Effects of the beta-blocker propranolol on cued and contextual fear conditioning in humans.
BACKGROUND
Beta-adrenergic receptors are involved in the consolidation of emotional memories. Yet, a number of studies using Pavlovian cued fear conditioning have been unable to demonstrate an effect of beta-adrenergic blockade on acquisition or retention of fear conditioning. Evidence for the involvement of beta-adrenergic receptors in emotional memories comes mostly from studies using fear inhibitory avoidance in rodents. It is possible that fear inhibitory avoidance is more akin to contextual conditioning than to cued fear conditioning, suggesting that context conditioning may be disrupted by beta-adrenergic blockade.


OBJECTIVE
This study investigated the effects of the beta-adrenergic blocker propranolol on cued and contextual fear conditioning in humans.


METHODS
Subjects were given either placebo (n=15) or 40 mg propranolol (n=15) prior to differential cued conditioning. A week later, they were tested for retention of context and cued fear conditioning using physiological (startle reflex and electrodermal activity) and subjective measures of emotional arousal.


RESULTS
The results were consistent with the hypothesis. The skin conductance level (SCL) and the subjective measure of arousal suggested reduced emotional arousal upon returning to the conditioning context in the propranolol group, compared to the placebo group. The acquisition and retention of cued fear conditioning were not affected by propranolol.


CONCLUSIONS
These results suggest that beta-adrenergic receptors are involved in contextual fear conditioning.
Mood and Anxiety Disorder Program, NIMH/NIH/DHHS National Institute of Mental Health, Bethesda, MD 20892-2670, USA. christian.grillon@nih.gov
Christian
C
Grillon
Jeremy
J
Cordova
Charles Andrew
CA
Morgan
Dennis S
DS
Charney
Michael
M
Davis
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000328:Adult; D003216:Conditioning, Operant / Q000187:drug effects; D003463:Cues; D004311:Double-Blind Method; D005239:Fear / Q000187:drug effects* / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D011433:Propranolol / Q000494:pharmacology*; D013216:Reflex, Startle / Q000187:drug effects
D000319:Adrenergic beta-Antagonists; D011433:Propranolol