July 17, 2007
Learned Fear Response Reversible In Mice

Identification of a molecular mechanism involved in learned fear response suggests that chronic disabling fears might be extinguishable.

CAMBRIDGE, Mass.--Researchers from MIT's Picower Institute for Learning and Memory have uncovered a molecular mechanism that governs the formation of fears stemming from traumatic events. The work could lead to the first drug to treat the millions of adults who suffer each year from persistent, debilitating fears - including hundreds of soldiers returning from conflict in Iraq and Afghanistan.

A treatment for post traumatic stress disorder and other learned fears would help a lot of people.

Kinase enzymes attach phosphate groups onto proteins and this gets used in cells to regulate many aspects of cellular activity. Inhibition of a kinase called Cdk5 undoes a learned fear response.

Li-Huei Tsai, Picower Professor of Neuroscience in the Department of Brain and Cognitive Sciences, and colleagues show that inhibiting a kinase (kinases are enzymes that change proteins) called Cdk5 facilitates the extinction of fear learned in a particular context. Conversely, the learned fear persisted when the kinase's activity was increased in the hippocampus, the brain's center for storing memories.

Cdk5, paired with the protein p35, helps new brain cells, or neurons, form and migrate to their correct positions during early brain development. In the current work, the MIT researchers looked at how Cdk5 affects the ability to form and eliminate fear-related memories.

"Remarkably, inhibiting Cdk5 facilitated extinction of learned fear in mice. This data points to a promising therapeutic avenue to treat emotional disorders and raises hope for patients suffering from post-traumatic stress disorder or phobia," Tsai said.

I wonder if the Cdk5 inhibitor just extinguishes the fear response to the original memory or does it wipe out the original memory?

Share |      Randall Parker, 2007 July 17 10:33 PM  Brain Emotion Alteration

Vincent said at July 18, 2007 7:18 AM:

How could it wipe out a memory?

Brock said at July 18, 2007 10:58 AM:

It wiped out the fear. If you read the story closely you'll see that the mice displayed "rational caution", just without being afraid.

Joe K. said at July 18, 2007 4:43 PM:

Is this what propranolol does? It sounds like it doesn't necessarily block the memory, but rather disconnects the memory from some of the strong negative emotional response.

"But encouraging new research suggests that the beta-blocker drug propranolol, by inhibiting the release of certain stress-related hormones, may stop such unwanted memories from being reinforced in our brains. Unlike the creepy device that erases undesirable recalls just like files on a computer in the recent film Eternal Sunshine of the Spotless Mind, propranolol won't cause PTSD sufferers to forget their ghastly memories, "but it can take out the sting," says professor of psychiatry Roger K. Pitman."


Bob Badour said at July 20, 2007 5:53 AM:

Beta blockers stop the body from releasing adrenaline into the bloodstream. Since adrenaline is a large part of the fight or flight response, they block that too.

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