Yu Minzhong, Peachey Neal S
Cole Eye Institute (I-31), Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195, USA.
Doc Ophthalmol. 2007 Nov;115(3):173-86. doi: 10.1007/s10633-007-9058-9. Epub 2007 May 4.
To examine changes in inner retinal function of nob2 mice, expressing a null mutation in Cacna1f encoding the Ca(V)1.4 subunit of voltage-dependent calcium channels. CACNA1F mutations underlie one form of incomplete X-linked congenital stationary night blindness (CSNB2). In addition to a loss of dark-adapted (rod-driven) visual sensitivity, electroretinogram (ERG) b-waves and oscillatory potentials (OPs) are decreased in CSNB2 patients.
ERGs were recorded under dark-and light-adapted conditions from the corneal surface of nob2 mice, WT littermates and nob4 mice. ERG frequency spectra were calculated by fast Fourier transform (FFT). A FFT-based high-pass filter was used to derive OP waveforms.
Under dark-adapted conditions, the dominant frequency of the OPs varied between 90 to 120 Hz in WT mice. In WT mice, OP frequency first increased with flash intensity and then decreased at the highest flash levels while overall OP amplitude increased monotonically with increasing flash intensity. In response to low stimulus flashes, reliable OPs were not obtained from nob2 mice. OPs were only seen at stimulus intensities at or above -1.8 log cd s/m(2), where they occurred at a lower frequency range (70-90 Hz) than for WT mice. When flash stimuli were superimposed against a steady rod-desensitizing adapting field, the amplitude and frequency of WT OPs increased with flash intensity above 0.4 log cd s/m(2). In comparison to WT results, cone-mediated OPs obtained from nob2 mice were smaller in amplitude, of lower frequency and had delayed implicit times. We compared the extent to which OPs and the b-wave were reduced in nob2 mice, by normalizing to the results obtained from WT mice. In comparison to the b-wave, the OPs were relatively spared, under both dark- and light-adapted conditions.
In nob2 mice, rod- and cone-driven OPs are reduced in amplitude and occur at a lower frequency range. Since Ca(V)1.4 is expressed in both the inner and outer plexiform layers, these changes are likely to reflect reduced transmission from photoreceptors to bipolar cells as well as alterations in inner retinal function. That the OPs were better preserved than b-waves suggests that inner retinal pathways may be reorganized in response to the decreased bipolar cell response in nob2 mice.
研究nob2小鼠视网膜内层功能的变化，该小鼠在编码电压依赖性钙通道Ca(V)1.4亚基的Cacna1f基因中存在无效突变。CACNA1F突变是不完全X连锁先天性静止性夜盲（CSNB2）的一种形式。除了暗适应（视杆细胞驱动）视觉敏感度丧失外，CSNB2患者的视网膜电图（ERG）b波和振荡电位（OPs）也降低。
在暗适应和明适应条件下，从nob2小鼠、野生型同窝小鼠和nob4小鼠的角膜表面记录ERG。通过快速傅里叶变换（FFT）计算ERG频谱。使用基于FFT的高通滤波器导出OP波形。
在暗适应条件下，野生型小鼠OPs的主导频率在90至120Hz之间变化。在野生型小鼠中，OP频率首先随闪光强度增加，然后在最高闪光水平时降低，而总体OP振幅随闪光强度增加单调增加。对于低强度刺激闪光，未从小鼠获得可靠的OPs。仅在刺激强度等于或高于-1.8 log cd s/m(2)时观察到OPs，此时它们出现的频率范围（70 - 90Hz）低于野生型小鼠。当闪光刺激叠加在稳定的视杆细胞脱敏适应场时，野生型OPs的振幅和频率在闪光强度高于0.4 log cd s/m(2)时增加。与野生型结果相比，从小鼠获得的视锥细胞介导的OPs振幅较小、频率较低且隐含时间延迟。通过将结果归一化为野生型小鼠获得的结果，我们比较了小鼠中OPs和b波降低的程度。与b波相比，在暗适应和明适应条件下，OPs相对保留较好。
在小鼠中，视杆细胞和视锥细胞驱动的OPs振幅降低且出现在较低频率范围。由于Ca(V)1.4在内网状层和外网状层均有表达，这些变化可能反映了从光感受器到双极细胞的传递减少以及视网膜内层功能的改变。OPs比b波保存得更好表明，视网膜内层通路可能因小鼠双极细胞反应降低而发生重组。
