Journal: Neural Regeneration Research

Article Title: Topical administration of GLP-1 eyedrops improves retinal ganglion cell function by facilitating presynaptic GABA release in early experimental diabetes

doi: 10.4103/NRR.NRR-D-24-00001

Figure Lengend Snippet: GLP-1 enhances mIPSCs of normal RGCs in a concentration-dependent manner. (A) Schematic illustration of the experimental protocol for continuously recording mIPSCs from an RGC for 28 minutes. Data were statistically analyzed at the following time periods: 6–9 minutes of Ctrl, 15–18 minutes of GLP-1 application, and 25–28 minutes of washout. (B) Micrographs of the same retinal section taken with an infrared interferometric phase microscope (left) and a fluorescence microscope (right), showing a representative Lucifer yellow dye-filled ON-RGC with dendrite arborizations in the proximal part of the IPL. Scale bar: 10 μm. (C) Representative current traces showing the effect of 10 nM GLP-1 on GABAergic mIPSCs of an ON-RGC (top trace) and the mIPSC currents on an expanded time scale (bottom traces). (D, E) Scatterplots of mIPSC frequency and amplitude from individual recordings, demonstrating a GLP-1-mediated reversible increase in mIPSC frequency (D), but not amplitude (E) in ON-RGCs ( n = 10). (F) Representative micrographs showing a typical Lucifer yellow-filled OFF-RGC with dendrite arborizations in the distal part of the IPL. Scale bar: 10 μm. (G) Current traces showing the effect of GLP-1 on mIPSCs of an OFF-RGC. (H, I) GLP-1 reversibly incrased mIPSC frequency (H), but not amplitude (I) in OFF-RGCs ( n = 9). (J) Normalized mIPSC frequency recorded in 26 RGCs. (K) Increases in mIPSC frequencies under GLP-1 concentrations of 5, 10, and 100 nM, but not 0.05, 0.5, or 1000 nM. All data normalized to the control values obtained before GLP-1 application. Cell numbers are marked inside the bars in panels J and K. Data are presented as mean ± SEM; * P < 0.05, ** P < 0.01, *** P < 0.001, determined by one-way repeated measures analysis of variance with Tukey’s multiple comparisons test (D, E, H–J) and paired t -test (K). ACSF: Artificial cerebrospinal fluid; Ctrl: control; D-APV: D-2-amino-5-phosphonopentanoic acid; DNQX: 6,7-dinitroquinoxaline-2,3-dione; GABA: γ-aminobutyric acid; GCL: ganglion cell layer; GLP-1: glucagon-like peptide-1; INL: inner nuclear layer; IPL: inner plexiform layer; mIPSC: miniature inhibitory postsynaptic current; RGC: retinal ganglion cell; TTX: tetrodotoxin.

Article Snippet: To isolate GABAergic miniature inhibitory postsynaptic currents (mIPSCs), QX-314 (4 mM) was included in the internal solution to block rapid Na + currents, and the following drugs were added to the perfusate: tetrodotoxin (TTX, 0.5 μM; Tocris Bioscience, Ellisville, MO, USA), to eliminate spontaneous action potentials; and strychnine (10 μM; Sigma-Aldrich), 6,7-dinitroquinoxaline-2,3-dione (DNQX, 10 μM; Sigma-Aldrich), and D-2-amino-5-phosphonopentanoic acid (D-APV, 50 μM; Tocris Bioscience), to block glycine receptors, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainic acid receptors, and N-methyl-D-aspartic acid receptors, respectively.

Techniques: Concentration Assay, Microscopy, Fluorescence, Control

Journal: Neural Regeneration Research

Article Title: Topical administration of GLP-1 eyedrops improves retinal ganglion cell function by facilitating presynaptic GABA release in early experimental diabetes

doi: 10.4103/NRR.NRR-D-24-00001

Figure Lengend Snippet: GLP-1-induced increase in mIPSC frequency is blocked by Ex-9-39. (A) Representative recordings of an RGC (top trace) after the application of TTX + DNQX + D-APV + strychnine, showing Ex-9-39-mediated blockage of GLP-1-induced changes in mIPSC frequency. The bottom traces (A1–A5) show the currents on an expanded time scale. A1, control condition; A2, GLP-1 application; A3, washout; A4, Ex-9-39 application; and A5, Ex-9-39 + GLP-1 application. (B, C) Bar charts showing statistical analyses of the mIPSC frequency (B) and amplitude (C) ( n = 8) under the different conditions. Data (normalized by the Ctrl group) are presented as mean ± SEM; **** P < 0.0001, determined by one-way repeated measures analysis of variance with Tukey’s multiple comparisons test. Ctrl: Control; D-APV: D-2-amino-5-phosphonopentanoic acid; DNQX: 6,7-dinitroquinoxaline-2,3-dione; Ex-9-39: exendin-9-39, GLP-1 receptor antagonist; GLP-1: glucagon-like peptide-1; mIPSC: miniature inhibitory postsynaptic current; RGC: retinal ganglion cell; TTX: tetrodotoxin.

Article Snippet: To isolate GABAergic miniature inhibitory postsynaptic currents (mIPSCs), QX-314 (4 mM) was included in the internal solution to block rapid Na + currents, and the following drugs were added to the perfusate: tetrodotoxin (TTX, 0.5 μM; Tocris Bioscience, Ellisville, MO, USA), to eliminate spontaneous action potentials; and strychnine (10 μM; Sigma-Aldrich), 6,7-dinitroquinoxaline-2,3-dione (DNQX, 10 μM; Sigma-Aldrich), and D-2-amino-5-phosphonopentanoic acid (D-APV, 50 μM; Tocris Bioscience), to block glycine receptors, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainic acid receptors, and N-methyl-D-aspartic acid receptors, respectively.

Techniques: Control