The Cortical Acidic Response To Intravenous NahCO₃ and The Nature of Blood Brain Barrier Damage

Abstract

The cortical adicic response to intravenous NaHCO₃ in the cat was analyzed critically, and its relation to the blood brain barrier to HCOI was considered. Correct measurement of the response requires intact cortical and piaarachnoid blood vessels, accurate identification and recording of DC and pH potential differences at the brain surface, and control of ventilation. Changes in the response could be quantified and used to demonstrate damage of the blood brain barrier to HCOI. With progressive damage, HCOI probably enters the brain more readily and the acidic response changes until, with severe damage, the response is only alkaline and resembles the alkaline change of the blood following i.v. NaHCO₃. Reduction of the response is graded and may depend on the extent and site of vessel damage. The response is resistant to anoxia and metabolic inhibitors, but is reduced by topically applied alcohols and surface active compounds. Analysis of the changes following increasing quantities of concentrated solutions suggests that some agents may damage the barrier osmotically by shrinking barrier cells, possibly at the vascular endothelium. In its resistance to change, the acidic response resembles the blood brain barrier to trypan blue.

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Notes on contributors

Stanley I. Rapoport

Joyce Laing works in the Department of Child and Family Psychiatry, Playfield House, Cupar, Fife, and is a Consultant Art Therapist to Psychiatric Hospitals and Prisons and Chairwoman of the Scottish Society of Art and Psychology.