Interactions between enkephalin and gamma-aminobutyric acid in the larval tiger salamander retina

Both double-label and intracellular electrophysiological recording techniques were utilized to investigate the interactions between enkephalin and gamma-aminobutyric acid in the larval tiger salamander retina. Double-label studies revealed that the vast majority (greater than 96%) of enkephalin-immunostained amacrine cells also exhibit high affinity uptake of [3H]gamma-aminobutyric acid. Electrophysiological evidence demonstrated that morphine and gamma-aminobutyric acid exert opposite effects on a population of On-Off ganglion cells. gamma-Aminobutyric acid decreased the activity of these cells, while enkephalin increased their activity. These findings support the idea that opiate-mediated pathways inhibit GABAergic pathways in the vertebrate retina.