Depletion of retinal dopamine does not affect the ERG b-wave increment threshold function in goldfish in vivo.
Increment threshold functions of the electroretinogram (ERG) b-wave were obtained from goldfish using an in vivo preparation to study intraretinal mechanisms underlying the increase in perceived brightness induced by depletion of retinal dopamine by 6-hydroxydopamine (6-OHDA). Goldfish received unilateral intraocular injections of 6-OHDA plus pargyline on successive days. Depletion of retinal dopamine was confirmed by the absence of tyrosine-hydroxylase immunoreactivity at 2 to 3 weeks postinjection as compared to sham-injected eyes from the same fish. There was no difference among normal, sham-injected or 6-OHDA-injected eyes with regard to ERG waveform, intensity-response functions or increment threshold functions. Dopamine-depleted eyes showed a Purkinje shift, that is, a transition from rod-to-cone dominated vision with increasing levels of adaptation. We conclude (1) dopamine-depleted eyes are capable of photopic vision; and (2) the ERG b-wave is not diagnostic for luminosity coding at photopic backgrounds. We also predict that (1) dopamine is not required for the transition from scotopic to photopic vision in goldfish; (2) the ERG b-wave in goldfish is influenced by chromatic interactions; (3) horizontal cell spinules, though correlated with photopic mechanisms in the fish retina, are not necessary for the transition from scotopic to photopic vision; and (4) the OFF pathway, not the ON pathway, is involved in the action of dopamine on luminosity coding in the retina.
Lin
Z S
ZS
Department of Neurobiology and Behavior, University at Stony Brook, NY 11794-5230.
Yazulla
S
S
D000818:Animals; D003623:Dark Adaptation; D004298:Dopamine / Q000378:metabolism*; D004596:Electroretinography; D006054:Goldfish; D008027:Light; D016627:Oxidopamine / Q000633:toxicity; D010293:Pargyline / Q000633:toxicity; D012160:Retina / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D012684:Sensory Thresholds / Q000502:physiology*; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism; D014796:Visual Perception / Q000502:physiology
D016627:Oxidopamine; D010293:Pargyline; D014446:Tyrosine 3-Monooxygenase; D004298:Dopamine