RESUMO
BACKGROUND: Use of antiepileptic drugs (AED's) is common in the neurocritical care setting. However, there remains a great deal of controversy regarding the optimal agent. Studies associating the prophylactic use of AED's with poor outcomes are heavily biased by the prevalent use of phenytoin, an agent highly associated with deleterious effects. In the current study, we evaluate lacosamide for neuroprotective properties in a murine model of closed head injury. METHODS: Mice were subjected to moderate closed head injury using a pneumatic impactor, and then treated with either low-dose (6 mg/kg) or high-dose (30 mg/kg) lacosamide or vehicle at 30 min post-injury, and twice daily for 3 days after injury. Motor and cognitive functional assessments were performed following injury using rotarod and Morris Water Maze, respectively. Neuronal injury and microglial activation were measured by flourojade-B, NeuN, and F4/80 staining at 1 and 7 days post-injury. Timm's staining was also performed to assess lacosamide effects on mossy fiber axonal sprouting. To evaluate possible mechanisms of lacosamide effects on the inflammatory response to injury, an RNA expression array was used to evaluate for alterations in differential gene expression patterns in injured mice following lacosamide or vehicle treatments. RESULTS: High-dose lacosamide was associated with improved functional outcome on both the rotarod and Morris Water Maze. High-dose lacosamide was also associated with a reduction of neuronal injury at 24 h post-injury. However, the reduction in neuronal loss observed early did not result in greater neuronal density at 31 days post-injury based on unbiased stereology of NeuN staining. High-dose lacosamide was also associated with a significant reduction in microglial activation at 7 days post-injury. The therapeutic effects of lacosamide are associated with a delay in injury-related changes in RNA expression of a subset of inflammatory mediator genes typically seen at 24 h post-injury. CONCLUSIONS: Administration of lacosamide improves functional performance, and reduces histological evidence of acute neuronal injury and neuroinflammation in a murine model of closed head injury. Lacosamide effects appear to be mediated via a reduction or delay in the acute inflammatory response to injury. Prior clinical and animal studies have found antiepileptic treatment following injury to be detrimental, though these studies are biased by the common use of older medications such as phenytoin. Our current results as well as prior work on levetiracetam suggest the newer AED's may be beneficial in the setting of acute brain injury.
