Amnestic effects of lormetazepam and their reversal by the benzodiazepine antagonist Ro 15-1788.

Abstract

A combined visual (pictures) and auditory (word lists) memory test developed to trace the course of information processing under pharmacological or other influences was validated in a group of 20 subjects (control group) and then applied to determine the amnesic effects of lormetazepam and the reversal of these effects by the benzodiazepine antagonist Ro 15-1788. Three groups of n = 10 subjects received either 0.02 mg/kg IV lormetazepam (groups B and C) or placebo (group A) followed 14 min later by 0.03 mg/kg IV Ro 15-1788 (groups A and C) or placebo (group B). The time course of memory performance in the three groups was investigated and compared across three consecutive 14-min phases: before (phase 1) and after (phase 2) the first intravenous administration, and after the second treatment (phase 3). Results were also compared with those of 20 subjects from a drug-free control group in order to verify the memory test. Lormetazepam clearly impaired immediate and delayed free recall as well as recognition in both visual and auditory tasks. These effects were completely reversed by Ro 15-1788, which alone had no clear effect on memory performance in this study. Psychometric scales indicated concomitant sedation and impaired concentration after lormetazepam alone. Interestingly, lormetazepam retrogradely enhanced performance in the visual test of delayed free recall. The impaired acquisition of new information after the administration of lormetazepam may be associated with an improvement of the consolidation process of information acquired before drug treatment.