RESUMEN
On one hand this paper used co-culture method of rat normal or injuried sciatic nerves with newborn rat superior cervical ganglia (SCG) to observe that the neurite outgrowth of SCG induced by the nerve, on the other hand we made normal or injuried sciatic nerve extracts in order to observe their neurite-promoting effects on PC12 cells to various dilutions of nerve extracts. The results show that normal and injuried sciatic nerves contain neurite-promoting factors (NPFs) for SCG sympathetic neurons. However, the NPF activity of injuried nerve is higher than that of normal nerve and has no significant differences from 1-41 days postlesion. We have also observed the neurite-promoting effects of normal or injuried sciatic nerve extracts on PC12 cells. There is a maximal effect with the injuried nerve extract prepared at 4 days post-lesion. The neurite-promoting activity of injuried (12 hours to 42 days post-lesion) nerve extracts remain constant. The rate of neurite elongation in PC12 cells relate to the dilution of nerve extracts. Experimental analysis suggests that the nerve NPFs may be not the single but two or more factors which may be produced and released by Schwann cells.