Comparable effects of flickering and steady patterns of light adaptation on photomechanical responses of cones in amphibian (Xenopus laevis) retina.
The effects of two distinct patterns of light stimulus, steady and flicker, on cone photomechanical movements (PMMs) in the Xenopus laevis retina were investigated. For both patterns studied, the effects on PMMs were assessed by quantitative analysis of the cone positions in the outer retina. Steady light adaptation was found to be equally effective as flicker in causing cone contractions. This was unlike the situation previously found in the cyprinid fish retina, in which flickering light was significantly more effective than steady. This difference could be related to the light-evoked response characteristics and circuitry of dopaminergic retinal neurones in the two vertebrate classes. The role of dopamine and other possible neuromodulator(s) in light adaptive control of vertebrate retinae is discussed.
Angotzi
A R
AR
Department of Biology, Imperial College of Science, Technology and Medicine, London, UK.
Hirano
J
J
Haamedi
S
S
Murgia
R
R
Vallerga
S
S
Djamgoz
M B
MB
D000221:Adaptation, Ocular / Q000502:physiology*; D000818:Animals; D003623:Dark Adaptation / Q000502:physiology; D004298:Dopamine / Q000502:physiology; D010775:Photic Stimulation; D010786:Photoreceptor Cells / Q000502:physiology*; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology / Q000528:radiation effects*; D014982:Xenopus laevis
D004298:Dopamine