Some science news are impossible to describe in a simple way. For example, recently scientists from Riken institute in Japan have developed a method of using positron emission tomography scanning to observe neuron proliferation in the subventricular zone and subgranular zone of the hippocampal dentate gyrus. Telling in more simple words, scientists developed a new method for depression diagnosis and evaluation of drug therapy effectiveness.
Subventricular zone and subgranular zone of the hippocampal dentate gyrus are two regions where stem cells produce new neurons. Hippocampal neurogenesis is known to be associated with depression and effectiveness of antidepressants among other things, such as learning and memory. For effective research scientists want to monitor cell proliferation in these areas, but it is hard to do so in a non-invasive manner. Magnetic resonance is a good way, but it is still invasive as tracers have to be injected into the brain directly.
Positron emission tomography imaging is another technique, which is non-invasive. This method uses molecule called [18F]FLT, but scientists noticed that it was not working as expected, because signal strength difference between the regions with and without cell growth was small. Yasuhisa Tamura, one of the authors of the study, said that even though the team was not sure why it is like that, they “surmised that it is because the body actively pumps the molecule out of the brain through the blood-brain barrier, using active transport mechanisms. This means that it is difficult for [18F]FLT to accumulate in the brain in sufficient concentrations to allow effective imaging”.
To counteract this effect, scientists used probenecid in their mouse models, as this drug inhibits transportation of [18F]FLT molecule. This allowed them to identify signals of neurogenesis in the two areas of the adult brain. Scientists found that in case of depression these signals in the hippocampal dentate gyrus are significantly decreased. This allows better diagnosis and provides information about effectiveness of new anti-depressant drugs.
Now scientists will attempt similar experiments with people, to see if PET scanning will work as effectively. It is a great achievement, because it allows non-invasive drug testing and depression diagnosis. It is a quicker and more effective route towards novel therapies to combat this condition.