[Aspartate transfer across the blood-retina barrier (author's transl)]

Permeability of the blood-brain barrier is restricted with respect to amino acids involved in neurotransmission. This finding is well-documented in the case of gamma-amino-butyric acid (GABA) and glycine. Aspartic acid, which is also considered to be a transmitter, equally does not cross the blood-brain barrier in the rat with ease. This amino acid is also thought to be a transmitter in the retina. In order to examine the permeability of the blood-retina barrier with respect to aspartic acid, and investigation was undertaken of the effect of asparate on the light-induced sum potential of the retina in the isolated, perfused cat eyeball, a preparation which guarantees intact retinal circulation. The findings were compared with findings in the isolated retina where the substance was brought into direct contact with the retinal neurons. It was found that aspartate crossed the vascular barrier only to a limited extent and with delay. These results support the hypothesis that aspartic acid is involved in the retinal information processing.