[The effect of hydrocortisone on the impulse activity of cat cerebral cortex neurons]

The pulse activity of the neurons (50 in all) was studied in the brain somatic cortex by glass microelectrodes in acute experiments on 22 cats after an intravenous injection of hydrocortisone-hemisuccinate in doses of 0.03-8.0 mg/kg. 36 of 50 neurons changes their activity after the injection. Three types of reactions prevailed: an increase of the pulse frequency, its rarefaction, and a two-phase reaction in which the activation was followed by depression. As a rule the reaction occurred 10 to 60 sec after cortisone injection; this suggests a possibility of the direct action of the hormone on the brain cortex. A possible mechanism of variable neuronal reactions to hydrocortisone is discussed.