ORIGINAL RESEARCH article
Front. Neural Circuits
Volume 19 - 2025 | doi: 10.3389/fncir.2025.1644572
Dendritic synaptome of calcium-binding protein containing GABAergic interneurons in the mouse primary visual cortex
Provisionally accepted
- Debreceni Egyetem, Debrecen, Hungary
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Here we provide a synaptic input database called, dendritic synaptome, for dendrites of calciumbinding protein containing interneurons (calbindin-D28K, CB+; calretinin, CR+; parvalbumin, PV+) employing a modified correlated light and EM method, the "mirror-technique" that allows for investigating neuronal compartments while preserving utmost ultrastructural quality (Talapka et al., 2021). Nine dendrites and all presynaptic boutons (n=815) impinging on their surface were traced and reconstructed in three-dimensions (3D) using ssTEM. The following basic parameters of the synapses were determined: The ratio of symmetrics (ss or putative inhibitory) and asymmetric (as or putative excitatory) synapses, the number of synapses per unit length of dendrite (i.e. density of as and ss), surface area and volume of presynaptic boutons, and area of the active zones of synapses. Significant differences in the morphometric parameters of asymmetricexcitatory, but not in symmetricinhibitory synapsesinputs were detected between the three interneuron subtypes. Surface extent and the number of synapsestic inputs on PV+ dendrites were the largest compared to the other two subtypes.Interestingly, no difference in the basic parameters of presynaptic excitatory and inhibitory boutons were found between IN subtypes. Although the distribution of presynaptic boutons differed between dendrites clustering of the presynaptic boutons could be revealed only for PV+ dendrites. Based on our ssEM reconstructions and corresponding LM databases of CBP dendrites it was calculated that on average a single CB+, CR+, and PV+ interneuron receives 2136, 2148, and 2589 synapses, respectively, of which 74.6%, 81.5%, and 85.3% are excitatory, i.e. asymmetric, and the remaining inhibitory, i.e. symmetric.Our findings provide essential quantitative information to establish realistic computational models for studying the synaptic function of neuronal ensembles in the mouse primary visual cortex.
Keywords: Electron microscopy, Neocortex, dendritic input synapses, GABAergic Neurons, 3D Reconstruction, Calcium binding proteins (CBPs)
Received: 10 Jun 2025; Accepted: 15 Aug 2025.
Copyright: © 2025 Talapka, Kocsis, Marsi, Szarvas and Kisvárday. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Zoltán Kisvárday, Debreceni Egyetem, Debrecen, Hungary
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