The Effect of Combination Treatment of Melatonin and Hypothermia on Hypoxic-Ischemic Brain Injury in Neonatal Rats

ABSTRACT

PURPOSE: Melatonin is a naturally occurring hormone produced by the pineal gland. Melatonin has many pharmacological effects in different tissues or organs. Melatonin is especially known to have antioxidant and neuroprotective effects. Hypothermia is a therapeutic tool against hypoxia-ischemia (HI) of the brain. This study examines the effect of combined therapy using melatonin and hypothermia in neonatal rats with HI. METHODS: Seven-day old rats were subjected to HI and randomized into four groups : vehicle, melatonin alone, vehicle and hypothermia, and melatonin and hypothermia. Melatonin (30 mg/kg) was intraperitoneally administered in two doses: immediately following HI, and 24 h later. Hypothermia consisted of whole-body cooling (3 hours, 27degrees C). Sham-treated animals not subjected to HI were also studied. P10, P14, and P35 rats were sacrificed for experiments. RESULTS: Vehicle-treated P10 rats increased in brain infarction compared to controls in TTC staining study. And also, P35 rats decreased in brain volume of injured hemisphere in H&E stain. Melatonin or hypothermia alone did not show any protective effect against HI. However, a combination of melatonin and hypothermia effectively reduced the brain injury. In addition, the results of in situ zymography, TUNEL assay and immunofluorescence studies showed that neuroprotective effects were achieved only with combined therapy. CONCLUSION: Melatonin may contribute to synergistic effects to neuroprotection of hypothermia on brain damage after HI.