Endogenous neurosteroids affect brain excitability during physiological states such as pregnancy and the menstrual cycle, and during conditions of acute and chronic stress. The neurosteroid allotetrahydrodeoxycorticosterone (THDOC) is an allosteric modulator of the GABA(A) receptor. Although the role of THDOC within the brain is undefined, recent studies indicate that stress induces THDOC to levels that can activate GABA(A) receptors. These results might have significant implications for human stress-sensitive conditions such as epilepsy, post-traumatic stress disorder and depression.