Adenosine A2A Receptor Up-Regulates Retinal Wave Frequency via Starburst Amacrine Cells in the Developing Rat Retina

Abstract

BackgroundDeveloping retinas display retinal waves, the patterned spontaneous activity essential for circuit refinement. During the first postnatal week in rodents, retinal waves are mediated by synaptic transmission between starburst amacrine cells (SACs) and retinal ganglion cells (RGCs). The neuromodulator adenosine is essential for the generation of retinal waves. However, the cellular basis underlying adenosine's regulation of retinal waves remains elusive. Here, we investigated whether and how the adenosine A2A receptor (A2AR) regulates retinal waves and whether A2AR regulation of retinal waves acts via presynaptic SACs.Methodology/Principal FindingsWe showed that A2AR was expressed in the inner plexiform layer and ganglion cell layer of the developing rat retina. Knockdown of A2AR decreased the frequency of spontaneous Ca2+ transients, suggesting that endogenous A2AR may up-regulate wave frequency. To investigate whether A2AR acts via presynaptic SACs, we targeted gene expression to SACs by the metabotropic glutamate receptor type II promoter. Ca2+ transient frequency was increased by expressing wild-type A2AR (A2AR-WT) in SACs, suggesting that A2AR may up-regulate retinal waves via presynaptic SACs. Subsequent patch-clamp recordings on RGCs revealed that presynaptic A2AR-WT increased the frequency of wave-associated postsynaptic currents (PSCs) or depolarizations compared to the control, without changing the RGC's excitability, membrane potentials, or PSC charge. These findings suggest that presynaptic A2AR may not affect the membrane properties of postsynaptic RGCs. In contrast, by expressing the C-terminal truncated A2AR mutant (A2AR-ΔC) in SACs, the wave frequency was reduced compared to the A2AR-WT, but was similar to the control, suggesting that the full-length A2AR in SACs is required for A2AR up-regulation of retinal waves.Conclusions/SignificanceA2AR up-regulates the frequency of retinal waves via presynaptic SACs, requiring its full-length protein structure. Thus, by coupling with the downstream intracellular signaling, A2AR may have a great capacity to modulate patterned spontaneous activity during neural circuit refinement.

Blockade of microglial adenosine A2A receptor suppresses elevated pressure‐induced inflammation, oxidative stress, and cell death in retinal cells

“…Previous reports from us and others show that A 2A R is expressed in the retina, including in microglia (Huang et al, ; Liou et al, ; Madeira, Elvas, et al, ; Vindeirinho, Costa, Correia, Cavadas, & Santos, ; Zhong, Yang, Huang, & Luo, ). The expression of A 2A R has been demonstrated to be upregulated in brain chronic noxious conditions (Cunha, ; Vindeirinho et al, ; Wittendorp, Boddeke, & Biber, ).…”

Presynaptic SNAP-25 regulates retinal waves and retinogeniculate projection via phosphorylation

“…Moreover, to promptly increase the PKA activity for SN25b phosphorylation, we applied the A 2A R agonist CGS 21680 (Fig. 3F), shown to enhance A 2A R-cAMP-PKA signaling in retinal neurons (15). We found that overexpression of SN25b in SACs dampened the CGS-induced changes in the fluorescence intensity compared with Ctrl or SN25b-T138A in SACs (Fig.…”

“…All procedures were performed in accordance with protocols approved by the institutional animal care and use committees of National Taiwan University. Immunostaining, retinal explant culture and transfection, live Ca 2+ imaging of retinal waves, and whole-cell voltage-clamp recordings were modified from previous studies (7,15). Detailed procedures regarding plasmid information, imaging of SAC exocytosis, in vivo electroporation, anterograde axonal tracing and tissue processing, analysis of the retinogeniculate projection, RT-qPCR, Western blotting, coimmunoprecipitation, and statistics are described in SI Appendix, SI Materials and Methods.…”

Caffeine Prevents Blood Retinal Barrier Damage in a Model, In Vitro, of Diabetic Macular Edema

“…Except for this latter, the other receptors are present in Müller cells, instead astrocytes and microglia cells express all four receptors. The pericytes express A 1 Rs and A 2A Rs, endothelial cells possess A 2A Rs and A 2B Rs, whereas epithelial cells shown all four receptors [Wan et al, ; Wurm et al, ; Li et al, ; Huang et al, ].…”