MS

thesisNumerous studies have been carried out on the adrenocortical steroids during the last fifteen years. The effects of adrenocortical steroids on carbohydrate, fat, electrolyte and protein metabolism of various tissues and organs, and the specificity of these hormonal actions continue to be investigated. The adrenocortical steroids have been found to have important actions on the central nervous systems they can alter the motor excitability of the brain (Woodbury and Sayers,1950; Woodbury, 1952). In rats, deoxycorticosterone increases the threshold for electrical excitability, whereas cortisone and hydrocortisone cause hyperexcitability. The influence of adrenocortical steroids on brain excitability can be related to their effects on electrolyte metabolism,, Desocycorticosterone stimulates active transport of Na out of brain cells (Woodbury et al., 1957) and by this process decreases brain excitability. Cortisone^ in contrast,, inhibits active Na transport and thereby causes an increase in both intracellular brain Na concentration and brain excitability. The present study is designed to contribute further knowledge concerning the effects of adrenocortical steroids on brain function and metabolism. The study of the effect of adrenocortical steroids on brain amino acids arises from the observations that? (a) glutamic acid and gluta-mine are implicated in transport of K by brain cells (Terner et al., 1950), (b) adrenocortical steroids are known to alter profoundly the amino acid composition of various tissues (Dubreuil and Timiras, 1953), and (c) ?-aminobutyric acid5 a metabolic product of glutamic acid5 has recently been suggested to have an inhibitory effect on brain excitability (Elliott and Florey, 1956). The following investigations were carried outs a) effect of age on brain amino acid concentration! b) effect of cortisone and deoxycorticosterone on brain amino acid and electrolyte concentrationsj and c) effect of adrenalectomy on brain amino acid and electrolyte concentrations