[Ischemia-induced neurotrophic activity detected in the peri-infarcted brain tissue]

In the experimental ischemia induced by occlusion of the rat middle cerebral artery, axons of both cortical and thalamic neurons were affected. However, cortical neurons survived thereafter and thalamic neurons died because of retrograde degeneration. The fate in these two groups of neurons was remarkably different and may be related to neurotrophic activity induced by ischemia. To detect ischemia-induced neurotrophic activity, fetal cortical neuron was cultured and neurotrophic activity was detected by applying tissue extract to the culture system. Fetal neurons obtained from 17 days rat embryo were cultured for 24 hours at 3.75 x 10(4) cells per 15 mm well in modified Eagle's minimum essential (MEM) supplemented by 10% fetal bovine serum (FBS), then for next 3 to 7 days with Dulbecco's modified Eagle's medium/Ham's nutrient mixture F-12 (DME/F-12) supplemented with insulin 5 mg/l, transferrin 10 mg/l, progesterone 6.3 micrograms/l, Na2SeO3 5.2 micrograms/l. The tissue extract was obtained from the rat subjected to ischemia and homogenized with DME/F-12. The homogenate was centrifuged at 100,000 g for 90 minutes and the supernatant was obtained. Application of peri-ischemic cortical extract improved neurons' survival by 50% as compared to extract of the contralateral side. However, the thalamic extract of the ischemic side had no neurotrophic activity as compared to the contralateral side. The activity was detected in the extract obtained at 8 days after ischemia but not detected in the extract obtained at 4 days after ischemia. The neurotrophic activity was disappeared by heating the extract at 90 degrees C for 10 minutes.(ABSTRACT TRUNCATED AT 250 WORDS)