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Abstract
The purpose of this study was to determine what contributions are made to the rat full-field electroretinogram (ERG) by ganglion cells (GCs). To that end, the ERG was assessed longitudinally following optic nerve transection (ONTx). Additional studies were conducted using intravitreal injections of pharmacologically active substances. The ERG was recorded simultaneously from both eyes of anaesthetized adult Brown-Norway rats (ketamine: xylazine: acepromazine, 55: 5: 1 mg kg(-1)) using custom silver chloride electrodes. Stimuli were brief, white xenon discharges delivered via a Ganzfeld under dark-adapted and light-adapted conditions (150 cd m(-2)). ERGs were obtained 1, 2, 3, 4 and 9 weeks after ONTx (n = 8) or sham (n = 8) operations. ONTx reduced both positive and negative components of the scotopic threshold response (pSTR and nSTR). Scotopic ERG responses to brighter flashes, including a-waves, b-waves and oscillatory potentials (OPs) were unaffected by ONTx. ONTx reduced the photopic b-wave and OPs. TTX (6 microM) reduced the pSTR and nSTR, but not the scotopic a-wave, b-wave or OPs. TTX had dramatic effects on the photopic ERG, surpassing the effects of ONTx. TTX application 9 weeks post-ONTx had little additional effect on the STR. Inhibition of inner retinal responses using GABA (10 mM) or NMDA (0.8 mM) reduced the nSTR substantially. Similar results were obtained with antagonists of AMPA/KA ionotropic glutamate receptors 6-cyano-7-nitroquinoxaline-2,3(1H,4H)-dione (CNQX, 0.2 mM) or cis-2,3-piperidinedicarboxylic acid (PDA, 5 mm); however, both also reduced the scotopic b-wave by approximately 40 %. By contrast, the NMDA receptor antagonist D(-)-2-amino-7-phosphonoheptanoic acid (D-AP7, 0.2 mM) had no effect alone, but the combination of D-AP7 and CNQX completely abolished the STR. The results of this study indicate that: (1) both pSTR and nSTR components in the rat depend directly upon intact GC responses, and that amacrine cell contributions to these components are relatively small; (2) scotopic ERG response components to brighter flashes receive little influence from GCs; (3) the rat photopic ERG also reflects GC signals and may serve as an additional useful test of GC function; (4) TTX had dramatic effects on the rat photopic ERG that were not attributable to GC currents, but rather to voltage-gated sodium currents in amacrine or interplexiform cells; (5) a small residual negative STR persisted after ONTx that was likely to be generated by graded responses of third-order retinal cells, most likely amacrine cells.
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Affiliation(s)
- Bang V Bui
- Discoveries in Sight, Legacy Clinical Research & Technology Centre, 1225 NE 2nd Avenue, Portland, OR 97232, USA
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202
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Affiliation(s)
- Martha Neuringer
- Oregon National Primate Research Center, and Department of Medicine, Oregon Health and Science University, Beaverton, Oregon 97006, USA
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203
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Goto Y, Taniwaki T, Shigematsu J, Tobimatsu S. The long-term effects of antiepileptic drugs on the visual system in rats: electrophysiological and histopathological studies. Clin Neurophysiol 2003; 114:1395-402. [PMID: 12888021 DOI: 10.1016/s1388-2457(03)00128-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE We quantified the long-term effects of antiepileptic drugs (AEDs) on the visual system of rats using electroretinograms (ERGs) and visual evoked potentials (VEPs). METHODS Twenty adult Sprague-Dawley rats were divided into 4 groups (n=5). Each animal was treated by monotherapy of phenytoin (PHT), valproic acid (VPA), zonisamide (ZNS) or physiological saline as control. The AEDs were injected intraperitoneally daily for 180 days. ERGs and VEPs were recorded before the medication and on Days 30 and 180. RESULTS There were no significant changes in the 4 groups on Day 30. On Day 180, the amplitudes of a- and b-waves of dark-adapted (DA) ERGs were reduced in the PHT group compared with those of the control group. In the VPA group, the amplitudes of the DA ERG a- and b-waves, light-adapted ERG b-wave and the DA VEP were reduced. No significant changes were observed in the ZNS group. There were no histopathological changes of the retina and visual cortex in all groups. CONCLUSIONS Our results indicate that neurons along the visual pathways have different sensitivity to each AED. This may result from the differential pharmacological actions of each AED on visual neurons. SIGNIFICANCE Our findings suggest that epileptic patients on long-term use of AEDs might have subclinical influences to the visual systems.
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Affiliation(s)
- Yoshinobu Goto
- Department of Clinical Neurophysiology, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-Ku, Fukuoka 812-8582, Japan.
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204
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Racine J, Behn D, Simard E, Lachapelle P. Spontaneous occurrence of a potentially night blinding disorder in guinea pigs. Doc Ophthalmol 2003; 107:59-69. [PMID: 12906123 DOI: 10.1023/a:1024435911882] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Several hereditary retinal disorders such as retinitis pigmentosa and congenital stationary night blindness compromise, sometimes exclusively, the activity of the rod pathway. Unfortunately, there are few animal models of these disorders that could help us better understand the pathophysiological processes involved. The purpose of this report is to present a pedigree of guinea pigs where, as a result of a consanguineous mating and subsequent selective breeding, we developed a new and naturally occurring animal model of a rod disorder. Analysis of the retinal function with the electroretinogram reveals that the threshold for rod-mediated electroretinograms (ERGs) is significantly increased by more than 2 log-units compared to that of normal guinea pigs. Furthermore, in response to a suprathreshold stimulus, also delivered under scotopic condition, which yield a mixed cone-rod response in normal guinea pigs, the ERG waveform in our mutant guinea pigs is almost identical (amplitude and timing of a- and b-waves) to that evoked in photopic condition. The above would thus suggest either a structural (abnormal development or absence) or a functional deficiency of the rod photoreceptors. We believe that our pedigree possibly represents a new animal model of a night blinding disorder, and that this condition is inherited as anautosomal recessive trait in the guinea pig population.
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Affiliation(s)
- Julie Racine
- Departments of Ophthalmology and Neurology-Neurosurgery, McGill University-Montreal Children's Hospital Research Institute, Montréal, Québec, Canada
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205
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Lowry B, Beaumont P. Light rise of the human electroretinogram is normal in retinitis pigmentosa. Clin Exp Ophthalmol 2003; 31:262-4. [PMID: 12786781 DOI: 10.1046/j.1442-9071.2003.00642.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
AIM To determine if the electroretinogram (ERG) light rise is reduced below normal in patients with retinitis pigmentosa (RP) and whether it is greater in patients with smaller ERG. METHODS Both eyes of 31 normal subjects and 59 subjects with RP had photopic ERGs on ISCEV standard and brighter backgrounds, before and after dark adaptation. Recordings <2.5 micro V were excluded. RESULTS Ratios of amplitudes before and after dark adaptation varied little. The b-wave averaged 1.88 (SD 0.41) in normal subjects and 1.66 (SD 0.62) in RP subjects, and a-waves averaged 1.44 (SD 0.42) and 1.31 (SD 0.73), respectively. None of eight t-tests were significant (<2.4). There was a positive (not negative) correlation between RP subjects' initial b-wave amplitude and light rise but not for a-waves. A-wave light rises were smaller. CONCLUSION Retinitis pigmentosa does not reduce the light rise of recordable ERG. The light rise of the ERG is larger in those RP subjects with larger initial b-waves. This confirms previous findings. The difference between a- and b-waves in RP suggests post-receptoral processes are involved.
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206
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Rufiange M, Dassa J, Dembinska O, Koenekoop RK, Little JM, Polomeno RC, Dumont M, Chemtob S, Lachapelle P. The photopic ERG luminance-response function (photopic hill): method of analysis and clinical application. Vision Res 2003; 43:1405-12. [PMID: 12742110 DOI: 10.1016/s0042-6989(03)00118-4] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
With progressively brighter stimuli, the amplitude of the photopic b-wave first increases, briefly saturates and then decreases gradually to reach a plateau, where the amplitude of the b-wave equals that of the a-wave; a phenomenon previously presented as the photopic hill. The unique presentation of this luminance-response function seriously complicates its analysis with curve fitting equations such as that of Naka-Rushton used for scotopic electroretinogram. We report a method of analysis of the photopic hill based on easily identifiable and reproducible features of the ascending and descending limbs of this function. The clinical usefulness of these parameters is illustrated with selected cases of retinal disorders.
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Affiliation(s)
- Marianne Rufiange
- Department of Ophthalmology (D-164), McGill University, Montreal Children's Hospital Research Institute, 2300 Tupper Street, Que., H3H 1P3, Montreal, Canada
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207
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Pennesi ME, Howes KA, Baehr W, Wu SM. Guanylate cyclase-activating protein (GCAP) 1 rescues cone recovery kinetics in GCAP1/GCAP2 knockout mice. Proc Natl Acad Sci U S A 2003; 100:6783-8. [PMID: 12732716 PMCID: PMC164524 DOI: 10.1073/pnas.1130102100] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Mediated by guanylate cyclase-activating proteins (GCAPs), cytoplasmic Ca2+ levels regulate the activity of photoreceptor guanylate cyclase (GC) and the synthesis of cGMP, the internal transmitter of phototransduction. When GCAP1 is expressed in transgenic mice on a GCAP null background, it restores the wild-type flash responses in rod photoreceptors. In this communication, we explored the role of GCAP1 in cone photoreceptors by using electroretinograms (ERGs). Under cone isolation conditions, ERGs recorded from mice lacking both GCAP1 and GCAP2 had normal amplitudes of the saturated a-wave and b-wave. However, recordings from these mice demonstrated a widened b-wave and increased sensitivity of both M- and UV-cone systems. Paired-flash ERGs revealed a delayed recovery of both the cone driven b-wave and a-wave and suggest that the delay originated from the photoreceptors. To test whether GCAP1 could restore normal cone response recovery, mice that expressed only transgenic GCAP1 in the absence of wild-type GCAP expression were tested. Immunohistochemical analysis demonstrated that cones of these mice expressed high levels of GCAP1. Paired-flash ERGs showed that the recovery of the cone-driven a-wave was restored to normal, whereas recovery of the cone-driven b-wave was slightly faster than that observed in wild-type mice. These studies reveal that, similar to rods, deletion of GCAP1 and GCAP2 delays the recovery of light responses in cones and GCAP1 restores the recovery of cone responses in the absence of GCAP2.
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Affiliation(s)
- Mark E Pennesi
- Department of Ophthalmology, Cullen Eye Institute, Baylor College of Medicine, Houston, TX 77030, USA.
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208
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Abstract
We have been in search of an alternate species for the monkey to study the effects of drugs on the I-type photopic electroretinogram (ERG) response that is typically seen in the cone-rich retina of the primate. The guinea pig has two types of cones, one of which contains a middle-wavelength sensitive pigment otherwise found only in Old World primates. We studied the Ganzfeld electroretinogram (ERG) of the guinea pig in relation to monkey and rat ERGs to learn whether the guinea pig might be a good animal model to study the 'primate-like' cone ERG. The guinea pig scotopic ERG was similar to other mammal ERGs and was not electronegative when fully dark-adapted. We saw no evidence of a negative-going scotopic threshold response (STR). The guinea pig photopic ERG a-wave is larger than that of the rat but much smaller than the primate a-wave, and it lacked a phasic d-wave. PDA eliminated guinea pig photopic a-wave and caused the OFF-response to long stimuli to invert polarity, as seen in monkey but not in rat. The guinea pig overall shows a weak I-type response and may be a useful substitute for primate in some studies of the photopic ERG.
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Affiliation(s)
- Bo Lei
- Department of Ophthalmology and Visual Science, W.K. Kellogg Eye Center, University of Michigan, Ann Arbor, MI 65211, USA.
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209
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Popova E, Mitova L, Vitanova L, Kupenova P. Participation of the GABAergic system in the action of 2-amino-4-phosphonobutyrate on the OFF responses of frog retinal ganglion cells. Vision Res 2003; 43:607-16. [PMID: 12604097 DOI: 10.1016/s0042-6989(03)00008-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Perfusion of dark adapted frog eyecups with the ON pathway blocker 2-amino-4-phosphonobutyrate (APB) not only abolished the ganglion cells (GCs)' ON responses and the ERG b-wave, but it markedly potentiated the OFF responses of all ON-OFF and phasic OFF GCs and the d-wave amplitude of a simultaneously recorded ERG as well. The blockade of GABA(A) and GABA(C) receptors by picrotoxin eliminated this potentiating effect in 24 out of 41 GCs, although in the rest of the cells it did not produce any change in the APB effect. On the other hand, the d-wave potentiation was preserved during the GABAergic blockade in all experiments. Our results indicate that GABAergic transmission is involved in the inhibition exerted by the ON upon the OFF channel in part of the ON-OFF and phasic OFF GCs in the frog retina. The tonic OFF GCs probably do not receive an inhibitory input from the ON channel, because their light responses were not altered either by APB alone or by APB during blockade of GABA(A) and GABA(C) receptors.
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Affiliation(s)
- E Popova
- Department of Physiology, Medical Faculty, Medical University, Elka Popova, 1431, Sofia, Bulgaria.
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210
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Robson JG, Saszik SM, Ahmed J, Frishman LJ. Rod and cone contributions to the a-wave of the electroretinogram of the macaque. J Physiol 2003; 547:509-30. [PMID: 12562933 PMCID: PMC2342654 DOI: 10.1113/jphysiol.2002.030304] [Citation(s) in RCA: 128] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2002] [Accepted: 11/21/2002] [Indexed: 11/08/2022] Open
Abstract
The electroretinogram (ERG) of anaesthetised dark-adapted macaque monkeys was recorded in response to ganzfeld stimulation and rod- and cone-driven receptoral and postreceptoral components were separated and modelled. The test stimuli were brief (< 4.1 ms) flashes. The cone-driven component was isolated by delivering the stimulus shortly after a rod-saturating background had been extinguished. The rod-driven component was derived by subtracting the cone-driven component from the mixed rod-cone ERG. The initial part of the leading edge of the rod-driven a-wave scaled linearly with stimulus energy when energy was sufficiently low and, for times less than about 12 ms after the stimulus, it was well described by a linear model incorporating a distributed delay and three cascaded low-pass filter elements. Addition of a simple static saturating non-linearity with a characteristic intermediate between a hyperbolic and an exponential function was sufficient to extend application of the model to most of the leading edge of the saturated responses to high energy stimuli. It was not necessary to assume involvement of any other non-linearity or that any significant low-pass filter followed the non-linear stage of the model. A negative inner-retinal component contributed to the later part of the rod-driven a-wave. After suppressing this component by blocking ionotropic glutamate receptors, the entire a-wave up to the time of the first zero-crossing scaled with stimulus energy and was well described by summing the response of the rod model with that of a model describing the leading edge of the rod-bipolar cell response. The negative inner-retinal component essentially cancelled the early part of the rod-bipolar cell component and, for stimuli of moderate energy, made it appear that the photoreceptor current was the only significant component of the leading edge of the a-wave. The leading edge of the cone-driven a-wave included a slow phase that continued up to the peak, and was reduced in amplitude either by a rod-suppressing background or by the glutamate analogue, cis-piperidine-2,3-dicarboxylic acid (PDA). Thus the slow phase represents a postreceptoral component present in addition to a fast component of the a-wave generated by the cones themselves. At high stimulus energies, it appeared less than 5 ms after the stimulus. The leading edge of the cone-driven a-wave was adequately modelled as the sum of the output of a cone photoreceptor model similar to that for rods and a postreceptoral signal obtained by a single integration of the cone output. In addition, the output of the static non-linear stage in the cone model was subject to a low-pass filter with a time constant of no more than 1 ms. In conclusion, postreceptoral components must be taken into account when interpreting the leading edge of the rod- and cone-driven a-waves of the dark-adapted ERG.
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Affiliation(s)
- John G Robson
- College of Optometry, University of Houston, Houston, TX 77204-2020, USA
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211
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Aldebasi YH, Drasdo N, Morgan JE, North RV. Cortical OFF-potentials from the S-cone pathway reveal neural damage in early glaucoma. Vision Res 2003; 43:221-6. [PMID: 12536143 DOI: 10.1016/s0042-6989(02)00435-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We used background adaptation and silent substitution techniques to record full-field ON and OFF-visually evoked cortical potentials (VECPs) selectively from the S-cone and L- and M-cone pathways in 15 patients with primary open angle glaucoma (POAG), and 15 normal controls. The most statistically significant (P=0.01) VECP test for POAG was a voltage change in the S-cone pathway cortical OFF-response. A sensitivity of 93% was achieved, with 60% specificity at minimum error rate. This is presumed to reflect reduced activity in the S-cone and magnocellular visual pathways, and may provide an effective method for research and monitoring change in early glaucoma.
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212
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Hanitzsch R, Küppers L. The effects of GABA and vigabatrin on horizontal cell responses to light and the effect of vigabatrin on the electroretinogram. Doc Ophthalmol 2002; 105:313-26. [PMID: 12539856 DOI: 10.1023/a:1021270201902] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
When used as an antiepileptic drug in humans vigabatrin, which is a GABA analogue and an inhibitor of GABA-aminotransferase, often causes peripheral visual field loss. This could result from increases in endogenous GABA levels. Accordingly we have investigated the effects of GABA on horizontal cells (HCs) of the rabbit retina, and of vigabatrin, when applied for only a few minutes, on HCs and on the electroretinogram (ERG). The intracellular HC and ERG records were first obtained from isolated rabbit retinas during perfusion with a physiological solution. The perfusate was then changed to one containing GABA (2 mM) or vigabatrin (25, 40 or 150 microM) for at least 5 min, and then returned to the control solution. 2 mM GABA significantly but reversibly reduced the light responses of HCs elicited by diffuse light (at -4 log intensity) to 52 +/- 17% (SD, n = 7). Vigabatrin had no significant effect on the light responses of HCs (n = 7), and no effect on the b-wave (n = 4), but the PIII-component of the ERG was slightly but significantly reduced to 84 +/- 5% (SD, n = 5). The high dosage of GABA needed to affect the light responses of HCs could be due to strong GABA uptake systems in the intact rabbit retina. It is, however, possible that in humans receiving long-term treatment with vigabatrin, high levels of GABA occur because of the inhibition of GABA- aminotransferase. It seems, from these observations, that neurons like on-bipolar cells, which are contributors to the b-wave, and HCs are uninfluenced by vigabatrin in short-term experiments. The slightly reduced slow PIII-component, however, indicates an influence on the glial Müller cells which are the main contributors to the slow PIII-component.
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Affiliation(s)
- R Hanitzsch
- Carl-Ludwig-Institute of Physiology, University of Leipzig, Leipzig, Germany.
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213
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Hare WA, Ton H. Effects of APB, PDA, and TTX on ERG responses recorded using both multifocal and conventional methods in monkey. Effects of APB, PDA, and TTX on monkey ERG responses. Doc Ophthalmol 2002; 105:189-222. [PMID: 12462444 DOI: 10.1023/a:1020553020264] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Results from studies of human subjects suggest that the multifocal ERG technique developed by Erich Sutter and colleagues has considerable potential for assessment of retinal function in both the clinic and laboratory. While the utility of this measure depends to a large extent upon an understanding of the physiological origin for the different response components, relatively little is known in this regard. For the experiments described in this report, we made ERG recordings using both multifocal and conventional methods. Intravitreal injections of APB, PDA, and TTX were used to identify contributions from activity in ON pathway, OFF pathway, and third order retinal neurons, respectively. The results show that photoreceptor activity makes a small direct contribution to 1st and 2nd order multifocal photopic luminance responses. TTX-sensitive activity in third order retinal neurons contributes to both 1st and 2nd order responses with relatively greater contribution to the 2nd order response. Blockade of TTX-sensitive activity in third order cells produces effects on the 2nd order response which are very similar to changes observed in eyes suffering selective loss of retinal ganglion cells resulting from experimental glaucoma. Effects of these intravitreally injected test agents were also determined, in the same recording session, for flash, 30 Hz flicker, and oscillatory potential responses.
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Affiliation(s)
- William A Hare
- Department of Biological Sciences, Allergan Pharmaceuticals, Irvine, CA 92612, USA
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214
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Drasdo N, Aldebasi YH, Mortlock KE, Chiti Z, Morgan JE, North RV, Wild JM. Ocular optics, electroretinography and primary open angle glaucoma. Ophthalmic Physiol Opt 2002; 22:455-62. [PMID: 12358318 DOI: 10.1046/j.1475-1313.2002.00078.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Advancing the knowledge of ocular image quality is important in the development of new tests for the earlier detection of primary open angle glaucoma (POAG). Loss of blue sensitivity is an important feature of POAG; however, it is difficult to separate this loss from the effects of wavelength related intraocular light scatter and media absorption. A technique for recording the S-cone electroretinogram is described which may solve these problems. The effect of scattered light is avoided by a Ganzfeld stimulus and the absorption of short wavelength light is compensated by a photometric balancing of blue and green stimuli using the M-cone response. The modulation transfer function of the eye has enabled the true spatial tuning function of the retina to be determined by pattern electroretinography (PERG). This has demonstrated the role of retinal ganglion cells in the generation of the PERG. These techniques are shown to be highly sensitive tests in the early stages of POAG.
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Affiliation(s)
- Neville Drasdo
- Department of Optometry and Vision Sciences, Cardiff University, UK.
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215
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Abstract
We investigated the effects of photoreceptor degeneration on the anatomy and physiology of inner retinal neurons in a mouse model of retinitis pigmentosa, the retinal degeneration (rd) mutant mouse. Although there is a general assumption that the inner retinal cells do not suffer from photoreceptor death, we confirmed major changes both accompanying and after this process. Changes include sprouting of horizontal cells, lack of development of dendrites of rod bipolar cells, and progressive atrophy of dendrites in cone bipolar cells. Electrophysiological recordings demonstrate a selective impairment of second-order neurons that is not predictable on the basis of a pure photoreceptor dysfunction. Our data point out the necessity to prove integrity of the inner retina before attempting restoring visual function through photoreceptor intervention. This is even more important when considering that although intervention can be performed before the onset of any symptoms in animals carrying inherited retinopathies, this is obviously not true for human subjects.
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216
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Langrová H, Gamer D, Friedburg C, Besch D, Zrenner E, Apfelstedt-Sylla E. Abnormalities of the long flash ERG in congenital stationary night blindness of the Schubert-Bornschein type. Vision Res 2002; 42:1475-83. [PMID: 12044753 DOI: 10.1016/s0042-6989(02)00068-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We investigated abnormalities of the retinal cone ON- and OFF-pathways in 24 males with Schubert-Bornschein congenital stationary night blindness (CSNB). Substantial differences were found between both CSNB types. In incomplete type, a-, b- and d-waves were reduced and delayed, whereas in complete type only the b-wave showed significant changes. Oscillatory potentials (OPs) were not discernible from noise in incomplete CSNB and showed significant peak alterations of the ON-OPs only in complete CSNB. In the complete CSNB type, the ON pathway appeared to be mainly affected. In the incomplete CSNB form marked involvement of both the ON and the OFF pathways was noted.
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Affiliation(s)
- Hana Langrová
- Department of Pathophysiology of Vision and Neuroophthalmology, University Eye Hospital, 72075 Tübingen, Germany.
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217
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Rufiange M, Rousseau S, Dembinska O, Lachapelle P. Cone-dominated ERG luminance-response function: the Photopic Hill revisited. Doc Ophthalmol 2002; 104:231-48. [PMID: 12076014 DOI: 10.1023/a:1015265812018] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
PURPOSE In response to progressively brighter stimuli, the b-wave of the photopic ERG gradually augments in amplitude, reaches a plateau for a narrow range of intensities and then rapidly decreases with further increments in the luminance of the flash. This unique luminance-response function was originally introduced as the Photopic Hill. The purpose of this study was to further characterize this unique feature of the cone ERG, investigate if it was only limited to b-wave measurements and if it could be obtained under different photopic background luminances. METHODS Photopic ERGs and oscillatory potentials were generated in response to flashes of light ranging from 0.5 to 16 cd m(-2) s in intensity and presented against photopic backgrounds varying from 18 to 525 cd m(-2) in luminance. RESULTS All but the brightest background yielded a clear Photopic Hill like luminance-response function which could only be evidenced with the b-wave, the i-wave and OP4 amplitude measurements. Interestingly, the maximal amplitude reached remained almost identical irrespective of the background luminance. CONCLUSIONS Our results suggest that the retinal mechanisms at the origin of the Photopic Hill effect could represent a voltage limitation mechanism, intimately tied to the OFF pathway. The latter would however be intrinsic to the cone system only and not to the entire retinal network since significantly higher peak amplitudes are reached with dark adaptation.
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Affiliation(s)
- Marianne Rufiange
- Department of Ophthalmology, McGill University, Montreal Children's Hospital Research Institute, Quebec, Canada
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218
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Shinoda K, Ohde H, Inoue R, Ishida S, Mashima Y, Oguchi Y. ON-pathway disturbance in two siblings. ACTA OPHTHALMOLOGICA SCANDINAVICA 2002; 80:219-23. [PMID: 11952493 DOI: 10.1034/j.1600-0420.2002.800219.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
PURPOSE To present two clinical cases diagnosed with predominant cone dystrophy and demonstrating early disturbance in the on-centre bipolar cells (ON-pathway). METHODS Electrophysiological findings are presented in two siblings with predominant cone dystrophy. The subjects showed no remarkable ophthalmoscopic or fluorescein angiographic retinal changes, but demonstrated progressive visual disturbance during their 20s. RESULTS The electroretinograms (ERGs) showed reduced dark-adapted responses but the positive component of the photopic ERG was absent. Response to 30 Hz flicker was severely reduced. Electroretinograms elicited by long-duration stimuli showed a loss of the b-wave, and the off-response was slightly reduced. In both patients, multifocal ERGs (m-ERGs) were more reduced within the central 10 degrees, where the ON-pathway is normally a major contributor. CONCLUSION We conclude that these patients may be affected by an abnormality of the synapses of the cone receptors and that their decrease in vision might, at least initially, be due to selective ON-pathway dysfunction.
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Affiliation(s)
- Kei Shinoda
- Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan.
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219
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Imaizumi M, Matsumoto CS, Kimoto KI, Furushima M, Nakatsuka K. "On" response dysfunction in multifocal posterior pigment epitheliopathy. Retina 2002; 22:33-6. [PMID: 11884875 DOI: 10.1097/00006982-200202000-00006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE To determine the electroretinographic properties of one patient with multifocal posterior pigment epitheliopathy. METHODS Rod and cone electroretinograms (ERGs) and photopic ERGs elicited by long-duration stimuli were studied in a patient with multifocal posterior pigment epitheliopathy. RESULTS The amplitudes of both the rod and cone ERGs were significantly reduced. Photopic ERGs elicited by long-duration stimuli demonstrated that the b-wave ("on" response) was abolished but the d-wave ("off" response) was reduced by only amplitude. CONCLUSION The ERG findings in multifocal posterior pigment epitheliopathy indicate that there is dysfunction not only of the photoreceptors but also in the signal transmission specific for the "on" pathway.
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Affiliation(s)
- Masamoto Imaizumi
- Department of Ophthalmology, Oita Medical University, Hasama-machi, Oita-ken, Japan
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220
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Harwerth RS, Crawford MLJ, Frishman LJ, Viswanathan S, Smith EL, Carter-Dawson L. Visual field defects and neural losses from experimental glaucoma. Prog Retin Eye Res 2002; 21:91-125. [PMID: 11906813 DOI: 10.1016/s1350-9462(01)00022-2] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Glaucoma is a relatively common disease in which the death of retinal ganglion cells causes a progressive loss of sight, often leading to blindness. Typically, the degree of a patient's visual dysfunction is assessed by clinical perimetry, involving subjective measurements of light-sense thresholds across the visual field, but the relationship between visual and neural losses is inexact. Therefore, to better understand of the effects of glaucoma on the visual system, a series of investigations involving psychophysics, electrophysiology, anatomy, and histochemistry were conducted on experimental glaucoma in monkeys. The principal results of the studies showed that, (1) the depth of visual defects with standard clinical perimetry are predicted by a loss of probability summation among retinal detection mechanisms, (2) glaucomatous optic atrophy causes a non-selective reduction of metabolism of neurons in the afferent visual pathway, and (3) objective electrophysiological methods can be as sensitive as standard clinical perimetry in assessing the neural losses from glaucoma. These experimental findings from glaucoma in monkeys provide fundamental data that should be applicable to improving methods for assessing glaucomatous optic neuropathy in patients.
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Affiliation(s)
- Ronald S Harwerth
- College of Optometry, University of Houston, 505 J. Davis Armistead Building, TX 77204-2020, USA.
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221
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Fortune B, Johnson CA. Decline of photopic multifocal electroretinogram responses with age is due primarily to preretinal optical factors. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2002; 19:173-184. [PMID: 11778721 DOI: 10.1364/josaa.19.000173] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Age-related changes in photopic retinal function were evaluated topographically with the multifocal electroretinogram (mfERG). Thirty-two subjects between the ages of 16 and 69 participated. There was a strong dependence on age for all mfERG response measures that was strongest for the group of central retinal responses (i.e., within 5 deg eccentricity) and approximately equal for responses between 5 and 20 deg. After adjustment for crystalline lens optical density and pupil diameter, significant effects of age were limited to central first-order (i.e., within 5 deg) and second-order response kernels. Simulation studies support an optical basis for the observed age-related changes. It is concluded that mfERG changes between the ages of 20 and 70 are due predominantly to preretinal optical factors.
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Affiliation(s)
- Brad Fortune
- Discoveries in Sight Research Laboratories, Devers Eye Institute, Portland, Oregon 97208-3950, USA
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222
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Khan NW, Jamison JA, Kemp JA, Sieving PA. Analysis of photoreceptor function and inner retinal activity in juvenile X-linked retinoschisis. Vision Res 2001; 41:3931-42. [PMID: 11738458 DOI: 10.1016/s0042-6989(01)00188-2] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Thirteen retinoschisis males with genotyped XLRS1 gene mutations were examined by electroretinogram (ERG) techniques to determine photoreceptor involvement and ON-pathway and OFF-pathway sites of dysfunction. Parameters R(max) and logS determined by fitting the mathematical model of the activation phase of phototransduction to the scotopic and photopic a-wave responses, were not significantly different from normal. However, the XLRS photopic a-wave amplitudes were significantly lower than normal across all intensities, consistent with defective signaling in the OFF pathway. Long flash (150 ms) ON-OFF photopic responses showed reduced b-wave amplitude but normal d-wave amplitude, giving a reduced b/d ratio of <1.32 Hz photopic flicker ERG fundamental frequency responses showed reduced amplitude and delayed phase, consistent with abnormal signaling by both the ON- and OFF-pathway components. These results indicate that the XLRS1 protein appears not to affect photoreceptor function directly for most XLRS males, and that ERG signaling abnormalities occur in both the ON- and OFF-pathway components that originate in the proximal retina.
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Affiliation(s)
- N W Khan
- Department of Ophthalmology and Visual Sciences, W. K. Kellogg Eye Center, University of Michigan, 1000 Wall Street, Ann Arbor, MI 48105, USA
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223
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Mizunoya S, Kuniyoshi K, Arai M, Tahara K, Hirose T. Electroretinogram contact lens electrode with tri-color light-emitting diode. ACTA OPHTHALMOLOGICA SCANDINAVICA 2001; 79:497-500. [PMID: 11594987 DOI: 10.1034/j.1600-0420.2001.790514.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
PURPOSE This study was performed to evaluate a new electroretinogram (ERG) contact lens electrode containing four light-emitting diodes (LEDs) that are used for both stimulus and background light. METHODS The luminance of each LED could be changed independently and used as stimulus light. Red, blue, bright white, and flickering ERGs were recorded in 12 normal subjects and two patients with progressive cone dystrophy. The long-duration light stimuli separated the on- and off-responses of the ERG. This equipment is not according to the ISCEV standard. RESULTS The tri-color LED electrode contact lens can efficiently produce and record ERG responses. Off-responses were recordable separately from on-responses by lengthening the stimulus duration. CONCLUSION This combined stimulus-electrode system is compact and portable. Combined with the portable amplifier and the recorder, the ERGs can be recorded easily in an operating room, at patients' bedside, and in remote locations away from clinics and hospitals.
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Affiliation(s)
- S Mizunoya
- Schepens Eye Research Institute, Department of Ophthalmology, Harvard Medical School and Schepens Retina Associates, Boston, Massachusetts, USA.
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224
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Goto Y, Furuta A, Tobimatsu S. Magnesium deficiency differentially affects the retina and visual cortex of intact rats. J Nutr 2001; 131:2378-81. [PMID: 11533282 DOI: 10.1093/jn/131.9.2378] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
To determine the influence of magnesium (Mg) on the visual system, electroretinograms (ERG) and visual evoked potentials (VEP) were recorded under dark-(DA) and light-adapted (LA) conditions in intact rats. Weanling rats were fed either a Mg-deficient (Mg-D) or a control diet for 17 d before the tests, and ERG, VEP and immunohistopathological analyses of retinae and cortices were made. In the Mg-D rats, ear congestion, hair loss and loss of body weight were observed, and serum Mg concentration was approximately 25% of that in the control rats (P < 0.01). The amplitudes of the DA a-wave and the second positive peak of the oscillatory potentials (OP2) of the ERG, and the negative component of the VEP (N1) in Mg-D rats were significantly greater than those of control rats. However, the amplitudes of the DA b-wave, LA 2 Hz b-wave, the 20 Hz flicker responses and the implicit times of all response components did not differ between the two groups. The immunohistopathologic results also were not altered in the Mg-D rats. We suggest that the functional abnormalities induced by Mg deficiency may depend not only on the hyperactivity of the N-methyl-D-aspartate (NMDA) receptor, but also on the behavior of the Ca(2+) and Mg(2+) ions in the intact eye.
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Affiliation(s)
- Y Goto
- Department of Clinical Neurophysiology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
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225
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Kasuga T. Effect of glutamate analogues on red-green opponent interaction in monkey electroretinograms. Exp Eye Res 2001; 73:311-20. [PMID: 11520106 DOI: 10.1006/exer.2001.1043] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effect of glutamate analogues on red-green opponent interaction was electrophysiologically investigated in anesthetized cynomolgus monkeys (Macaca fascicularis). Two approaches were employed: amplitude measurement and principal component analysis. Electroretinograms were recorded for 23 monochromatic stimuli (400-700 nm) at an equal energy with white light adaptation before and after treatment with the glutamate analogues, 2-amino-4-phosphonobutyric acid, cis -2,3-piperidine-dicarboxylic acid, or both. Before treatment, although spectral amplitude curves of the a- and d-waves showed single, broad peaks at about 550 nm, the b-wave curve had three peaks at about 460, 540 and 600 nm, indicating the occurrence of the red-green opponent interaction. Principal component analysis performed on these waveforms extracted three components with short, middle, and long wavelength peaks, well defined characteristics of the red-green opponency. After vitreal injection of 2-amino-4-phosphonobutyric acid, the a- and d-wave amplitudes were enhanced while the b-wave amplitude was almost completely diminished. However, principal component analysis showed basically similar characteristics to those before drug, suggesting that the red-green opponency was not affected. In contrast, after application of cis -2,3-piperidine-dicarboxylic acid, the a- and d-waves were diminished and the b-wave was enhanced as expected, however the enhancement was observed only in the short and middle wavelengths. As a result of this partial enhancement, the b-wave spectral amplitude curve showed only a single peak, unlike in the control. In addition, principal component analysis revealed a quite different result from the control; only two components with short and middle wavelength peaks and the component with long wavelength peak disappeared. Similar two components were also separated after the conjunction of both drugs. These results demonstrate that red-green opponency is greatly inhibited by cis -2,3 piperidine-dicarboxylic acid, and thus suggest that horizontal cells are related to a generation of the red-green opponency through a cone type selective or nonselective negative feedback.
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Affiliation(s)
- T Kasuga
- Safety Research Laboratories, Yamanouchi Pharmaceutical Co., Ltd, 1-8 Azusawa 1-Chome, Itabashi-ku, Tokyo 174-8511, Japan.
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226
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Abstract
An important role for docosahexaenoic acid (DHA) within the retina is suggested by its high levels and active conservation in this tissue. Animals raised on n-3-deficient diets have large reductions in retinal DHA levels that are associated with altered retinal function as assessed by the electroretinogram (ERG). Despite two decades of research in this field, little is known about the mechanisms underlying altered retinal function in n-3-deficient animals. The focus of this review is on recent research that has sought to elucidate the role of DHA in retinal function, particularly within the rod photoreceptor outer segments where DHA is found at its highest concentration. An overview is also given of human infant studies that have examined whether a neonatal dietary supply of DHA is required for the normal development of retinal function.
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Affiliation(s)
- B G Jeffrey
- Department of Paediatrics and Child Health, Flinders Medical Centre, The Flinders University of South Australia, Bedford Park, Adelaide, South Australia 5042, Australia
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227
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Abstract
HEPES-buffered solutions, mostly used in studies of isolated cells, and bicarbonate-buffered solutions, mostly used in studies of isolated retinal tissues, have both been used to superfuse an isolated rabbit retina preparation. The responses of horizontal cells (HCs) to light, detected by intracellular microelectrodes filled with Lucifer Yellow, were recorded. Buffering of the superfusate with 100% HEPES completely, but reversibly, abolished the responses of A-type HCs, and is not, therefore, suitable for studies on isolated rabbit retinas. The responses remained when buffering was partially with HEPES and partially with bicarbonate, but were changed: in A-type HCs the overshoot was reduced and the afterpotential was increased. The overshoot may be caused by feedback of HCs on the cones and might be dependent on pHi at the synaptic structure between HCs and photoreceptors.
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Affiliation(s)
- R Hanitzsch
- Carl-Ludwig-Institute of Physiology, University of Leipzig, Liebigstr. 27, D-04103 Leipzig, Germany.
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228
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Affiliation(s)
- D R Pepperberg
- Lions of Illinois Eye Research Institute, Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, College of Medicine, 1855 West Taylor Street, Chicago, IL 60612, USA.
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229
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Hood DC, Bearse MA, Sutter EE, Viswanathan S, Frishman LJ. The optic nerve head component of the monkey's (Macaca mulatta) multifocal electroretinogram (mERG). Vision Res 2001; 41:2029-41. [PMID: 11403788 DOI: 10.1016/s0042-6989(01)00010-4] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To search for an optic nerve head component (ONHC) in the monkey's (Macaca mulatta) multifocal electroretinogram (mERG), mERGs from three animals were recorded with different electrode configurations. A component with a latency that varied with distance from the optic nerve head was easily identified by eye in recordings from the speculum of a Burian-Allen electrode referenced to a DTL on the unstimulated eye. This component was reasonably well isolated by subtracting a weighted version of a Burian-Allen bipolar recording or by employing the extraction algorithm of Sutter and Bearse (1999, Vision Research, 39, 419-436). The waveform of this component resembles the ONHC reported for the human mERG.
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Affiliation(s)
- D C Hood
- Department of Psychology, Columbia University, 1190 Amsterdam Ave, 10027-7004, New York, NY, USA.
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230
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Abstract
Experimental evidence exists to suggest that zinc can have positive and negative effects on the physiology of cells depending on the "local" concentration, localisation (extracellular vs. intracellular) and/or state (bound vs. free). The retina contains particularly high amounts of zinc suggesting a pivotal role in the tissue. There is also suggestive evidence that zinc deficiency in humans may result in abnormal dark adaptation and/or age-related macular degeneration. The purpose of this article is to provide an overview of various proposed functions for zinc, particularly in the retina. Endogenous chelatable zinc in the retina is localised mainly to the photoreceptors and retinal pigment epithelial cells. Moreover, the zinc localisation in the photoreceptors varies in dark and light, suggesting a role for zinc in a light-regulated process. Some zinc is also located to other areas of the retina but clearly defined zinc-enriched neurones could not be identified as has been shown to occur in certain areas of the brain. Neurones post-synaptic to zinc-enriched neurones in the brain have been suggested to be particularly vulnerable in ischaemia. The role of zinc in retinal ischaemia has been investigated to determine how it is involved in the process. It would appear that when zinc is administered in low concentrations it generally has a positive effect on an insulted retina as in ischaemia. However, higher concentrations of zinc exacerbates the influence of the insult and also acts as a toxin. Use of zinc supplements in diet must, therefore, be taken with caution.
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Affiliation(s)
- M Ugarte
- Nuffield Laboratory of Ophthalmology, University of Oxford, Walton Street, Oxford OX2 6AW, UK
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231
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Wurziger K, Lichtenberger T, Hanitzsch R. On-bipolar cells and depolarising third-order neurons as the origin of the ERG-b-wave in the RCS rat. Vision Res 2001; 41:1091-101. [PMID: 11301082 DOI: 10.1016/s0042-6989(01)00026-8] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In the retinas of Royal College of Surgeons (RCS) rats light induces an increase in distal extracellular potassium irrespective of the age, between days 19-24 and days 29-35 postpartum, but by days 29-35 the ERG b-wave has become reduced. The synaptic blocker 2-amino-4-phosphonobutyric acid (APB) causes the abolition of both the b-wave and the potassium increase at any age. MgCl2 greatly reduces the b-wave at all ages and abolishes the potassium increase in older rats, but in younger rats the potassium increase is enlarged. Since this increase occurs in the absence of the b-wave it is unlikely that the on-bipolar cells are the only sources of the b-wave. Because the NMDA receptor blocker ketamine reduces the b-wave, third order neurons, which possess NMDA receptors, could contribute to the b-wave.
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Affiliation(s)
- K Wurziger
- Carl-Ludwig-Institute of Physiology, University of Leipzig, Liebigstr. 27, D-04103, Leipzig, Germany
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232
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Shinoda K, Ohde H, Mashima Y, Inoue R, Ishida S, Inoue M, Kawashima S, Oguchi Y. On- and off-responses of the photopic electroretinograms in X-linked juvenile retinoschisis. Am J Ophthalmol 2001; 131:489-94. [PMID: 11292413 DOI: 10.1016/s0002-9394(00)00858-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
PURPOSE To examine the physiologic condition of the middle retinal layer of patients with X-linked juvenile retinoschisis (xlRS) by studying the on- and off-responses of the photopic electroretinograms (ERGs). METHODS Eleven unrelated Japanese men (mean age; 24.9 +/- 7.6 years) who were clinically diagnosed with xlRS and molecularly confirmed as having XLRS1 mutations were investigated. For the photopic ERGs, the a-, b- and d-wave amplitudes elicited by long duration stimuli were recorded, and the responses from the xlRS patients were compared to those recorded from normal subjects (n = 14, mean age, 27.5 +/- 4.5 years). We also examined the relationship between the photopic ERG responses and the genotype. RESULTS No significant difference was found between the a- and d-wave amplitudes in the xlRS patients (34.2 +/- 8.7 microV, 52.5 +/- 10.4 microV, respectively), and those in normal subjects (40.4 +/- 10.3 microV, 44.7 +/- 6.3 microV, respectively). The mean b-wave amplitude in the xlRS patients was significantly smaller (10.5 +/- 7.7 microV) than the mean of normal subjects (46.4 +/- 10.2 microV) (P < 0.0001). No significant correlation was found between the ERG responses and the locus of the mutation. CONCLUSION The photopic ERG demonstrated considerable impairment of the on-pathway arising from an abnormality of the on-bipolar cells or possibly secondary to Müller cell abnormality in xlRS.
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Affiliation(s)
- K Shinoda
- Department of Ophthalmology, Keio University School of Medicine, Shinjuku-ku, Tokyo, Japan.
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233
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Kondo M, Miyake Y. Assessment of local cone on- and off-pathway function using multifocal ERG technique. Doc Ophthalmol 2001; 100:139-54. [PMID: 11142743 DOI: 10.1023/a:1002779619050] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
There is evidence that recording the photopic ON- and OFF-responses with long-duration stimuli is useful for determining the contribution of the cone ON- and OFF-pathways to the primate photopic electroretinogram (ERG). In this study, the optimal conditions for recording multifocal ON-OFF responses are described, and the technique is applied to normal subjects and two patients with unusual retinal diseases. The results from the normal subjects demonstrated that there were topographical variations of the photopic ERG waveform: when responses were normalized to the ON-response (b-wave) amplitude, the OFF-response (d-wave) amplitude increased with increasing eccentricity. The changes in the waveform in two patients suggested relatively greater defects of the hyperpolarizing or depolarizing bipolar cells. We conclude that the multifocal ERG technique with long-duration stimuli can be a useful tool to assess the function of local cone ON- and OFF-pathways in normal and diseased retinas.
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Affiliation(s)
- M Kondo
- The Department of Ophthalmology, Nagoya University School of Medicine, Japan.
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234
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Hankins MW, Jones SR, Jenkins A, Morland AB. Diurnal daylight phase affects the temporal properties of both the b-wave and d-wave of the human electroretinogram. Brain Res 2001; 889:339-43. [PMID: 11166727 DOI: 10.1016/s0006-8993(00)03182-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Aspects of the anatomy and physiology of the cone pathway are known to vary according to the phase of the natural light cycle. Using a prolonged flash stimulus ( approximately 200 ms), we have examined the human electroretinogram (ERG) over a 24 h period. We report that whilst the a-wave of the photopic ERG does not alter, there are profound effects upon the implicit times of both the b-wave and d-wave components. Both components are significantly slower in the night-time period and systematically become faster (15-22% reduction in implicit time), reaching a peak at around midday. The daily variation in the temporal properties of the ERG is abolished by constant light, but is retained during constant darkness. The data suggest that the changes in the temporal properties of the cone pathway affect both cone-ON and cone-OFF pathways. This suggests that the diurnal effect is presynaptic to the second order neurones, and most likely resides in the cone synapse.
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Affiliation(s)
- M W Hankins
- Imperial College School of Medicine, Departments of Academic Ophthalmology and Integrative & Molecular Neuroscience, Division of Neuroscience, Charing Cross Campus, Fulham Palace Road, W6 8RF, London, UK.
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235
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Nomura R, Kondo M, Tanikawa A, Yamamoto N, Terasaki H, Miyake Y. Unilateral cone dysfunction with bull's eye maculopathy. Ophthalmology 2001; 108:49-53. [PMID: 11150264 DOI: 10.1016/s0161-6420(00)00450-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
OBJECTIVE To report a Japanese subject who presented with an acute-onset, unilateral cone dysfunction with bull's eye maculopathy and to describe the functional changes determined by psychophysical and electrophysiologic tests. DESIGN A single observational case report. METHODS In addition to a complete ophthalmic examination, the subject underwent some electrophysiologic and psychophysical tests. MAIN OUTCOME MEASURES Kinetic visual field test, cone and rod perimetry (two-color perimetry), full-field electroretinograms (ERGs), focal macular ERGs, and multifocal ERGs. RESULTS The full-field ERGs and two-color perimetry showed a predominant loss of cone function in the right eye, whereas the left eye was normal. Cone perimetry and multifocal ERGs revealed that there were small regions functioning normally and other retinal areas that were severely altered in the right eye. CONCLUSIONS The topographical function analysis suggested that the disorder affected the retina unevenly. The cause of this rare case of unilateral cone dysfunction with bull's eye maculopathy still remains unknown.
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Affiliation(s)
- R Nomura
- Department of Ophthalmology, Nagoya University School of Medicine, Nagoya, Japan
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236
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Jenkins A, Hankins MW. Long-term light history modulates the light response kinetics of luminosity (L)-type horizontal cells in the roach retina. Brain Res 2000; 887:230-7. [PMID: 11134611 DOI: 10.1016/s0006-8993(00)03073-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
We have examined the effects of prolonged periods of darkness on the responses of luminosity-type horizontal cells (L-HCs) in the freshwater cyprinid, Rutilus rutilus. Two groups of retinae were compared, those recorded after 10 min dark adaptation (SA) and those recorded after 3 h dark adaptation (LA). The results suggest that long-term light history does not modify the general responsiveness of the L-HCs in this species. However, there are apparent changes in the receptive field of the cells and modifications to the kinetics of the light-evoked response. The kinetics changes involve both a delay in the onset of light response and a selective effect on the hyperpolarizing light-ON response. Thus the mean time constant (tau) for the SA cells was 32.4+/-2.39 ms (n=62), whilst that for the LA cells was 53.4+/-3.03 ms (n=61). These effects occur in the absence of changes in the relative spectral sensitivity or threshold sensitivity of the HCs. The results suggest that in some vertebrate retinae, prolonged darkness (light-history) may regulate long-term plasticity in the kinetics of the cone-HC pathway.
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Affiliation(s)
- A Jenkins
- Imperial College School of Medicine, Division of Neuroscience and Psychological Medicine, Department of Integrative and Molecular Neuroscience, Fulham Palace Road, W6 8RF, London, UK
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237
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Alexander KR, Fishman GA, Grover S. Temporal frequency deficits in the electroretinogram of the cone system in X-linked retinoschisis. Vision Res 2000; 40:2861-8. [PMID: 10960656 DOI: 10.1016/s0042-6989(00)00119-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
We investigated the extent of, and basis for, abnormalities in the flicker electroretinogram (ERG) of the cone system of patients with X-linked retinoschisis (XLRS), a form of hereditary vitreoretinal degeneration. ERGs were recorded from six patients with XLRS and from six visually normal subjects using high-contrast sinusoidal flicker that ranged in temporal frequency from 8 to 96 Hz, and that was presented against a rod-desensitizing adapting field. Compared to the control subjects, the patients with XLRS showed a significant reduction in the amplitude of the ERG response fundamental at temporal frequencies of 32 Hz and higher. In addition, their response phases were at or below the lower limits of normal (representing a phase lag) for temporal frequencies greater than 8 Hz. The higher harmonics of the patients' ERG responses to a low frequency stimulus were attenuated over the same temporal frequency range as was the response fundamental. This finding indicates that a major component of the abnormal temporal filtering responsible for the ERG abnormalities in XLRS occurs beyond the level of the early retinal nonlinearity that generates the harmonic components of the ERG response, and therefore is most likely postreceptoral in origin. Consistent with this interpretation, the ERG waveforms of the XLRS patients showed a significant attenuation of the ON-response component, with a normal OFF response. The overall pattern of results suggests that the marked reduction of ERG response amplitudes and the phase lag at the higher temporal frequencies in XLRS stem, at least in part, from a predominant attenuation of the ON-bipolar cell contribution to the flicker ERG.
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Affiliation(s)
- K R Alexander
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 60612, Chicago, IL, USA.
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238
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Abstract
With the multifocal technique, as developed by Erich Sutter and colleagues, scores of focal electroretinogram (ERG) responses can be obtained in a matter of minutes. Although this technique is relatively new, it has already provided insights into the mechanisms of retinal disease. However, because it is new, there also remain questions about how it works and what it measures. This chapter considers some of these insights and some of these questions. The first part (Section 2) describes how the multifocal ERG (mERG) is recorded and considers its relationship to the full-field ERG. The mERG responses are shown to be from relatively local regions of the retina and are comprised of the same components as the full-field ERG. The diagnostic advantage of the mERG as compared to the full-field ERG is also illustrated. In Section 3, the effects of damage to different cell layers of the retina are shown to affect the mERG differently, and these changes are summarized within a conceptual framework. It is argued, for example, that when diseases of the receptor outer segment, like retinitis pigmentosa, result in small, depressed mERG responses, then the damage is, as expected, at the outer segment. However, when these diseases result in mERG responses that are reasonably large but very delayed, then the damage is beyond the outer segment, probably in the outer plexiform layer. The implicit time of the mERG, not amplitude, is the more sensitive measure of damage in degenerative diseases of the receptors. On the other hand, diseases, like glaucoma, which act on the ganglion axon, do not result in easily identified changes to the mERG unless inner retinal damage is involved as well. Inner retinal damage changes the waveform of the mERG and decreases the naso-temporal variation normally observed. Finally, diseases, like diabetes, that act on more than one layer of the retina can have a range of effects. In Section 4, recent work with the monkey mERG is reviewed, with emphasis on the relevance to human diseases. For example, blocking the sodium-based action potentials produced by ganglion and amacrine cells eliminates the naso-temporal variation in the monkey mERG and these altered mERG responses resemble those from some patients with diabetes or glaucoma. Finally, in Section 5 the second-order kernel is described. The presence of a second-order kernel has important implications for understanding the shape of the mERG response (first-order kernel). Full-field simulations of the mERG paradigm illustrate that the first-order kernel is comprised of responses with different waveforms. Further, it is argued that the nonlinear, adaptive mechanisms that produce the second-order kernel are involved in shaping the time course of the response. Patients with large, but abnormally delayed mERG responses (first-order kernel), do not have a detectable second-order kernel. It is speculated that a markedly diminished second-order kernel is diagnostic of outer plexiform layer damage, not inner plexiform layer damage as is commonly assumed.
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Affiliation(s)
- D C Hood
- Department of Psychology, Columbia University, 116th and Broadway, NY 10027-7004, New York, USA.
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239
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Rousseau S, Lachapelle P. Transient enhancing of cone electroretinograms following exposure to brighter photopic backgrounds. Vision Res 2000; 40:1013-8. [PMID: 10720670 DOI: 10.1016/s0042-6989(99)00245-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Normal subjects were first light adapted to a standard photopic background and a control photopic ERG was obtained. The subjects were then light adapted to a brighter background for 5 min at the end of which the luminance was returned to the control background and ERGs were taken at regular intervals. Most of the ERG/OP components were transiently enhanced following the above procedure. Given that the previously reported photopic light adaptation effect occurred following an increase in the luminance of the adapting field (from dark adaptation to light adaptation) while that reported in the present study is triggered following a decrease in the level of light adaptation, the opposite effects noted might suggest that the two retinal events result from the same, not yet identified, cone adaptation mechanisms which are solicited in an opposite way.
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Affiliation(s)
- S Rousseau
- Departments of Neurology-Neurosurgery, McGill University, Montreal Children's Hospital Research Institute, 2300 Tupper Street, Montreal, Canada
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240
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Arnarsson A, Eysteinsson T. Modification of the Xenopus electroretinogram by actions of glycine in the proximal retina. ACTA PHYSIOLOGICA SCANDINAVICA 2000; 169:249-58. [PMID: 10886039 DOI: 10.1046/j.1365-201x.2000.00736.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The electroretinogram (ERG) was recorded from the Xenopus retina, to examine the effects of glycine and strychnine on these responses and to determine the origins of these changes. Glycine at concentrations between 0.1 and 10 mM reduced the b- and d-waves of the ERG in a dose-dependent manner, while strychnine increased their amplitude. 2-Amino-4-phosphonobutyric acid (APB) reduced the b-wave and blocked the effect of glycine, but not strychnine, on the d-wave. When the d-wave had first been blocked by kynurenic acid (KYN) or reduced by (+/-)cis-2,3-piperidine dicarboxylic acid (PDA) the b-wave was enhanced by glycine, but not by strychnine. N-methyl-DL-aspartate (NMDLA), which alters responses in the proximal retina only, blocked the effects of glycine and strychnine on the ERG. This suggests that the glycinergic effects on the ERG are at least partly mediated by processes in the proximal retina. The results further support the suggestion that inhibitory neurotransmitters in the proximal retina may modulate both the b- and d-waves of the Xenopus ERG.
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Affiliation(s)
- A Arnarsson
- Department of Physiology, University of Iceland, Reykjavik, Iceland
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241
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Dong CJ, Hare WA. Contribution to the kinetics and amplitude of the electroretinogram b-wave by third-order retinal neurons in the rabbit retina. Vision Res 2000; 40:579-89. [PMID: 10824262 DOI: 10.1016/s0042-6989(99)00203-5] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The ERG b-wave is widely believed to reflect mainly light-induced activity of on-center bipolar cells and Müller cells. Third-order retinal neurons are thought to contribute negligibly to generation of the b-wave. Here we show that pharmacological agents which affect predominantly third-order neurons alter significantly both the kinetics and amplitude of the b-wave. Our results support the notion that changes in the amplitude and kinetics of light-induced membrane depolarization in third-order neurons produce similar changes in the amplitude and kinetics of the b-wave. We conclude that activity in third-order neurons makes a significant contribution to b-wave generation. Our results also provide evidence that spiking activity of third-order neurons truncates the a-wave by accelerating the onset of the b-wave.
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Affiliation(s)
- C J Dong
- Department of Biological Sciences, RD-2C Allergan Inc., Irvine, CA 92612, USA.
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242
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Popova E, Mitova L, Vitanova L, Kupenova P. Effect of 2-amino-4-phosphonobutyrate on the OFF responses of frog retinal ganglion cells and local ERG after glycinergic blockade. Comp Biochem Physiol C Toxicol Pharmacol 2000; 126:139-51. [PMID: 11050686 DOI: 10.1016/s0742-8413(00)00107-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Perfusion with the ON channel blocker 2-amino-4-phosphonobutyrate (APB) of dark adapted frog eyecups not only abolished the ganglion cells' (GC) ON responses and the ERG b-wave, but markedly potentiated the OFF responses of ON-OFF and phasic OFF-GCs and the d-wave amplitude of simultaneously recorded local ERG. Glycinergic blockade by strychnine prevented this potentiating effect in 31 out of 69 GCs, but did not change it at all in the other cells. At the same time the d-wave potentiation was preserved during the glycinergic blockade in all eyecups. The results indicate that glycinergic transmission is involved in the inhibition exerted from ON upon OFF channel in some but not all frog retinal GCs.
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Affiliation(s)
- E Popova
- Department of Physiology, Medical University, Sofia, Bulgaria.
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243
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Brown J, Kimura AE, Gorin MB. Clinical and electroretinographic findings of female carriers and affected males in a progressive X-linked cone-rod dystrophy (COD-1) pedigree. Ophthalmology 2000; 107:1104-10. [PMID: 10857830 DOI: 10.1016/s0161-6420(00)00086-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
OBJECTIVE To study the clinical and electroretinographic findings of affected males and female carriers in a family with X-linked cone-rod dystrophy (COD-1). DESIGN Observational case series. PARTICIPANTS Twenty-five members of a five-generation pedigree were examined. METHODS A history of visual impairment including age at onset, loss of acuity, color vision abnormalities, photophobia, and nyctalopia was obtained. A complete ophthalmologic examination was performed, including kinetic perimetry with a Goldmann perimeter, FM 100-hue testing, and standardized Ganzfeld electroretinography following the ISCEV protocol. MAIN OUTCOME MEASURES Patients were classified as affected or unaffected on the basis of the clinical examination. All carrier females had affected sons. RESULTS Nine affected males and seven female carriers were identified. Affected males noted decreased visual acuity and poor color vision within the first two decades of life. Early in the disease, macular retinal pigment epithelial (RPE) changes were found that progressed to an atrophic macular scar by the fifth decade. Evidence of progression from macular pigment mottling to an atrophic macular lesion over a 13-year period was identified in one patient. The photopic, single-flash, b-wave amplitude was low in all affected males and declined with age. The 30-Hz flicker b-wave implicit times were abnormally prolonged in all affected males. Female carriers were asymptomatic although three had slightly abnormal color vision and small paracentral field defects and subtle RPE defects were found in three carriers. Carriers demonstrated prolongation of the 30-Hz flicker b-wave implicit time and interocular asymmetry. Five of seven carriers and two affected males demonstrated reduced oscillatory potentials and an abnormal-appearing flattened photopic a-wave. Five men and two women demonstrated a characteristic tapetal-like retinal sheen. CONCLUSIONS Affected patients in this pedigree demonstrate early loss of visual acuity and poor cone function with late rod involvement. Female carriers may appear clinically normal or may be identified by subtle color vision defects, fundus abnormalities, prolongation of the 30-Hz flicker implicit time with interocular asymmetry, or an abnormal flattened photopic a-wave. Genetic linkage analysis of this family was recently reported and the disease-causing gene has been mapped to an approximately 1-Mb interval on chromosome Xp11.4.
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Affiliation(s)
- J Brown
- Department of Ophthalmology and Visual Sciences, University of Iowa Hospitals and Clinics, Iowa City, USA
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244
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Xu X, Quiambao AB, Roveri L, Pardue MT, Marx JL, Röhlich P, Peachey NS, Al-Ubaidi MR. Degeneration of cone photoreceptors induced by expression of the Mas1 protooncogene. Exp Neurol 2000; 163:207-19. [PMID: 10785460 DOI: 10.1006/exnr.2000.7370] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Although transgenic expression of oncogenes typically leads to tumorigenesis, oncogene expression directed to the rod photoreceptors leads to cell death without tumor formation. To evaluate the cellular and functional changes induced in cone photoreceptors by an oncogene, the Mas1 protooncogene was targeted to the cones of transgenic mice by the human red/green opsin promoter. Mas1 was chosen because of its exclusive expression in the nervous system and its homology to opsin. The overall histologic appearance of the transgenic retina was normal and retinal tumors were never observed. While rod-mediated electroretinograms were normal in all respects, cone-mediated responses were diminished in direct relationship to the level of transgene expression as determined by Northern blot analysis. Responses of UV- and green-sensitive cones were reduced equivalently, and Northern analysis and immunocytochemistry indicated that cone photoreceptor densities were markedly diminished throughout transgenic retinas. These results indicate that oncogene expression in cones induces cell death without tumor formation and support the possibility that aberrant oncogene expression may underlie some forms of hereditary retinal diseases. The Mas1 transgenic mice may be useful in understanding the cone photoreceptor degeneration that occurs in cone dystrophies and age-related macular degeneration and in evaluating potential therapies for these disorders.
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Affiliation(s)
- X Xu
- Research Service (151), Hines VA Hospital, Hines, Illinois 60141, USA
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245
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Abstract
Light-adapted cone ERG in response to white stimuli with long duration (200 ms) was studied in seven normal cats and six cats with early to moderate, inherited retinal dystrophy. The stimuli typically elicited an ERG consisting of an a- and b-wave in response to light onset, whereas light-offset was followed by a cornea-positive d-wave and subsequent negative dip and occasionally a second positive peak in both normal and dystrophic cats, although b- and d- waves had less distinct peaks in cats with moderately advanced retinal dystrophy. Linear regression models indicated a positive correlation between d-wave amplitude and stimulus luminance, whereas a negative correlation was found between amplitude and background light luminance in normal cats. The d-wave implicit time was independent of both stimulus and background light luminance in normal cats. The d-wave amplitude was not significantly different in dystrophic cats, whereas the implicit time was increased when affected cats were compared to normal cats. The significant increase in implicit time in dystrophic cats could not be explained with a reduced sensitivity of the off-pathway to background or stimulus light. This is supported by the finding that d-wave amplitude was not significantly altered in early to moderately advanced dystrophic cats.
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Affiliation(s)
- B Ekesten
- Faculty of Veterinary, Medicine, Swedish University of Agricultural Sciences, Uppsala.
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246
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Abstract
PURPOSE Because the mouse lacks a typical Purkinje shift, we have examined its light-adapted ERG to determine whether there was other evidence in addition to tolerance to background light, that could be used to identify cone function in the ERG. METHODS Full field corneal ERGs to white flashes, double flashes and flash trains were examined in the presence of a strong full field light adaptation and compared with the human cone ERG. RESULTS The following cone-like properties could be identified. (1) The light-adapted murine ERG increases in amplitude gradually during the first 10 minutes of light-adaptation; (2) It is capable of responding to a 50 Hz stimulus, although its overall frequency response is slower than that of the human cone ERG; (3) A corneal positive d-wave occurs to the termination of a flash train; (4) The response increases linearly with light intensity. CONCLUSION The light-adapted murine ERG has several properties of cones but it has a slower response than the human cone ERG.
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Affiliation(s)
- B Ekesten
- Faculty of Veterinary Medicine, Swedish University of Agricultural Sciences, Uppsala.
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247
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Abstract
An increase in the amplitude of horizontal cell (HC) potentials, a decrease in the extracellular potassium around the photoreceptors and an increase in the PIII component of the ERG that occur with increasing light stimulus intensity are shown to be concomitant occurrences, which could, therefore, be causally related. With high intensity light stimuli the PIII component is prominent and the HC potentials exhibit an afterpotential. Within the range of intensities tested the peak times of the HC afterpotentials coincide with the peak times of PIII. This indicates the likelihood that the HC potential contributes to the PIII, although these results do not allow a quantitative assessment of the contribution of HC potentials to the PIII-component.
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Affiliation(s)
- R Hanitzsch
- Carl-Ludwig-Institute of Physiology, University of Leipzig, Germany
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248
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Murayama K, Kawabata H, Adachi-Usami E. An electrophysiological follow-up study on acquired unilateral nyctalopia. Eye (Lond) 1999; 13 ( Pt 5):629-34. [PMID: 10696314 DOI: 10.1038/eye.1999.171] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
PURPOSE To describe the clinical picture and electrophysiological findings in acquired unilateral nyctalopia. METHODS A patient who had acquired unilateral visual loss with normal fundus was followed for a period of 2.5 years with basic ophthalmological examinations including standard electroretinogram and photopic on and off responses. RESULTS A 46-year-old woman suffered from acquired unilateral nyctalopia. She complained of photopsia and blurred vision in her left eye. The initial examination of the left eye showed 1+ cells in the anterior chamber and a granular appearance in the fovea. After 1 month of treatment she still complained of photopsia in her left eye. Ophthalmoscopy and fluorescein angiography revealed no abnormality in either eye. A bright flash electroretinogram (ERG) in the left eye was a negative shape. Photopic ERG elicited by a 150 ms stimulus showed a depressed b-wave and enhanced a- and d-waves in the left eye. CONCLUSIONS This ERG waveform suggested that the transmission between photoreceptor and on-bipolar cell might be affected by idiopathic retinal disease.
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Affiliation(s)
- K Murayama
- Department of Ophthalmology, Saitama Medical School, Japan.
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249
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Banin E, Cideciyan AV, Alemán TS, Petters RM, Wong F, Milam AH, Jacobson SG. Retinal rod photoreceptor-specific gene mutation perturbs cone pathway development. Neuron 1999; 23:549-57. [PMID: 10433266 DOI: 10.1016/s0896-6273(00)80807-7] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Rod-specific photoreceptor dystrophies are complicated by the delayed death of genetically normal neighboring cones. In transgenic (Tg) swine with a rod-specific (rhodopsin) gene mutation, cone photoreceptor physiology was normal for months but later declined, consistent with delayed cone cell death. Surprisingly, cone postreceptoral function was markedly abnormal when cone photoreceptor physiology was still normal. The defect was localized to hyperpolarizing cells postsynaptic to the middle wavelength-sensitive cones. Recordings throughout postnatal development indicated a failure of cone circuitry maturation, a novel mechanism of secondary cone abnormality in rod dystrophy. The results have implications for therapy for human retinal dystrophies and raise the possibility that rod afferent activity plays a role in the postnatal maturation of cone retinal circuitry.
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Affiliation(s)
- E Banin
- Scheie Eye Institute, Department of Ophthalmology, University of Pennsylvania, Philadelphia 19104, USA
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250
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Abstract
Electroretinography (ERG) is an objective method of evaluating retinal function. Since its introduction to clinical practice in the 1940s, it has become a useful and routine diagnostic clinical tool in ophthalmology. This review summarizes the role of ERG as a clinical technique for evaluating the progression of diabetic retinopathy and as a research tool for increasing our understanding of the pathophysiology of diabetic retinopathy. Most studies show unequivocally that the different types of ERG tests detect local abnormalities or widespread pathology, even in very early stages of the disease. It seems plausible that measurements from ERG recordings, particularly the oscillatory potentials, may be useful for predicting progression from nonproliferative to the more sight-threatening stages--preproliferative or proliferative--of diabetic retinopathy. Some recent work implies that the ERG can also be a useful diagnostic method for discriminating between eyes with diabetic retinopathy and those without the condition.
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Affiliation(s)
- R Tzekov
- Retina Foundation of the Southwest, Dallas, Texas 75231, USA
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