LASIK术中瞬时高眼压对兔视网膜功能影响的研究

目的 探讨LASIK术中负压吸引致瞬时高眼压对兔视网膜功能的影响.方法 32只健康新西兰大耳白兔随机分为正常对照组、实验对照组、负压吸引20 s组和3 min组.实验对照组只进行激光治疗,负压吸引20 s组和负压吸引3 min组先分别用负压发生器吸引兔眼角巩膜缘20 s及3 min.分别于术后不同修复期通过闪光-视觉诱发电位和闪光-视网膜电图观察视网膜视神经功能的变化,并与正常对照组进行比较.结果 正常对照组和实验对照组左右眼的视网膜电图(electroretinogram,ERG)a波波幅和b波波幅比较差异无统计学意义(P＞0.05).与正常对照组相比,负压吸引20 s组和3 min组术后30 min～7 d各时间点ERG的b波振幅相比,差异有统计学意义(F=5.18,P＜0.05),负压吸引20 s组修复10 min ERG b波波幅为(112.01±11.08)μV较正常对照组(84.96±13.48)μV升高(P＜0.05),修复20 min逐渐降低,为(94.51±14.43)μV;负压吸引3 min组修复10 min ERG b波波幅为(55.89±9.46)μV较正常对照组明显降低(P＜0.05),修复20 min ERG b波波幅逐渐降低为(67.73±16.42)μV,修复30 min时兔眼ERG b波波幅仍低,与正常相比差异有统计学意义(P＜0.05).随着负压吸引时间的延长,各时间点ERG的b波振幅降低,随着修复时间的延长,ERG的b波振幅逐渐恢复正常.而ERG的a波波幅和潜伏期、视觉诱发电位各波波幅和潜伏期均无差异.结论 LASIK术中负压吸引引起的眼压急剧升高,不会影响视网膜的功能.     

大鼠不同颜色光视网膜电图特点

目的：探索正常SD大鼠及视网膜锥体失功能(RCD)大鼠不同颜色光视网膜电图特点及其可能存在的诊断价值。

方法：成年雄性SD大鼠及RCD大鼠,各6只,分别进行红、白、绿及蓝色光的视网膜电图记录,刺激所用的红光波长为625nm,绿光波长为525nm,蓝光波长为470nm,白光为混合光。

结果：正常SD大鼠各颜色光ERG表现为短波长的绿光及蓝光刺激条件下波幅值较红光及白光高; 而RCD大鼠各颜色光暗适应ERG的b波波幅值无显著差别,但各颜色光的波幅值均小于SD大鼠; 而各颜色光明适应ERG均未记录到明显波形。

结论：大鼠对短波长的绿光及蓝光较为敏感,建议可使用蓝光或者绿光作为大鼠视网膜电图记录的刺激光源。RCD大鼠对各颜色光无特异性的反应,尚不能用颜色光视网膜电图作为其特异的诊断指标。     

大鼠生长发育早期视网膜电图变化特点

目的研究正常SD大鼠早期睁眼前视网膜电图(electroretinogram,ERG)随生长发育的变化特点。方法分别测量30只(30眼)SD大鼠在出生后第9天、第10天、第11天、第12天和第13天的杆体、最大混合反应、明适应及闪烁光ERG和振荡电位。结果出生后第9天时即可记录到闪烁光ERG的存在,潜伏期为(34.20±7.10)ms,振幅(0.59±0.16)μV;出生后第10天时可以记录到最大混合反应-ERG a波潜伏期(23.30±3.90)ms,振幅(1.58±0.58)μV,振荡电位O1波潜伏期(18.60±3.00)ms,振幅(0.53±0.22)μV。杆体-ERG、最大混合反应-ERG b波、明适应-ERG在大鼠眼睑开放前无法引出。结论本实验初步探讨了大鼠早期睁眼前ERG的记录方法及其生长发育的变化特点,为进一步研究ERG的波形起源提供了一定的依据。     

大鼠四氧化二氮中毒后多焦视网膜电图改变

目的:研究大鼠在航天推进剂四氧化二氮染毒后多焦视网膜电图改变.方法:正常雄性winstar大鼠,用15mg四氧化二氮溶液ip染毒,1h及7d检查的大鼠为6～10只,在晚上固定时间进行苯巴比妥钠溶液ip麻醉及多焦视网膜电图检查.用Microsof Excel自带的统计软件对数据进行分析.结果:四氧化二氮15mg染毒后1h组的大鼠与正常大鼠的MERG的总和波及各环b波的潜伏期的差异具有显著意义(P值0.005～0.034,P＜0.05);染毒后7d的大鼠与正常大鼠MERG的总和波及各环b波的潜伏期的差异没有显著意义;两组染毒大鼠与正常大鼠MERG的总和波及各环b波的波幅值的差异均无显著意义.染毒后1h组与染毒后7d组之间的MERG的总和波及各环b波的潜伏期的差异其部分指标具有显著意义(P值0.006～0.017,P＜0.05),其余部分指标的差异无显著意义;而两组之间波幅值的差异无显著意义.结论:1h及7d四氧化二氮染毒大鼠的MERG潜伏期的差异其部分指标具有显著意义,MERG总和波及各环b波潜伏期有不同程度的差异,其影响随着时间延长而减弱.     

早期糖尿病视网膜病变的视网膜电图研究

目的：研究早期糖尿病视网膜病变（diabeticretinopathy,DR) 的视网膜电图震荡电位（Oscillatory potentials,OPs)和图形视网膜电图（Pettern electroretinogram,P-ERG)的变化特点,借以早期诊断DR。方法：对20例（40眼）正常和50例（113眼）糖尿病病人进行OPs和P－ERG检测。结果：当糖尿病病人眼底尚未出现改变时,P－ERG的b波波幅和OPs各子波波幅及总波幅已降低。随着DR的发展,各参数的异常率逐渐上升,各波波幅也随之下降,潜伏期延长。OPs的O3波波幅和总波幅以及P－ERG的b波波幅较其它指标具有较高的敏感性,其中O3波波幅为最敏感的指标。结论：OPs的O3波波幅和总波幅等参数能够作为视觉电生理的功能性指标预测DR的发生,在DR的早期诊断和评价DM的疗效方面有临床应用价值。     

小鼠视网膜电图随生长发育的变化特点

目的：研究小鼠视网膜电图随生长发育的变化特点。

方法：我们分别测量50只50眼昆明种小鼠在出生后第14、21、28、35和56d视网膜电图,分析比较各时间点Rod-ERG b波、Max-ERG a及b波、Cone-ERG的a及b波、OPs O1及O2波幅值及峰潜时、Flick-ERG幅值。

结果：Max-ERG a波峰潜时(各时间点95%可信区间依次为15.00～18.60、12.00～15.00、13.20～14.40、13.20～15.00、13.20～15.00ms)、OPs O1波峰潜时(各时间点95%可信区间依次为15.00～19.80、13.80～18.00、13.20～14.40、13.80～15.60、13.80～15.60ms)和Flick-ERG幅值(各时间点95%可信区间依次为0.97～3.28、0.85～2.32、0.91～3.49、0.94～2.68、0.98～3.69μV)在各周龄间无统计学差异(P>0.05); Cone-ERG a波峰潜时(各时间点95%可信区间依次为25.20～55.20、27.00～40.20、27.00～38.40、25.20～43.80、23.40～37.80ms)在出生后14d和28d间存在统计学差异(P<0.05)、出生后14d与出生后21d、28d间Cone-ERG b波峰潜时(各时间点95%可信区间依次为70.80～88.20、56.40～78.60、60.00～75.60、60.60～87.00、62.40～81.60ms)均有统计学差异; 同时出生后第14d与其他时间点间Rod-ERG b波峰潜时(各时间点95%可信区间依次为87.00～114.00、53.40～73.80、52.2～63.6、55.20～71.40、57.60～67.80ms)及幅值(各时间点95%可信区间依次为64.21～195.07、133.79～355.71、130.62～355.96、190.92～448.97、239.26～462.40μV)、Max-ERG b波峰潜时(各时间点95%可信区间依次为67.20～107.40、32.40～54.60、31.20～36.60、31.80～42.00、34.20～41.40ms)及幅值(各时间点95%可信区间依次为160.64～344.48、281.74～590.09、284.91～716.80、358.64～737.55、406.98～810.55μV)、OPs O2波峰潜时(各时间点95%可信区间依次为49.8～69.6、29.40～42.60、28.80～33.60、28.80～37.80、31.20～37.20ms)和波幅值(各时间点95%可信区间依次为5.43～24.84、54.38～147.52、65.55～201.60、46.33～164.79、49.07～148.32μV)以及OPs O1(各时间点95%可信区间依次为11.60～21.36、6.77～53.71、32.96～76.42、34.06～70.37、35.58～63.35μV)和Cone-ERG b波幅值(各时间点95%可信区间依次为5.10～15.85、9.61～24.88、14.96～40.73、14.87～28.54、13.83～51.98μV)均存在统计学差异。OPs O1波在P14时即已存在,而有一只小鼠(1/10)OPs第二波群在第2wk时波形不明显。

结论：本实验结果在一定程度上证实了小鼠ERG中各波形的起源。由于小鼠ERG在发育过程中的变化,在测量小鼠ERG时应当考虑到小鼠发育阶段对结果的影响。     

正常成年SD大鼠明视闪光视网膜电图特征

目的:探讨正常成年SD大鼠的明视视网膜电图(Electroretinogram,ERG)特征.方法:选取正常9～12周SD大鼠60只,使用罗兰视觉电生理仪记录大鼠右眼的明视闪光ERG.使用SPSS统计分析a波、b波和明视负波反应(Photopic negative response,PhNR)的隐含期和振幅.比较雄性和雌性SD大鼠明视ERG特征.结果:每只SD大鼠均能记录到稳定的a波、b波和PhNR,其中a波的隐含期和PhNR的隐含期及振幅均符合正态分布,而其余指标均不符合正态分布.PhNR的隐含期为124.6±8.5ms,其变异系数最小(0.07).PhNR的振幅为(11.3±4.2)μV,变异系数为0.37.雄性和雌性SD大鼠明视ERG的各反应波之间无显著差异.结论:在正常成年SD大鼠,明视闪光ERG是一项客观评价大鼠明视状态下视网膜功能的手段,PhNR可以作为一项稳定的评价内层视网膜功能的指标.     

视网膜色素上皮变性大鼠随生长发育的视网膜电图改变

背景RCS—rdy-P’大鼠随着生长发育会逐渐发生视网膜色素变性（RP）,记录其生长发育过程中的视网膜电图（ERG）改变可为该模型鼠的进一步研究奠定基础。目的观察RCS—rdy-P’大鼠视网膜发育过程中的ERG变化,研究ERG随发育的变化特点。方法采用RETI-port系统、环形角膜电极和不锈钢针状电极分别记录生后21、32、37、45、60d的RCS-rdy-P’大鼠的系列暗适应ERG,每个年龄组6只鼠。取相同时间点及数量的同种系正常的RCS-rdy-P’大鼠作为正常对照。暗适应不同时间的ERG对比采用RCS-rdy＋P’生后60d大鼠共9只,每组3只。结果在刺激光强、刺激频率、体温相同的情况下,RCS-rdy-P’大鼠ERGb波振幅与暗适应时间有关,随着暗适应时间的延长,b波振幅增加,当暗适应时间超过12h时,即使暗适应时间增加,b波振幅不再增长,说明暗适应超过12h可以得到RCS-rdy＋-P’大鼠一个较为稳定的ERG波形。与RCS—rdy＋一P’大鼠比较,RCS—rdy-P’大鼠在生后21d时ERG已出现a波、b波振幅的下降,同时隐含时明显延长,以a波改变为主。随着RCS—rdy-P’大鼠年龄增长及RP的进展,ERGa波、b波振幅进一步下降,隐含时延长,RCS—rdy-P’大鼠生后60d时,其ERG反应记录不到。对照组大鼠在21d时,ERG的a波、b波均振幅较低;生后32d时RCS—rdy-P’大鼠b波振幅增加,但隐含时缩短;到生后45d仅小幅增加,45～60d再次出现b波振幅显著增加,隐含时缩短。结论RCS—rdy一一P’大鼠随着年龄的增长发生视网膜功能的变化,其暗适应ERG改变符合RP的进展过程。     

正常SD大鼠多焦闪光视网膜电图特性

目的　探讨SD大鼠的多焦视网膜电图 (mfERG)特性及记录方法的可靠性。方法　正常SD大鼠 10只 ,按照本实验室建立的方法在暗适应条件下记录mfERG ,并比较注视点改变和重复记录对结果的影响。为避免记录时间和麻醉药物的可能影响 ,每次记录间隔 3d。结果　注视点位于屏幕中心时 ,mfERG总和反应P1波的潜伏期为 (4 5 44±2 77)ms ,幅值为 (14 4 16± 6 19) μV ,上半视野的P1波的潜伏期较下半视野显著延长 (P <0 0 5 ) ,幅值随离心度的增加而减少 (P <0 0 5 )。重复记录结果没有显著性差异 (P >0 0 5 )。注视点偏离屏幕刺激中心点 5mm后 ,对检查结果有明显影响 ,与注视点位于刺激中心点时比较 ,旁中心注视的各象限以及第 1环和第 5环N1波的潜伏期在各位置间即有变化 (P <0 0 5 )。结论　正常SD大鼠mfERG幅值呈离心分布可能与光感受器在视网膜的密度有关 ,潜伏期呈上下分布与大鼠习性有关。实验室建立的mfERG记录方法能够可靠地记录SD大鼠视网膜的功能变化     

腺病毒载体介导的色素上皮衍生因子对大鼠视网膜缺血再灌注损伤后视觉电生理的影响

目的:观察重组腺病毒介导的色素上皮衍生因子(Ad-PEDF)对大鼠视网膜缺血再灌注损伤后视网膜电流图的影响。方法:选用健康大鼠24只,随机分为正常组、缺血再灌注组、缺血再灌注+Ad-CMV组,缺血再灌注+Ad-PEDF组,以前房加压的方法制备大鼠视网膜缺血再灌注模型,缺血再灌注+Ad-CMV组,缺血再灌注+Ad-PEDF组分别玻璃体腔注射Ad-CMV或Ad-PEDF1μL(滴度3.8×109/PFU),每组按照时间点12,24,72,168h分为4亚组,以ERG分别测量双眼各时期ERGb波、Ops波波幅。结果:缺血再灌注后ERGb及Ops波幅明显降低,与正常组相比在各时间点有明显的统计学差异,缺血再灌注组ERGb波及Ops波幅24h降低最为明显,与缺血12,72,168h相比差异具有显著性。AD-PEDF能够明显促进ERGb波及Ops波幅恢复,与缺血组、缺血再灌注+AD-CMV在各时间点均有明显统计学差异。结论:腺病毒介导的色素上皮衍生因子玻璃体腔注射能够促进大鼠视网膜缺血再灌注损伤功能恢复。     

Asymmetry of focal ERG in human macular region

Electroretinograms (ERGs) were elicited by hemicircular (half-disc) stimuli to the upper, lower, temporal and nasal maculas of 26 normal subjects, and the amplitudes and implicit times of the ERGs from opposing macular regions were compared. The amplitudes of a-wave, b-wave and oscillatory potentials (OPs) were significantly larger in the upper macular region than in the lower macular region (P less than 0.05). The amplitudes of a- and b-waves did not differ significantly between temporal and nasal macular regions, but OPs showed enormous asymmetry, with significantly larger amplitudes in the temporal retina than in the nasal retina (P less than 0.001). The implicit times of a-waves, b-waves and OPs did not differ significantly between upper and lower retina, or between temporal and nasal retina. These findings aided analysis of the ERG of a patient with a retinal defect.     

热休克反应对大鼠视网膜缺血再灌注损伤的防御作用

目的 观察热休克反应对大鼠视网膜缺血再灌注损伤的防御作用。 方法 将20只Wistar大鼠20只眼随机分为4组，每组5只大鼠。行前房灌注（perfusion）平衡盐溶液制造急性高眼压模型,为高眼压组(P组)；在制造急性高眼压模型前24 h向大鼠腹腔内注射槲皮素(quercetin) (400 mg/kg)，为高眼压＋槲皮素组(P+Q组)；在制造急性高眼压模型前24 h 热休克(heat shock)大鼠，为高眼压＋热休克组(P+H组)；分别在制造急性高眼压模型前48 、24 h，向大鼠腹腔内注射槲皮素、热休克大鼠，为高眼压＋槲皮素+热休克组(P+Q+H组) 。按照国际临床视觉电生理学会的标准化方案，采用国特医疗系统对热休克反应后实验性高眼压大鼠模型和HSP70被槲皮素特异性抑制后实验性高眼压大鼠模型进行暗适应视网膜电图(dark adapted electroretinogram, D-ERG)、振荡电位(oscillatory potentials, OPs)和明适应E RG(light adapted ERG, L-ERG)记录。采用Western blotting方法检测各组大鼠视网膜HSP 70表达情况。 结果 P+H组大鼠视网膜HSP70表达在各组大鼠中最高，P+Q、P+Q+H组大鼠视网膜HSP70表达受到抑制。前房灌注后各组大鼠ERG各波潜伏期延长、幅值减小，P+H组D-ERG的b波、OPs的O₂波的幅值较P组高。灌注0 h后，P+H组各波幅值显著增高(P值均<0.05)；灌注24 h 后，P+H组大鼠视网膜功能恢复较P组好。P+Q、P+Q+H组大鼠灌注后ERG各波及OPs的O₂波潜伏期最长，幅值最低，甚至消失。 结论 热休克反应可以提高大鼠视网膜细胞对缺血再灌注损伤的防御作用。 （中华眼底病杂志，2003，19：117-120）     

利用锥体细胞失功能大鼠和先天性静止性夜盲大鼠对视锥与视杆通路振荡电位的分离研究

背景 振荡电位(OPs)是评估视网膜缺血缺氧性疾病视网膜功能变化的重要工具,利用视网膜退行性病变动物模型对视锥、视杆通路起源的OPs特点进行研究非常重要. 目的 在两种自发性视网膜退行性病变模型大鼠中分离视锥、视杆通路,对比分析视杆、视锥通路起源的OPs波的特点. 方法 采用雄性SD大鼠、锥体细胞失功能(RCD)大鼠、先天性静止性夜盲(CSNB)大鼠各6只,以RETI-scan视觉生理记录系统分别在暗适应(12h)和明适应(10 min)条件下,用不同强度的刺激光(-35、-25、-15、-5、0、5 db)进行刺激,记录各组大鼠的闪光视网膜电图(FERG),通过Matlab 7.0的Butterworth滤波提取OPs,采用快速傅里叶变换(FFT)对所得OPs进行频谱分析.结果 暗适应条件下SD大鼠和RCD大鼠的ERG均可见a波和b波,但CSNB大鼠b波阙如;明适应条件下,SD大鼠和CSNB大鼠可见b波,但RCD大鼠各波阙如.暗适应较高刺激光强度下,SD大鼠和RCD大鼠均有低频(主频)和高频(次频)两个明显的频峰,分别为75 ～ 110 Hz、90～120 Hz和90～ 120 Hz、110 ～ 135 Hz;不同刺激光强度下,CSNB大鼠只有一个频峰,为70～100 Hz.而明适应不同刺激光强度下,SD大鼠和CSNB大鼠均只有一个频峰,分别为75～95 Hz和70～85 Hz.明适应条件下与SD大鼠比较,CSNB大鼠b波隐含时延长,b波振幅明显下降,差异均有统计学意义(P＜0.05);暗适应条件下,RCD大鼠b波隐含时和振幅与SD大鼠比较,差异无统计学意义(P＞0.05);与SD大鼠比较,RCD和CSNB大鼠OPs波振幅下降,隐含时延长,差异均有统计学意义(P＜0.05);明适应条件下不同刺激光强度下CSNB大鼠OPs波的隐含时明显长于SD大鼠,振幅明显低于SD大鼠,差异均有统计学意义(P＜0.05). 结论 视锥、视杆通路起源的OPs有不同特性,自发性视网膜退行性改变大鼠的视杆OPs有两个频峰,正常情况下,视杆通路对OPs的贡献比视锥通路大.     

Loss of retinal function in aged DBA/2J mice - New insights into retinal neurodegeneration

The DBA/2J mouse is a common animal model of glaucoma. The intraocular pressure increases with age, and retinal ganglion cells (RGC) degenerate, usually starting at an age of approximately six months. In this study, we used two-year-old DBA/2J mice presuming an end-point of RGC degeneration. We investigated visual function in these animals using electroretinography (ERG) and visual evoked potentials (VEP), and we checked the number of remaining RGC by retrograde staining. Almost no RGC were left in the retina, and VEP were hardly recordable. Surprisingly, also ERG amplitudes of scotopic a-waves and b-waves, photopic b-waves and oscillatory potentials were decreased significantly by approximately 40% compared to amplitudes measured in age-matched C57BL/6J mice. The latencies were not changed in DBA/2J mice compared to C57BL/6J mice, and so were the ratios between amplitudes of a-waves, b-waves and oscillatory potentials. Our results indicate that, in addition to degeneration of RGC, also photoreceptors are affected by pathological processes in the eye caused by the mutations present in DBA/2J mice.     

Development of the electroretinographic oscillatory potentials in normal and ROP rats

PURPOSE: To study the development of the electroretinographic (ERG) oscillatory potentials (OPs) in rats and to compare normal OPs with those in a rat model of retinopathy of prematurity (ROP). METHODS: Following a longitudinal design, ERG responses to a greater than 5 log unit range of full-field stimuli were recorded in dark-adapted rats at postnatal day (P) 18, P31, P47, and P67. The ERG records were digitally filtered (60-235 Hz), and the trough-to-peak amplitudes and implicit times of OP2, OP3, OP4, and OP5 were measured. Additionally, rats with oxygen-induced retinopathy, a model of ROP, were studied at P31. RESULTS: Generally, OP amplitude increased and implicit time decreased with increasing stimulus intensity. The shape of the stimulus-response functions changed with age. The amplitudes of OP2, OP3, and OP4 were largest at P31. OP5 was largest at P47. All OPs were significantly affected in ROP rats; OP5 was least affected by ROP. CONCLUSIONS: A prolonged normal course of OP development, which featured waxing and waning of amplitudes, was observed and might have been consequent to maturation and then to final refinements of inner retinal circuitry. In ROP rats, marked attenuation of early OPs was consistent with persistent dysfunction of photoreceptors, and significant attenuation of the late OP5 was evidence of compromised function of inner retinal circuitry.     

Modulation of the components of the rat dark-adapted electroretinogram by the three subtypes of GABA receptors

The separate components of the dark-adapted electroretinogram (ERG) are believed to reflect the electric activity of neurones in both the inner and the outer layers of the retina, although their precise origin still remains unclear. The purpose of this study was to examine whether selective blockage or stimulation of the different subtypes of GABA receptors might help further elucidate the cellular origin of the components of the dark-adapted ERG. The rat retina is of interest since the localization and physiology of GABA receptors in that retina have been examined in great detail. GABA agonists and antagonists, known to affect the responses of neurons in the inner plexiform layer, were injected into the vitreous of one eye while ERG responses evoked by flashes of white light were recorded. GABA and the GABAa agonist isoguvacine completely removed the oscillatory potentials (OPs) and reduced the amplitude of the a- and b-waves. TPMPA, a GABAC antagonist, reduced the a- and b-waves but had no significant effect on the OPs. Baclofen, a GABAb agonist, reduced the amplitude of the a- and b-waves, without having any effects on the amplitude of the OPs. The GABAb antagonist CGP35348 increased the amplitudes of the a- and b-wave without having an effect on the amplitudes of the OPs. The GABAb receptor ligands had significant and opposite effect on the latency of the OPs. These results indicate that retinal neurons, presumably a subpopulation of amacrine cells, that have GABAb receptors are not the source of the OPs of the ERG, although they may modulate these wavelets in some manner, while contributing to the generation of the dark-adapted a- and b-waves. OPs are modified by stimulation of GABAa receptors, and the a- and b-waves by stimulation of all GABA receptor subtypes.     

The postnatal development of the oscillatory potentials of the electroretinogram. I. Basic characteristics

The postnatal development of the oscillatory potentials (OPs) of the rat electroretinogram (ERG) was studied. The appearance and/or completion of the development of the individual oscillatory peaks differed from that of the a- and b-waves as well as from each other. The OPs appeared postnatally one to two days later than the a- and b-waves, respectively. The first oscillatory peak, O1, was present before the second, O2, which appeared before the later wavelets, O3, O4 and O5. The pattern of maturation of the oscillatory peaks in relatively more scotopic conditions differed from that in relatively more photopic ones. The summed amplitudes of the OPs attained adult size earlier (about two weeks) during relatively more scotopic conditions. The peak time of each oscillation gradually decreased with age. These findings show that the origin of the OPs is different from that of the a- and b-waves of the ERG and strongly indicate different origins of the earlier OPs from the later ones. Thirdly, the scotopic mechanism underlying the OPs seems to mature faster than the photopic system involved in the generation of the OPs.     

Electroretinographic abnormalities in a rat glaucoma model with chronic elevated intraocular pressure

The purpose of this study was to determine the ability of electroretinographic (ERG) measurements to document progression of the retinopathy in a rat glaucoma model. Thirty four rats with a chronic intraocular pressure (IOP) elevation induced in one eye by cautery of three episcleral/extra-orbital veins were studied in four separate groups. ERGs were recorded sequentially in Group A rats (n = 12) at baseline, and after approximately 20, 40 and 60 days of high IOP, and in three additional groups of rats (n = 6 or 10 per group) after approximately 58, 30 and 175 days of high IOP, respectively. Scotopic ERG parameters recorded simultaneously from both eyes in Group A rats were: a- and b-wave amplitudes, implicit times, oscillatory potential amplitudes (OPs) determined at three different light-flash intensities, and the light-adapted (photopic) ERG b-wave amplitude. In the other groups of rats, only scotopic ERG a-wave, b-wave and OP amplitudes were measured.In Group A rats that were followed sequentially, all the ERG parameters recorded with attenuated stimuli showed significant time-dependent changes in glaucomatous eyes relative to their contralateral normal eyes, with OPs showing the earliest significant difference after only 3 weeks of high IOP. When different groups of unilateral glaucomatous rats were compared beyond 8 weeks of elevated IOP only the OPs showed a continued decrease with time and good discrimination between glaucoma and normal eyes. Over a 25 week period of high IOP the scotopic OPs measured with attenuated light stimuli declined at the rate of approximately 1.5% per week and provided the best ERG measure to monitor progression of retinal pathophysiology in the vein-occlusion rat glaucoma model.     

Contribution of N-methyl-dl-aspartic acid (NMDA)-sensitive neurons to generating oscillatory potentials in Royal College of Surgeons rats

Purpose

We investigated how the N-methyl-dl-aspartic acid (NMDA) receptor contributes to generating oscillatory potentials (OPs) of the electroretinogram (ERG) in the Royal College of Surgeons (RCS) rat.

Methods

Scotopic ERGs were recorded from dystrophic and wild-type congenic (WT) RCS rats (n = 20 of each) at 25, 30, 35, and 40 days of age. The stimulus intensity was increased from ?2.82 to 0.71 log cd-s/m² to obtain intensity-response function. NMDA was injected into the vitreous cavity of the right eyes. The left eyes were injected with saline as controls. The P3 obtained by a-wave fitting was digitally subtracted from the scotopic ERG to isolate the P2. For the OPs, the P2 was digitally filtered between 65 and 500 Hz. The amplitudes of OP1, OP2, OP3, and OP4 were then measured and summed and designated as ΣOPs. The implicit times of OP1, OP2, and OP3 were also measured. The frequency spectra of the OPs were analyzed using fast Fourier transform (FFT).

Results

The maximum ERG a- and b-waves as well as ΣOPs amplitudes reduced with age in dystrophic rats. Compared with intravitreal saline injection, administration of NMDA decreased ΣOPs amplitudes from 30 days of age in dystrophic rats, while it did not attenuate ΣOPs amplitudes in WT rats. The implicit times of the OPs of the maximum ERG were prolonged by NMDA injections in WT and dystrophic rats. NMDA/saline ratios of ΣOPs amplitudes area under the FFT curves were significantly lower in dystrophic rats from 30 days of age than that in WT rats.

Conclusion

In the early stage of photoreceptor degeneration, intravitreal NMDA injection attenuated OPs amplitudes in dystrophic rats. This indicates that NMDA receptors play a significant role in generating OPs amplitudes with advancing photoreceptor degeneration.