As instructors who teach laboratory courses in biological psychology/behavioral neuroscience, we have often been at a loss to find appropriate experiments where students are able to play both the role of experimenter and subject. The difficulty arises because there are few biological parameters representing CNS activity that can ethically be examined in human participants. As a result, the go-to experiments that allow students to act as both experimenter and subject tend to be electrophysiological in nature (e.g., EEG, GSR, etc.). It was our desire to create a laboratory module that would allow students to collect and analyze a biochemical measure of human neural activity. We report here the development of an experiment module that utilizes an easily obtainable enzyme immunoassay (EIA) kit (nearly identical to the ELISA) to measure human salivary cortisol.
Cortisol is a hormone of the adrenal cortex that can be used as a peripheral indicator of hypothalamic neural activity. Plasma (and salivary) cortisol levels rise due to circadian influences as well as perturbations in the organism’s environment (i.e., stressors) that make it possible to detect rather robust experimental effects. Also, there has been much debate on the role of cortisol and hypothalamic-pituitary-adrenal axis dysregulation in the pathophysiology of depression making for a clinically relevant extension to the lecture portion dealing with the “stress axis” (hypothalamic-pituitary-adrenal or HPA axis).
Collection of salivary cortisol is simple, painless, and non-invasive and can be performed at any time the subject desires. Sample storage is convenient as the samples can be kept in a home freezer. Repeated freeze-thaws do not adversely affect the determination of cortisol levels, so the students can just bring them in on the day of the assay without need of in-transport refrigeration or instructor/student coordination. The assay can be performed successfully by anyone with access to a plate reader and a few commonly-used laboratory items. A single plate assay can be completed in two hours (two to three hours by an inexperienced group of students under supervision).
With the available cortisol kit, our students have examined both circadian effects and stressor/relaxation effects on salivary cortisol levels in a laboratory class setting. The module has been employed twice and we intend to include it in each semester that the course is taught. One further impact of the module is that student
Kalman, B.A., and Grahn, R.E. (2004). Measuring salivary cortisol in the behavioral neuroscience laboratory. Journal for Undergraduate Neuroscience Education, 2 (2), A41-A49. http://www.funjournal.org/
The views expressed in this paper are solely those of the author.