WESTPORT, CT (Reuters Health) Jan 25 - Astrocytes, which constitute nearly half of the brain's cells, increase the number of functional synapses between neurons in the central nervous system, according to a report published in the January 26th issue of Science.
Dr. Ben A. Barres and colleagues from the Stanford University School of Medicine in California assessed the function of glial cells by culturing and analyzing neurons in the presence and absence of astrocytes.
The authors found that not only did few neuronal synapses occur in the absence of glial cells, but also that the synapses that did occur were functionally immature. In vitro analysis indicated that astrocytes were needed for synaptic maintenance and that a sevenfold increase in the number of functional neuronal synapses occurred in the presence of astrocytes. In vivo analysis revealed that synaptic generation was usually concurrent with glial development.
These findings indicate that "glia may play important and unexpected roles in adult neural plasticity underlying learning and memory," the investigators note. Also, "our results raise the question of whether the gliosis produced by brain injury increases synapse number, potentially leading to epilepsy and excitotoxic neurodegenerative changes."
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