tokens: The analogs tested were : 11-ketopregnenolone sulphate ( an agent that is inactive at GABA ( A ) Rs and NMDARs ), epipregnanolone ([3beta-hydroxy-5beta-pregnan-20-one] sulphate , an inhibitor of both GABA ( A ) Rs and NMDARs ), and a newly synthesized (-) PREGS enantiomer ( which is identical to PREGS in effects on GABA ( A ) Rs and NMDARs ). The memory - enhancing effects of PREGS and its analogs were tested in the passive avoidance task using the model of scopolamine - induced amnesia .