Department of Clinical Biochemistry, Bispebjerg Hospital, Faculty of Health Sciences, University of Copenhagen, Bispebjerg Bakke 23, DK-2400, Copenhagen, Denmark.
Cell Tissue Res. 2010 May;340(2):243-55. doi: 10.1007/s00441-010-0950-3. Epub 2010 Mar 26.
The retinal ganglion cell layer of the eye comprises a subtype of cells characterized by their intrinsic photosensitivity and expression of melanopsin (ipRGCs). These cells regulate a variety of non-image-forming (NIF) functions such as light entrainment of circadian rhythms, acute suppression of locomotor activity (masking), and pupillary light reflex. Two neurotransmitters have been identified in ipRGCs, glutamate and pituitary adenylate cyclase-activating polypeptide (PACAP). To date, little is known about their release and interplay. Here, we describe the presence and co-localization of vesicular glutamate transporter 2 (VGLUT2; a marker of glutamate signaling) and PACAP in ipRGCs and their projections in the brain. Nine adult male Wistar rats were assigned to one of three groups; anterograde tracing (n = 3), eye enucleation (n = 3), and untreated (n = 3). Under anaesthesia, rats were transcardially perfusion-fixated, after which the brains and eyes were removed for double immunohistochemical staining using a polyclonal anti-VGLUT2 antibody and a mouse monoclonal anti-PACAP antibody. Results revealed that VGLUT2- and PACAP-immunoreactivity (-ir) were present in ipRGCs and co-localized in their projections in the suprachiasmatic nucleus, the intergeniculate leaflet, and the olivary pretectal nucleus. We conclude that there is evidence to support the use of glutamate and PACAP as neurotransmitters in NIF photoperception by rat ipRGCs, and that these neurotransmitters are co-stored and probably released from the same nerve terminals. Furthermore, we conclude that VGLUT2 is the preferred subtype of vesicular transporter used by these cells.
眼睛的视网膜神经节细胞层包含一类以固有光敏性和黑视素表达为特征的细胞亚型（ipRGCs）。这些细胞调节多种非成像（NIF）功能，如光对昼夜节律的诱导、运动活动的急性抑制（掩蔽）和瞳孔光反射。已经在 ipRGCs 中鉴定出两种神经递质，即谷氨酸和垂体腺苷酸环化酶激活肽（PACAP）。迄今为止，人们对它们的释放和相互作用知之甚少。在这里，我们描述了囊泡谷氨酸转运体 2（VGLUT2；谷氨酸信号的标志物）和 PACAP 在 ipRGCs 及其在大脑中的投射中的存在和共定位。将 9 只成年雄性 Wistar 大鼠分为三组；顺行示踪组（n = 3）、眼球摘除组（n = 3）和未处理组（n = 3）。在麻醉下，大鼠经心脏灌注固定，然后取出大脑和眼睛，用多克隆抗 VGLUT2 抗体和小鼠单克隆抗 PACAP 抗体进行双重免疫组织化学染色。结果表明，VGLUT2 和 PACAP 免疫反应性（-ir）存在于 ipRGCs 及其在视交叉上核、中间脑叶和橄榄前脑核中的投射中，并共定位。我们得出结论，有证据支持谷氨酸和 PACAP 作为大鼠 ipRGCs 中 NIF 光感知的神经递质，并且这些神经递质被共同储存并可能从相同的神经末梢释放。此外，我们得出结论，VGLUT2 是这些细胞使用的首选囊泡转运体亚型。
