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Full-Text Articles in Ophthalmology
Feedback From Horizontal Cells To Rod Photoreceptors In Vertebrate Retina., Wallace B. Thoreson, Norbert Babai, Theodore M M. Bartoletti
Feedback From Horizontal Cells To Rod Photoreceptors In Vertebrate Retina., Wallace B. Thoreson, Norbert Babai, Theodore M M. Bartoletti
Journal Articles: Ophthalmology
Retinal horizontal cells (HCs) provide negative feedback to cones, but, largely because annular illumination fails to evoke a depolarizing response in rods, it is widely believed that there is no feedback from HCs to rods. However, feedback from HCs to cones involves small changes in the calcium current (I(Ca)) that do not always generate detectable depolarizing responses. We therefore recorded I(Ca) directly from rods to test whether they were modulated by feedback from HCs. To circumvent problems presented by overlapping receptive fields of HCs and rods, we manipulated the membrane potential of voltage-clamped HCs while simultaneously recording from rods in …
Paired-Pulse Depression At Photoreceptor Synapses., Katalin Rabl, Lucia Cadetti, Wallace B. Thoreson
Paired-Pulse Depression At Photoreceptor Synapses., Katalin Rabl, Lucia Cadetti, Wallace B. Thoreson
Journal Articles: Ophthalmology
Synaptic depression produced by repetitive stimulation is likely to be particularly important in shaping responses of second-order retinal neurons at the tonically active photoreceptor synapse. We analyzed the time course and mechanisms of synaptic depression at rod and cone synapses using paired-pulse protocols involving two complementary measurements of exocytosis: (1) paired whole-cell recordings of the postsynaptic current (PSC) in second-order retinal neurons and (2) capacitance measurements of vesicular membrane fusion in rods and cones. PSCs in ON bipolar, OFF bipolar, and horizontal cells evoked by stimulation of either rods or cones recovered from paired-pulse depression (PPD) at rates similar to …
Kinetics Of Exocytosis Is Faster In Cones Than In Rods., Katalin Rabl, Lucia Cadetti, Wallace B. Thoreson
Kinetics Of Exocytosis Is Faster In Cones Than In Rods., Katalin Rabl, Lucia Cadetti, Wallace B. Thoreson
Journal Articles: Ophthalmology
Cone-driven responses of second-order retinal neurons are considerably faster than rod-driven responses. We examined whether differences in the kinetics of synaptic transmitter release from rods and cones may contribute to differences in postsynaptic response kinetics. Exocytosis from rods and cones was triggered by membrane depolarization and monitored in two ways: (1) by measuring EPSCs evoked in second-order neurons by depolarizing steps applied to presynaptic rods or cones during simultaneous paired whole-cell recordings or (2) by direct measurements of exocytotic increases in membrane capacitance. The kinetics of release was assessed by varying the length of the depolarizing test step. Both measures …