Dose related effects of 6-OHDA on rabbit retinal dopamine concentrations and ERG B-wave amplitudes.
The purpose of this study was to examine the dose related effects of 6-hydroxydopamine (6-OHDA) on the electroretinographic (ERG) B-wave amplitude and on retinal concentrations of dopamine (DA) and its main metabolites homovanillic acid (HVA) and dihydroxyphenylacetic acid (DOPAC). Doses of 6-OHDA (60, 300 or 1200 micrograms) were dissolved in a 0.9 percent NaCl and ascorbic acid solution and administered intravitreally in 300 microliter volume in one eye of adult pigmented rabbits. The fellow eye received a similar volume of the drug vehicle. With the smallest dose of 6-OHDA (60 micrograms) no changes in ERG B-wave amplitude or retinal concentrations of DA, DOPAC or HVA were found. With the largest dose of 6-OHDA (1200 micrograms) complete extinction of the ERG and almost total disappearance of DA, DOPAC and HVA were observed. With the intermediate dose of 300 micrograms 6-OHDA significant increases in B-wave amplitudes and decreases in retinal DA, DOPAC and HVA concentrations were obtained. This latter dose did not affect retinal concentrations of serotonin (5-HT), 5-hydroxyindole acetic acid (5-HIAA) and norepinephrine (NE). These results demonstrate that selective reductions of retinal dopamine and its metabolites can be obtained with a single intravitreal injection of 300 micrograms 6-OHDA in rabbits. The observed concomitant increase in B-wave amplitudes lends support to the hypothesis that DA acts as a mediator of lateral inhibition in the retina.
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000818:Animals; D004298:Dopamine / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004596:Electroretinography; D006719:Homovanillic Acid / Q000378:metabolism; D006892:Hydroxydopamines / Q000494:pharmacology*; D008845:Microinjections; D016627:Oxidopamine; D011817:Rabbits; D012160:Retina / Q000187:drug effects* / Q000502:physiology; D014822:Vitreous Body
D006892:Hydroxydopamines; D015102:3,4-Dihydroxyphenylacetic Acid; D016627:Oxidopamine; D004298:Dopamine; D006719:Homovanillic Acid