A test to pick up depression in patients and work out whether treatments will work could follow US research on brain cells.
A team from the University of Illinois College of Medicine in Chicago have found a change in the location of a protein in the brain could indicate whether someone is depressed or not.
If further research bears this out, it might lead to the development of a test that could identify people very quickly and let them know if a particular drug therapy works. Antidepressants don’t usually start to work straight away and can take two to three weeks before people start to feel better, says the Royal College of Psychiatrists.
The scientists, led by Mark Rasenick, a professor of physiology and biophysics, compared brain samples from 16 depressed people who had committed suicide with cadavers controls who had no history of psychiatric disorders.
In depressed individuals, they found greater numbers of a signalling protein called Gs alpha were on certain areas of the cell membrane called lipid rafts than in those that were not depressed. Other G proteins were distributed in the same way in both samples.
The protein activates adenylyl cyclase, a link in signal transduction, which is responsible for the action of serotonin and other neurotransmitters.
"These 'rafts' are thick, viscous, almost gluey areas, that either facilitate or impede communication between membrane molecules," Professor Rasenick said. "When Gs alpha is caught in these rafts, its ability to couple with and activate adenylyl cyclase is markedly reduced."
In animal experiments with rats and looking at individual cells, the team was able to see the effect of antidepressants on Gs alpha.
"Antidepressants help to move the Gs alpha out of these rafts and facilitate the action of certain neurotransmitters," he said.
The team went on to show that this change could be picked up through a blood test. By comparing a patient's blood before medication and four or five days after treatment has started, they could see if this change in location had happened. Testing with both selective serotonin reuptake inhibitors and tricyclic antidepressants found both classes of drugs could produce shifts.
"This would spare patients the agony of waiting a month or more to find out if they are on the correct therapeutic regimen," Professor Rasenick said.
The research is published in the March 12 issue of the Journal of Neuroscience.