Psychophysiological stress induces heat shock cognate protein 70 messenger RNA in the hippocampus of rats.

Psychophysiological stress has been shown to increase 70,000 mol. wt heat shock protein messenger RNAs with northern blotting in rats. However, its localization is unknown. With in situ hybridization, we tested our hypothesis that restraint water-immersion stress may induce heat shock cognate protein 70 messenger RNA expression simultaneously with some morphological changes selectively in the hippocampus of rats. Stress for 6 h significantly increased heat shock cognate protein 70 messenger RNAs in the hippocampus, with maximal intensity in the CA3 subfield of the Ammon's horn and to a lesser extent in CA2. Stress for 12 h significantly increased heat shock cognate protein 70 messenger RNAs in the whole hemisphere including the cerebral cortex, the thalamus, the hypothalamus, and the hippocampus with the highest density in CA3. Heat shock cognate protein 70 messenger RNA in rats with stress for 6 h followed by recovery for 6 h significantly increased at CA3 and CA2 compared with the controls or rats stressed for 6 h without recovery. No overt histological changes were detected in neuronal or glial cells in the slides of hematoxylin-eosin or Cresyl Violet staining. These results show that psychophysiological stress induces heat shock cognate protein 70 messenger RNA in the most stress-vulnerable brain structure, hippocampal CA3, probably for cytoprotection.