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Full-Text Articles in Ophthalmology
Calcium Regulates Vesicle Replenishment At The Cone Ribbon Synapse., Norbert Babai, Theodore M. Bartoletti, Wallace B. Thoreson
Calcium Regulates Vesicle Replenishment At The Cone Ribbon Synapse., Norbert Babai, Theodore M. Bartoletti, Wallace B. Thoreson
Journal Articles: Ophthalmology
Cones release glutamate-filled vesicles continuously in darkness, and changing illumination modulates this release. Because sustained release in darkness is governed by vesicle replenishment rates, we analyzed how cone membrane potential regulates replenishment. Synaptic release from cones was measured by recording postsynaptic currents in Ambystoma tigrinum horizontal or OFF bipolar cells evoked by depolarization of simultaneously voltage-clamped cones. We measured replenishment after attaining a steady state between vesicle release and replenishment using trains of test pulses. Increasing Ca(2+) currents (I(Ca)) by changing the test step from -30 to -10 mV increased replenishment. Lengthening -30 mV test pulses to match the Ca(2+) …
Anion-Sensitive Regions Of L-Type Cav1.2 Calcium Channels Expressed In Hek293 Cells., Norbert Babai, Nataly Kanevsky, Nathan Dascal, George J. Rozanski, Dhirendra P. Singh, Nigar Fatma, Wallace B. Thoreson
Anion-Sensitive Regions Of L-Type Cav1.2 Calcium Channels Expressed In Hek293 Cells., Norbert Babai, Nataly Kanevsky, Nathan Dascal, George J. Rozanski, Dhirendra P. Singh, Nigar Fatma, Wallace B. Thoreson
Journal Articles: Ophthalmology
L-type calcium currents (I(Ca)) are influenced by changes in extracellular chloride, but sites of anion effects have not been identified. Our experiments showed that CaV1.2 currents expressed in HEK293 cells are strongly inhibited by replacing extracellular chloride with gluconate or perchlorate. Variance-mean analysis of I(Ca) and cell-attached patch single channel recordings indicate that gluconate-induced inhibition is due to intracellular anion effects on Ca(2+) channel open probability, not conductance. Inhibition of CaV1.2 currents produced by replacing chloride with gluconate was reduced from approximately 75%-80% to approximately 50% by omitting beta subunits but unaffected by omitting alpha(2)delta subunits. Similarly, gluconate inhibition was …