Investigation of dopamine content, synthesis, and release in the rabbit retina in vitro: I. Effects of dopamine precursors, reserpine, amphetamine, and L-DOPA decarboxylase and monoamine oxidase inhibitors.
The basal catecholamine content of rabbit retina was determined by liquid chromatography with electrochemical detection (LC-EC) and 3,4-dihydroxyphenylethylamine (dopamine, DA) found to be the major catecholamine. The immediate DA precursor, 3,4-dihydroxyphenylalanine (L-DOPA), and the metabolite, 3,4-dihydroxyphenylacetic acid (DOPAC), were also detected at about 2.8% and 17% of DA levels, respectively. When added exogenously, L-tyrosine did not increase the rate of DA synthesis over the basal level. In contrast, exogenous L-DOPA led to a 3.5-fold increase in DA, and to a 20-fold increase in DOPAC content. The monoamine oxidase inhibitors pargyline and (-)-deprenyl differentially affected the degradation of DA, since 100 microM pargyline was apparently more effective than 100 microM (-)-deprenyl. Reserpine and (+/-)-amphetamine each induced a Ca2+-independent decrease of DA stores. The separate actions of reserpine and (+/-)-amphetamine in lowering tissue DA levels were additive, suggesting two separate pools of DA available for release from presynaptic stores. The present study demonstrates that the LC-EC technique may be used to investigate the modulation of the synthesis and release of retinal DA in vitro, without the prior uptake of radiolabelled transmitter.
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000661:Amphetamine / Q000494:pharmacology; D000818:Animals; D065105:Aromatic Amino Acid Decarboxylase Inhibitors; D004298:Dopamine / Q000378:metabolism*; D005260:Female; D007980:Levodopa / Q000378:metabolism; D008297:Male; D008996:Monoamine Oxidase Inhibitors / Q000494:pharmacology; D010293:Pargyline / Q000494:pharmacology; D011817:Rabbits; D012110:Reserpine / Q000494:pharmacology; D012160:Retina / Q000187:drug effects / Q000378:metabolism*; D012642:Selegiline / Q000494:pharmacology; D014443:Tyrosine / Q000378:metabolism / Q000494:pharmacology
D065105:Aromatic Amino Acid Decarboxylase Inhibitors; D008996:Monoamine Oxidase Inhibitors; D015102:3,4-Dihydroxyphenylacetic Acid; D012642:Selegiline; D014443:Tyrosine; D007980:Levodopa; D012110:Reserpine; D010293:Pargyline; D000661:Amphetamine; D004298:Dopamine