Abstract: The invention provides a compound of the formula I: wherein R is methyl, ethyl, propyl, isopropyl, butyl, pentyl, neo-pentyl or cyclohexyl, or a salt or solvate thereof. These compounds are selective GABAC receptor antagonists. The invention also provides pharmaceutical compositions comprising a compound of formula I or a pharmaceutically acceptable salt or solvate thereof. The invention also provides methods of enhancing the cognitive activity of an animal and methods of stimulating memory capacity in an animal, comprising the step of administering to the animal an effective amount of a compound of formula I or a pharmaceutically acceptable salt or solvate thereof.