Protective effect of MK801 in experimental brain injury.

The effect of a noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist, MK801, was studied in a model of closed head injury in rats. Head trauma (HT) was induced over the left cerebral hemisphere by a calibrated weight-drop device. One or 3 h later, MK801 in saline was given i.p. in a single bolus of either 1, 3, or 10 mg/kg. The rats were killed at 4, 24, or 48 h after HT. Cortical tissue samples were taken from the injured zone and from the corresponding region of the contralateral hemisphere and analyzed for specific gravity (SG) by linear gradient columns. The neurological status of the traumatized rats was evaluated by a neurological severity score (NSS) 1 h after trauma and just before death. Pathological evaluation, based on size and severity of the lesion, was performed 24 and 48 h after HT on control and MK801-treated rats. A dose of 3 mg/kg MK801 given 1 h after trauma effectively prevented the reduction in tissue SG only at 24 h. The NSS could not be evaluated at 24 h after trauma because of the sedating effect of the drug. At 48 h posttrauma, however, the drug significantly improved the neurological state of the rats. No significant difference was found in the pathological score between treated and untreated rats. The results demonstrate neuroprotective properties of MK801, as expressed in two different variables--reduced edema formation and improved neurological recovery after HT. These findings support existing evidence that pharmacological intervention with NMDA receptor antagonist after head injury may be of clinical value in the management of head-injured patients.