PROX1 IMMUNREACTIVITY AND ELECTRICAL SYNAPSE DENSITY IN THE MAMMALIAN RETINA
Katalin Fusz1, 3,Cecília Horváth1, 3, Péter Kóbor1, 3, Tamás Kovács-Öller2, 3, Béla Völgyi2, 3, Edina Szabó-Meleg2, 3, 4, Péter Buzás1, 3, Ildikó Telkes1, 3
Introduction: Recently, we have identified two patterns of gap junction distribution in the cat retina: one that is eccentricity dependent and is linked to AII amacrine cells, and an eccentricity independent pattern. Objective: Here, we were interested if similar patterns are found in the rat retina.Methods: As a test, we mapped the expression patterns of the homeodomain protein Prox1 and the major neuronal gap junction protein, connexin-36 across the retinal layers and at various retinal locations using fluorescence immunohistochemistry in the rat retina. We analysed the laminar distribution and areal density of the labelled structures. We used the density of Prox1-positive horizontal cells as a measure of eccentricity. Results: We found Prox1 immunoreactivity in the cell bodies of subpopulations of horizontal, bipolar, amacrine and ganglion cells. Connexin-36 plaques were found in the inner plexiform layer of all retinal areas, with the highest density in the ON-sublamina. Here, plaque density correlated significantly with horizontal cell density (r = 0.44, p = 0.05). Conclusions: We found Prox1 immunoreactivity in all neurone types except photoreceptors of the rat retina. The data are compatible with an eccentricity dependent decrease in electrical coupling in the inner plexiform layer.