Fyhrquist N, Govardovskii V, Leibrock C, Reuter T
Department of Biosciences, University of Helsinki, Finland.
Vision Res. 1998 Feb;38(4):483-6. doi: 10.1016/s0042-6989(97)00177-6.
Behavioural experiments and ganglion cell recordings indicate that the visual sensitivity of dark-adapted toads is limited by the occurrence of spontaneous isomerization-like noise events in the rods. The frequency of these "false photons" has previously been studied (with micropipette recording) in the toad species Bufo marinus, while the behavioural thresholds were determined using Bufo bufo toads. Thus, it was necessary to check that the noise event frequency is roughly the same in these two species. Here we show that it is, in both species, close to 0.02 events per second and rod (at 22 degrees C). Using microspectrophotometry we further show that the absorption spectra of these two rhodopsins are very similar, peaking around 503.3 and 501.8 nm for B. marinus and B. bufo, respectively.
行为实验和神经节细胞记录表明，暗适应蟾蜍的视觉敏感度受视杆细胞中自发异构化样噪声事件的限制。此前已对海蟾蜍（Bufo marinus）这一物种的这些“假光子”频率进行了研究（使用微吸管记录），而行为阈值则是通过中华蟾蜍（Bufo bufo）确定的。因此，有必要检查这两个物种中的噪声事件频率是否大致相同。在此我们表明，在这两个物种中，该频率均接近每秒0.02次事件/视杆细胞（在22摄氏度时）。使用显微分光光度法，我们进一步表明，这两种视紫红质的吸收光谱非常相似，海蟾蜍和中华蟾蜍的峰值分别约为503.3纳米和501.8纳米。
