title: The contribution of Shaker K+ channels to the information capacity of Drosophila photoreceptors.
abstract: An array of rapidly inactivating voltage-gated K+ channels is distributed throughout the nervous systems of vertebrates and invertebrates. Although these channels are thought to regulate the excitability of neurons by attenuating voltage signals, their specific functions are often poorly understood. We studied the role of the prototypical inactivating K+ conductance, Shaker, in Drosophila photoreceptors by recording intracellularly from wild-type and Shaker mutant photoreceptors. Here we show that loss of the Shaker K+ conductance produces a marked reduction in the signal-to-noise ratio of photoreceptors, generating a 50% decrease in the information capacity of these cells in fully light-adapted conditions. By combining experiments with modelling, we show that the inactivation of Shaker K+ channels amplifies voltage signals and enables photoreceptors to use their voltage range more effectively. Loss of the Shaker conductance attenuated the voltage signal and induced a compensatory decrease in impedance. Our results demonstrate the importance of the Shaker K+ conductance for neural coding precision and as a mechanism for selectively amplifying graded signals in neurons, and highlight the effect of compensatory mechanisms on neuronal information processing.
authors.affiliation: Physiological Laboratory, University of Cambridge, Cambridge CB2 3EG, UK.
authors.forename: Jeremy E
authors.initials: JE
authors.lastname: Niven
authors.forename: Mikko
authors.initials: M
authors.lastname: Vähäsöyrinki
authors.forename: Mika
authors.initials: M
authors.lastname: Kauranen
authors.forename: Roger C
authors.initials: RC
authors.lastname: Hardie
authors.forename: Mikko
authors.initials: M
authors.lastname: Juusola
authors.forename: Matti
authors.initials: M
authors.lastname: Weckström
mesh_terms: D000818:Animals; D002712:Chlorides / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000166:cytology* / Q000235:genetics / Q000378:metabolism*; D004553:Electric Conductivity; D015640:Ion Channel Gating; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D017956:Photoreceptor Cells, Invertebrate / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D051637:Shaker Superfamily of Potassium Channels; D015398:Signal Transduction
chemical_list: D002712:Chlorides; D029721:Drosophila Proteins; D015221:Potassium Channels; C496929:Sh protein, Drosophila; D051637:Shaker Superfamily of Potassium Channels; D011188:Potassium