The CNS acute inflammatory response to excitotoxic neuronal cell death.

Acute inflammation is a stereotyped non-specific response to tissue injury which results in the recruitment of neutrophils and monocytes within minutes. In this study the myelomonocytic and microglial reaction to neuronal destruction following unilateral hippocampal injection of kainic acid neurotoxin was investigated. Despite extensive acute neuronal necrosis and notwithstanding a leaky blood-brain-barrier, there is no neutrophil recruitment and a 2-day delay before any increase in macrophage-microglial cell numbers. Resident microglia are capable of reversible upregulation to an activated morphology and the macrophage-microglial reaction is seen not only at the injection site, but also at distant sites related to the axonal pathways and synaptic terminals of the killed neurons.