Selegiline treatment after transient global ischemia in gerbils enhances the survival of CA1 pyramidal cells in the hippocampus

Abstract

Selegiline ( l-deprenyl) has shown neuroprotective effects in a variety of degenerative processes. The present experiments were designed to test whether post-ischemia administered selegiline would alleviate delayed 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 after 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 hybridization 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 significantly lower damage score (scale 0–3: 0, normal; 1, <10% of the neurons damaged; 2, 10–50% damaged; 3, >50% damaged) compared to the saline-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 expression of hsp70 mRNA in the CA1 pyramidal cell layer was strong still 3 days after the ischemic insult but vanished by 7 days. Densitometric measurements using 14C-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 not serve as a quantitative marker for CA1 neuronal injury in this model. 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 delayed hippocampal neuronal death in gerbils when administered 2 h after an ischemic insult.