Changes in regional polyamine profiles in rat brains after transient cerebral ischemia (single versus repetitive ischemia): evidence for release of polyamines from injured neurons.

Reversible cerebral ischemia (of 5 min, 15 min, or 3-times 5 min) was produced in 14 Mongolian gerbils by occluding both common carotid arteries. After 72 h of recirculation, brains were frozen and processed for measuring regional levels of the polyamines putrescine, spermidine and spermine using HPLC and fluorescent detector. Ischemia induced a marked increase in putrescine levels throughout the brain, most pronounced after 3-times 5 min ischemia (P less than or equal to 0.05 - P less than or equal to 0.001). Spermine levels were significantly reduced, in the hippocampal CA1-subfield after 5 min of ischemia and, in addition, in the striatum and thalamus after 3-times 5 min ischemia. It is suggested that polyamines are released from necrotic neurons and cleared into the blood. Spermine, released from neurons into the extracellular compartment, may bind to the N-methyl-D-aspartate (NMDA) receptor of cells located in close vicinity and may thus render neurons vulnerable to otherwise subtoxic levels of excitotoxins.