Zimov Sarah, Yazulla Stephen
Graduate Program in Neuroscience, Stony Brook University, Stony Brook, New York 11794, USA.
Vis Neurosci. 2007 Jul-Aug;24(4):581-91. doi: 10.1017/S095252380707054X. Epub 2007 Aug 9.
Fatty acid amide hydrolase (FAAH) is the degradative enzyme for anandamide (AEA), an endogenous ligand for the vanilloid receptor (TRPV1) and cannabinoid receptor 1. As FAAH and TRPV1 are integral membrane proteins, FAAH activity could modulate the availability of AEA for TRPV1 activation. Previous studies in this laboratory reported an extensive endocannabinoid system in goldfish retina. Immunocytochemistry was used to determine the relative distributions of FAAH-immunoreactivity (IR) and TRPV1-IR in goldfish retina. Here, we show the first example in an intact neural system in which TRPV1-IR co-localizes in subpopulations of FAAH-immunoreactive neurons, in this case amacrine cells. These cells are rare and consist of three subtypes: 1. ovoid cell with granular-type dendrites restricted to sublamina a, 2. pyriform cell with smooth processes in sublamina b, and 3. fusiform cell with smooth processes that project to sublaminae a and b. The varied appearances of reaction product in the dendrites suggest different subcellular localization of TRPV1, and hence function of FAAH activity regarding TRPV1 stimulation among the cell types. Ovoid and pyriform amacrine cells, but not fusiform cells, labeled with GAD-IR and constituted subsets of GABAergic amacrine cells. TRPV1 amacrine cells, though rare, are represented in the ON, OFF and ON/OFF pathways of the retina. As TRPV1 stimulation increases intracellular calcium with numerous downstream effects, co-localization of TRPV1 and FAAH suggests an autoregulatory function for anandamide. Due to the rarity of these cells, the three vanilloid amacrine cell types may be involved in global effects rather than feature extraction, for example: sampling of ambient light or maintaining homeostasis.
脂肪酸酰胺水解酶（FAAH）是花生四烯乙醇胺（AEA）的降解酶，AEA是香草酸受体（TRPV1）和大麻素受体1的内源性配体。由于FAAH和TRPV1是整合膜蛋白，FAAH活性可调节AEA用于激活TRPV1的可用性。本实验室先前的研究报道了金鱼视网膜中广泛存在的内源性大麻素系统。免疫细胞化学用于确定FAAH免疫反应性（IR）和TRPV1-IR在金鱼视网膜中的相对分布。在这里，我们展示了完整神经系统中的首个例子，其中TRPV1-IR共定位于FAAH免疫反应性神经元的亚群中，在这种情况下是无长突细胞。这些细胞很罕见，由三种亚型组成：1. 卵形细胞，其颗粒状树突仅限于a亚层；2. 梨形细胞，其在b亚层有光滑的突起；3. 梭形细胞，其光滑的突起投射到a和b亚层。树突中反应产物的不同外观表明TRPV1在亚细胞水平的定位不同，因此FAAH活性在不同细胞类型中对TRPV1刺激的功能也不同。卵形和梨形无长突细胞，而非梭形细胞，用GAD-IR标记，构成了GABA能无长突细胞的亚群。TRPV1无长突细胞虽然罕见，但在视网膜的ON、OFF和ON/OFF通路中均有存在。由于TRPV1刺激会增加细胞内钙并产生许多下游效应，TRPV1和FAAH的共定位表明花生四烯乙醇胺具有自调节功能。由于这些细胞很罕见，三种香草酸无长突细胞类型可能参与全局效应而非特征提取，例如：环境光的采样或维持体内平衡。
