Scopolamine-induced amnesia in humans: lack of effects of the benzodiazepine receptor antagonist b-carboline ZK 93426

It has been suggested from pharmacological studies in animals that ZK 93426 may improve memory and other cognitive processes in humans. Scopolamine has been used to model aspects of memory impairment. To test the effects of ZK 93426 alone and in combination with scopolamine, ZK 93426 (0.04 mg/kg) or vehicle (Intralipid R) was administered intravenously (i.v.) to normal controls, pre-treated with either scopolamine 0.5 mg administered subcutaneously (s.c.) or the same volume of saline. A visual (presentation of pictures) and a verbal (words list) memory test were applied. Both drugs on their own and in combination were found to be safe and well tolerated. ZK 93426 did not antagonize the scopolamine-induced impairment of acquisition of the words list. Scopolamine did not impair delayed recall of visual or verbal material. ZK 93426 alone improved performance in delayed recall of visual material presented after drug application, whereas it impaired performance in delayed recall of visual material presented before drug administration.