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Changes in the Interaction between Astrocyte Processes and Synaptic Terminals in the Generation of Epileptiform Activity

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The aim of the present work was to compare the structural organization of excitatory synaptic contacts in intraocular septal transplants showing normal and epileptiform activity. Experiments were performed using Wistar rats. Donor material for transplants was obtained from the septal area of the brain from 17-day-old rat fetuses. The electrophysiological properties of transplants were tested three months after surgery using short-term stimulation with single electrical pulses. Test results were used to divide transplants into two groups: those with normal and those with epileptiform activity. Microscopic examination of neurotransplants of both groups showed that nerve and glial cells, as well as the neuropil, consisting of axons, dendrites, synaptic terminals, and astrocyte processes, were well differentiated. Axodendritic and axospinous synaptic terminals were regarded as three-component structural complexes (tripartite synapses), which included not only pre- and postsynaptic components, but also their surrounding astrocyte processes. Most had the morphological signs of excitatory contacts with clear postsynaptic densities whose sizes were taken as a correlate of the effi ciency of nervous transmission. Morphometric analysis of these synapses from functionally different types of transplants revealed no significant differences in the extent of postsynaptic densities or the cross-sectional areas or perimeters of presynaptic boutons. At the same time, large differences were seen in the extent to which synapses were surrounded by astrocyte processes. The proportion of perisynaptic processes was 1.8 times lower in transplants characterized by epileptiform activity than in controls. These data provide evidence that presynaptic astrocyte processes were the first to react to electrical stimulation and initiated the development of epileptiform activity. It is suggested that decreases in astrocyte sheaths of excitatory synapses promoted the propagation of neurotransmitters across intercellular spaces and the involvement of neighboring neurons in synchronized neuron activity.

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Authors and Affiliations

  1. Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Russia

    Z. N. Zhuravleva & E. I. Samokhina

  2. Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Russia

    G. I. Zhuravlev

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  1. Z. N. Zhuravleva
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  2. G. I. Zhuravlev
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  3. E. I. Samokhina
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Correspondence to Z. N. Zhuravleva.

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Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 105, No. 6, pp. 707–715, June, 2019.

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Zhuravleva, Z.N., Zhuravlev, G.I. & Samokhina, E.I. Changes in the Interaction between Astrocyte Processes and Synaptic Terminals in the Generation of Epileptiform Activity. Neurosci Behav Physi 50, 633–638 (2020). https://doi.org/10.1007/s11055-020-00945-8

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  • DOI: https://doi.org/10.1007/s11055-020-00945-8

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