Figure 4. The stimulated release of glutamine is mediated by glial cells.

A, postsynaptic currents induced by the application of d-aspartate to the synapse are significantly inhibited by incubating the tissue in the glutamine synthetase inhibitor l-MSO (10 mm), which depletes astrocytes of glutamine. B, incubating the tissue with the glial-specific metabolic toxin fluoroacetate (FAc; 10 mm) also severely compromised the d-aspartate-induced postsynaptic current, further demonstrating the role of glial cells in the activated pathway. C, averaged data indicating the similar levels of inhibition of the postsynaptic d-aspartate-induced current by l-MSO (64%) and FAc (67%).