Can Individual Differences in the Range of Stress Hormone Production Predict Behavioral Coping with Challenge?

Open Access
Author:
Platz, Erin Renee
Area of Honors:
Biology
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Victoria A Braithwaite, Thesis Supervisor
  • James Harold Marden, Honors Advisor
Keywords:
  • Sprague Dawley
  • rats
  • reactive scope
  • stress
  • corticosterone
  • successive negative contrast
  • SNC
  • coping
  • stress hormone
Abstract:
Every animal handles unexpected stimuli and situations differently. An individual’s ability to cope with challenge is dependent upon prior experience and intrinsic factors such as endocrine sensitivity. Our study assesses how the physiological range of stress hormone production, intrinsic to an animal, influences how it responds to chronic stress over time. In this experiment, we evaluate the hormone production of 30 male Sprague Dawley rats exposed to either chronic stress or control housing conditions. Normal, circulating, and challenged corticosterone levels were assessed before and after the stress treatment was applied. To assess the behavioral response to challenge, we conducted a successive negative contrast (SNC) test. This test assesses how the animal copes with a sudden decrease in reward value. Animals that are more sensitive to challenges show a greater sensitivity to this unexpected downshift in the reward value. After the SNC test took place, a third and final round of blood collections occurred. The corticosterone levels were evaluated using a radioimmunoassay kit and it was determined that the chronic stress period resulted in decreased peak corticosterone production [RMANOVA, F(1, 28) = 5.54, P < 0.03], and decreased reactive scope of corticosterone production [RMANOVA, F(1, 27) = 5.120, P = 0.03]. The SNC responses were not different between the stress and control rats [RMANOVA, F(1, 28) = 0.02, P = 0.90]. Comparisons were then conducted on the hormone profiles of the animals with their behavioral response to the SNC challenge. A direct trend between reactive scope and SNC recovery score was found after the stress period at time point 2 and 3 [R = 0.70, P < 0.01] and [R = 0.51, P < 0.01] showing that stress does in fact cause individual variations in reactive scope and therefore coping ability.