SELEGILINE TREATMENT AFTER TRANSIENT GLOBAL-ISCHEMIA IN GERBILS ENHANCES THE SURVIVAL OF CA1 PYRAMIDAL CELLS IN THE HIPPOCAMPUS

Selegiline (L-deprenyl) has shown neuroprotective effects in a variety of degenerative processes, The present experiments were designed to t est whether post-ischemia administered selegiline would alleviate dela yed neuronal death of the gerbil hippocampal pyramidal cells following transient global ischemia. Common carotid arteries were occluded for 5 min, Saline or selegiline, 0.25 mg/kg s.c., was administered 2 h aft er the ischemia followed by a daily injection for either 3 or 7 days. After decapitation, the delayed death of the hippocampal CA1 pyramidal cells was assessed using Nissl-stained sections. In situ hybridizatio n was used to reveal the expression of hsp70 mRNA 1, 3 or 7 days after the ischemia. Animals treated with selegiline for 7 days showed signi ficantly lower damage score (scale 0-3: 0, normal; 1, < 10% of the neu rons damaged; 2, 10-50% damaged; 3, > 50% damaged) compared to the sal ine-treated animals 1.73 +/- 0.18 and 2.41 +/- 0.16 (mean +/- S.E.M., P = 0.0133), respectively. A similar trend was found in animals after the 3-day treatment: 1.68 +/- 0.32 vs. 2.06 +/- 0.25 (P > 0.5). The ex pression of hsp70 mRNA in the CA1 pyramidal cell layer was strong stil l 3 days after the ischemic insult but vanished by 7 days. Densitometr ic measurements using C-14-plastic standards showed that the intensity of the CA1a hsp70 signal on the 3rd day correlated negatively to the cell-damage score (r = -0.72, P < 0.001), suggesting that hsp70 does n ot serve as a quantitative marker for CA1 neuronal injury in this mode l. Instead, the hsp70 expression was associated with improved neuronal survival lasting often longer in selegiline-treated animals (P > 0.5) . The results show that a low dose of selegiline can alleviate the del ayed hippocampal neuronal death in gerbils when administered 2 h after an ischemic insult.