The Effects of Cortisol and Catecholamines to Acute Stress Exposure. Brandon Beazer

Transcription

1 The Effects of Cortisol and Catecholamines to Acute Stress Exposure Brandon Beazer Biology 493 BYUH Biology Department Mentor: Dr. Randy Day Fall 2008

2 Abstract The overall objective of this study was to determine which would be an accurate marker for acute stress, cortisol or catecolamines and which of these hormones showed any correlations with standardized stress surveys. An Immunology exam at Brigham Young University- Hawaii was given to 22 students which acted as the acute stressor. Saliva samples were initially taken one month prior to the examination and again right before the exam. Saliva samples were analyzed for changes in cortisol and alpha-amylase. The mean (± SD) cortisol concentration before the stressor was 0.20 µg/dl, after exposure to the stressor the mean was 0.16 µg/dl. The mean (± SD) salivary alpha-amylase also showed a higher concentration before the stressor of U/mL and after the stressor a concentration of U/mL. Results from a paired T- test performed on cortisol and salivary alpha-amylase levels before and after the exam were not significant. However, there was a possible correlation between the two stress surveys and cortisol base levels. Introduction The physiological response to stress is controlled by the limbic system (Stegeren et al. 2007). When excited the limbic system activates two other systems, the sympathetic-adrenal medullary (SAM) and the hypothalamic-anterior pituitary-adrenal cortex (HPA). The SAM and HPA direct the release of hormones including epinephrine (adrenaline), norepinephrine and cortisol (Flinn and England 1995). During periods of stress, cortisol, a glucocorticoid regulated by the HPA system, is secreted by the adrenal cortex in response to adrenocorticotropic hormone (ACTH) released from the pituitary gland (Risch et al. 1980). During the fight-or-flight response, the sympathetic nervous system acting via splanchnic nerves to the adrenal medulla (SAM) stimulates the release of catecolemines (epinephrine and norepinephrine) into the blood stream (Axelrod and Reisine 1984). Catecholamines and cortisol, along with other hormones, increase blood pressure, open airways in the lungs, induce vasoconstriction in the skin and intestines, and induce vasodilatation in the major muscle groups. The release of cortisol, and catecolamines (epinephrine and norepinephrin) from the adrenal are the two major endocrine responses to stress (Stegern et al. 2007). Persistent high stress levels produce an unhealthy level of cortisol and catecholamines. At sustained high levels of stress, increased cortisol and catecholamines 1

3 gradually result in destruction of muscle and bones, retards healing and cell regeneration, impairs digestion (gastric ulcerations), inhibit immune response and may lead to hypertension, sterility, atherosclerosis, and personality changes (Westman and Walters 1981). Both cortisol and catecholamine levels can vary regardless of whether the stress is emotional or as a result of strenuous activity, an infection, or injury (Miles et al. 1991). During periods of stress, cortisol and catecholamines are detectable in the blood, urine and saliva (Patrick et al., 2000). Cortisol follows a circadian rhythm. Levels tend to be higher in the early morning and lower in the evening (Gotch 1981). Physical exercise, caffeine and alcohol consumption, smoking and use of drugs, such as the contraceptive pill, may affect stress hormones either increasing or decreasing catecholamine and cortisol levels (Pollard 1997). Salivary cortisol levels have been reputed to correlate well with stress as indicated by the limbic hypothalamic-pituitary-adrenal (LHPA) response. Salivary levels are easy to measure and are highly reproducible (Patrick et al. 2000). In contrast, catecholamine levels are not detectable in saliva. However, salivary alpha-amylase has been found to correlate well with catecholamine levels (Patrick et al. 2000). There are many ways in which an individual may perceive they are under stress. They may experience different types of responses, such as physical symptoms (muscle tension), affective symptoms (irritability), or behavioral symptoms of disorganization (increased procrastination). Bio psychologists have attempted to understand how stress affect humans behaviorally by developing surveys which assess the degree of stress experienced both acutely and chronically. Measures which attempt to validate stress 2

4 surveys by correlation with psychological measurements of stress hormones have reported high correlation with salivary cortisol, but little is known about the correlation of salivary alpha-amylase, a measure of catecholamines on dispositional stress. The purpose of this study was to compare and validate cortisol and catecolamines as markers of stress, and determine if correlations exist between the stress survey measurements and salivary cortisol and alpha-amylase data. Method After approval from the Brigham Young University-Hawaii Human Subjects Committee, saliva samples from a class of 22 students were taken at 1400 hours in a normal classroom setting. Saliva sampling is preferred over urine or plasma samples because it is non-invasive, painless, inexpensive, and shows high compliance rates. Saliva sampling is also beneficial because one can assay for alpha-amylase and corisol from the same sample (Patrick et al. 2000). A second saliva sample was taken one month later, right before an exam. The exam was considered a stressor. In addition, participants took a Stress Attribution Survey (SAS) and the Perceived Stress Scale (PSS) survey. Saliva samples were collected by placing a small salivette (cotton roll) into the mouth of each participant for one minute. Salivettes were then collected, labeled and stored in a -20 C freezer. Initial samples served as a baseline for resting cortisol and salivary amylase (catecholamine) levels for each participant. The saliva samples were sent to Salimentrics for an analysis of cortisol and salivary amylase by immunoassay. Data were analyzed by repeated mean ANOVA and Pearson s correlation. 3

5 Results The data show that of the 22 participants, a total of eight experienced an increase in cortisol concentration after being introduced to the acute stressor while 14 decreased. Alpha-amylase showed similar results to cortisol in that seven students increased after exposure to the acute stressor and 15 deceased. The mean (± SD) cortisol concentration before the stressor was 0.20 µg/dl, after exposure to the stressor the mean was 0.16 µg/dl (Fig. 1). The mean (± SD) salivary alpha-amylase also showed a higher concentration before the stressor of U/mL and after the stressor a concentration of U/mL (Fig 2). Fig. 1. The mean (± SD) cortisol concentrations before and after a stressor. 4

6 Fig. 2. The mean (± SD) salivary alpha-amylase concentrations before and after a stressor. A paired t-test was performed on cortisol and salivary alpha-amylase. Data revealed no significant changes in either cortisol or catecolamine concentrations as a result of the stressor. The p-value for cortisol was 0.26 and the p-value for alpha-amylase was 0.06 (Table 1). Table 1. Paired t-test results of cortisol and alph-amylase before and after a stressor Substance Cortisol Alpha Amylase Before After Before After Mean 0.20 (±0.05) 0.16 (±0.06) (±37.10) (±32.84) P(T<=t) two tail Correlations between the SAS and the PSS survey and cortisol and alpha-amylase were assessed using Pearson s Correlation Coefficient analysis. The correlation between PSS and salivary cortisol was 0.40 while the correlation of cortisol with the SAS was 0.47 (Tabel 2). Salivary alpha-amylase had a correlation of 0.12 with the SAS and a correlation of 0.26 with the PSS (Table 2). 5

7 Table 2. Pearson s correlation coefficients for cortisol and alpha-amylase with two stress surveys. Substance Cortisol Alpha amylase SAS PSS Discussion The exam used as the stressor in this experiment did not illicit a significant (p>0.05) change in cortisol or alpha-amylase concentrations. Thus, there was not sufficient data to determine which would be a better marker for acute stress, cortisol or catecolamines. Possible reasons for suppressed cortisol and catecolamine concentrations are that they both tend to follow a circadian rhythm. Cortisol tends to peak early morning and decrease toward mid-day however; catecolamines are the opposite, low in the morning and peak towards mid-day. Even though the before and after saliva samples were taken at the same time of day this rhythm can be offset as a result of little or no sleep. This is a very common occurrence with students the night before a major exam. Other possible reasons for the decrease in cortisol concentrations could be the result of: increased caffeine consumptions, physical exercise (Pollard 1997) and emotionally charged events (Flinn and England 1995). Although there was not sufficient information to determine whether cortisol or catecolamines were a better marker for acute stress, Pearson s correlation coefficient indicated that the SAS and PSS surveys can be used as an indicator for chronic stress, when comparing SAS and PSS data to base levels of cortisol but not alpha-amylase. Cortisol had a PSS value of 40% and a SAS value of 47%, both moderately significant. However, alpha-amylase had a much lower PSS and SAS values of 26% and 12% respectively, indicating that there was no definitive relationship between the surveys and 6

8 alpha-amylase. Thus, for this experiment the only clear comparison to be made was that there was a correlation between base-level concentrations of cortisol with the SAS and PSS surveys. If an individual has a high score on the stress survey, indicating they are under chronic stress, they will tend to have an higher base-level concentration of cortisol. These results may be used clinically to validate the use of stress surveys as a marker of stress as determined by a correlation with a biological stress marker. Acknowledgements A special thanks to Dr. Randy Day, my mentor, for his invaluable insights with this experiment; his patience, time, statistical expertise, and help in editing. Thank you to the biology faculty department as well for their comments in editing rough drafts and finally to the FAST program and the Science Department for financing and providing materials to perform the experiment. Works Cited Axelrod, J and T D. Reisine Stress Hormones: Their Interaction and Regulation. Science 224: Flinn, M. V and B. G. England Childhood Stress and Family Environment. Current Anthropology 36: Gotch, P. M Teaching Patients about Adrenal Corticosteroids. The American Journal of Nursing 81: Miles, P. D., K. Yamatani H., L. A. Lickley., and M. Vranic Mechanism of Glucoregulatory Responses to Stress and Their Deficiency in Diabetes. Proceedings of the National Academy of Sciences of the United States of America 88: Patrick, S. D., R. T. Chatterton Jr., T. Swisher and S. Park Modulation of attentional inhibition by norepinephrine and cortisol after psychological stress. Internal Journal of Psychophysiology 36: Pollard, T.M Physiological Consequences of Everyday Psychosocial Stress. Collegium Antropologicum 21:

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