Diazepam inhibits retroactive interference of memory in humans: pretreatment with naltrexone does not alter this effect.

1. In a double-blind study of the effects of diazepam and naltrexone on retroactive memory interference, 88 healthy human volunteers were asked to study a text on the 1954 World Soccer Cup and were submitted to a written questionnaire on the material 48 h later. Three hours after reading the text, 58 of the subjects were exposed to a non-factual, derogatory comment on the World Cup. 2. All subjects were given either placebo or naltrexone (50 mg) before reading the text, and either placebo or diazepam (5 mg), per os, 2 h after reading the text (1 h prior to the comment). Subjects were assigned to the different treatment groups by a double-blind design. 3. Exposure to the derogatory comment caused retroactive memory interference with the retention of material from the text. Diazepam blocked the retroactive interference and had no effect of its own on retention of the text. Pretreatment with naltrexone did not influence retention, retrograde interference, or the effect of diazepam on these variables. 4. The results obtained here extend to healthy adult humans observations made on rats and mice in which diazepam blocked retroactive memory interference.