title: Frequency-selective transmission of graded signals in large monopolar neurons of blowfly Calliphora vicina compound eye.
abstract: The functional roles of voltage-gated K(+)(Kv) channels in visual system interneurons remain poorly studied. We have addressed this problem in the large monopolar cells (LMCs) of the blowfly Calliphora vicina, using intracellular recordings and mathematical modeling methods. Intracellular recordings were performed in two cellular compartments: the synaptic zone, which receives input from photoreceptors, and the axon, which provides graded potential output to the third-order visual neurons. Biophysical properties of Kv conductances in the physiological voltage range were examined in the dark with injections of current in the discontinuous current-clamp mode. Putative LMC types 1/2 and 3 (L1/2 and L3, respectively) had dissimilar Kv channelomes: L1/2 displayed a prominent inactivating Kv conductance in the axon, while L3 cells were characterized by a sustained delayed-rectifier Kv conductance. To study the propagation of voltage signals, the data were incorporated into the previously developed mathematical model. We demonstrate that the complex interaction between the passive membrane properties, Kv conductances, and the neuronal geometry leads to a resonance-like filtering of signals with peak frequencies of transmission near 15 and 40 Hz for L3 and L1/2, respectively. These results point to distinct physiological roles of different types of LMCs.
authors: Centre for Molecular Materials Research, Biophysics, University of Oulu, Oulu, Finland juha.rusanen@oulu.fi.
authors: Juha
authors: J
authors: Rusanen
authors: Centre for Molecular Materials Research, Biophysics, University of Oulu, Oulu, Finland.
authors: Matti
authors: M
authors: Weckström
mesh_terms: D000200:Action Potentials; D000818:Animals; D054910:Compound Eye, Arthropod / Q000166:cytology / Q000502:physiology*; D004175:Diptera; D019476:Insect Proteins / Q000378:metabolism; D009474:Neurons / Q000378:metabolism / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated / Q000378:metabolism
chemical_list: D019476:Insect Proteins; D024642:Potassium Channels, Voltage-Gated
keywords: compound eye; graded potential; lamina; large monopolar cell; potassium channel; visual system