The Journal of Neuroscience, January 11, 2006, ():
Modulation by Brain Natriuretic Peptide of GABA Receptors on Rat Retinal ON-Type Bipolar Cells
J. Neurosci. Yu et al.
26: 696
Supplemental data
Files in this Data Supplement:
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Supplemental material
- supplemental material
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Supplemental Figure 1. Calibration of changes in [Ca2+]i. Fluorescence intensities at 340 and 380 nM (F 340 and F380) were first monitored for 4 min, which was followed by measuring those in nominal Ca2+-free Ringer’s added by 1 µM ionomycin and 10 mM EGTA. The decrease in [Ca2+]i resulted in a decline in the F340/F380 ratio. When 20 mM Ca2+-containing Ringer’s with 1 µM ionomycin was applied, the ratio significantly increased. The timing of application of different extracellular solutions is indicated by the bar at the bottom.
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Supplemental Figure 2. Effects of BNP on bipolar cells of increasing concentration. A, In this cell for which 50 nM BNP-responsive cell, application of 200 nM BNP induced a larger current. Note that the currents emerged with much delay. B, In this 50 nM BNP-non-responsive cell, BNP of either 100 nM or 200 nM still failed to induce currents.
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Supplemental Figure 3. A schematic diagram that shows the putative signal pathways mediating BNP-induced reduction of GABA currents of rat ON type bipolar cells. BNP activates NPR-A, thus causing an increase of intracellular cGMP levels by stimulating pGC, which in turn activates the cGMP/PKG pathway. Activation of PKG leads to an increase in calcium release from intracellular stores mediated through the ryanodine sensitive pathway, and the increased intracellular concentration of calcium up-regulates the activity of calmodulin, which reduces GABA currents. Increased intracellular cGMP levels could make more cGMP-gated channels open, resulting in generation of an inward current. PDE on the membrane degrades cGMP to 5’-GMP, keeping a dynamic equilibrium of intracellular cGMP levels. R-A, natriuretic peptide receptor A; GABAA-R, GABAA receptor; RyR, ryanodine receptor; CaM, calmodulin; PDE, phosphodiesterase; PKG, cGMP-dependent protein kinase G; GTP, guanosine triphosphate; pGC, particle guanylyl cyclase; cGMP, guanosine-3’:5’-cyclic monophosphate; CGC, cGMP-gated channel; +, activation; -, inhibition.
