Intravenous administration of melatonin reduces the intracerebral cellular inflammatory response following transient focal cerebral ischemia in rats

: We have previously shown that exogenous melatonin improves the preservation of the blood–brain barrier (BBB) and neurovascular unit following cerebral ischemia–reperfusion. Recent evidence indicates that postischemic microglial activation exaggerates the damage to the BBB. Herein, we explored whether melatonin mitigates the cellular inflammatory response after transient focal cerebral ischemia for 90 min in rats. Melatonin (5 mg/kg) or vehicle was given intravenously at reperfusion onset. Immunohistochemistry and flow cytometric analysis were used to evaluate the cellular inflammatory response at 48 hr after reperfusion. Relative to controls, melatonin‐treated animals did not have significantly changed systemic cellular inflammatory responses in the bloodstream (P > 0.05). Melatonin, however, significantly decreased the cellular inflammatory response by 41% (P