Induction of c-fos by excitatory amino acids in developing chick retina is affected by changes in cellular interactions.

Cell contact is important for normal maturation of chicken retinal Müller cells. In order to gain a better understanding as to how this occurs, we examined the ability of retinal cells with altered cell contacts to respond to an environmental stimulus. The response of Müller cells cultured under conditions which alter cell contacts was measured by activating intracellular signaling systems leading to induction of the early-inducible gene c-fos. Chicken retinal cells were cultured as explants, reaggregates, and monolayers and exposed to extracellular stimuli in the form of the excitatory amino acids D,L-alpha aminoadipic acid (AAA) and N-methyl-D,L-aspartic acid (NMDA). Each culture was exposed to 1.25 mM AAA, 2.5 mM AAA, 50 microM NMDA, or 100 microM NMDA. Toxicity was assessed histologically and by immunocytochemical labeling of Müller cells after 2 days of exposure. Activation of c-fos was determined by Western blot analysis for Fos protein after 30, 60, and 120 minutes of exposure. Exposure to AAA led to a loss of Müller cells in explant and reaggregate cultures; however, Müller cells in monolayer culture were not susceptible to AAA at either dose. NMDA was toxic to a specific population of neurons under all three culture conditions. Fos protein expression paralleled the histologic findings. Fos protein was significantly elevated after exposure to either dose of AAA in explant and reaggregate cultures but not in monolayer cultures.(ABSTRACT TRUNCATED AT 250 WORDS)