Silveira Luiz Carlos L, Saito Cézar A, da Silva Filho Manoel, Kremers Jan, Bowmaker James K, Lee Barry B
Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, Pará, Brazil; Núcleo de Medicina Tropical, Universidade Federal do Pará, Belém, Pará, Brazil.
Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, Pará, Brazil.
PLoS One. 2014 Nov 18;9(11):e113321. doi: 10.1371/journal.pone.0113321. eCollection 2014.
The howler monkeys (Alouatta sp.) are the only New World primates to exhibit routine trichromacy. Both males and females have three cone photopigments. However, in contrast to Old World monkeys, Alouatta has a locus control region upstream of each opsin gene on the X-chromosome and this might influence the retinal organization underlying its color vision. Post-mortem microspectrophotometry (MSP) was performed on the retinae of two male Alouatta to obtain rod and cone spectral sensitivities. The MSP data were consistent with only a single opsin being expressed in each cone and electrophysiological data were consistent with this primate expressing full trichromacy. To study the physiological organization of the retina underlying Alouatta trichromacy, we recorded from retinal ganglion cells of the same animals used for MSP measurements with a variety of achromatic and chromatic stimulus protocols. We found MC cells and PC cells in the Alouatta retina with similar properties to those previously found in the retina of other trichromatic primates. MC cells showed strong phasic responses to luminance changes and little response to chromatic pulses. PC cells showed strong tonic response to chromatic changes and small tonic response to luminance changes. Responses to other stimulus protocols (flicker photometry; changing the relative phase of red and green modulated lights; temporal modulation transfer functions) were also similar to those recorded in other trichromatic primates. MC cells also showed a pronounced frequency double response to chromatic modulation, and with luminance modulation response saturation accompanied by a phase advance between 10-20 Hz, characteristic of a contrast gain mechanism. This indicates a very similar retinal organization to Old-World monkeys. Cone-specific opsin expression in the presence of a locus control region for each opsin may call into question the hypothesis that this region exclusively controls opsin expression.
吼猴（Alouatta sp.）是新大陆唯一呈现常规三色视觉的灵长类动物。雄性和雌性都有三种视锥光色素。然而，与旧大陆猴不同的是，吼猴在X染色体上每个视蛋白基因的上游有一个基因座控制区，这可能会影响其色觉背后的视网膜组织。对两只雄性吼猴的视网膜进行了死后显微分光光度测定（MSP），以获得视杆和视锥的光谱敏感度。MSP数据与每个视锥中仅表达一种视蛋白一致，电生理数据也与这种灵长类动物表达完全三色视觉一致。为了研究吼猴三色视觉背后视网膜的生理组织，我们使用各种消色差和彩色刺激方案，从用于MSP测量的同一只动物的视网膜神经节细胞进行记录。我们在吼猴视网膜中发现了MC细胞和PC细胞，其特性与之前在其他三色灵长类动物视网膜中发现的类似。MC细胞对亮度变化表现出强烈的相位反应，对彩色脉冲反应很小。PC细胞对颜色变化表现出强烈的紧张性反应，并对亮度变化表现出较小的紧张性反应。对其他刺激方案（闪烁光度法；改变红色和绿色调制光的相对相位；时间调制传递函数）的反应也与在其他三色灵长类动物中记录的反应相似。MC细胞对彩色调制也表现出明显的频率加倍反应，并且在亮度调制反应饱和时伴随着10 - 20 Hz之间的相位提前，这是对比增益机制的特征。这表明其视网膜组织与旧大陆猴非常相似。在每个视蛋白都存在基因座控制区的情况下，视锥特异性视蛋白表达可能会对该区域专门控制视蛋白表达的假说提出质疑。
