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.

Abstract: The invention provides compounds of the formula II: wherein R represents propyl, butyl, pentyl, neo-pentyl or cyclohexyl, and salts thereof. These compounds are selective GABAC receptor antagonists. The invention also provides a method of enhancing the cognitive activity of an animal and a method of stimulating memory capacity in an animal, comprising administering to the animal an effective amount of a compound of formula II or a pharmaceutically acceptable salt thereof.

Abstract: The invention provides compounds of the formula II: wherein R represents propyl, butyl, pentyl, neo-pentyl or cyclohexyl, and salts thereof. These compounds are selective GABAC receptor antagonists. The invention also provides a method of enhancing the cognitive activity of an animal and a method of stimulating memory capacity in an animal, comprising administering to the animal an effective amount of a compound of formula II or a pharmaceutically acceptable salt thereof.

Abstract: The invention provides methods for enhancing cognitive activity and stimulating memory capacity, comprising the step of administering an effective amount of a compound with GABAC receptor antagonist activity to an animal in need of such treatment. Preferably the compound has selective GABAc receptor antagonist activity, and more preferably comprises a phosphinic acid group. The invention also provides novel compounds and compositions. The methods of the invention are useful in the treatment of dementias and conditions involving cognitive deficit, or memory impairment.

Abstract: The A21 receptor extracelluar site and the A2 receptor extracellular site of adenosine analogues are structurally different and that binding orientations of adenosine or adenosine analogues are different at these sites and this may be used to determine their structure. Novel pyrimidine compounds are described.