Ultrastructural features of the astrocytes involved in the phagocytic response to excitotoxins and anoxia in vitro.

The present ultrastructural studies demonstrate the morphological evidence of phagocytic response of astroglia to excitotoxins and anoxia in vitro. The studies were performed on organotypic cultures of the rat hippocampus exposed to various excitatory amino acids (QUIN, KA, GLU) or pure nitrogen atmosphere. In all these pathological conditions, the extensive neuronal degeneration was accompanied by marked astroglial reaction. The astrocytes revealed ultrastructural abnormalities consisting of swelling of their cytoplasm followed by more or less advanced fibrillar changes. Numerous reactive astrocytes demonstrated morphological evidence of phagocytic activity during the process of neurodegeneration. They exhibited the presence of ingested degenerating neurons or neuronal debris and accumulation of dense bodies. The results support a possible phagocytic role of astroglia after neuronal injury in various pathological states. The phagocytic response of astrocytes may interfere with other glial functions in CNS and may play a role in tissue recovery.