EFFECTS OF STRESS ON BEHAVIOUR AND SLEEP Cortisol: a stress hormone and a wake hormone Anton Coenen Radboud University Nijmegen The Netherlands Lviv Ukraine October 5, 2017

Effects of stress on sleep

Effects of stress on sleep (see bottom trace)

The balance between sympathetic and parasympathetic activity pupil miosis The balance between sympathetic and parasympathetic activity

Relation between the degree of ‘efficient’ behaviour and the level of arousal (curve of Yerkes and Dodson, 1908) (inverted U-shaped relationship).

Stress ↓ HPA axis activation CRF Releasing Factor ACTH Cortisol CORTISOL AS A STRESS HORMONE

CORTISOL AS A WAKE HORMONE

The circadian rhythm of cortisol under basal conditions meal meal The circadian rhythm of cortisol under basal conditions

A breakthrough: cortisol binds to two receptor subtypes (Reul and de Kloet, 1985) Mineralocorticoid receptor Type I Glucocorticoid receptor Type II Type I high affinity in limbic structures and hippocampus Type II low affinity in the same structures and in frontal cortical areas

At the peak in the cortisol rhythm, both type I and type II receptors are activated, while at the cortisol trough there is only activation of the high affinity type I receptors (after: Lupien et al. 2007).

The Type I/Type II ratio hypothesis of cortisol and memory performance (de Kloet, Oitzl and Joels, 1999) memory performance level of cortisol When type I receptors are saturated with partial occupancy of type II, there is maximal memory performance. But when both type I and II are not occupied (left), or when both are saturated (right), there are memory impairments.

100%Type I 50%Type II 100%Type I 100%type II 0%Type I and II Proposed analog explanation of the inverted U-shaped relationship) between performance and level of arousal.

Cortisol is a adrenal gland hormone that supplies the body for its activities. It does this also under stress conditions. But high stressful conditions, associated with high cortisol levels, are adverse. Cortisol binds to two receptor subtypes: high affinity type I and low affinity type II, also with differences in location. It appears that under high cortisol levels when high affinity type 1 receptors are saturated, also type II receptors become saturated. Saturation of low affinity type II receptors is associated with negative effects on memory, on performance and on behaviour.