Evidence that a-wave latency of the electroretinogram is determined solely by photoreceptors.
OBJECTIVE
To identify the retinal cells that determine the a-wave latency of rats.


METHODS
Electroretinograms (ERGs) were recorded from the rod-dominated (0.85% cones) retinas of Long-Evans rats following an intravitreal injection of 1 microL of 40 mM 2-amino-4-phosphonobutyric acid to block the activity of the ON pathway of the second order retinal neurons. ERGs were also recorded following an intraperitoneal injection of sodium iodate to destroy the retinal pigment epithelial (RPE) cells. Damage to a large area of the retina was produced by constant light exposure, and focal damage to the retina was induced by argon laser photocoagulation. The effects of age and anesthesia level on the a-wave latency were also determined.


RESULTS
Blocking the activity of the ON pathway of the second order retinal neurons did not alter the a-wave latency, and destroying the RPE cells also did not alter the a-wave latency. Damage to a large area of the retina resulted in prolonging the latency but focal retinal damage did not alter the a-wave latency. The a-wave latency was longer in young rat pups but was adult-like by 18 days. The level of anesthesia had no effect on the latency except at very deep stages.


CONCLUSIONS
The a-wave latency is determined solely by the activity of the photoreceptors. A prolonged latency would indicate that the photoreceptors are damaged over a large area of the retina.
Qiu
Hui
H
Department of Ophthalmology, Hamamatsu University Medical School, Hamamatsu, Japan.
Fujiwara
Eriko
E
Liu
Mu
M
Lam
Byron L
BL
Hamasaki
D I
DI
D000613:Aminobutyrates / Q000633:toxicity; D000818:Animals; D004596:Electroretinography; D007452:Iodates / Q000633:toxicity; D009474:Neurons / Q000187:drug effects; D020419:Photoreceptor Cells, Vertebrate / Q000502:physiology*; D010857:Pigment Epithelium of Eye / Q000187:drug effects; D051381:Rats; D020318:Rats, Long-Evans; D011930:Reaction Time; D012165:Retinal Ganglion Cells / Q000187:drug effects
D000613:Aminobutyrates; D007452:Iodates; C012729:2-amino-4-phosphonobutyric acid; C032285:sodium iodate