Figure 4. Evidence that the gamma-aminobutyric acid_A receptor (GABA_AR) agonist muscimol, the antagonist picrotoxin and the GABA_Aρ antagonist 1,2,5,6-tetrahydropyridin-4-yl) methylphosphinic acid (TPMPA) can modify the intracellular calcium concentration ([Ca²⁺]i) in the cultured human RPE. A: Muscimol (100 μM) increased the [Ca²⁺]i in cultured human RPE cells in buffer with Ca²⁺ (paired t-test, p<0.05). B: Pretreatment with picrotoxin (300 μM) completely inhibited the muscimol (100 μM) induced increase of [Ca²⁺]i in buffer with Ca²⁺. C: Pretreatment with TPMPA (500 μM) completely blocked the muscimol (100 μM) induced increase of [Ca²⁺]i in buffer with Ca²⁺. D: Muscimol (100 μM) increased the [Ca²⁺]i in cultured human RPE cells in buffer without Ca²⁺ (paired t-test, p<0.05). E: Pretreatment with picrotoxin (300 μM) completely inhibited the muscimol (100 μM) induced increase of [Ca²⁺]i in buffer without Ca²⁺. F: Pretreatment with TPMPA (500 μM) completely blocked the muscimol (100 μM) induced increase of [Ca²⁺]i in buffer without Ca²⁺. Left, representative images (1, 8, and 15 images were acquired, respectively). Right, fluorescent intensity in the images acquired before and after muscimol application. The red bar represents the time when muscimol was added. FI represents the fluorescence intensity color scale, with the direction of the arrow indicating higher intensity. *indicates a p<0.05, and ** indicates a p<0.01, compared to the baseline, paired t-test, n=5 for each group.