Journal: The Journal of Physiological Sciences : JPS

Article Title: Acidification of the synaptic cleft of cone photoreceptor terminal controls the amount of transmitter release, thereby forming the receptive field surround in the vertebrate retina

doi: 10.1007/s12576-012-0220-0

Figure Lengend Snippet: Surround illumination augments cone I Ca. A I Ca of a cone in newt retinal slice was recorded under the whole-cell voltage clamp condition at a holding potential of −40 mV. The Cs+-based pipette solution contained 20 mM BAPTA to minimize any Ca2+-activated currents. Depolarizing voltage steps from −50 mV to +8 mV (2 mV step) induced inward currents. I Ca of a cone in newt retinal slice was recorded under the whole-cell voltage clamp condition at a holding potential of −40 mV. The I Ca was abolished by extracellular cadmium, a blocker of Ca channels (plots with open squares shown in the right panel). Five representative traces, voltage-clamped at −40, −26, −24, −16 and −4 mV, are shown. Diffuse illumination (4,000 μm in diameter used for ‘surround illumination’: shorter bar) was applied every 4 s, while the spot illumination (30 μm in diameter: top bar) was maintained. An additional 2-mV depolarization was applied to mimic an ephaptic (field) effect (external voltage drop) after withdrawing the diffuse illumination. Note that at −4 mV (pink trace), diffuse illumination evoked an inward current, while a +2-mV pulse evoked an outward current. The current amplitude was sampled at the time indicated by the symbols to construct the I–V curves shown in B a and B b. B a Leak-subtracted I–V curve of cone I Ca in the presence of the spot (filled squares) and during diffuse illumination (open squares). Inset shows activation curves fitted to the Boltzmann function derived from the I–V curves. B b Leak-subtracted I–V curve of cone I Ca in the presence of the spot light (filled circles) and during a +2-mV depolarizing pulse (open circles). Inset shows activation curves fitted to the Boltzmann function derived from the I–V curves. Boxed inset isolation method of I–V curves of cone I Ca obtained from a different cone in A. Top The I–V curvers were obtained in the control solution [filled squares (1)] and in a 3 mM Cd containing solution [open squares (2)]. Bottom (open circles) I–V curve of the cone I Ca obtained by subtracting the I–V curve in a 3 mM Cd containing solution from that in the control solution [(1)–(2)]. Filled circles I–V curve obtained by subtracting the I–V curve from the extrapolated leakage current from that in the control solution [(1)–(3)] (from Hirasawa and Kaneko [28])

Article Snippet: B c Activation curves fitted to the Boltzmann function derived from the data in B b (from Hirasawa and Kaneko [28]).

Techniques: Transferring, Construct, Activation Assay, Derivative Assay, Isolation, Control

Journal: The Journal of Physiological Sciences : JPS

Article Title: Acidification of the synaptic cleft of cone photoreceptor terminal controls the amount of transmitter release, thereby forming the receptive field surround in the vertebrate retina

doi: 10.1007/s12576-012-0220-0

Figure Lengend Snippet: Modulation of cone I Ca by a high-pH solution applied to the cone terminal layer. A Alkalinized Ringer’s solution (pH 9.0) was focally ejected to cone synaptic terminal layer in newt retinal slice. The cone was voltage-clamped at various voltages in the range of −50 to +6 mV in 8-mV steps. The representative four traces, voltage clamped at −42, −26, −18 and +6 mV, are shown. The current was sampled at the points marked by a symbol to construct the I–V curves shown in B. Small spot illumination (30 μm in diameter) was maintained throughout. B Top leak-subtracted I–V curve of cone I Ca in normal Ringer’s solution (pH 7.4, filled squares) and in response to a high-pH solution (pH 9.0, open circles). Bottom activation curves derived from the I–V curves fitted to the Boltzmann function (from Hirasawa and Kaneko [28])

Article Snippet: B c Activation curves fitted to the Boltzmann function derived from the data in B b (from Hirasawa and Kaneko [28]).

Techniques: Construct, Activation Assay, Derivative Assay

Journal: The Journal of Physiological Sciences : JPS

Article Title: Acidification of the synaptic cleft of cone photoreceptor terminal controls the amount of transmitter release, thereby forming the receptive field surround in the vertebrate retina

doi: 10.1007/s12576-012-0220-0

Figure Lengend Snippet: Cone I Ca and its surround response recorded in a superfusate enriched with HEPES. A Effects of 10 mM HEPES-enriched buffer on cone I Ca and surround response. The cone in newt retinal slice was depolarized from the holding voltage of −40 to −26 mV. Diffuse light illumination (4,000 μm in diameter used for surround illumination: shorter bar) was given during the step depolarization in the presence of a small spot light (30 μm in diameter: top bar). Changing the superfusate from control solution (black trace) to one supplemented with 10 mM HEPES increased cone I Ca and prevented any additional inward current upon surround illumination (gray trace). Inset shows horizontal cell (HC) responses to a large light spot (4,000 μm in diameter) in the control solution and in the solution enriched with HEPES. B a Reversible effects of 10 mM HEPES-enriched buffer on cone I Ca and surround response. The small spot light (30 μm in diameter: top bars) was kept on throughout. Diffuse light illumination (4,000 μm in diameter: shorter bar) was given during the step depolarization in the presence of the small spot. The cone was held at −40 mV and polarized to voltages ranging from −50 to +6 mV in 8 mV steps. The current traces before, during and after application of 10 mM HEPES-enriched buffer. The recording sequence was left column (−34, −18 and −10 mV) followed by the middle column and finally the right column. The leak conductance of 2.26 nS did not change either in the HEPES-containing solution or during the washout (current traces at −34 mV). In the HEPES-containing solution, inward I Ca in darkness was reversibly increased, and the surround response was reversibly suppressed (current traces at −18 and −10 mV). Symbols denote the sampling points for calculation of the I–V curves of I Ca in B b. In the control solution, the inward current produced by I Ca was counterbalanced by the outward leak current (at −18 and −10 mV in the control and washout solutions). B b I–V curves of cone I Ca recorded in B a. The leak conductance was subtracted. Filled and open squares in the control solution without and with surround illumination, respectively; filled and open gray circles in the HEPES-containing solution without and with surround illumination, respectively. Inset shows the voltage dependence of the surround response in the control solution (filled squares) and in the HEPES-containing solution (open circles). B c Activation curves fitted to the Boltzmann function derived from the data in B b (from Hirasawa and Kaneko [28])

Article Snippet: B c Activation curves fitted to the Boltzmann function derived from the data in B b (from Hirasawa and Kaneko [28]).

Techniques: Control, Sequencing, Sampling, Produced, Activation Assay, Derivative Assay