Induction of heat shock protein 70 and glial fibrillary acidic protein in the postischemic gerbil hippocampus

Astroglial activation accompanies heat shock protein upregulation in rat brain following single oral dose of geranylgeranylacetone

Geranylgeranylacetone (GGA), more commonly known as an antiulcer agent, reportedly induces the heat shock protein 70 (HSP70) family in the gastric mucosa, liver and heart of rats. However, it has not been reported whether HSPs, and other factors that contribute to neuroprotection, are inducible in the brain following a single oral dose of GGA. The present study evaluated the consequences of oral GGA on astrocytic activation and the expression of HSP and revealed that a single oral dose caused a transient increase in the immunoreactivity (IR) of HSP70 and glial fibrillary acidic protein (GFAP) in the hippocampus of the rat brain.

Ribonuclease improves the state of hippocampal sections in the post-ischemic period

Living hippocampal slices from Wistar rats were used to study the dynamics of changes in population electrical responses in field CA1 to electrical stimulation of Shaffer collaterals during the development of ischemia (imposed by exclusion of oxygen and glucose from the perfusion solution). These studies showed that during ischemia, addition of ribonuclease (a blocker of protein synthesis) to the perfusion solution resulted in a significantly smaller increase in the latent period of the response and slowed the onset of the reduction in the amplitude of the evoked potential, and promoted faster recovery of the response after the ischemia session ended. It is suggested that the reduction in protein synthesis due to ribonuclease preserved energy reserves in the nerve tissue, which in turn promoted more complete recovery of neuron function in the post-ischemic period.

Post-ischaemic alteration of excitatory amino acid transport sites in the gerbil hippocampus

Sodium-dependent [3H]D-aspartate binding as a marker of excitatory amino acid transport sites in the gerbil hippocampus was evaluated by quantitative receptor autoradiography 1 h to 7 days after transient cerebral ischaemia for 10 min. Sodium-dependent [3H]D-aspartate binding in the hippocampal CA1 and CA3 sectors significantly increased in the early post-ischaemic stage. After 7 days, a conspicuous elevation of sodium-dependent [3H]D-aspartate-binding was observed in the hippocampal CA1 sector and dentate gyrus. However, no significant change in the binding was found in the hippocampal CA3 sector. A histological study revealed that transient ischaemia caused severe neuronal damage in the hippocampal CA1 sector and mild damage in the hippocampal CA3 sector. However, no ischaemic neuronal damage was observed in the dentate gyrus. An immunohistochemical study also showed that numerous reactive astrocytes were evident in the hippocampus, particularly in the hippocampal CA1 sector, 7 days after ischaemia. These results demonstrate that transient cerebral ischaemia can cause marked elevation in excitatory amino-acid transport sites in the hippocampus. Furthermore, our results suggest that the post-ischaemic increase in excitatory amino acid transport sites might reflect expression of reactive astrocytes. These findings are of interest in relation to the mechanisms of ischaemic hippocampal damage.