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首页> 外文期刊>BMC Neuroscience >Cellular elements for seeing in the dark: voltage-dependent conductances in cockroach photoreceptors
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Cellular elements for seeing in the dark: voltage-dependent conductances in cockroach photoreceptors

机译：在黑暗中看到的细胞元素：蟑螂感光器中的电压依赖性电导

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Background The 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. Results Whole-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. Conclusions The 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.
机译：背景技术在昆虫感光器中，电压依赖性电导在感觉信息处理中的重要性已得到充分确立。在这里，我们介绍了蟑螂（Periplaneta americana）的感光细胞的电学特性，这是一种夜间昆虫，具有适用于昏暗光线的视觉系统。结果全细胞膜片钳光感受器具有高电容和输入电阻，表明较大的光敏横纹适合于在低光照水平下有效捕获光子并放大小光电流。在感光器中发现了两种电压依赖性钾电导：延迟整流型（KDR）和快速瞬态失活型（KA）。 KDR的激活发生在光刺激引起的生理电压反应期间，而KA在黑暗的静息电位下已几乎完全失活。另外，感光体的超极化激活了至少部分地由氯介导的小幅度向内整流（IR）电流。计算机模拟表明，KDR通过对抗光诱导的去极化并加快膜时间常数来塑造光响应，而KA和IR在大多数细胞中的作用微不足道。但是，在较小且快速适应的感光器中发现了较大的KA电导，其中KA可能具有功能性作用。结论蟑螂光感受器中KA和KDR的相对表达与先前假设的暗活性昆虫构架相反，因此有必要在电导上进行进一步的比较工作。通常，在昆虫光感受器中刻板的K + 电导的变化部署突显了它们在神经编码中的功能灵活性。

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