New research explores role of serotonin

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http://www.eurekalert.org/pub_releases/2008-06/uoc-nre060308.php

 

Genevieve Maul

University of Cambridge

 

New research explores role of serotonin

 

Findings provide insight into clinical disorders characterised by low

serotonin level, such as depression, obsessive compulsive disorder and

severe anxiety

 

New research by scientists at the University of Cambridge suggests

that the neurotransmitter serotonin, which acts as a chemical

messenger between nerve cells, plays a critical role in regulating

emotions such as aggression during social decision-making.

 

Serotonin has long been associated with social behaviour, but its

precise involvement in impulsive aggression has been controversial.

Though many have hypothesised the link between serotonin and

impulsivity, this is one of the first studies to show a causal link

between the two.

 

Their findings highlight why some of us may become combative or

aggressive when we haven't eaten. The essential amino acid necessary

for the body to create serotonin can only be obtained through diet.

Therefore, our serotonin levels naturally decline when we don't eat,

an effect the researchers took advantage of in their experimental

technique.

 

The research also provides insight into clinical disorders

characterised by low serotonin levels, such as depression and

obsessive compulsive disorder (OCD), and may help explain some of the

social difficulties associated with these disorders.

 

This research, funded by the Wellcome Trust and the Medical Research

Council, suggests that patients with depression and anxiety disorders

may benefit from therapies that teach them strategies for regulating

emotions during decision making, particularly in social scenarios.

 

The researchers were able reduce brain serotonin levels in healthy

volunteers for a short time by manipulating their diet. They used a

situation known as the 'Ultimatum Game' to investigate how individuals

with low serotonin react to what they perceive as unfair behaviour. In

this game one player proposes a way to split a sum of money with a

partner. If the partner accepts, both players are paid accordingly.

But if he rejects the offer, neither player is paid.

 

Normally, people tend to reject about half of all offers less than

20-30% of the total stake, despite the fact that this means they

receive nothing - but rejection rates increased to more than 80% after

serotonin reductions. Other measures showed that the volunteers with

serotonin depletion were not simply depressed or hypersensitive to

lost rewards.

 

PhD student Molly Crockett, a Gates Scholar at the University of

Cambridge Behavioural and Clinical Neuroscience Institute, said: " Our

results suggest that serotonin plays a critical role in social

decision-making by normally keeping aggressive social responses in

check. Changes in diet and stress cause our serotonin levels to

fluctuate naturally, so it's important to understand how this might

affect our everyday decision-making. "

 

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1. The article 'Serotonin Modulates Behavioural Reactions to

Unfairness' will appear in Science Express on 06 June 2008.

 

2. Authors of the paper include: M.J. Crockett; L. Clark; T.W.

Robbins; University of Cambridge, G. Tabibnia; M.D. Lieberman;

University of California, Los Angeles.

 

3. Serotonin: The only way to get the raw material for serotonin

(tryptophan) is through the diet. Therefore, serotonin levels are

lower when you haven't eaten, an effect that the researchers take

advantage of in their experimental technique. Eating tryptophan rich

foods like poultry (chicken soup) and chocolate can boost serotonin

levels - some have speculated that this is why these are " feel good "

foods.

 

4. The Wellcome Trust is the largest charity in the UK. It funds

innovative biomedical research, in the UK and internationally,

spending around £500 million each year to support the brightest

scientists with the best ideas. The Wellcome Trust supports public

debate about biomedical research and its impact on health and

wellbeing. http://www.wellcome.ac.uk

 

5. The Medical Research Council is dedicated to improving human health

through excellent science. It invests on behalf of the UK taxpayer.

Its work ranges from molecular level science to public health

research, carried out in universities, hospitals and a network of its

own units and institutes. The MRC liaises with the Health Departments,

the National Health Service and industry to take account of the

public's needs. The results have led to some of the most significant

discoveries in medical science and benefited the health and wealth of

millions of people in the UK and around the world. http://www.mrc.ac.uk

 

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