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NEURONS AND THEIR FUNCTIONING
RESEARCH PROVIDED BY - JANELLE STANTON, PHD.
In neuroscience research, understanding how neurons communicate at synapses is crucial for studying brain function and dysfunction. Synapses are the junctions where neurons transmit signals to each other, and they consist of pre-synaptic and post-synaptic components. Researchers use various markers to study these components, enabling them to unravel the complexities of synaptic communication. Here’s an in-depth introduction to some of the key pre-synaptic and post-synaptic markers used in these studies.
PRE-SYNAPTIC MARKERS
Pre-synaptic markers are proteins and molecules that are localized in or associated with the pre-synaptic terminal, where neurotransmitter release occurs.
1. Synaptophysin: This is a membrane protein found in synaptic vesicles, which are responsible for storing neurotransmitters. Synaptophysin is commonly used to identify and quantify synaptic vesicles, providing insights into the density and distribution of synapses.
2. Synaptotagmin: A family of proteins that serve as calcium sensors for neurotransmitter release. Synaptotagmin plays a crucial role in the exocytosis of synaptic vesicles, making it an essential marker for studying the mechanisms of neurotransmitter release.
3. Synapsin: This protein helps regulate the reserve pool of synaptic vesicles and their availability for release. Synapsin is often used to study synaptic plasticity and the dynamics of synaptic vesicle pools.
4. Vesicular Transporters (e.g., VGLUT, VGAT): These proteins transport neurotransmitters into synaptic vesicles. VGLUT (vesicular glutamate transporter) is specific for glutamate, while VGAT (vesicular GABA transporter) is specific for GABA. These markers help identify the types of neurotransmitters stored in vesicles and released by neurons.
POST-SYNAPTIC MARKERS
Post-synaptic markers are proteins and molecules localized in or associated with the post-synaptic density (PSD), a specialized region of the neuron receiving the neurotransmitter signal.
1. PSD-95 (Postsynaptic Density Protein 95): A scaffolding protein that helps organize other proteins in the post-synaptic density. PSD-95 is crucial for the formation and maintenance of synapses, particularly excitatory synapses, and is a key marker for studying synaptic strength and plasticity.
2. Gephyrin: A scaffolding protein that anchors inhibitory neurotransmitter receptors, such as GABA_A receptors, at inhibitory synapses. Gephyrin is essential for the clustering and function of these receptors, making it a vital marker for studying inhibitory synaptic transmission.
3. GluR and NMDAR Subunits: These are subunits of glutamate receptors, including AMPA receptors (GluR) and NMDA receptors (NMDAR). These receptors are critical for excitatory synaptic transmission and plasticity. Researchers often study specific subunits (e.g., GluA1, GluA2 for AMPAR; NR1, NR2A for NMDAR) to understand receptor composition and function at synapses.
4. GABA Receptors: These include GABA_A and GABA_B receptors, which mediate inhibitory neurotransmission. Studying these receptors helps researchers understand inhibitory signaling and its role in maintaining the balance between excitation and inhibition in the brain.
APPLICATIONS OF PRE AND POST-SYNAPTIC MARKERS
Researchers use these markers in various experimental techniques to study synaptic function and structure:
IMMUNOHISTOCHEMISTRY AND IMMUNOFLUORESCENCE
These techniques involve using antibodies to label pre- and post-synaptic markers in brain tissue or cultured neurons, allowing visualization and analysis of synapses under a microscope.
WESTERN BLOTTING
This method quantifies the presence of specific proteins in a sample, helping to measure the levels of pre- and post-synaptic markers and assess changes in synaptic composition under different conditions. Immunocytochemistry and immunohistochemistry is typically followed by western blotting and ELISAs to confirm what is seen in these images. (WB left of image)
ELECTRON MICROSCOPY
Provides high-resolution images of synapses, enabling detailed studies of synaptic structure and the localization of markers at the ultrastructural level.
ELECTROPHYSIOLOGY
Techniques like patch-clamp recording can be combined with the study of synaptic markers to correlate molecular changes with functional synaptic activity.
By utilizing these pre- and post-synaptic markers, researchers can gain a deeper understanding of synaptic function and its role in neural circuits, which is essential for uncovering the mechanisms underlying neurological diseases and developing targeted therapies.
