Propranolol erases physiological effects of trauma, study finds
SUNDAY, Feb. 15 (HealthDay News) -- Imagine being able to decouple bad memories from the fear and anxiety they produce with just a pill.
That's the promise of a new report from Dutch researchers published in the Feb. 15 advance online issue of Nature Neuroscience.
Merel Kindt and colleagues used a beta blocker called propranolol (Inderal) to erase, at least in the short-term, the fear response induced by a laboratory-induced painful memory in humans.
Such findings could one day help individuals suffering from pathological anxiety disorders from the debilitating physiological effects of their fears. Yet many questions remain, experts note, such as how permanent the effect is, and whether it can affect traumatic memories that may be decades old.
"I think it's a very interesting and exciting study," said Jane Taylor, a professor of psychiatry at Yale University, who studies memory reconsolidation in rats. "It will be interesting to know how long-lasting this effect is, and whether it only works on recently consolidated memories."
Mark Bouton, a professor of psychology at the University of Vermont, echoed that sentiment. "This study is a solid step forward in our understanding of how to reduce fear," he said. "The big question is whether this treatment will reduce all forms of relapse, including the return of fear that can occur with the passage of time."
Human memory often is compared to computer storage. Some memories exist in a sort of neurological flash RAM, whereas others are stored for the long term, on the brain's hard disk. The analogy works to a point, but it isn't perfect, as it turns out to be quite difficult to permanently erase files in the brain's memory banks.
"Fear memories can be surprisingly resilient," Bouton explained.
To try to break at least the physiological hold these fears have over individuals, Kindt induced a kind of Pavlovian fear response in 60 undergraduate students at the University of Amsterdam.
The study lasted three days. On the first day, the subjects learned to associate images of spiders with a mild electrical shock. Fear was measured by assessing each individual's startle response -- how much their eyes blinked in response to the stimulus. That fear memory was then consolidated -- written to the hard disk, if you will.
The next day, the memory was recalled, but only after the subjects had been given either placebo or propranolol. The idea, Bouton explained, is that at this point, the memory becomes "open to modification" -- just as a computer file can be changed and then rewritten to the hard disk.
Propranolol had already been shown to impact memory reconsolidation in rodents; the question was, would it have the same effect in people. The answer came on day three, when the subjects were tested again: The physiological response to the fear-inducing cue -- pictures of spiders -- was eliminated in the propranolol group, but not in the placebo group, Kindt found.
"In principle," said Bouton, "this is a step toward finding a clinical treatment for people with pathological fears."
Indeed, the authors noted that their findings "are consistent with those of a recent preliminary study of patients with post-traumatic stress disorder in which post-retrieval propranolol seemed to reduce subsequent physiological responding to traumatic memory."
Yet much remains unknown. For instance, the current research involved only a very short period of time. Though the memory appeared erased on day three, would that still be true a month later? And, it's unclear how effective will propranolol be against longer-term memories, such as traumatic childhood memories that persist into adulthood.
Besides, the experimental memories were not exactly erased in this study, Taylor noted: The propranolol-treated subjects no longer flinched in reaction to the stimulus, yet they knew that they should. That, Taylor suggested, could limit propranolol's clinical utility.
"Being afraid of something doesn't just involve a physiological response," Taylor said, "it's how you think about it and how it affects your behavior."
For more about anxiety disorders, visit the U.S. National Institute of Mental Health.
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