Signaling mechanism for modulation by ATP of glycine receptors on rat retinal ganglion cells

Abstract

ATP modulates voltage- and ligand-gated channels in the CNS via the activation of ionotropic P2X and metabotropic P2Y receptors. While P2Y receptors are expressed in retinal neurons, the function of these receptors in the retina is largely unknown. Using whole-cell patch-clamp techniques in rat retinal slice preparations, we demonstrated that ATP suppressed glycine receptor-mediated currents of OFF type ganglion cells (OFF-GCs) dose-dependently, and the effect was in part mediated by P2Y1 and P2Y11, but not by P2X. The ATP effect was abolished by intracellular dialysis of a Gq/11 protein inhibitor and phosphatidylinositol (PI)-phospholipase C (PLC) inhibitor, but not phosphatidylcholine (PC)-PLC inhibitor. The ATP effect was accompanied by an increase in [Ca2+]i through the IP3-sensitive pathway and was blocked by intracellular Ca2+-free solution. Furthermore, the ATP effect was eliminated in the presence of PKC inhibitors. Neither PKA nor PKG system was involved. These results suggest that the ATP-induced suppression may be mediated by a distinct Gq/11/PI-PLC/IP3/Ca2+/PKC signaling pathway, following the activation of P2Y1,11 and other P2Y subtypes. Consistently, ATP suppressed glycine receptor-mediated light-evoked inhibitory postsynaptic currents of OFF-GCs. These results suggest that ATP may modify the ON-to-OFF crossover inhibition, thus changing action potential patterns of OFF-GCs.

Müller glia fused with adult stem cells undergo neural differentiation in human retinal models

“…Increased differentiation might be assessed in the future not only by analyzing the voltage channels after ATP stimulation, but also by measuring the response of Cannabinoid, P2 £ 7 or glycine receptors. 71,72 Even if we observed neural electrophysiological features, the expression of the pan-neuronal marker TUJ1 together with the development of a stable resting membrane potential and soma polarization suggest that the differentiation towards a neuronal phenotype has initiated, but is not yet completed after 48h. Glycosylation levels can change in the neural stem cells along with the fate conversion, and glycosylation can prime the astroglia towards a ganglion cell fate.…”

“…Increased differentiation might be assessed in the future not only by analyzing the voltage channels after ATP stimulation, but also by measuring the response of Cannabinoid, P2 × 7 or glycine receptors. 71 , 72 …”

Activation of retinal glial (Müller) cells by extracellular ATP induces pronounced increases in extracellular H+ flux

“…The lack of an effect by adenosine, coupled with the reduction of the ATP-induced increase in H+ flux by PPADS and suramin and activation by UTP and ADP, suggest that the changes in H+ flux are mediated by activation of metabotropic P2Y receptors known to be present on these cells [ 27 ]. We also examined the effect of the compound MRS 2365, reported to be a selective agonist of P2Y1 receptors ([ 28 , 29 ]), on H+ flux from isolated Müller cells. In seven cells tested, 1 μM MRS 2365 increased the signal from H+-selective self-referencing sensors from a pre stimulus level of 53 ± 6 μV to 253 ± 65 μV (p = 0.012); in the same cells, 10 μM ATP applied after wash out of MRS 2365 increased the signal associated with H+ flux from 99 ± 6 μV to 453 ± 6 μV (p = 0.005).…”

Orexin-A Suppresses Signal Transmission to Dopaminergic Amacrine Cells From Outer and Inner Retinal Photoreceptors

“…Retina dissection, electrophysiologic recording, infrared differential interference contrast (IR-DIC) and fluorescence imaging, and light stimulation were performed as described previously. 14 , 20 , 34 , 35 Briefly, the retina was dissected under dim red light and was then placed with the photoreceptor side down in a recording chamber mounted on the stage of an upright conventional fluorescence microscope. Oxygenated extracellular medium continuously perfused the recording chamber, which was kept in darkness for approximately 1 hour prior to recording.…”

“… 34 Cell-attached activity was recorded from ipRGCs using an HEKA patch-clamp amplifier and data acquisition system (HEKA, Lambrecht, Germany). 34 , 35 A 3-second duration light pulse with a peak wavelength of 470 nm was delivered to the retina either through the objective lens (for some DAC recordings and all ipRGC recordings) 20 or via the microscope condenser (for some DAC recordings). 14 …”