The neurotoxicity of zinc in the rat hippocampus.

Intrahippocampal injections of zinc chloride (5-10 nmol) caused a discrete lesion in the rat hippocampus, involving all neuronal perikarya. In addition to the necrosis, the lesion was also characterized by a decrease in staining of the neuropil, the presence of pyknotic neurons, and occasionally infarction. Pathological changes occurred within 8 h of an injection, and neuronal loss, as judged by the loss of Nissl staining, was complete within 24 h. On the other hand, the loss of acidophilic staining of the neurons was more gradual, as acid fuchsin staining was still present in neurons in the periphery of the damaged area 4 days later. In comparison with an excitotoxic lesion, glial infiltration into the damaged area was minimal, even up to 3 weeks later, suggesting that some glial cell toxicity also occurred.