Neurobiological fundamentals of posttrumatic stress disorder – a possible role of circadian rhythms deregulations

Abstract

Posttraumatic stress disorder is a complex anxiety disorder induced by a stress factor. It is believed that this fear conditioning impairment may be crucial to PTSD development. Stress induced electrophysiological and neurohormonal changes within the hippocampus, amygdala, prefrontal cortex or locus coeruleus may impair other regional functions of the central nervous system like suprachiasmatic nuclei functions. Furthermore, the activation of llocus coeruleus or its impact on the activity of superchiasmatic nuclei may influence the circadian rhythm. The influence of stress factor on the hypothalamus – pituitary – adrenal gland axis (HPA) activity is well documented. Also PTSD accompanied changes of the HPA axis are well known. Unfortunately, due to methodological problems, the evaluation of stress induced HPA axis circadian rhythm changes is limited. Another physiological parameter, characterised by circadian rhythm is body temperature. Stress factor exposure induced a strong decrease in the daily rhythm amplitude during day/night cycles in the animal model of PTSD. Described disturbances to the rhythm was suprachiasmatic nuclei activity independent.