Effects of Exposure to Stressors of Varying Predictability on Adrenal Function in Rats

• Published in: Behavioral neuroscience 1995-08, Vol.109 (4), p.767-776
• Main Authors: Pitman, D. L, Natelson, B. H, Ottenweller, J. E, McCarty, R, Pritzel, T, Tapp, W. N
• Format: Article
• Language: English
• Subjects: Adrenal glands; Adrenal Glands - innervation; Animal; Animals; Arousal - physiology; Association Learning - physiology; Behavioral psychophysiology; Biochemistry; Biological and medical sciences; Conditioning, Classical - physiology; Corticosterone; Corticosterone - blood; Epinephrine; Epinephrine - blood; Fear - physiology; Fundamental and applied biological sciences. Psychology; Hormones and behavior; Male; Norepinephrine; Norepinephrine - blood; Prolactin; Prolactin - blood; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Rats; Rats, Sprague-Dawley; Rodents; Stimulus Novelty; Stress; Stress Reactions; Stress, Psychological - complications; Sympathetic Nervous System - physiology
• ISSN: 0735-7044; 1939-0084
• DOI: 10.1037/0735-7044.109.4.767

For 5 days, rats were exposed to shocks that were signalled by a light 0, 33, 66, or 100% of the time. Basal hormone levels and responses to a light-shock pair were measured daily. Greater predictability was associated with higher basal plasma corticosterone and norepinephrine levels indicative of chronic stress. Habituation of the corticosterone response was also less in the groups with greater predictability. However, predictability did not affect plasma prolactin or epinephrine responses. Because the endocrine systems responded differently, it is unlikely that the changes were due to a unitary process. Greater predictability appeared to be more stressful in this paradigm. Both associative and nonassociative factors have major roles in determining the hormonal responses to repeated presentation of stressors.