Stress-induced changes in sleep in rodents: models and mechanisms

Abstract

Psychological stressors have a prominent effect on sleep in general, and rapid eye movement (REM) sleep in particular. Disruptions in sleep are a prominent feature, and potentially even the hallmark, of posttraumatic stress disorder (PTSD) (Ross, R.J., Ball, W.A., Sullivan, K., Caroff, S., 1989. Sleep disturbance as the hallmark of posttraumatic stress disorder. American Journal of Psychiatry 146, 697-707). Animal models are critical in understanding both the causes and potential treatments of psychiatric disorders. The current review describes a number of studies that have focused on the impact of stress on sleep in rodent models. The studies are also in Table 1, summarizing the effects of stress in 4-h blocks in both the light and dark phases. Although mild stress procedures have sometimes produced increases in REM sleep, more intense stressors appear to model the human condition by leading to disruptions in sleep, particularly REM sleep. We also discuss work conducted by our group and others looking at conditioning as a factor in the temporal extension of stress-related sleep disruptions. Finally, we attempt to describe the probable neural mechanisms of the sleep disruptions. A complete understanding of the neural correlates of stress-induced sleep alterations may lead to novel treatments for a variety of debilitating sleep disorders.

Figure 1

The effect of reexposure to the shock context 24 hr after conditioning on REM sleep percent (of total sleep time) and sleep efficiency (total sleep time/total recording time). N = 7. Data analyzed via a repeated measures ANOVA, * p < 0.05, different from baseline.

Figure 2

The effect of exposure to the neutral context 24 hr and 48 hr after conditioning on REM sleep percent (of total sleep time) and sleep efficiency (total sleep time/total recording time). N = 8. Data analyzed via a repeated measures ANOVA, * p < 0.05, different from baseline.

Figure 3

The effect of reexposure to the shock cues 24 hr and 14 days on: [A] sequential REM amount (min); [B] sequential REM count; [C] sequential REM cluster amount (min); [D] sequential REM cluster count; [E] sequential REM cluster episode length (min); [F] REM sleep amount (percent of total sleep time). N = 6. Data analyzed via a repeated measures ANOVA, * p < 0.05, ** p < 0.01, different from baseline.