Simple blood test could show whether an antidepressant is working

Mar 11 2008

Researchers in the United States have discovered that a single protein in the brain changes its location within a cell membrane when an antidepressant is working.

They say a simple blood test will establish whether an antidepressant is working.

The researchers at the University of Illinois in Chicago have found that the change in location of the protein occurs within days of taking the drug.

At present people suffering from depression wait weeks before they learn whether the drug they are taking will bring relief.

But researchers say the possibility exists that blood from a patient on day zero and day four or five, will show whether the antidepressant is effective.

Lead author Dr. Mark Rasenick and his team compared the brains of 16 clinically depressed people who committed suicide to the brains of cadavers with no history of psychiatric disorders and found a key difference in the location of a signaling protein known as Gs alpha.

Gs alpha is important for the action of neurotransmitters or message-carrying chemicals such as serotonin.

Dr. Rasenick says in people with depression, this protein is trapped in what he calls a "lipid raft" inside the cell membrane and when stuck in this thick, gluey area of the cell, the signaling protein seemed less effective at directing the action of message-carrying chemicals.

Rasenick's team conducted tests on rats and in cell cultures done in the lab, and found antidepressants helped move the Gs alpha protein into an area of the cell where it could be more effective.

Dr. Rasenick says the study demonstrates that in depression this G protein was more than twice as likely to be imprisoned in those lipid rafts and antidepressants help to move the Gs alpha out of these rafts and facilitate the action of certain neurotransmitters.

He says the method worked with selective serotonin reuptake inhibitors, or SSRIs, such as Prozac, as well as the older tricyclic antidepressants.

Rasenick says by using the protein as a biomarker, a simple blood test could be made that would confirm a depression diagnosis or determine whether an antidepressant is working and also gives a clearer picture of the chemical changes in the brain underlying depression.

The study is published in the Journal of Neuroscience.