The newest research in neuroscience has paved way to our understanding of  the physiological role of  the glial cell line- derived neurotrophic factor (GDNF) in the function of the brain’s dopamine systems. In a very recent study, researchers established that  GDNF is an important physiological regulator of the functioning of the brain’s dopamine neurons.

Dopamine neurons have an important role in cognitive control, learning and motor control. GDNF is best known for its ability to protect dopaminergic neurons from damage, which is why it is currently in clinical trials for treatment of Parkinson's patients. Nevertheless, the significance of endogenous GDNF that is produced in our brains for the regulation of the dopamine systems is still poorly understood.

The new research results indicate that the GDNF produced in the brain regulates dopamine reuptake. Mice with no GDNF in their brains displayed significantly stronger reuptake of dopamine into nerve endings.

The reuptake of dopamine is the most important factor regulating the brain's dopamine balance and signalling. In practice this means that differences in GDNF levels might explain certain differences in people's ability to learn or focus, explains a researcher of this study.

In addition, the transgenic mice had an atypically low reaction to amphetamine, which specifically targets the dopamine transporter in the brain. These observations were associated with changes in the functionality, amount and localization of the dopamine transporter in the nerve endings.

It has been previously identified that GDNF regulates the amount and localization of the dopamine transporter in the neurons, but there may be additional mechanism involved. And it seems that the relationship between GDNF and dopamine transporter is surprisingly complex, which is of great interest to researchers. Mice with GDNF removed from their brain in adulthood displayed very similar changes. This indicates that the underlying cause for the changes is not the impact of GDNF on brain development.

In a previous study, researchers who studied using the same mouse models demonstrated a research outcome contrary to what is expected, the removal of GDNF does not lead to the destruction of dopamine neurons. This means that these new results significantly expand our understanding of physiological GDNF, from a factor protecting dopamine neurons to a dynamic regulator of their function.

This knowledge is crucial for developing new treatments for not just Parkinson's disease, but also for addiction, ADHD and bipolar disorder, as all of these diseases are associated with some type of disorder in the function of the dopamine neurons, and specifically in the dopamine transporter, says a research of the study.