Schnakenberg J
Institut für Theoretische Physik, Rheinisch-Westfälische Technische Hochschule, Aachen, Federal Republic of Germany.
Biol Cybern. 1989;60(6):421-30. doi: 10.1007/BF00204697.
It is shown that the models for the transduction process in photoreceptors which treat latency and amplification as integrated phenomena ("integrated models") yield time scales for single photon signals ("quantum bumps") which distinctly conflict with the experimentally observed ones for the ventral nerve photoreceptor of Limulus: the ratio of bump duration/latency tB/tlat is predicted by integrated models to be approximately 3 in contrast to the experimental result of approximately 0.5. Moreover, integrated models lead to a predicted value of an extinction rate of approximately 50%, i.e., 50% of the absorbed photons should be expected to cause no signal in the dark adapted state of the cell. In this paper it is shown that separation of latency and amplification in such a way that the latency causing process precedes amplification in the transduction process eliminates these discrepancies. In addition, the separate modeling of latency and amplification resolves the rather large ambiguity in determining the exponent n of the initial signal current J(t) approximately tn reported in the literature to be between n approximately 2 (from noise analysis) up to n approximately 17 (from flash experiments). Two alternative models for the latency part of transduction are suggested which give a qualitatively much better agreement with the experimental histograms of latencies.
结果表明，将潜伏期和放大作为综合现象来处理的光感受器转导过程模型（“综合模型”）得出的单光子信号（“量子脉冲”）时间尺度与鲎腹神经光感受器的实验观测结果明显冲突：综合模型预测的脉冲持续时间/潜伏期之比tB/tlat约为3，而实验结果约为0.5。此外，综合模型得出的消光率预测值约为50%，即预计在细胞暗适应状态下，50%的吸收光子不会产生信号。本文表明，以潜伏期产生过程在转导过程中先于放大的方式将潜伏期和放大分开，可消除这些差异。此外，对潜伏期和放大进行单独建模解决了在确定初始信号电流J(t)≈tn的指数n时存在的相当大的模糊性，文献报道该指数n在约2（来自噪声分析）到约17（来自闪光实验）之间。本文提出了两种转导潜伏期部分的替代模型，它们与潜伏期的实验直方图在定性上有更好的一致性。
