Objective: Effect of melatonin treatment on ovariectomized rat brain after traumatic brain injury (TBI) was investigated with diffusion-weighted imaging (DWI).

Materials-Methods: Twenty-four young Wistar-albino rats were studied. 18 of them were bilaterally ovariectomized, and the remaining 6 were surgically incised but not ovariectomized. After 7 days postoperatively, they were assigned to four groups with equal number of animals. Groups were named as Group 1, sham operated; Group 2, ovariectomized; Group 3, ovariectomized + TBI; Group 4, ovariectomized + TBI + treated with melatonin. Group 3 received vehicle (0.1% etanol) whereas group 4 had received 4 mg/kg melatonin intraperitoneally. Drug administration started immediately before injury and continued for 7 days. DWIs were obtained one week post injury, and apparent diffusion coefficient (ADC) maps were constructed.

Results: There is no significance between the ADC values of sham operated and ovariectomized rats (p=0,861). The placebo treatment group (group 3) had lower ADC values than ADC values of sham and ovariectomized groups but the difference was not statistically significant (p=0.146 and 0.197). ADC values in rats with melatonin treatment were higher than the placebo group (p=0,002) and are similar to sham group (p=0,062) that implied a physiological state. TBI resulted in the decreased ADC values that are compatible with cytotoxic edema. The results after one week show a significant increase in ADC values which is concordant with effective treatment of melatonin.

Conclusion: Traumatic brain injury generates an initial period of cerebral cytotoxic edema. Melatonin administration prevents the disruptive effects of TBI in ovariectomized rat brains.

Keywords: Ovariectomy, traumatic brain injury, melatonin, diffusion weighted imaging