小鼠视网膜胆碱能无长突细胞和方向选择性神经节细胞树突野发育的相关性研究

Relationship between cholinergic amacrine cell and development of direction-selective ganglion cell dendritic field in mouse retina

目的探讨小鼠视网膜方向选择性神经节细胞(DSGC)树突野(DF)的发育及其与胆碱能细胞阵列的关系。方法选用中国科学院生物物理研究所实验动物中心繁殖的清洁级YFP(H)品系的转基因小鼠(种鼠来源于The Jackson实验室)共36只,0～1月龄,雌雄不限。对出生后不同发育时期(P8、P13及成年)的小鼠视网膜中ON/OFF DSGC及OFF DSGC的DF范围内包含的胆碱能细胞的数目采用单因素方差分析进行比较,当差异有统计学意义时,进一步两两比较。结果 ON/OFF DSGC作为经典的方向选择性神经节细胞,其树突具有两层树突结构,分别分布在视网膜内网状层的ON和OFF亚层中,其树突弯曲度和树突分支之间的夹角比较大,分支多向胞体方向返回呈半环状,显著的特点是同一细胞的树突不会发生交叉。P8时,D2亚类神经节细胞(即ON/OFF DSGC) DF范围中分别包含(25.6±4.8)个内核层(INL)的胆碱能无长突细胞和(28.4±5.7)个视网膜神经节细胞(GCL)的胆碱能无长突细胞(n=7); P13时,D2亚类神经节细胞DF范围中分别包含(30.8±9.5)个INL的胆碱能无长突细胞和(35.2±10.4)个GCL的胆碱能无长突细胞(n=10);成年时,D2亚类神经节细胞DF范围中分别包含(33.7±7.4)个INL的胆碱能无长突细胞和(32.1±5.6)个GCL的胆碱能无长突细胞(n=9),三个时期的胆碱能无长突细胞的数目差异均无统计学意义(F=2.16,1.55; P>0.05)。而视网膜中另外一种方向选择性神经节细胞OFF DSGC的DF范围内无长突细胞的数目从P8到P13先增多,然后从P13到成年又减少。P8时,该类细胞DF范围内位于GCL的无长突细胞数目为(20.0±2.5,n=8)个,明显少于P13时的(32.0±7.1,n=6)个;成年时,数目又减少到(23.7±7.5,n=14)个。,三个时期的胆碱能无长突细胞的数目差异均无统计学意义(F=6.19,1.55; P<0.05)。结论小鼠视网膜ON/OFF DSGC的DF在出生后早期就已经发育成熟,并和胆碱能细胞形成稳定的联系,不再受后期双极细胞及光刺激的影响,而OFF DSGC的DF发育可能包含不同的分子和细胞机制。

Objective To investigate the growth of retinal direction-selective ganglion cell’sdendritic field(DF) and it’s relationship with cholinergic amacrine mosaic. Methods Thirty six cleanYFP(H) strains of transgenic mice were selected from the Laboratory Animal Center of Institute ofBiophysics,Chinese Academy of Sciences. They were 0-1 month old,male and female. We compared thenumbers of cholinergic amacrine cells within dendritic field of ON/OFF DSGC and OFF DGGC at severalpostnatal stages(P8,P13 and adulthood) in mouse retina. Results As a classical directional selectiveganglion cell,the dendrites of ON/OFF DSGC have two layers of dendritic structure. They are distributed inthe ON and OFF sublayers of reticular layer in the retina. The angle between the curvature of the dendritesand the branches of the dendrites is relatively large. The branches return in the direction of themultidirectional cell bodies in a semi circular pattern. The prominent feature is the dendrites of the same cell.There will be no crossover. At P8,cholinergic amacrine cells in the DF range of D2 subclass ganglion cellscontained(25. 6 ± 4. 8) inner nuclear layers and(28. 4 ± 5. 7) retinal ganglion cells respectively; at P13,cholinergic amacrine cells and(35.2±1.0) cholinergic amacrine cells in the DF range of D2 subclassganglion cells contained(30.8±9.5) INL,respectively.(35.2±10.4) cholinergic amacrine cells of GCL; inadulthood,the DF range of D2 subclass ganglion cells contained(33.7± 7.4) cholinergic amacrine cells ofINL and(32.1±5.6) cholinergic amacrine cells of GCL,respectively. There was no significant difference inthe number of cholinergic amacrine cells between the three periods(F = 2.16,1.55; P> 0.05). In the DFrange of OFF DSGC,the number of amacrine cells increased from P8 to P13,then decreased from P13 toadulthood. At P8,the number of amacrine cells in the DF range of GCL was(20. 0 ± 2. 5),which wassignificantly less than that at P13(32.0±7.1). In adulthood,the number decreased to(23.7± 7.5). Therewas no significant difference in the number of cholinergic amacrine cells between the three periods(F = 6.19,1.55; P< 0. 05). Conclusions Our results indicated that ON/OFF DSGC achieved mature dendritic fieldsize at very early postnatal stage which highly depended on cholinergic amacrine mosaic but was notinfluenced by bipolar cells input and light stimulation. While OFF DSGC likely involved different cellular andmolecular mechanism.