Temporal contrast adaptation in the input and output signals of salamander retinal ganglion cells.
We investigated how the light-evoked input and output signals of salamander retinal ganglion cells adapt to changes in temporal contrast, i.e., changes in the depth of the temporal fluctuations in the light intensity about the mean. Increasing the temporal contrast sped the kinetics and reduced the sensitivity of both the light-evoked input currents measured at the ganglion cell soma and the output spike trains of the cell. The decline in sensitivity of the input currents after an increase in contrast had two distinct kinetic components with fast (<2 sec) and slow (>10 sec) time constants. The recovery of sensitivity after a decrease in contrast was dominated by a single component with an intermediate (4-18 sec) time constant. Contrast adaptation differed for on and off cells, with both the kinetics and amplitude of the light-evoked currents of off cells adapting more strongly than those of on cells. Contrast adaptation in the input currents of a ganglion cell, however, was unable to account for the extent of adaptation in the output spike trains of the cell, indicating that mechanisms intrinsic to the ganglion cell contributed. Indeed, when fluctuating currents were injected into a ganglion cell, the sensitivity of spike generation decreased with increased current variance. Pharmacological experiments indicated that adaptation of spike generation to the current variance was attributable to properties of tetrodotoxin-sensitive Na(+) channels.
Kim
K J
KJ
Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98195, USA. kerrykim@u.washington.edu
Rieke
F
F
D000200:Action Potentials / Q000187:drug effects; D000221:Adaptation, Ocular / Q000502:physiology*; D000557:Ambystoma; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015350:Contrast Sensitivity / Q000502:physiology*; D004558:Electric Stimulation; D066298:In Vitro Techniques; D008959:Models, Neurological; D010775:Photic Stimulation; D011188:Potassium / Q000378:metabolism; D026902:Potassium Channel Blockers; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D012165:Retinal Ganglion Cells / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D026941:Sodium Channel Blockers; D015222:Sodium Channels / Q000378:metabolism; D013779:Tetrodotoxin / Q000494:pharmacology
D002121:Calcium Channel Blockers; D026902:Potassium Channel Blockers; D026941:Sodium Channel Blockers; D015222:Sodium Channels; D013779:Tetrodotoxin; D011188:Potassium; D002118:Calcium