Cellular elements for seeing in the dark: voltage-dependent conductances in cockroach photoreceptors

BMC Neuroscience

Research Article

Mikko Vähäsöyrinki¹  Esa-Ville Immonen¹  Matti Weckström¹  Yani Krause¹  Roman Frolov¹  Iikka Salmela¹  Stephan Krause¹ 

[1] Department of Physics, University of Oulu, Oulu, Finland;

关键词: Potassium channel;    Sensory neuron;    Photoreceptor;   

DOI  :  10.1186/1471-2202-13-93

 received in 2012-04-03, accepted in 2012-07-12,  发布年份 2012

来源: Springer

【 摘 要 】

BackgroundThe importance of voltage-dependent conductances in sensory information processing is well-established in insect photoreceptors. Here we present the characterization of electrical properties in photoreceptors of the cockroach (Periplaneta americana), a nocturnal insect with a visual system adapted for dim light.ResultsWhole-cell patch-clamped photoreceptors had high capacitances and input resistances, indicating large photosensitive rhabdomeres suitable for efficient photon capture and amplification of small photocurrents at low light levels. Two voltage-dependent potassium conductances were found in the photoreceptors: a delayed rectifier type (KDR) and a fast transient inactivating type (KA). Activation of KDR occurred during physiological voltage responses induced by light stimulation, whereas KA was nearly fully inactivated already at the dark resting potential. In addition, hyperpolarization of photoreceptors activated a small-amplitude inward-rectifying (IR) current mediated at least partially by chloride. Computer simulations showed that KDR shapes light responses by opposing the light-induced depolarization and speeding up the membrane time constant, whereas KA and IR have a negligible role in the majority of cells. However, larger KA conductances were found in smaller and rapidly adapting photoreceptors, where KA could have a functional role.ConclusionsThe relative expression of KA and KDR in cockroach photoreceptors was opposite to the previously hypothesized framework for dark-active insects, necessitating further comparative work on the conductances. In general, the varying deployment of stereotypical K+ conductances in insect photoreceptors highlights their functional flexibility in neural coding.

【 授权许可】

Unknown   
© Salmela et al.; licensee BioMed Central Ltd. 2012. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.