Propranolol (Adrenalin armor)

I just read the excellent Not Rocket Science for the first time. He has a nice writeup of the propranolol story that is making the rounds. Some researchers conditioned some subjects to get stressed when they saw a picture of a spider by shocking them while viewing spider pictures. Then, everyone got more spider pictures (with no shocks), this time with loud noises! The fear response to these picture/noise combos was measured by observing the subjects' blinking.

On the second day of the experiment, everyone got a pill with their spider picture and loud noise. Some of them got a placebo, and some got propranolol.


Propranolol is a "beta-adrenergic antagonist" - that is, it blocks (antagonizes) a certain subset (beta) of adrenergic receptors (which respond to small molecules like adrenalin). Because the response to stimuli like loud noises, shocks, and spiders is often adrenalin-mediated, it's reasonable (in fact, well-known) that propranolol will have an effect on one's response to this sort of stressor. Of course, placebos work, too, and both groups actually mellowed out a little when subjected to spider+noise.

The next (third) day, the shock-propranolol group had an attenuated fear response relative to the shock-placebo group. The authors go on to speculate that neurotransmitters like adrenalin play a role in the maintenance of these frightening memories, and blocking the molecule's action at the time the memory is recalled attenuates the associated emotions.


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Yay! There hasn't been a new molecule in a while. Glad you are back. I love little stories about molecules.

By Vince Noir (not verified) on 16 Feb 2009 #permalink

Yay! I love molecules that you can directly relate to human behavior. :)

So, in the Atenolol molecule, is it the extra little H2N on the left or the CH3s on the right which keep it from crossing the blood-brain barrier?

This brings to mind the relatively recent usage of propranolol to help alleviate the fear of public speaking. Nice to see that side of the drug's effects expanded on.

And propranolol is banned from sports as a performance enhancing drug. It was used in ski jumping to quell fears and in shooting to slow the heart rate so that a more accurate shot could be made between heartbeats,

By natural cynic (not verified) on 19 Feb 2009 #permalink