin injections. Blood samples were collected at the start of the study, then again after 3 and 6 weeks. Acute stress tests were conducted using the resident-intruder test (RIT) at 6 weeks to determine if treatment had any effect on stress responsiveness. Anhedonia, a behavioral index of depression, was measured using sucrose solution preference tests to determine depression-like symptoms throughout the study. We found that six weeks of chronic isolation lead to increased CORT levels, oxidative damage, telomere degradation and anhedonia. However, daily oxytocin injections in isolated individuals prevented these negative consequences as compared to those who were isolated with and without daily vehicle injections. During the RIT, I prairie voles had elevated CORT levels at baseline and stress-induced time points, which continued to increase during the recovery time point. IO prairie voles had a similar stress response in terms of CORT secretion to the P, PO and tremetn groups. Oxidative damage markers (ROMs) were elevated in the I and IV groups during the stress-induced time point of the RIT, but returned to baseline levels by the recovery time point. However, baseline levels of ROMs were still significantly higher in the I and IV treatment groups than all other treatments. IO prairie voles had no change in ROMs during the RIT, similar to the paired groups. Antioxidant capacity stayed the same for all groups until the recovery sample during the RIT when all treatment groups significantly declined in TAC. This demonstrates that isolation caused elevated biological aging, stress and depression-like behavior. This is the first study to link social isolation with oxidative stress and telomere shortening.

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