Contrary to expectations that the neurotransmitter GABA only inhibited neuronal firing in the adult brain, RIKEN-led research has shown that it can also excite interneurons in the hippocampus of the rat brain by changing the conductance of ions across the membranes of these cells1.
According to conventional wisdom, activation of the GABAA receptor subtype at the communication junction between neurons—the synapse—strongly increases membrane conductance of ions, triggering a process called shunting, which inhibits neuronal firing. Led by Alexey Semyanov of the RIKEN Brain Science Institute in Wako, the team demonstrated that activation of these receptors outside of synaptic junctions, so-called ‘extrasynaptic receptors’ can also excite the neurons.
Further activation of these extrasynaptic receptors by application of higher concentrations of GABA turn excitation into inhibition. “To our knowledge, this is the first demonstration that changes in membrane conductance can switch the action of a neurotransmitter from excitation to inhibition,” Semyanov says.
Semyanov and colleagues treated slices of the mouse hippocampus with low or high concentrations of GABA and compared the effects. They showed that the more GABA they added, the more they could detect an increase in the conductance of the membranes of hippocampus cells called CA1 interneurons. The increased conductance was mediated through extrasynaptic GABAA receptors.
The CA1 interneurons could spontaneously fire action potentials—electrical impulses that transfer signals in the network of interconnected neurons. Adding low concentrations of GABA increased the rate of action potential firing, while high concentrations of GABA reduced action potential firing in the cells. Because the concentration of GABA that slowed neuronal firing had also enhanced membrane conductance, the researchers argue that increasing this conductance by activating extrasynaptic GABAA receptors can result in inhibition via shunting along the membrane, which would cause a decrease in action potential generation in the neurons.
The hippocampus plays a key role in learning and memory, and GABA concentrations are known to increase in this part of the brain during exploratory behavior in rats. The findings therefore raise the intriguing possibility that changes in GABA concentration in the brain during some behavioral tasks could bidirectionally change neuronal excitability; this could be a characteristic of the hippocampal neuronal network that may be required for some behavioral tasks in animals.
“Many clinically used drugs, such as sedatives or anti-epileptics, target GABA receptors,” notes Semyanov. “Our findings could potentially explain their therapeutic action as well as some of their unwanted side effects.”
The corresponding author for this highlight is based at the Semyanov Research Unit, RIKEN Brain Science Institute
Satellites, airport visibility readings shed light on troops' exposure to air pollution
09.12.2016 | Veterans Affairs Research Communications
Oxygen can wake up dormant bacteria for antibiotic attacks
08.12.2016 | Penn State
Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.
Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
09.12.2016 | Life Sciences
09.12.2016 | Ecology, The Environment and Conservation
09.12.2016 | Health and Medicine