Determining the mechanisms that cause what is being called "post-stimulus activated release" and how they maintain dopamine levels could have important implications for understanding and treating neurological and psychiatric disorders caused by an imbalance of dopamine function including schizophrenia, attention deficit hyperactivity disorder, Tourette's syndrome, Parkinson's disease and addiction.
According to Bita Moghaddam, Ph.D., professor of neuroscience and psychiatry, who led the study, in addition to its clinical benefits, post-stimulus activated release can be used to explain how brief events that activate neurons for short periods of time can influence brain function long after the events. For example, it can be used to explain how smelling freshly baked cookies could evoke childhood memories of spending time with a beloved grandparent, leading a person to reminisce long after the smell is gone and take the unplanned or impulsive action of baking or buying cookies.
Dopamine is a neurotransmitter associated with learning and memory, motor control, reward perception and executive functions such as working memory, behavioral flexibility and decision making. When a novel or salient stimulus occurs, the dopamine neurons in the brain increase their firing rate, boosting the release of dopamine. The dopamine is diffused into the extracellular space of the brain until it can be transported or metabolized.
In a rat model, the researchers have been attempting to understand increases in extracellular levels of dopamine during behaviorally active states, such as completing a cognitive task or experiencing stressful situations and in response to the electrical stimulation of neurons. In their studies, they have observed that dopamine levels remain above the baseline long after neurons had been stimulated – from five to 20 minutes in the ventral tegmental area (VTA) and 40 to 100 minutes in the nucleus accumbens and prefrontal cortex.
Attempting to discern the cause of the elevated levels, researchers stimulated the VTA of the brain of a rat model by using an electrode. The VTA is a nucleus in the midbrain where dopamine neurons are located. After stimulating the neurons, the researchers measured the amount of dopamine in the extracellular fluid of the nucleus accumbens and prefrontal cortex – two areas where the VTA is known to send signals. They found that dopamine levels increased during stimulation, and remained elevated for an hour after stimulation.
Dopamine levels wane as dopamine is taken back into cells by an active transport system. Yet this active transport system is not abundant in the ventral striatum and prefrontal cortex areas, leading researchers to think that perhaps the dopamine levels remained elevated due to an excess that had yet to be absorbed. To test this hypothesis, they applied tetrodotoxin (TTX), a neurotoxin that blocks the active release of dopamine, to the nucleus accumbens and prefrontal cortex. TTX caused dopamine levels to drop, indicating that the dopamine levels remained elevated because dopamine was being actively released after the neurons fired and not because there was residual dopamine in the brain.
Dr. Moghaddam and colleagues are currently conducting experiments in efforts to identify the exact mechanism causing post-stimulus activated release.
Jocelyn Uhl | EurekAlert!
3D images of cancer cells in the body: Medical physicists from Halle present new method
16.05.2018 | Martin-Luther-Universität Halle-Wittenberg
Better equipped in the fight against lung cancer
16.05.2018 | Friedrich-Alexander-Universität Erlangen-Nürnberg
So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics
Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...
The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A...
A team led by Austrian experimental physicist Rainer Blatt has succeeded in characterizing the quantum entanglement of two spatially separated atoms by observing their light emission. This fundamental demonstration could lead to the development of highly sensitive optical gradiometers for the precise measurement of the gravitational field or the earth's magnetic field.
The age of quantum technology has long been heralded. Decades of research into the quantum world have led to the development of methods that make it possible...
Cardiovascular tissue engineering aims to treat heart disease with prostheses that grow and regenerate. Now, researchers from the University of Zurich, the Technical University Eindhoven and the Charité Berlin have successfully implanted regenerative heart valves, designed with the aid of computer simulations, into sheep for the first time.
Producing living tissue or organs based on human cells is one of the main research fields in regenerative medicine. Tissue engineering, which involves growing...
A team of scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg investigated optically-induced superconductivity in the alkali-doped fulleride K3C60under high external pressures. This study allowed, on one hand, to uniquely assess the nature of the transient state as a superconducting phase. In addition, it unveiled the possibility to induce superconductivity in K3C60 at temperatures far above the -170 degrees Celsius hypothesized previously, and rather all the way to room temperature. The paper by Cantaluppi et al has been published in Nature Physics.
Unlike ordinary metals, superconductors have the unique capability of transporting electrical currents without any loss. Nowadays, their technological...
02.05.2018 | Event News
13.04.2018 | Event News
12.04.2018 | Event News
18.05.2018 | Power and Electrical Engineering
18.05.2018 | Information Technology
18.05.2018 | Information Technology