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!
Penn study identifies new malaria parasites in wild bonobos
21.11.2017 | University of Pennsylvania School of Medicine
NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures
17.11.2017 | National Institute of Standards and Technology (NIST)
The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.
Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.
Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
22.11.2017 | Life Sciences
22.11.2017 | Life Sciences
22.11.2017 | Materials Sciences