title: Aspartate separation of the scotopic threshold response (STR) from the photoreceptor a-wave of the cat and monkey ERG.
abstract: We recorded ERG responses at the cornea of cat and monkey and identified the initial negative wave elicited by very dim stimuli as the scotopic threshold response (STR) comparable to that previously recognized by intraretinal recordings of cat. The STR, but not the photoreceptor a-wave, was eliminated by intravitreal aspartate in both cat and monkey, which demonstrated that the STR origin was post-photoreceptoral. Intraretinal recordings before and after aspartate confirmed that the a-wave of cat with bright light was fast-PIII from photoreceptors, and further showed that there was minimal or no extracellular activity recordable near the photoreceptors with very dim stimuli after aspartate. This study showed practical ways to separate the STR from the photoreceptor a-wave in corneal records, by the range of stimulus intensity (STR with dim stimuli; photoreceptor a-wave with bright stimuli) and by response latency (STR, long latency; photoreceptor a-wave, short latency). These recordings provide the first evidence that the monkey has an STR, and that it is post-photoreceptoral like the STR of cat. Further, this provides support to consider that the corneal negative STR wave of the human ERG with dim light may also be post-photoreceptoral.
authors.affiliation: Department of Ophthalmology, W. K. Kellogg Eye Center, University of Michigan, Ann Arbor 48105.
authors.forename: K
authors.initials: K
authors.lastname: Wakabayashi
authors.forename: J
authors.initials: J
authors.lastname: Gieser
authors.forename: P A
authors.initials: PA
authors.lastname: Sieving
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001224:Aspartic Acid / Q000494:pharmacology*; D002415:Cats; D003315:Cornea / Q000187:drug effects / Q000502:physiology; D003623:Dark Adaptation / Q000187:drug effects; D004596:Electroretinography; D008253:Macaca mulatta; D010786:Photoreceptor Cells / Q000187:drug effects / Q000502:physiology*; D012160:Retina / Q000187:drug effects / Q000502:physiology
chemical_list: D001224:Aspartic Acid