Colocalization of enkephalin and glycine in amacrine cells of the chicken retina.

The present double-label study combines enkephalin immunocytochemistry with either autoradiography of glycine high-affinity uptake or glycine immunocytochemistry to investigate the coexistence of glycine in enkephalin-amacrine cells of the chicken retina. A regional analysis revealed that the percentage coexistence of glycine high-affinity uptake in enkephalin-amacrine cells did not vary appreciably throughout the retina. Overall, 54.9% of enkephalin-amacrine cells exhibited high-affinity glycine uptake. Double-label immunofluorescence cytochemistry revealed that 52.5% of enkephalin-amacrine cells expressed glycine immunoreactivity. These double-immunolabeled cells were observed throughout the center and periphery of the retina. The present study reveals a similar percentage of chicken enkephalin-amacrine cells expressing either glycine high-affinity uptake (54.9%) or glycine immunoreactivity (52.5%) and therefore, provides supportive evidence for identifying these cells as glycinergic. The present study also suggests a functional diversity in the population of enkephalin-amacrine cells in the chicken retina relative to their coexisting/non-coexisting relationship with glycine.