The purpose of the present study was to evaluate the effects of melatonin and pinealectomy on histopathological changes resulting from brain ischemia-reperfusion method.

Rats were divided into three groups: sham-operated (control), pinealectomized with melatonin, pinealectomized. Rats were operated for 3 months before the ischemia-repefusion studies. Melatonin (4 mg/kg i.p) was given to pinealectomized rats for last 30 days. To produce brain damage, middle cerebral arter was occluded for 60 min, followed by 24 h reperfusion. At the end of each in vivo study, the rats were sacrified and the brains were quickly removed, and were in formaldehyde solution for routine histopathological examination.

Depending on ischemia-reperfusion, widespread necrotic areas, vacuolization, eosinophilic degeneration and vascular congestion were observed in the brain slices. Pinealectomy leads to markedly increasing this damage resulted from brain ischemia-reperfusion. These data suggest that physiologic melatonin release as well as exogenously given melatonin has a neuroprotective effect in focal cerebral ischemia.