title: Enkephalin in the goldfish retina.
abstract: Enkephalin-like immunoreactive amacrine cells were visualized using the highly sensitive avidin-biotin method. The somas of these cells were situated in the inner nuclear and ganglion cell layers. Enkephalin-stained processes were observed in layers 1, 3, and 5 of the inner plexiform layer. The biosynthesis of sulfur-containing compounds in the goldfish retina was studied by means of a pulse-chase incubation with 35S-methionine. A 35S-labeled compound, which comigrated with authentic Met5-enkephalin on high-performance liquid chromatography (HPLC), was synthesized and was bound competitively by antibodies to enkephalin and by opiate receptors. This compound was tentatively identified as "Met5-enkephalin." The newly synthesized 35S-Met5-enkephalin was released upon depolarization of the retina with a high K+ concentration. This K+-stimulated release was greatly suppressed by 5 mM Co2+, suggesting that the release was Ca2+ dependent. Using a double-label technique, enkephalin immunoreactivity and gamma-aminobutyric acid (GABA) uptake were colocalized to some amacrine cells, whereas others labeled only for enkephalin or GABA. The possible significance of enkephalin-GABA interactions is also discussed.
mesh_terms: D000818:Animals; D001345:Autoradiography; D003530:Cyprinidae / Q000378:metabolism*; D004744:Enkephalin, Methionine / Q000096:biosynthesis; D004745:Enkephalins / Q000378:metabolism*; D006054:Goldfish / Q000378:metabolism*; D006651:Histocytochemistry; D007120:Immunochemistry; D011957:Receptors, Opioid / Q000378:metabolism; D012160:Retina / Q000378:metabolism*; D013462:Sulfur Radioisotopes; D014316:Tritium; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D004745:Enkephalins; D011957:Receptors, Opioid; D013462:Sulfur Radioisotopes; D014316:Tritium; D005680:gamma-Aminobutyric Acid; D004744:Enkephalin, Methionine