Assessing the Impact of Stress on Sleep




Associate Professor of Anesthesiology and Critical Care

Project Summary

The Bhatnagar Laboratory in the Department of Anesthesiology and Critical Care at the Perelman School of Medicine focuses its research on the effects of stress using rat models.  This summer I worked closely with Dr. Laura Grafe, a postdoc in Dr. Bhatnagar’s lab, on a project that investigates sex differences in sleep disturbances and temperature due to restraint stress. Dr. Grafe recently published data that demonstrates increased orexin expression and activation in female rats compared to male rats. Now, as the project continues, we are looking to discover how or if orexin plays a role in stress-induced sleep disruptions. Throughout the summer, I helped Dr. Grafe with brain sectioning, immunohistochemical staining, sleep stage analysis, and general data analysis.

I assisted with two major animal studies.  Sprague-Dawley rats were first implanted with telemetry devices to allow us to measure sleep/wake states based on EEG and EMG as well as core body temperature. Data were collected over two baseline days, five consecutive days of 30-minute restraint stress using cylindrical Plexiglas restrainers, and two recovery days. The first study simply assessed sleep and body temperature after repeated stress in male and female rats. We found that repeated stress tends to increase wake and decrease REM sleep for females, but not males.  In the next study, the same paradigm was used to assess the role orexin plays in stress-induced sleep disturbances. Orexins are neuropeptides exclusively expressed in the lateral hypothalamus that are important for regulating wakefulness, attention, and stress response. To test the role of orexins in stress-induced sleep disturbances we inhibited orexins using DREADDs viruses. We found that stress increases body temperature more in females than males and orexin appears to play an instrumental role in this difference. Throughout both studies, we used the software Neuroscore to code data from the telemeters, and then I analyzed it further using excel and prism. After the recovery days, the subjects were sacrificed, and I helped section the rats’ brains using a cryostat. Then, I stained the sections with an immunohistochemical stain to study orexin neural activation in various brain regions.  These studies are still ongoing, but the preliminary conclusions that we have reached thus far seem promising.

This summer research experience in Dr. Bhatnagar’s lab has given me vast insight into the research world. It is impossible to understand the great effort and work that underlies modern science and medicine without first-hand experience. Now that I have spent a few months in this lab, not only have I gained skills in brain sectioning, staining, and data analysis, but I have also gained a new understanding and immense respect for all people in the research world. I look forward to seeing further results of Dr. Grafe’s project and working with her again in the future. 

Assessing the Impact of Stress on Sleep