Introducing the brain: synaptic alterations (Introduction)

by David Turell , Thursday, June 11, 2020, 20:49 (1624 days ago) @ David Turell

They play a huge role in thought processing:

https://science.sciencemag.org/content/368/6496/eaay4631?utm_campaign=toc_sci-mag_2020-...

"The number of neurotransmitter receptors and their spatial organization on the postsynaptic site is a central determinant of synaptic efficacy. Sophisticated techniques to visualize and track the movement of single molecules have provided us with profound new insights into these dynamics. We now know that neurotransmitter receptors undergo movements on different scales. Groc and Choquet review our present understanding of the mechanisms that regulate glutamate receptor localization and clustering. Receptor movements are fundamental to basic synaptic function and participate in many forms of synaptic plasticity.

***

"As cell biologists established the major roles of receptor trafficking in cell function, neurophysiologists still largely viewed synapse function as based on unitary receptor properties and control of transmitter release. It has been only about 20 years since the two fields cross-fertilized and the regulation of receptor movements into and out of synapses emerged as a fundamental mechanism for synaptic plasticity.

"Largely based on the development of imaging approaches, including single-molecule tracking, receptors have been demonstrated to undergo a variety of movements, from long-range rapid motor-based intracellular transport, to short-range Brownian surface diffusion, and intercompartment exchange by membrane trafficking. For efficient synaptic transmission, receptors must accumulate in front of neurotransmitter release sites. This is accomplished through a set of interactions with intracellular scaffold proteins, transmembrane auxiliary subunits, or adhesion proteins and other extracellular elements. This duality of receptor movements and stabilization has led to the important concept that the number of functionally responsive receptors at synapses results from the interplay between reversible receptor stabilization and dynamic equilibrium between pools of receptors in the synaptic, extrasynaptic, and intracellular compartments. Coarse receptor distribution along dendrites is largely achieved by intracellular transport. Because exchange of receptors between surface and intracellular compartments seems to occur largely at extrasynaptic sites, reversible surface receptor diffusion trapping at synapses has emerged as a central mechanism to control their availability for synaptic activation. Receptor stabilization and movements are all profoundly regulated by short- and long-term neuronal activity patterns. Reciprocally, evidence has accumulated that receptor movements participate in many forms of synaptic plasticity.

***

"Neurotransmitter receptors undergo a variety of large- and small-scale movements.
Movements of large amplitude constantly reshuffle the receptor distribution (e.g., surface diffusion and intracellular transport). Movements at interfaces (e.g., between synaptic and extrasynaptic sites, between intracellular and surface compartments) are of small amplitude but have huge functional impacts. Each of these movements is highly regulated and finely tuned in physiological and pathological conditions."

"Abstract
Regulation of neurotransmitter receptor content at synapses is achieved through a dynamic equilibrium between biogenesis and degradation pathways, receptor stabilization at synaptic sites, and receptor trafficking in and out synapses. In the past 20 years, the movements of receptors to and from synapses have emerged as a series of highly regulated processes that mediate postsynaptic plasticity. Our understanding of the properties and roles of receptor movements has benefited from technological advances in receptor labeling and tracking capacities, as well as from new methods to interfere with their movements."

Comment: Extremely complex article. This synopsis carries the impression of how plastic synapses have to be for the advanced functions of our brain. It is not just the number of neurons and their intricate axonal webs, but also how the synapses handle the impulses arriving and leaving.