Effects of melatonin on anxiety- like behaviors induced by post–traumatic stress disorder in rat

Introduction: Post traumatic stress disorder (PTSD) is an anxiety disorder. This study was aimed to evaluate the effect of multiple injections of melatonin on anxiety like behaviors induced by PTSD. Materials and methods: PTSD induced in 60 male wistar rats, by combining the shock and single-prolonged stress method (S;SPS). Animals received electric shock (1 mA, 2s) for 5 days, and then on the day 6 they underwent three stages of SPS (restrained for 2 hours, forced swimming for 20 minutes and anesthetized by diethyl ether for 15 minutes). Seven days after PTSD induction, elevated plus maze (EPM) and open field tests were performed to measure anxiety profile. Animals received multiple subcutaneous injections of melatonin (5, 10, 15 mg/kg) or saline, within the 7 days after PTSD. Results: The control (saline) and treated (melatonin) groups showed significant differences in the percentage of time spent in open arms of the EPM. Melatonin, at dose of 15mg/kg, significantly increased the time spent in open arms of the EPM than the corresponding control group. Animals who received 10mg/kg melatonin showed a significant increase in crossing behavior in open field test than the corresponding control group. Conclusion: Our study showed that melatonin is able to reduce PTSD-induced anxiety-like behaviors in rats.