Effects of alpha-aminoadipate isomers on the morphology of the isolated chick embryo retina.

The glutamate analogue, alpha-aminoadipate (alpha AA), was administered in the DL-, D-, and L-forms to chick embryo retinas in vitro. Two-hour incubation of retinas, with each form of alpha AA, resulted in glial swelling of progressive severity as the concentration of the adipate increased. Damage was most severe with the L-isomer, which produced a mixed glial-neuronal lesion that affected inner neuronal structures. The effect of the D,L racemic mixture was limited to glia and was less severe than damage seen with the L-isomer. The D-isomer produced effects similar to, but less severe than, those seen with the D,L mixture. Neuronal damage was seen subsequent to extensive Müller cell swelling in longterm cultures (24 hours) with the L- and DL-isomers. In contrast, the D-isomer did not produce discernible neurotoxicity even after a 24-hour treatment with 2.4 mM. Morphologic changes resulting from 2-hour adipate treatment were, to a large extent, reversible.