Cytochemical demonstration of aspartate aminotransferase in the mossy-fibre system of the rat hippocampus.

A lead-salt procedure was used for the cytochemical demonstration of aspartate aminotransferase (AT) in the CA3 of the rat hippocampus. Cytoplasmic- and mitochondrial-AT isoenzymes were demonstrated in different neuronal structures, but not in astrocytes. Of special interest was the localization of cytoplasmic AT in most mossy-fibre boutons. This might indicate that cytoplasmic AT is responsible for the production of releasable glutamate in the glutamatergic/aspartatergic mossy fibre system.