New Research Finding On Experience Of Pain

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New Research Finding On Experience Of Pain

http://www.medicalnewstoday.com/articles/91478.php

Researchers at UQ's Queensland Brain Institute (QBI) have discovered

a new brain mechanism that plays an important role in regulating how

we experience pain.

Scientists from QBI's synaptic plasticity laboratory discovered the

new mechanism while studying the amygdala - the part of the brain

that deals with our emotional responses.

QBI has one of the relatively few laboratories around the world

currently looking at how the amygdala deals with pain inputs.

According to QBI's Dr Delaney, there are essentially two

aspects to pain.

" You have a sensory component that tells you where you are hurting

and what sort of hurt you've had, and there's the emotional response

you have to that event, " he said.

" The sensory part of pain is quite well understood, but until now

very little had been done to look at the emotional part of pain. "

QBI scientists used an anatomical technique which involved labelling

the neurons in what is essentially the brain's pain-relay station

[the parabrachial nucleus] to identify target cells in the amygdala

that receive inputs during pain.

Researchers were able to record electrical responses in the amygdala

when the pain inputs were stimulated electrically.

" People have long thought there's a connection between your

experience of pain and the emotional state that you're in, " Dr

Delaney said.

Historically, this has been borne out by first-hand reports from

people who have suffered a traumatic injury during the height of

combat and yet gone on to all but ignore their injury for some time.

A similar phenomenon happens on the sporting field where, during the

game's emotional zenith, a player injures a knee or ankle but

manages to finish the play or walk off.

For many years, this was thought to be a spinal cord effect, whereby

the release of hormones during heightened emotions inhibit the

transmission of pain - sometimes called the " gate theory " of pain.

" Our findings indicate that there is also an interaction between the

stress pathways in the brain and the pain pathway that targets the

amygdala, " Dr Delaney said.

" This seems to indicate that during times of stress, our emotional

response to pain may also be modulated, perhaps reducing the

emotional impact of a painful experience. "

The QBI scientists have shown, for the first time, that the stress

hormone noradrenaline acts as a fast modulatory transmitter in the

brain, and that the way this transmitter works at these pain

synapses was by scaling down the size of the pain inputs.

Such a mechanism had not previously been identified in the brain,

and it is one which is ideally suited to providing strong control

over the activation of the emotional response, even when strong

painful input activates the pathway to the amygdala.

According to QBI's Head of Synaptic Plasticity, Professor Pankaj

Sah, people who suffer chronic pain have higher incidence of anxiety

disorders, conditions known to involve dysfunctional processing in

the amygdala.

" This study reveals an important site for interaction between the

pain and emotional systems of the brain, potentially offering a key

connection to how this might be occurring, " he said.

" Ultimately understanding how these systems interact at the synaptic

level might reveal the nature of these dysfunctional states and

offer an insight into how we might better treat such conditions. "

The research - " Noradrenaline Modulates Transmission at a Central

Synapse by a Presynaptic Mechanism " - is published in the journal

Neuron.