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The effect was evaluated in puppies and adult dogs by measuring the rate of passage of radioactive iodinated human serum albumin from plasma into the cerebrospinal fluid and by determining the plasma and cerebrospinal fluid glutamic oxalacetic transaminase and lactic dehydrogenase activities. Arterial O2 concentration and saturation, CO2, and pH determinations were obtained. In puppies, hypercapnia was associated with marked respiratory acidosis and produced a great increase in the rate of transfer of albumin I131 from plasma to cerebrospinal fluid. Prolonged hypoxia also produced a definite increase in permeability of the blood-cerebrospinal fluid barrier. Increased concentration ratios of cerebrospinal fluid enzyme activity/plasma enzyme activity were observed in both groups. Hypoxia alone did not cause significant changes. In adult dogs, hypercapnia or hypoxia did not result in comparable findings.

The effect of prolonged convulsions (induced by Metrazol or electroshock) on the blood-cerebrospinal fluid barrier of puppies was evaluated with the use of radioiodinated human serum albumin by measuring its rate of passage from the plasma into the cerebrospinal fluid. Albumin I131 was injected intravenously and convulsions were induced immediately by intravenous Metrazol or the application of electroshock. A marked increase in the concentration ratio (cerebrospinal fluid radioactivity/ plasma radioactivity) occurred when seizures were maintained for 30 minutes or longer. The slope of cerebrospinal fluid albumin I131 concentration as a function of time was about 25 times as great in the convulsed puppies as in the controls. It is concluded that marked alteration in the permeability of the blood-cerebrospinal fluid barrier to albumin I131 was produced by prolonged seizures.

The effect of severe hypoxia on the blood-cerebrospinal fluid barrier of dogs was evaluated from the rate of passage of radioiodinated human serum albumin from plasma to cisternal fluid. Hypoxia was induced by intratracheal administration of varying mixtures of O2 and N2 or by use of a Smith-Jones pressure chamber. Radioiodinated albumin was injected intravenously and cisternal fluid and plasma samples were obtained at various intervals thereafter in experimental and control animals. Hypoxia maintained for 1 hour or longer resulted in a marked increase in the concentration ratio (cisternal fluid radioactivity)/(plasma radioactivity). The concentration ratio was frequently higher after 4 hours of hypoxia than after 24–48 hours in control animals. The slope of CSF albumin-I131 concentration as a function of time for the hypoxic animals was about five times that for the control animals. It is concluded that changes in rate of passage of albumin from plasma into cisternal fluid reflect alterations in the permeability of the blood-cerebrospinal fluid barrier to albumin.

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