OBJECTIVE: Mechanisms contributing to the post-traumatic stress disorder (PTSD) that involve several physiological systems, and the activation of the hypothalamic-pituitary-adrenal axis (HPA) is one of the most known systems in the PTSD
pathophysiology. The present study investigates the potential effects of methylprednisolone, metyrapone and their association with the noradrenergic system within the rostral pons, a region containing the locus coeruleus (LC) in a rat model of
PTSD induced with predator scent.
METHODS: In this study, Sprague-Dawley rats were exposed to the stress by exposure to the scent of dirty cat litter, which is
a natural stressor of a predator. One week later, the rats were re-exposed to a situational reminder (clean cat litter). The rats
were treated using either methylprednisolone, metyrapone or physiological saline before exposure to a situational reminder
(n=8 in each group). Noradrenaline (NA) levels in the rostral pons homogenates were analysed using ELISA.
RESULTS: The anxiety indices of the rats exposed to the trauma were found to be significantly higher than the anxiety
indices of the control rats. Metyrapone produced a significant increase in the anxiety indices of the non-stressed rats, and
methylprednisolone did not produce a change in the anxiety indices of the non-stressed rats. Methylprednisolone treatment
suppressed the anxiety in the stressed rats. Metyrapone treatment increased the anxiety indices in the stressed rats but still
being lower than that of the saline-treated stressed rats. Significant decrease in the freezing time was observed following the
methylprednisolone treatment both in the stressed and non-stressed rats. NA content in the rostral pons of the stressed rats
was significantly higher than that of the non-stressed rats. Methylprednisolone or metyrapone treatments decreased the NA
content in the non-stressed rats as compared to the saline treatment. However, these decreases were not significant.
CONCLUSION: In this study, findings suggest that stress may give rise to endocrine, autonomic and behavioural responses.
The anxiety indices and NA levels in the rostral pons increased with the traumatic event. The methylprednisolone treatment
may suppress anxiety through interactions between the LC and the HPA axis.