Amino acids in extracellular fluid in vasogenic brain edema

We have investigated if changes in brain dialysate, reflecting alterations in brain extracellular composition, can be detected during the development of vasogenic brain edema. The blood-brain barrier was opened by intracarotid infusion of 5 or 10 mg protamine sulphate. The rats were killed two hours after opening of the BBB when the brains were macroscopically edematous, after 10 mg but not 5 mg protamine sulphate. No significant alterations in the amino acid concentration in the dialysate were observed after the lower dose. 40 min after infusion of 10 mg protamine, the level of glutamate was significantly increased in the dialysate followed by that of aspartate, glycine, phosphoethanolamine and taurine 10 min later and a further delayed increase in GABA. We conclude that the development of vasogenic brain edema is associated with significant increases in extracellular concentration of excitatory amino acids, of taurine, and of phosphoethanolamine and GABA.