Spreading depression and the blood-brain barrier.

The propagation of spreading cortical depression was studied in rabbits during the reversible opening of the blood-brain barrier induced by hypertonic aqueous solutions of sodium chloride and sodium diatrizoate. The rupture of the blood-brain barrier was monitored by the leakage of Evans blue-albumin from pial vessels. Spreading depression was monitored by recording its characteristic slow voltage variations. Test substances were injected into the carotid artery or topically applied to the pia-arachnoid surface. Intracarotid injection of hypertonic solutions that open the blood-brain barrier do not block the propagation of spreading depression. Topical application of NaCl solutions can block the spread of the cortical depression reaction without opening the blood-brain barrier. Recurrent spreading depression waves at a mean frequency of one every 5 min, for 4 h do not cause the release of Evans blue-albumin complex from pial vessels.