@article{29fe0ce984594bf0951d07d19ed1c4b6,
title = "Intracellular cesium separates two glutamate conductances in retinal bipolar cells of goldfish",
abstract = "The responses of depolarizing bipolar cells to glutamate were investigated in the superfused isolated goldfish retina. In intracellular recordings with potassium-filled microelectrodes, glutamate hyperpolarized cells but did not alter the net input conductance. In recordings with cesium-filled microelectrodes, the glutamate-evoked hyperpolarization was associated with a net conductance decrease. In the presence of internal cesium, glutamate action had the same reversal potential as the actions of the glutamate analog 2-amino-4-phosphonobutyrate (APB) and the rod transmitter, suggesting that all three of these substances act at the same class of receptor. We propose that glutamate acts both at the APB-sensitive receptor that mediates rod inputs and at another receptor type that produces a conductance increase, is blocked by cesium, and may mimic the action of the cone transmitter.",
keywords = "Bipolar cell Retina Synaptic transmission Glutamate APB Goldfish Carassius auratus",
author = "Scott Nawy and Copenhagen, {David R.}",
note = "Funding Information: reversalp otentialo f appliedg lutamate( Hablitz the reversalpotentialof cone inputs to DBCs & Langmoen, 1982)o r evoked EPSPs (Hablitz (Saito et al., 1978,1979;Kaneko& Tachibana, & Langmoen, 1982;B rown & Johnston, 1983). 1978) support the existenceof at least one Although the microelectrodesin this present glutamate-gatedconductance(assumingcones study had higher input resistancest han mi-release glutamate) with a reversal potential croelectodesu sedi n previouss tudies,p roviding that is more negativethan the dark potential. a potentially greaterb arrier to the diffusion of Although current through such a conductance cesiumo ut of the electrodea nd into the cell, a could be carriedbyeitherchlorideorpotassium comparisono f the membranep ropertieso f cells ions, our ability to block the APB-insensitive recordedw ith cesiuma nd potassiumm icroelec-responsewithcesiumsuggststhatthe current is trodes suggestse nough cesium diffused out to carried predominantlyby potassiumions.Con-affect channelsi n the DBCs. The input resis-ventionalglutamateresponsesin other neurons tance of cells impaled with cesium-fillede lec-are carried by sodium and potassium ions, trodes was about twice the resistanceo f cells reversenear0mV, and are readily supportedby recorded with potassium-fillede lectrodes.In cesium(Mayer & Westbrook, 1987).Thus, the addition, the averaged ark resting potential of proposed glutamateresponsein DBCs differs cellsr ecordedw ith cesium-filledm icroelectrodes from conventionalresponsesin its ion selectiv-was about 10m V less negative than cells ity, and thereforein its reversalpotential,and recordedw ith potassium-fillede lectrodes.B oth susceptibilityto cesiumblock. of these observationsa re consistentw ith the idea that enough cesiumh ad enteredt he cells Takahashi and D. Dixon for critical readings of the Acknowiedgemen~s-We thank Drs R. A. J. Lester, K. to block, at least partially, voltage-dependent manuscript. We thank Joan Wedell for help with the and/or glutamate-gatecdo nductances. illustrationsT. his work was supportedb y grantsf rom NIH There are severalm echanismsb y which ce-(EY 01869a nd EY 07058). sium might block a glutamate-evokecdo nduc-",
year = "1990",
doi = "10.1016/0042-6989(90)90105-T",
language = "English (US)",
volume = "30",
pages = "967--972",
journal = "Vision research",
issn = "0042-6989",
publisher = "Elsevier Ltd",
number = "7",
}