Neuroprotective effects of melatonin and calpeptin in a rat model of focal cerebral ischemia

Abstract

Introduction: Melatonin is a potent-free radical scavenger and antioxidant. Previously, we have demonstrated beneficial effects of pretreatment with melatonin in mild and severe focal cerebral ischaemia in rodent models. Cerebral ischaemia increases intracellular Ca2+ concentrations, and activates several calcium-dependent proteases including calpain. Pretreatment with calpeptin, a novel calpain inhibitor, has been reported to reduce the cerebral infarct volume. In addition, it also decreases the neuronal apoptosis in hippocampal CA1 sector and improves the behavioural deficit in a rat stroke model. The aim of this study was to investigate the neuroprotective role of a post-ischaemia treatment with melatonin and / or calpeptin, and whether combining the two exerts synergistic or addictive effects in transient focal ischaemic stroke in rats. Methods: Male Sprague-Dawley rats (6-8 weeks) were anaesthetised with sodium pentobarbital to undergo right-sided endovascular middle cerebral artery occlusion (MCAO) for 90 minutes followed by 24 hours of reperfusion before being sacrificed. A single or a combined dose of melatonin (50 μg/kg) and / or calpeptin (50 μg/kg) were given via an intracerebroventricular injection at 10-15 minutes after onset of the reperfusion. Sham group with injection of vehicle only was used as a control group. Neurological behaviour was assessed using Neurological Deficit Scoring System (NDSS) test and cerebral infarction volumes were evaluated by TTCstaining. Results: Infarction volumes and NDSS scores were lower in the calpeptin group but not in melatonin group when compared with the control. The combining effects of melatonin and calpeptin will be studied further. Conclusion: Our results suggest that post-ischaemia treatment with calpeptin but not melatonin at 50 μg/kg protects against focal MCAO model in rats.