The effect of beta-adrenergic blockade after encoding on memory of an emotional event.
BACKGROUND
Animal and human studies lend support to the hypothesis that enhanced memory associated with emotional experiences involves activation of the beta-adrenergic system. Evidence for the role of noradrenaline in emotional memory in humans has been gathered from experimental studies where blockade of the beta-adrenergic system with a beta-blocker selectively impaired long-term memory for an emotionally arousing story (a slide show), when the beta-blocker was given before subjects were confronted with the emotional stimuli.


OBJECTIVE
The purpose of this study was to test whether effective beta-adrenergic blockade occurring only after the stage of encoding has a similar impairing effect on memory.


METHODS
In a double blind experimental design, 60 healthy adult subjects received randomly one tablet of either propranolol (Inderal, 40 mg) or placebo. Drugs were administered just before the slide show begun and (in view of its pharmacokinetics) propranolol reaches peak levels 1 h after drug intake. Physiological arousal was monitored by heart rate and blood pressure. Half of the beta-blocker and placebo groups watched either a neutral or an arousal version of an 11-slide presentation. Memory performance was tested with a surprise free recall and recognition test 1 week later.


RESULTS
Memory performance, specifically for the second phase in which emotional elements were introduced, was better in subjects who viewed the arousal version than subjects who saw the neutral version of the slide show. However, no effect of the beta-blocker condition was found.


CONCLUSIONS
This experiment does not support a role for noradrenaline in the post-encoding phase and on the later processes of consolidation and retrieval. Although it remains possible that with a different dosage or timing protocol a post-treatment effect of noradrenaline in humans can be found, this experiment could not find support for it.
van Stegeren
Anda H
AH
Department of Clinical Psychology, University of Amsterdam and Cognitive Science Centre Amsterdam, Roetersstraat 15, 1018 WB Amsterdam, The Netherlands. stegeren@psy.uva.nl
Everaerd
Walter
W
Gooren
Louis J G
LJ
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000328:Adult; D000704:Analysis of Variance; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D004311:Double-Blind Method; D004644:Emotions / Q000187:drug effects* / Q000502:physiology; D005260:Female; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006801:Humans; D008297:Male; D008568:Memory / Q000187:drug effects* / Q000502:physiology; D011433:Propranolol / Q000494:pharmacology; D021641:Recognition, Psychology / Q000187:drug effects / Q000502:physiology
D000319:Adrenergic beta-Antagonists; D011433:Propranolol