Evidence for the action of endogenous adenosine in the rabbit retina: modulation of the light-evoked release of acetylcholine.
Much evidence has accumulated supporting the hypothesis that the purine nucleoside adenosine may indeed function as a neuromodulator in the mammalian retina, but to date no reports have directly illustrated a physiological role for this nucleoside. In other regions of the CNS, adenosine agonists decrease transmitter release, whereas antagonists increase release. A similar role for adenosine in the retina is now apparent. The cholinergic amacrine cells of the rabbit retina were labeled with [3H]choline, and the effects of enzymatic adenosine degradation or adenosine antagonists on the light-evoked efflux of acetylcholine were evaluated. When endogenous adenosine was degraded by addition of adenosine deaminase, the light-evoked release of radioactivity derived from [3H]choline was significantly increased compared with control values. A similar response was observed when rabbit eyecups were superfused with a selective adenosine A1 receptor antagonist. The effect elicited by adenosine deaminase could be almost completely reversed by addition of cyclopentyladenosine, a highly selective A1 receptor agonist. These effects were observed in either the presence or the absence of picrotoxin. The results demonstrate a modulation of retinal physiology by adenosine.
Blazynski
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C
Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110.
Woods
C
C
Mathews
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GC
D000109:Acetylcholine / Q000378:metabolism*; D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology / Q000502:physiology*; D000818:Animals; D001667:Binding, Competitive; D008027:Light; D010660:Phenylisopropyladenosine / Q000378:metabolism; D011817:Rabbits; D012160:Retina / Q000378:metabolism / Q000502:physiology* / Q000528:radiation effects; D014970:Xanthines / Q000494:pharmacology
D014970:Xanthines; D010660:Phenylisopropyladenosine; C059953:1,3-dipropyl-7-methylxanthine; C027513:N(6)-cyclohexyladenosine; C051360:1,3-dipropyl-8-cyclopentylxanthine; D000241:Adenosine; D000109:Acetylcholine