Body’s Natural Painkillers Can Block Phobias

Magnetic resonance image showing a median sagittal cross section through a human head.

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Human body’s own pain-relief system has the ability to block phobias, claims a new study which is likely to soon throw light on the neural mechanisms behind anxiety and stress.

A international team, led by researchers at the University Medical Centre of Hamburg-Eppendorf, has found that the way humans are conditioned by fearful stimuli is to some extent damped down by the body’s own pain-relief system.

For their study, the researchers recruited 30 male volunteers who were asked to watch green triangles and blue pentagons on a screen inside an MRI scanner. One symbol was followed half the time by a moderately painful application of heat to the forearm; the other was never followed by pain.

Half the volunteers were infused with a drug that blocks the effects of opioids, while the others got saline solution as a control. The brain scans showed that in people whose opioid systems had been blocked, the amygdala showed a fear response that did not diminish with exposure. Every time they saw the symbol associated with pain, their amygdalas reacted strongly.

In the control group, however, the activation decreased over the course of the experiment. As the group receiving the drug was reacting fearfully, the researchers speculate, they were learning the association intensively.

At the beginning of each trial, volunteers had to perform a reaction time task – pressing a button to indicate on which half of the screen the symbol had appeared. Overall, the subjects reacted more quickly to the cue signalling pain than the cue signalling nothing – but the opioid-free subjects reacted significantly faster.

The team speculates that opioid deficiency could be a contributing factor to anxiety disorders and exaggerated fear responses.

Sources:The Times Of India

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