Scientists in Japan have developed a noninvasive PET technique to image regions of the brain that are known to be particularly affected by depression. Clinicians will now be able to obtain objective evidence of depression and determine the effectiveness of treatment.

Hippocampal neurogenesis is known to be associated with depression and the effect of antidepressant medication. It’s also involved in learning and memory, so the scientists worked to find techniques that monitor cell proliferation in the region.

However, neurogenesis is difficult to monitor noninvasively. MR imaging can be used, but the radiotracers don’t enter into the brain effectively, so it must be injected into the brain fluid, which is a difficult procedure.
PET is another method, but when it’s used along with the marker for cell proliferation [18F]FLT there is only a slight difference in signal strength between regions with and without cell growth. The scientists infer that it’s because the body pumps it out of the brain through the blood-brain barrier.



As an experiment, the scientists administered corticosterone to rats to trigger depression and injected them with a drug called probenecid to prevent [18F]FLT from leaving the brain. The strategy worked and they were able to find clear signals of neurogenesis in two areas of the brain.

When they treated the rats with an antidepressant selective serotonin reuptake inhibitor, cell proliferation increased, which means that the drugs were preventing the loss of neurogenesis that was caused by corticosterone.

"This is a very interesting finding, because it has been a longtime dream to find a noninvasive test that can give objective evidence of depression and simultaneously show whether drugs are working in a given patient,” Yosky Kataoka, lead researcher of the study, said in a statement.

Going forward, Kataoka and his fellow researchers are going to test the technique in the clinic to determine if it’s effective in humans as well.

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