Data from: Co-expression of two subtypes of melatonin receptor on rat M1-type intrinsically photosensitive retinal ganglion cells

Intrinsically photosensitive retinal ganglion cells (ipRGCs) are involved in circadian and other non-image forming visual responses. An open question is whether the activity of these neurons may also be under the regulation mediated by the neurohormone melatonin. In the present work, by double-staining immunohistochemical technique, we studied the expression of MT1 and MT2, two known subtypes of mammalian melatonin receptors, in rat ipRGCs. A single subset of retinal ganglion cells labeled by the specific antibody against melanopsin exhibited the morphology typical of M1-type ipRGCs. Immunoreactivity for both MT1 and MT2 receptors was clearly seen in the cytoplasm of all labeled ipRGCs, indicating that these two receptors were co-expressed in each of these neurons. Furthermore, labeling for both the receptors were found in neonatal M1 cells as early as the day of birth. It is therefore highly plausible that retinal melatonin may directly modulate the activity of ipRGCs, thus regulating non-image forming visual functions.

固有光敏视网膜神经节细胞（Intrinsically photosensitive retinal ganglion cells, ipRGCs）参与昼夜节律及其他非成像视觉应答过程。目前尚存一个开放性研究问题：此类神经元的活动是否亦可受神经激素褪黑素介导的调控。本研究通过双重免疫组织化学染色技术，探究了哺乳动物褪黑素受体的两种已知亚型MT1与MT2在大鼠ipRGCs中的表达情况。经抗黑视蛋白（melanopsin）特异性抗体标记的单一视网膜神经节细胞亚群，呈现出M1型ipRGCs的典型形态特征。所有被标记的ipRGCs的细胞质中均清晰可见MT1与MT2受体的免疫阳性反应，表明这两种受体在该类神经元中存在共表达现象。进一步研究发现，早在出生当日，新生M1细胞中即可检测到两种受体的标记信号。由此可高度推测，视网膜褪黑素或可直接调控ipRGCs的活动，进而调节非成像视觉功能。