Akula James D, Lyubarsky Arkady L, Naarendorp Frank
Department of Psychology, Northeastern University, Boston, MA 02115, USA.
Vis Neurosci. 2003 Mar-Apr;20(2):109-17. doi: 10.1017/s0952523803202029.
In the retina of rat, cones make up approximately 0.85% of the photoreceptor population: 93% of these cones contain a midwave-sensitive pigment, the rest expresses a short-wave-sensitive pigment (Szel & Rohlich, 1992). We used normal adult Long Evans rats to determine the spectral sensitivity of the cone-driven electroretinogram (ERG) b-wave and its absolute sensitivity at lambda(max) of the cone pigments. ERGs were recorded at the cornea of anesthetized animals under dark- and light-adapted conditions. Rod responses were suppressed by steady rod-saturating orange backgrounds and/or by a flashed "white" background. Cone-driven b-waves were evoked by "white" or narrowband full-field stimuli of varying intensity. The action spectrum for the cone b-wave indicates the presence of an absorbance peak at 510 nm; a second, twofold lower, peak was found at 360 nm (after correction for transmittance by the lens). Chromatic adaptation experiments strongly suggest that retinal responses to midwave and UV stimuli are mediated by a single cone type. On a background producing approximately 17,000 R* rod(-1) s(-1), which completely suppressed the saturated a-wave, the absolute sensitivity of the cone b-wave was 18 nV photon(-1) microm2 at 510 nm and 4 nV photon(-1) microm2 at 360 nm which is 20-30 times higher than for the mouse. It is suggested that the relatively large number of on-cone bipolar cells in the retina of rat is responsible for the remarkable sensitivity of the cone b-wave.
在大鼠视网膜中，视锥细胞约占光感受器总数的0.85%：其中93%的视锥细胞含有中波敏感色素，其余的则表达短波敏感色素（塞尔和罗利克，1992年）。我们使用正常成年朗-埃文斯大鼠来确定视锥细胞驱动的视网膜电图（ERG）b波的光谱敏感性及其在视锥色素λ（max）处的绝对敏感性。在麻醉动物的角膜上于暗适应和明适应条件下记录ERG。通过稳定的使视杆细胞饱和的橙色背景和/或闪烁的“白色”背景来抑制视杆细胞反应。视锥细胞驱动的b波由不同强度的“白色”或窄带全视野刺激诱发。视锥细胞b波的作用光谱表明在510nm处存在一个吸收峰；在360nm处发现了第二个峰值，其强度低两倍（经晶状体透过率校正后）。颜色适应实验强烈表明，视网膜对中波和紫外线刺激的反应是由单一视锥细胞类型介导的。在产生约17,000R*视杆细胞-1秒-1的背景下，该背景完全抑制了饱和a波，视锥细胞b波在510nm处的绝对敏感性为18nV光子-1微米2，在360nm处为4nV光子-1微米2，这比小鼠高20 - 30倍。有人认为，大鼠视网膜中相对大量的on-视锥双极细胞是视锥细胞b波具有显著敏感性的原因。
