Repeated caffeine administration aggravates post-traumatic stress disorder-like symptoms in rats

Abstract

Background: Caffeine is the widely consumed central nervous system stimulant in form of coffee and other beverages. However, the repeated administration of caffeine induces anxiety, disturbance in hypothalamic-pituitary-adrenal (HPA) axis and psychiatric symptoms in humans. As much evidence links PTSD to HPA axis dysfunction, and anxiety is a hallmark symptom, repeated and/or large doses of caffeine may exacerbate symptoms of PTSD. Objective: In our present study, we evaluated the effect of repeated administration of caffeine on stress re-stress (SRS) model of PTSD. Methods: As per the protocol, male rats were restrained for 2 h followed by 20 min forced swim and halothane anaesthesia on day 2 (D-2). Then the rats were re-stressed (forced swim) at 6-days interval between D-8 to D-32. After exposure to SRS, depressive, anxiety-like behaviour, and cognitive functions were evaluated by forced swim test (FST), elevated plus maze (EPM) and Y-maze tests respectively. Caffeine (10, 20 and 30 mg/kg, i.p.) dosing was started from D-8 and continued up to D-32. The corticosterone level was measured in plasma followed by serotonin and glucocorticoid receptor (GR) and mineralocorticoid receptors (MR) estimation in hippocampus (HIP), prefrontal cortex (PFC) and amygdala (AMY). Results: SRS-induced depressive and anxiety-like behaviour was aggravated by caffeine at dose of 20 and 30 mg/kg. Caffeine (30 mg/kg) treated control animals showed depressive, anxiety-like behaviour and cognitive impairments. SRS-induced decrease in plasma corticosterone level and increase in serotonin (5HT) levels in the PFC, HIP and AMY were not altered by caffeine. Caffeine did not modulate the SRS-induced decrease in glucocorticoid receptor (GR) and mineralocorticoid receptor (MR). In contrast, caffeine per se decreased GR and MR expression and their ratio in unstressed animals. Conclusion: Repeated intake of caffeine aggravates PTSD-like symptoms in stress-exposed rats and induces PTSD-like symptoms in unstressed rats by altering the expression of glucocorticoid receptors. © 2019 Elsevier Inc.