Mechanical analysis for the initial process of stimulus tarnsduction in insect mechano-sensory cell

机械感受是动物与环境相互作用的基本要素，对于理解动物进化至关重要。机械感受主要被认为是一个相当简单和宏观的计划，离子通道变形的膜张力。据报道，在人类和草蛉的耳膜中，机械感受器的巨大高灵敏度为0.1埃，即氢原子直径的十分之一。然而，用位移来表示机械探测器的灵敏度显然是错误的。感觉细胞是将外界能量转化为信息熵的测量工具。灵敏度必须从能量的角度来讨论。所有的感觉细胞都接收一定量的能量，因为任何没有能量成本的测量都会导致麦克斯韦恶魔的热力学不一致。蟋蟀的风感觉细胞的能量阈值被测量为非常小的值，约为4×10^<-21>[焦耳]。这些机械能感受器会在单个分子的布朗运动的震动下产生反应，但机械能转化为细胞反应的途径，尤其是其初始过程，至今仍是我们所不了解的。为了揭示其细胞机制，我们尝试直接测量在布朗运动附近的极弱机械刺激下的感受器电流，通过电压钳电极测量感受器电流，同时也测量毛干的位移。1000米长的头发的毛干在100米处被剪掉，以通过毛干的中空部具有导电性。与作为刺激给出的机械能相比，在100 m剪切轴处响应于10-100 nm位移的电流估计的能量显示出约10^6倍的能量放大。结果提示，离子通道的开闭不是机械感受器细胞能量传递的直接起始过程。

Mechanoreception is a fundamental element of animal-environment interaction and it is essential for the understanding of animal evolution. Mechanoreception has mainly been considered by a rather simple and macroscopic scheme of ionic channels deformed by membrane tension. Enormous high-sensitivities of mechanoreceptors have been reported in the eardrums of human and lacewing as 0.1 Angstrom i.e. one-tenth of a hydrogen atom diameter. It is obviously erroneous, however, to express the sensitivity of mechanical detector by displacement. Sensory cell is a measurement tool that converts external energy to informational entropy. The sensitivity must be discussed in terms of energy. All sensory cells receive a certain amount of energy, because any measurement without energy cost results in the thermodynamic inconsistency of Maxwell's demon. Energy threshold of the wind sensory cells in cricket is measured as very small values about 4×10^<-21> [Joule]. These mechanoreceptors would give rise a response shaken by Brownian motion of a single molecule.Pathway of conversion from mechanical energy to cellular response, particularly of its initial process is still beyond our comprehension. In order to reveal its cellular mechanisms, a direct measurement of membrane current in response to the extremely weak mechanical stimuli near Brownian motion is attempted.The receptor current was measured through a voltage clamp electrode, which also gives displacement to hair shaft. Shaft of a 1000 m long hair is clipped at 100 m to have electrical conduction through the hollow of hair shaft. Amount of energy estimated for the electrical current in response to 10-100 nm displacement at 100 m clipped shaft showed an energy amplification of about 10^6 times when compared to the mechanical energy given as the stimulus. The result suggests that the open-close of ionic channels is not a direct initial process of energy transduction in the mechanoreceptor cell.