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Dillon McDevitt, Salvatore L Stella; Mapping the purine circuitry in the zebrafish retina. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2221.
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© ARVO (1962-2015); The Authors (2016-present)
ATP is an important signaling molecule in the vertebrate retina and regulated by a variety of retinal driven mechanisms. However, there is a paucity of information regarding the expression profile of key proteins involved in purinergic signaling in the zebrafish retina. The goal of this study was to map the circuits involved in ATP and adenosine signaling in the zebrafish retina.
Neurochemical circuits were mapped in the zebrafish retina using in situ hybridization techniques and immunohistochemistry. Antibodies targeted to purine receptors (P1 and P2 receptors), components of the purine signaling machinery (vesicular nucleotide transporter (VNUT), 5’-ectonucleotidase, NTDPase-1,-2,-3, and adenosine deaminase) and retinal cell specific markers were used to uncover purine neurochemical and protein signatures in the retina.
In situ hybridization revealed that A1 receptors were weakly expressed in the inner nuclear layer and ganglion cell layer. A2A receptors were highly expressed in all cell layers of the zebrafish retina, and A3 receptors were restricted to the horizontal cell layer. Immunohistochemical evidence identified strong P2X7 receptor expression in the outer retina and ganglion cell layer. NTDPase-1 and -2 were expressed throughout the retina with the strongest expression in the outer and inner retina as described previously. Adenosine deaminase was highly expressed at photoreceptor terminals and faintly in the inner retina. In addition, a likely source of ATP could be derived from VNUT which was localized to both horizontal cells in the outer retina and Müller cells in the inner retina.
Our findings indicate that purinergic circuits are regulated by presence of receptors, enzymes and VNUT expression. Potential ATP pools likely originate from Muller cells in the inner retina and horizontal cells in the outer retina. These findings on receptor expression suggest important roles for purines in modulating specific retinal circuits, including the nocturnally driven rod pathway, and inner retinal circuits. The strong expression profile of both adenosine receptors and ecto-enzymes involved in ATP degradation favors an important role for adenosine modulating retinal circuitry and synaptic inputs in both the inner and outer retina. Taken together, these findings highlight the far reaching modulatory implications of purine-mediated signaling on visual processing in the retina.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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