Moretti Milena, Vailati Silvia, Zoli Michele, Lippi Giordano, Riganti Loredana, Longhi Renato, Viegi Alessandro, Clementi Francesco, Gotti Cecilia
CNR, Institute of Neuroscience, Section of Cellular and Molecular Pharmacology, Department of Medical Pharmacology, University of Milan, Via Vanvitelli 32, 20129 Milano, Italy.
Mol Pharmacol. 2004 Jul;66(1):85-96. doi: 10.1124/mol.66.1.85.
By acting through retinal nicotinic acetylcholine receptors (nAChRs), acetylcholine plays an important role in the development of both the retina and central visual pathways. Ligand binding and immunoprecipitation studies with subunit-specific antibodies showed that the expression of alphaBungarotoxin (alphaBgtx) and high-affinity epibatidine (Epi) receptors is regulated developmentally and increases until postnatal day 21 (P21). The increase in Epi receptors is caused by a selective increase in the subtypes containing the alpha2, alpha4, alpha6, beta2, and beta3 subunits. Immunopurification studies revealed three major populations of Epi receptors on P21: alpha6() receptors (26%), which contain the alpha6beta3beta2, alpha6alpha4beta3beta2, and alpha6alpha3/alpha2beta3beta2 subtypes; alpha4(non-alpha6)() receptors (60%), which contain the alpha2alpha4beta2 and alpha4beta2 subtypes; and (non-alpha4/non-alpha6)() receptors (14%), which contain the alpha2beta2/beta4 and alpha3beta2/beta4 subtypes. These three populations can be pharmacologically discriminated using alphaconotoxin MII, which binds the alpha6() population with high affinity. In situ hybridization showed that the transcripts for all of the subunits are heterogeneously distributed throughout retinal neurons at P21, with alpha3, alpha6, and beta3 transcripts preferentially concentrated in the ganglion cell layer, alpha5 in the inner nuclear layer, and alpha4 and beta2 distributed rather homogeneously. To investigate whether nAChR expression is affected by visual experience, we also studied dark-reared P21 rats. Visual deprivation had no effect on the expression of alphaBgtx receptors or the developmentally regulated Epi receptors containing the alpha2, alpha6, and/or beta3 subunits but significantly increased the expression of the Epi receptors containing the alpha4 and beta2 subunits. Overall, this study demonstrates that the retina is the rat neural region that expresses the widest array of nAChR subtypes. These receptors have a specific distribution, and their expression is finely regulated during development and by visual experience.
通过作用于视网膜烟碱型乙酰胆碱受体（nAChRs），乙酰胆碱在视网膜和中枢视觉通路的发育中发挥重要作用。使用亚基特异性抗体进行的配体结合和免疫沉淀研究表明，α-银环蛇毒素（αBgtx）和高亲和力埃皮巴蒂啶（Epi）受体的表达在发育过程中受到调节，并持续增加直至出生后第21天（P21）。Epi受体的增加是由含有α2、α4、α6、β2和β3亚基的亚型选择性增加所致。免疫纯化研究揭示了P21时Epi受体的三个主要群体：α6()受体（26%），包含α6β3β2、α6α4β3β2和α6α3/α2β3β2亚型；α4（非α6）()受体（60%），包含α2α4β2和α4β2亚型；以及（非α4/非α6）()受体（14%），包含α2β2/β4和α3β2/β4亚型。使用能与α6()群体高亲和力结合的α-芋螺毒素MII可以从药理学上区分这三个群体。原位杂交显示，在P21时，所有亚基的转录本在整个视网膜神经元中呈异质性分布，α3、α6和β3转录本优先集中在神经节细胞层，α5在内核层，α4和β2分布较为均匀。为了研究nAChR表达是否受视觉经验影响，我们还研究了暗饲养的P21大鼠。视觉剥夺对αBgtx受体或含有α2、α6和/或β3亚基的发育调节型Epi受体的表达没有影响，但显著增加了含有α4和β2亚基的Epi受体的表达。总体而言，本研究表明视网膜是大鼠神经区域中表达最广泛的nAChR亚型的区域。这些受体具有特定的分布，并且它们的表达在发育过程中以及受视觉经验的影响下受到精细调节。
