Pharmacological reduction of brain edema induced by intracarotid infusion of protamine sulphate: a comparison between a free radical scavenger and an AMPA receptor antagonist.

The blood-brain barrier (BBB) of rats was opened by infusing 10 mg protamine sulphate (200 microliters in 30 s) into the right internal carotid artery. Ten minutes later, tirilazad, a 21-aminosteroid (3 mg/kg): NBQX, an AMPA receptor antagonist (5 mg/kg); or dixyrazine, a phenotiazine derivate (10 mg/kg), was administered intravenously and the rats were killed 2 h after protamine infusion. Brain specific gravity was determined in the frontal, parietal and occipital cortex and in the striatum. In separate experiments, serum albumin content was determined in the brain of rats by immunoelectrophoresis 2 h after protamine infusion with or without tirilazad pretreatment. Specific gravity was significantly higher in all of the studied brain regions in rats given tirilazad or NBQX than in those given vehicle or dixyrazine (p < 0.001). A combination of tirilazad and NBQX was significantly more efficient than either drug alone in reducing edema in the occipital cortex (p < 0.05) and more efficient than NBQX alone in the frontal and parietal cortex (p < 0.05). None of the drugs reduced the albumin content in CSF; in addition, tirilazad failed to reduce albumin extravasation in the brain and CSF when given before protamine infusion. We conclude that the anti-edematous effect of tirilazad and NBQX is related to cellular events within the brain and not to a reduction of leakage over the BBB.