PET Imaging May Aid Effective Use of Anti-Depressants

New imaging technique could allow physicians to see if an anti-depressant is effective in a patient.

Researchers recently imaged neuron proliferation in the brain with non-invasive positron emission tomography (PET).

They were able to capture images of neurogenesis in the subventricular zone and subgranular zone of the hippocampal dentate gyrus, which associated with depression and anti-depressive medications.

Current imagining techniques require magnetic resonance imaging tracers to be injected into the brain fluid and creative an invasive, difficult procedure, according to a study published by The Journal of Neuroscience. In previous tests, the molecule [18F]FLT was used as a marker for cell proliferation in PET, but researchers found an insignificant difference between signal strength between regions with and without cell growth.

“We were not exactly sure why this was happening, but surmised that it is because the body actively pumps the molecule out of the brain through the blood-brain barrier, using active transport mechanisms,” said researcher Yasuhisa Tamura. “This means that it is difficult for [18F]FLT to accumulate in the brain in sufficient concentrations to allow effective imaging.”

In the current study, researchers injected rats with probenecid since it is known to stop the active transport of [18F]FLT outside of the brain. Researchers discovered this method was successful, and were able to find clear signals of neurogenesis in these 2 areas of the brain.

Decreased signals were found in rats that received corticosterone to prompt depression. However, when these rats were treated with selective serotonin reuptake inhibitors, an anti-depressive, researchers found an increase in cell proliferation.

This suggests that the drugs increased neurogenesis.

“This is a very interesting finding, because it has been a longtime dream to find a non-invasive test that can give objective evidence of depression and simultaneously show whether drugs are working in a given patient,” said lead researcher Yosky Kataoka, MD, PhD. “We have shown that it is possible, at least in experimental animals, to use PET to show the presence of depression and the effectiveness of drugs. Since it is known that these same brain regions are involved in depression in the human brain, we would like to try this technique in the clinic and see whether it turns out to be effective in humans as well.”