The Journal of neuroscience : the official journal of the Society for Neuroscience
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 of release revealed two kinetic components to the increase in exocytosis as a function of the duration of a step depolarization. In addition to slow sustained components in both cell types, the initial fast component of exocytosis had a time constant ofcones, >10-fold faster than that of rods. Rod/cone differences in the kinetics of release were substantiated by a linear correlation between depolarization-evoked capacitance increases and EPSC charge transfer. Experiments on isolated rods indicate that the slower kinetics of exocytosis from rods was not a result of rod-rod coupling. The initial rapid release of vesicles from cones can shape the postsynaptic response and may contribute to the faster responses of cone-driven cells observed at light offset.
Animals, Benzothiadiazines, Dose-Response Relationship, Radiation, Electric Capacitance, Electric Stimulation, Excitatory Postsynaptic Potentials, Exocytosis, In Vitro Techniques, Kinetics, Patch-Clamp Techniques, Retinal Cone Photoreceptor Cells, Retinal Rod Photoreceptor Cells, Salamandra, Synaptic Transmission, Time Factors
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Rabl, Katalin; Cadetti, Lucia; and Thoreson, Wallace B., "Kinetics of exocytosis is faster in cones than in rods." (2005). Journal Articles: Ophthalmology. Paper 56.