Topographical organization of the dopamine-dependent adenylate cyclase of the chick embryo retina.

Retinas obtained from 9- and 16-day-old chick embryos and 5-day-old post-hatched chicken were analyzed with regard to the topographical distribution of the dopamine-stimulated adenylate cyclase system. The retinas were sectioned into 4 quadrants, namely ventroanterior, dorsoanterior, dorsoposterior and ventroposterior, taking the beak and the choroid fissure as references. Dopamine (0.1 mM) elicited the accumulation of cAMP in all 4 portions of tissue studied. However, when the ratio between the dopamine-stimulated vs the basal level of cAMP of 9-day-old embryo retina were compared in the different tissue portions, we observed that in the dorsoposterior quadrant the ratio was 15.5 while in the ventroanterior quadrant the ratio was approximately 6. The other two portions showed intermediate values. The same pattern was observed in retinas from 16-day-old embryos. However, the ratio between the dopamine-stimulated vs the basal cAMP levels were 4.6 and 3 in the dorsoposterior and ventroanterior quadrants respectively. Further, the retina responsiveness to dopamine from post-hatched chicken was evenly distributed in the tissue, showing a stimulated/basal cAMP ratio of approximately 2 in all 4 quadrants studied. Our results show that the dopamine-dependent cAMP accumulation of the chick retina is unevenly distributed in the embryonic tissue and tends to homogeneity as the tissue differentiates.