EFFECT OF ADRENALECTOMY, HYDROCORTISONE ACETATE AND DESOXYCORTICOSTERONE ACETATE ON BRAIN EXCITABILITY AND ELECTROLYTE DISTRIBUTION IN MICE

¹ Department of Pharmacology, University of Utah College of Medicine, Salt Lake City, Utah

The effects of adrenalectomy, hydrocortisone and desoxycorticosterone acetate (DCA) on brain excitability and electrolyte metabolism have been studied in mice.

The most important results can be listed as follows:

1. Adrenalectomy and hydrocortisone increased brain excitability in mice as indicated by a decrease in "psychomotor" and alternating current electroshock seizure thresholds. DCA, on the contrary, decreased brain excitability as indicated by an increase in threshold for both types of seizures.

2. Concomitantly with variations in brain excitability, adrenalectomy, hydrocortisone and DCA produced alterations in electrolyte distribution in the brain. In the brain of adrenalectomized mice, decreased extracellular Na concentration, increased intracellular Na concentration, decreased ratio of the two, and increased Na space were associated with increased brain excitability. In the brain of DCA-treated mice, increased extracellular Na concentration, decreased intracellular Na concentration, increased ratio of the two, and decreased Na space were associated with decreased brain excitability. Hydrocortisone increased Na and Cl spaces in the brain and also increased brain excitability. It is suggested that hydrocortisone affects electrolyte metabolism not only in the nervous tissue but also in the connective tissue of the brain.

3. Changes in electrolyte distribution and fat content of muscle, in body weight and in adrenal and thymus weights after electroshock, adrenalectomy and administration of hydrocortisone and DCA in mice are also described.

4. Changes in brain excitability as measured by threshold for "psychomotor" seizures and for alternating current electroshock seizures were found to be similar under the various experimental conditions employed.