ELECTROLYTE-INDUCED DEMYELINATION IN RATS .1. ROLE OF THE BLOOD-BRAIN-BARRIER AND EDEMA

The blood-brain barrier (BBB) was studied in rats with electrolyte-ind uced demyelnation (EID), an experimental model for central pontine mye linolysis. Intravenously injected peroxidase was extravasated at 3 h p ost hypertonic saline injection (PI-IS) into regions frequently involv ed in EID. Increased pinocytotic activity and focal interendothelial g aps were seen at 3 h PHS and less frequently at 48 h PHS. Measurement of total cerebral water content revealed an increase during the hypona tremic phase. This was followed by a marked increase at 3 h PHS with c ontinued increment at 48 h PHS. Intracellular edema with accumulation of fluid within neurites and astrocytic processes was noted during the hyponatremic phase, whereas extracellular edema developed after hyper tonic saline injection. The implications of disrupted BBB and its role in the pathogenesis of EID are discussed.