GABA_A和GABA_C受体各亚单位基因在鲫鱼视网膜内的分布──原位杂交组织化学法研究

LOCALIZATION OF GABA_A AND GABA_C RECEPTOR SUBUNIT mRNAs IN CARP RETINA──AN IN SITU HYBRIDIZATION ANALYSIS

应用原位杂交组织化学技术，利用同位素［￣（３５）Ｓ］－ｄＡＴＰ标记的寡核苷酸探针，在鲫鱼视网膜观察了含ＧＡＢＡＡ受体α１、α３、α４、α６，β１－３，γ１－２及ＧＡＢＡＣ受体ρ１亚单位ｍＲＮＡ的神经元分布。在外核层，所有测试的亚单位均无表达；而在内核层和神经节细胞层，除α４和γ２亚单位外，均有不同程度的表达。在不同区域标记神经元的数量和标记强度各不相同，α１亚单位广泛分布在内核层的远端、中部及神经节细胞层，呈强阳性；α３亚单位相对稀少，主要分布在内核层近端和神经节细胞层，呈中等阳性；α４和α６亚单位几乎无阳性表达，仅α６亚单位在神经节细胞层呈弱阳性。β１和β２亚单位在内核层及神经节细胞层呈中等阳性；β３亚单位主要分布在内核层，在神经节细胞层标记细胞较少，呈弱阳性。γ１亚单位分布在整个内核层，在神经节细胞层有零星阳性表达。ＧＡＢＡＣ受体主要分布在内核层，ρ１亚单位主要分布在内核层的远端及中间部分，呈强阳性，而在神经节细胞层表达相对较弱。这种独特的表达型式与其功能密切相关。

γ-Aminobutyric acid (GABA)is the major inhibitory transmitter in the vertebrate retina. In carp retina,many subclasses of horizontal and amacrine cells are GABAergic. In the present study, we studied the localization of GABAA receptor subunits (α1、α3、α4、α6, β1-3, γ1-2) and GABAC receptor subunit ρ1 mRNA in carp retina using in situ hybridization histochemistry. Sequence-specific 35 S-labeled oligonucleotide probes and in situ hybridization histochmistry were used to examine the distribution of GABAA receptor α1、α3、α4、α6,β1-3, γ1-2 subunits and GABAC ρ1 subunit mRNAS in carp retina. It was found that these mRNAs were expressed in different patterns. While none of them was expressed in the outer nuclear layer (ONL), these mRNAs, except for subunit α4 and γ2 of GABAA receptor, were expressed in the inner nuclear layer (INL) and ganglion cell layer (GCL) to different extents. The α1 variant mRNA was expressed by neurons distributed to all regions of the INL. Some discretely labeled cells were present in the GCL. Labeled cells were not observed in the ONL. GABAA α3,in contrast,showed a more limited distribution in the retina compared to the GABAA α1 variant mRNA, α4 and α6 mRNAs were not expressed, while α6 one showed weak positive in GCL.β1 and β2 mRNAs had a siynilar expression pattern, being medium positive. β3 subunits were predominantly present in INL and GCL, which were weakly labeled. γ1 mRNA was distributed in entire INL and localized in a few cells in the GCL.Furthermore, GABAcR ρ1 subunit mRNA was mainly located in the middle and outer parts of INL, where bipolar and horizontal cell reside. GCL was relatively weakly labeled.