Electrical synapses interconnecting axons revealed in the optic nerve head – a novel model of gap junctions’ involvement in optic nerve function

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Smedowski , A , Akhtar , S , Liu , X , Pietrucha-Dutczak , M , Podracka , L , Toropainen , E , Alkanaan , A , Ruponen , M , Urtti , A , Varjosalo , M , Kaarniranta , K & Lewin-Kowalik , J 2020 , ' Electrical synapses interconnecting axons revealed in the optic nerve head – a novel model of gap junctions’ involvement in optic nerve function ' , Acta Ophthalmologica , vol. 98 , no. 4 , pp. 408-417 . https://doi.org/10.1111/aos.14272

Title: Electrical synapses interconnecting axons revealed in the optic nerve head – a novel model of gap junctions’ involvement in optic nerve function
Author: Smedowski, Adrian; Akhtar, Saeed; Liu, Xiaonan; Pietrucha-Dutczak, Marita; Podracka, Lucia; Toropainen, Elisa; Alkanaan, Aljoharah; Ruponen, Marika; Urtti, Arto; Varjosalo, Markku; Kaarniranta, Kai; Lewin-Kowalik, Joanna
Contributor: University of Helsinki, Institute of Biotechnology
University of Helsinki, University of Eastern Finland (UEF)
University of Helsinki, University of Eastern Finland (UEF)
University of Helsinki, University of Eastern Finland (UEF)
University of Helsinki, Institute of Biotechnology
Date: 2020-06
Language: eng
Number of pages: 10
Belongs to series: Acta Ophthalmologica
ISSN: 1755-375X
URI: http://hdl.handle.net/10138/316969
Abstract: Abstract Purpose To characterize newly discovered electrical synapses, formed by connexin (Cx) 36 and 45, between neighbouring axons within the optic nerve head. Methods Twenty-five Wistar rats were killed by CO2 inhalation. Proximal and distal optic nerve (ON) stumps were collected and processed for immunostainings, electron microscopy (EM) with immunogold labelling, PCR and Western blots (WB). Additional 15 animals were deeply anaesthetized, and flash visual evoked potentials (fVEP) after retrobulbar injection of saline (negative control) or 100 ?m meclofenamic acid solution (gap junctions? blocker) were recorded. Human paraffin cross-sections of eyeballs for immunostainings were obtained from the Human Eye Biobank for Research. Results Immunostainings of both rat and human ON revealed the presence of Cx45 and 36 colocalizing with ?3-tubulin, but not with glial fibrillary acidic protein (GFAP). In WB, Cx36 content in optic nerve was approximately halved when compared with retina (0.58 ± 0.005 in proximal stump and 0.44 ± 0.02 in distal stump), Cx45 showed higher levels (0.68 ± 0.01 in proximal stump and 0.9 ± 0.07 in distal stump). In immunogold-EM of optic nerve sections, we found electric synapses (formed mostly by Cx45) directly coupling neighbouring axons. In fVEP, blocking of gap junctions with meclofenamic acid resulted in significant prolongation of the latency of P1 wave up to 160% after 30 min (p 
Subject: 3112 Neurosciences
conduction resistance
electrical synapses
impulse conduction
optic nerve
retinal ganglion cell axons
CELLS
CONNEXIN
AII AMACRINE
RETINAL NEURONS
NEUROPROTECTION
REDISTRIBUTION
GLAUCOMA
EXPRESSION
COMMUNICATION
MORPHOLOGY
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