Regional profile of polyamines in reversible cerebral ischemia of Mongolian gerbils.

Abstract

Reversible cerebral ischemia was produced in Mongolian gerbils (Meriones unguiculatus) by occluding both common carotid arteries. After 5 min ischemia brains were recirculated for 8, 24, 48, 72, or 96 h. An additional 6 animals were subjected to 10 min ischemia and 24 h recirculation. Sham-operated animals served as controls. At the end of the experiments, brains were frozen in situ and cut in a cryostat. Coronal sections, 10 micron thick, were taken for histological staining. In addition, tissue samples (2-4 mg each) were taken from the cortex, lateral caudoputamen, CA1-layer of the hippocampus, and thalamus. Polyamines (spermidine, spermine, and the precursor putrescine) were measured in these samples using reverse-phase HPLC and fluorescence detection after extraction and precolumn derivatization. Five-minute cerebral ischemia had no effect on the levels of putrescine, spermidine, or spermine. However, following recirculation, putrescine increased markedly with time, being most pronounced in the CA1-subfield of the hippocampus, less so in the cortex, and even less so in the thalamus. After prolonged recirculation, severe neuronal necroses could be observed only in regions exhibiting high putrescine levels. Spermidine or spermine did not change during recirculation, except in severely damaged regions: Here, spermine levels were markedly reduced following prolonged recirculation. The post-ischemic increase in putrescine is discussed in respect to the known multiple activities of putrescine.