Effect of dopamine and haloperidol on the c-wave and light peak of light-induced retinal responses in chick eye.
The relation between dopaminergic cells (and centrifugal fibers), the electroretinogram (ERG) c-wave, and the light peak were electrophysiologically investigated by observing the effects of a retrobulbar conduction block and intravitreal injection of either dopamine or haloperidol on these retinal responses. The retrobulbar conduction block (1% lidocaine) caused a decrease in the amplitude of the c-wave and the light peak in newly hatched chicks. Injections (2-20 microliters) containing dopamine (0.1-10 mM) or haloperidol (1.3-13 mM) were given intravitreously while the responses were recorded. Although intravitreous injection of saline for control resulted in no observable change in the responses, dopamine selectively augmented the c-wave of ERGs and the light peak, but not the a-, b-, and d-waves. Haloperidol decreased first the light peak and later the c-wave. The augmentation of the retinal responses by dopamine and their reduction by haloperidol was statistically significant. The estimated threshold concentration of dopamine in the vitreous cavity was 1-3.5 microM. Since in many species the interplexiform cells have been found to contain dopamine, we hypothesize that the modulatory effects on the c-wave and the light peak in this preparation may be due to a centrifugal feed-back loop which includes the interplexiform cells to the horizontal and bipolar cells and the horizontal cells to the cones.
Sato
T
T
Department of Physiology, School of Dentistry, Iwate Medical University, Japan.
Yoneyama
T
T
Kim
H K
HK
Suzuki
T A
TA
D000818:Animals; D002645:Chickens; D004298:Dopamine / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004596:Electroretinography; D006220:Haloperidol / Q000494:pharmacology*; D007267:Injections; D008012:Lidocaine / Q000494:pharmacology*; D012160:Retina / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission; D014822:Vitreous Body / Q000187:drug effects
D008012:Lidocaine; D006220:Haloperidol; D004298:Dopamine