mGluR5对大鼠视网膜对光反应的调控

目的探索代谢型谷氨酸受体5（mGluR5）对大鼠暗适应视网膜电图（ERG）不同成分的贡献。方法实验研究。出生后30日龄大鼠（RCS-rdy+-p+）12只，暗适应大于12 h后，分别行视网膜下腔注射mGluR5激动剂CHPG[（R，S）-2-chloro-5-hydroxyphenylglycine] 200 µmol（6只，CHPG组）和抑制剂MPEP[2-methyl-6-（phenylethynyl）-pyridine] 200 µmol（6只，MPEP组），对侧眼注射同等体积PBS作为对照。注射后2 d采用RETI-scan系统记录其系列刺激光强度下（-4.5、-2.5、-0.5、-0.02、0.5 1 logcd×m×s-2）的暗适应ERG。导出数据，采用配对t检验进行双眼间数据比较。结果CHPG组，a、b波幅值在不同光强下均显著降低（除最低光强）（-4.5＜t＜-2.3，P＜0.05），进一步分析得出a、b波最大幅值（Rmax和Vmax）均明显降低（-4.5＜t＜-2.3，P＜0.05），但其敏感度均未出现明显变化，且b/a未见明显变化。MPEP组，a、b波幅值在不同光强下均显著升高（除最低光强）（-3＜t＜-2，P＜0.05），进一步分析得出a、b波Rmax和Vmax均明显升高（-3＜t＜-2，P＜0.05），但其敏感度均未出现明显变化，且b/a未见明显变化。2组的振荡电位（OPs）与相应的对照眼比较未见明显差别。结论mGluR5激动后，ERG a、b波幅值明显降低，mGluR5主要调控外层视网膜的对光反应。

Contribution of mGluR5 to different components of the rat dark-adapted electroretinogram

Objective To investigate the contribution of the metabotropic glutamate receptor 5 (mGluR5) to the different components of the rat dark-adapted electroretinogram (ERG). Methods This was an experimental study. After 12 h dark adaptation, RCS-rdy+-p+ rats were subretinally injected with the 200 μmol agonist (R, S)-2-chloro-5-hydroxyphenylglycine (CHPG) and 200 μmol antagonist 2-methyl-6-(phenylethynyl)-pyridine (MPEP). The same volume of phosphate buffered saline (PBS) was injected into the fellow eye for comparison. The dark-adapted ERGs were recorded by a series of flashes [-4.5, -2.5, -0.5, -0.02, 0.5, and 1 log(cd×m/s-2)]. Output data were exported and compared by paired t-tests. Results In the CHPG group, the amplitudes of the a- and b-waves at all light intensities (except the lowest intensity) were significantly decreased compared with the PBS-injected eyes. The parameters of Rmax and Vmax were also significantly decreased, but sensitivities of the a- and b-waves, the b-wave to a-wave ratio, and the oscillatory potentials (OPs) were unchanged when compared with the PBS-injected eyes. In the MPEP group, the amplitudes of the a- and b-waves at all light intensities (except the lowest intensity) were significantly increased compared with the PBS-injected eyes. The parameters of Rmax and Vmax were also significantly increased, but the sensitivities of the a- and b-waves, the b-wave to a-wave ratio, and OPs were unchanged when compared with the PBS-injected eyes. Conclusion The mGluR5 agonist CHPG decreased the amplitudes of the ERG a- and b-waves. This suggests that mGluR5 regulates the light responses of the outer retina.