Recent developments in structure-activity relationships for steroid modulators of GABA_A receptors

GABAergic neurotransmission can be both positively and negatively modulated by steroids. The steroid effects are thought to be mediated by binding of steroids to specific sites on GABA_A receptors. It appears that the receptor sites for positive and negative modulatory steroids are different. Thus far, the location and number of binding sites for steroids on these receptors have not been established. In this brief review, we concentrate largely on results from our own structure-activity studies. Novel analogues have been studied to further delineate the structural features required for compounds to modulate receptor function via steroid binding sites. Non-naturally occurring enantiomers of both positive and negative modulators have been studied to provide further evidence for the existence of specific steroid binding sites on the receptors.