Summary: A new study provides insight into how synapses are formed in cortical neurons during early postnatal stages.
Source: Max Planck Florida.
Researchers from Max Planck Florida Institute for Neuroscience optimized a spatiotemporally controlled method that induces and visualizes the formation of synapses in cortical neurons.
The formation of excitatory and inhibitory synapses between neurons during early development gives rise to the neuronal networks that enable sensory and cognitive functions in humans. Inhibitory synapses decrease the likelihood of the firing action potential of a cell, while excitatory synapses increase its likelihood. Remarkably, both excitatory and inhibitory synapses are formed on dendrites of cortical neurons with high temporal and spatial precision, and it is believed that the spatial arrangement of synapses determines the functional consequences of excitation and inhibition of neuronal activities. However, studying the general mechanisms of synapse formation and distribution in dendrites has been challenging due to a lack of reliable methods that trigger and monitor synapse formation.
In their August publication in Science, MPFI researchers Won Chan Oh, Ph.D. and Hyung-Bae Kwon, Ph.D., describe how they precisely induced and visualized the formation of new synapses in real time in live animals. By using fine-scale optical techniques, they demonstrated that the local release of the inhibitory neurotransmitter, GABA, induces both inhibitory and excitatory synapse formation in the developing mouse cortex. The induction of synapses required signaling through GABAA receptors and voltage-gated calcium channels and the newly formed synaptic structures rapidly gain functions.
The scientists optimized a spatiotemporally controlled method that induces and visualizes the formation of inhibitory and excitatory synapses in cortical neurons in vitro and in vivo. According to Dr. Oh, these findings suggest a model in which GABA is the common molecule that sets the balance between inhibitory and excitatory synaptic contacts in early postnatal stages. “Given that abnormal synapse formation causes various neurodevelopmental diseases such as autism spectrum disorders and epilepsy, understanding activity-dependent mechanisms of initial synapse formation will be important for developing new therapeutic strategies for these conditions,” explained Dr. Kwon.
Source: Max Planck Florida
Image Source: This NeuroscienceNews.com image is adapted from the Max Planck Florida video.
Video Source: The video is credited to Max Planck Florida.
Original Research: Abstract for “De novo synaptogenesis induced by GABA in the developing mouse cortex” by Won Chan Oh, Stefano Lutzu, Pablo E Castillo, and Hyung-Bae Kwon in Science. Published online August 11 2016 doi:10.1126/science.aaf5206
[cbtabs][cbtab title=”MLA”]Max Planck Florida. “Visualization of Newly Formed Synapses With Unprecedented Resolution.” NeuroscienceNews. NeuroscienceNews, 11 August 2016.
<https://neurosciencenews.com/synapse-visualization-neuroscience-4834/>.[/cbtab][cbtab title=”APA”]Max Planck Florida. (2016, August 11). Visualization of Newly Formed Synapses With Unprecedented Resolution. NeuroscienceNew. Retrieved August 11, 2016 from https://neurosciencenews.com/synapse-visualization-neuroscience-4834/[/cbtab][cbtab title=”Chicago”]Max Planck Florida. “Visualization of Newly Formed Synapses With Unprecedented Resolution.” https://neurosciencenews.com/synapse-visualization-neuroscience-4834/ (accessed August 11, 2016).[/cbtab][/cbtabs]
De novo synaptogenesis induced by GABA in the developing mouse cortex
Dendrites of cortical pyramidal neurons contain intermingled excitatory and inhibitory synapses. Here we study the local mechanisms that regulate the formation and distribution of synapses. We show that local γ-aminobutyric acid (GABA) release on dendrites of mouse cortical layer 2/3 pyramidal neurons can induce gephyrin puncta and dendritic spine formation via GABAA receptor activation and voltage-gated calcium channels during early postnatal development. Furthermore, the newly formed inhibitory and excitatory synaptic structures rapidly gain functions. Bidirectional manipulation of GABA release from somatostatin-positive interneurons increased and decreased the number of gephyrin puncta and dendritic spines, respectively. These results highlight a non-canonical function of GABA as a local synaptogenic element shaping the early establishment of neuronal circuitry in mouse cortex.
“De novo synaptogenesis induced by GABA in the developing mouse cortex” by Won Chan Oh, Stefano Lutzu, Pablo E Castillo, and Hyung-Bae Kwon in Science. Published online August 11 2016 doi:10.1126/science.aaf5206