A key objective of this work is to clarify the extent to which hyperpolarizing bipolar and/or horizontal cells (HBC/HzCs) contribute to the electroretinogram (ERG), by performing intraretinal recordings and by pharmacological dissection of ERG responses. The ERG is an important tool to evaluate photoreceptor function noninvasively in animals and human patients. New analytical models for the human a-wave by Hood & Birch and by Bretton & Pugh will further increase its power. Although the a-wave commonly is thought to derive from photoreceptors rather directly, we have performed a pharmacological analysis of the monkey light-adapted ERG and have found that hyperpolarizing retinal second-order neurons appear to contribute a negative potential to the photopic a- and b-waves. HBC/HzC activity appears to shape the photopic b-wave and control its amplitude. Further, the negative wave from HBC/HzCs is sufficiently fast to add to the """"""""true"""""""" cone a-wave, particularity for stimulus conditions that are used clinically in human ERG diagnosis. If the existance of a proximal a-wave can be substantiated by further studies, this would change current clinical ERG analysis substantially. Finally, preliminary studies with glutamate analogs called into question the conventional idea that flicker ERG, measured at the cornea, reflects cone activity directly, since 30Hz flicker response all but disappeared after intravitreal injection of aspartate. Studies are proposed to learn the extent to which flicker ERG originates post-synaptic to photoreceptors. The ERG will be studied. Information developed should have direct application to the use of ERG in diagnosing human retinal dysfunction. The rodent ERG had gained additional importance as a non-invasive tool for the evaluating of naturally occurring and transgenetically engineered models of retinal dystrophies. Lastly, recording from these two species may provide insight into the biology underlying Granit's E-type and I- type ERG designations.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY006094-10
Application #
2159758
Study Section
Visual Sciences C Study Section (VISC)
Project Start
1986-05-01
Project End
1998-08-31
Budget Start
1995-09-01
Budget End
1996-08-31
Support Year
10
Fiscal Year
1995
Total Cost
Indirect Cost
Name
University of Michigan Ann Arbor
Department
Ophthalmology
Type
Schools of Medicine
DUNS #
791277940
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
Khan, Naheed Wali; Wissinger, Bernd; Kohl, Susanne et al. (2007) CNGB3 achromatopsia with progressive loss of residual cone function and impaired rod-mediated function. Invest Ophthalmol Vis Sci 48:3864-71
Khan, Naheed W; Kondo, Mineo; Hiriyanna, Kelaginamane T et al. (2005) Primate Retinal Signaling Pathways: Suppressing ON-Pathway Activity in Monkey With Glutamate Analogues Mimics Human CSNB1-NYX Genetic Night Blindness. J Neurophysiol 93:481-92
Kondo, Mineo; Sieving, Paul A (2002) Post-photoreceptoral activity dominates primate photopic 32-Hz ERG for sine-, square-, and pulsed stimuli. Invest Ophthalmol Vis Sci 43:2500-7
Felius, Joost; Thompson, Debra A; Khan, Naheed W et al. (2002) Clinical course and visual function in a family with mutations in the RPE65 gene. Arch Ophthalmol 120:55-61
Kondo, M; Sieving, P A (2001) Primate photopic sine-wave flicker ERG: vector modeling analysis of component origins using glutamate analogs. Invest Ophthalmol Vis Sci 42:305-12
Jamison, J A; Bush, R A; Lei, B et al. (2001) Characterization of the rod photoresponse isolated from the dark-adapted primate ERG. Vis Neurosci 18:445-55
Sieving, P A; Chaudhry, P; Kondo, M et al. (2001) Inhibition of the visual cycle in vivo by 13-cis retinoic acid protects from light damage and provides a mechanism for night blindness in isotretinoin therapy. Proc Natl Acad Sci U S A 98:1835-40
Khan, N W; Jamison, J A; Kemp, J A et al. (2001) Analysis of photoreceptor function and inner retinal activity in juvenile X-linked retinoschisis. Vision Res 41:3931-42
Machida, S; Chaudhry, P; Shinohara, T et al. (2001) Lens epithelium-derived growth factor promotes photoreceptor survival in light-damaged and RCS rats. Invest Ophthalmol Vis Sci 42:1087-95
Humphries, M M; Kiang, S; McNally, N et al. (2001) Comparative structural and functional analysis of photoreceptor neurons of Rho-/- mice reveal increased survival on C57BL/6J in comparison to 129Sv genetic background. Vis Neurosci 18:437-43

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