The "ON"-bipolar agonist, L-2-amino-4-phosphonobutyrate, blocks light-evoked cone contraction in xenopus eye cups.
Rhythmic photoreceptor metabolism in relationship to light-dark cycles is now thought to be regulated through a retinal feed-back mechanism with dopamine serving as a principal signal initiating light-evoked events. In order to test the hypothesis that depolarizing "ON"-bipolar neurons participate in the retinal signalling pathway, we determined the effects of L-2-amino-4-phosphonobutyrate (L-APB) on light-evoked cone contraction in eye cups from Xenopus laevis. L-APB blocked the response stereospecifically when applied over a broad concentration range. The high specificity of L-APB in retina suggests that sign-inverting bipolar neurons which depolarize in light are in the signalling pathway. One possibility is that this pathway conveys signals that regulate dopamine release.
Besharse
J C
JC
Department of Anatomy and Cell Biology, University of Kansas School of Medicine, Kansas City 66103.
D000613:Aminobutyrates / Q000494:pharmacology*; D000818:Animals; D004298:Dopamine / Q000378:metabolism / Q000494:pharmacology; D018492:Dopamine Antagonists; D008027:Light; D010786:Photoreceptor Cells / Q000187:drug effects* / Q000502:physiology; D015398:Signal Transduction; D014982:Xenopus laevis
D000613:Aminobutyrates; D018492:Dopamine Antagonists; C012729:2-amino-4-phosphonobutyric acid; D004298:Dopamine