Abstract
An early effect of methylene blue in the intact animal is to decrease the R.Q. 1 Methylene blue exerts a similar action on the R.Q. of excised cortical tissue of the brain 2 causing a decrease below the physiological value of unity. 3 This communication presents the results of preliminary experiments of the changes produced by methylene blue on the R.Q. of the brain in situ.
Ten cc. of 1% solution of methylene blue were injected into the common carotid artery of 4 dogs under amytal anesthesia. Blood samples from the femoral artery and the superior longitudinal sinus were analyzed for CO2 and O2, pH and specific gravity. The respiration and rectal temperature of the dogs were recorded.
The arterial-venous differences of CO2 and O2 indicated that the R.Q. of the brain diminished after the injection of methylene blue. At the same time the rectal temperature of the animals rose. This is in agreement with the greater O2 uptake noted previously. 1 The specific gravity of the blood increased as did the pulmonary ventilation, the latter producing a rise of the pH of the arterial blood. The results of a characteristic experiment are presented in tabular form.
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