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!
Finnish research group discovers a new immune system regulator
23.02.2018 | University of Turku
Minimising risks of transplants
22.02.2018 | Friedrich-Alexander-Universität Erlangen-Nürnberg
A newly developed laser technology has enabled physicists in the Laboratory for Attosecond Physics (jointly run by LMU Munich and the Max Planck Institute of Quantum Optics) to generate attosecond bursts of high-energy photons of unprecedented intensity. This has made it possible to observe the interaction of multiple photons in a single such pulse with electrons in the inner orbital shell of an atom.
In order to observe the ultrafast electron motion in the inner shells of atoms with short light pulses, the pulses must not only be ultrashort, but very...
A group of researchers led by Andrea Cavalleri at the Max Planck Institute for Structure and Dynamics of Matter (MPSD) in Hamburg has demonstrated a new method enabling precise measurements of the interatomic forces that hold crystalline solids together. The paper Probing the Interatomic Potential of Solids by Strong-Field Nonlinear Phononics, published online in Nature, explains how a terahertz-frequency laser pulse can drive very large deformations of the crystal.
By measuring the highly unusual atomic trajectories under extreme electromagnetic transients, the MPSD group could reconstruct how rigid the atomic bonds are...
Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...
For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.
In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...
Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale
Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...
15.02.2018 | Event News
13.02.2018 | Event News
12.02.2018 | Event News
23.02.2018 | Physics and Astronomy
23.02.2018 | Health and Medicine
23.02.2018 | Physics and Astronomy