Disclosed are compounds of formula (I) wherein: T is NH, O, or S; X is hydrogen, hydroxyl, lower alkyl, or an optionally substituted amide; the W ring is an optionally substituted aryl or heteroaryl group; and (a) represents an optionally substituted benzo group or an optionally substituted 5, 6, 7, or 8 membered ring. These compounds are highly selective agonists, antagonists or inverse agonists for GABAa brain receptors or prodrugs of agonists, antagonists or inverse agonists for GABAa brain receptors. These compouns are useful in the diagnosis and treatment of anxiety, sleep and seizure disorders, overdose with benzodiazepine drugs and for enhancement of memory.