Effects of Adrenalectomy and Replacement Therapy on Brain Circulation, Oxygen Consumption and the Electrocorticogram

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Abstract
A comparison of the relative rate of blood flow through heads of normal and adrenalectomized salt-maintained rats indicates that adrenalectomy considerably decreases the flow. In this particular prepn. approx. 70% of this blood flow measure represents venous blood from the brain. The decreased blood flow can be restored to normal in 2 hrs. with a adrenal cortical extract, [DELTA]5-pregnenolone or cortisone, but not with desoxycorti-costerone. Arterial-venous O2 measurements show that although the adrenalectomized rat utilizes more O2 per blood cycle through the head, the circulatory slowing results in a marked reduction of O2 consumption by the tissues. Restoration of O2 consumption is aided by adrenal cortical extract and [DELTA]5-pregnenolone, but not by desoxycorticosterone. The reduction in brain O2 consumption following adrenalectomy is accompanied by reduction of the electrocorticogram (ECG) frequency. Restoration of the ECG frequency is produced by the same steroids that restore blood flow and O2 consumption. Studies of blood flow through the brain itself, made by tapping the vein draining the transverse sinus at its point of emergence from the skull, also shows marked reduction of brain blood flow in adrenalectomized rats compared to normal rats. These blood flow studies combined with measurements of the O2 content of arterial and venous blood, the latter taken directly from the transverse sinus, show an 18% reduction of brain O2 consumption in adrenalectomized rats. Cortisone fully restores to normal the brain blood flow and O2 consumption.