Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 41 3 2003 09 15 183 187 M. Firouzi 2015 09 28 The effect of nerve growth factor (NGF) on regeneration of rat sciatic nerves in adult rat was studied. The sciatic nerve was cut out across a 6‑mm gap, then the proximal and distal stumps were inserted into the silicone tube chamber. 7s NGF was extracted from submaxillary gland and then was injected into the silicone in experimental group. After seven months nerve was transected and stained with toluidine blue. Semithin sections (1 µm from middle of silicone (control group, without NGF) showed that regenerated axons (mostly unmyelinated) were dispersed randomly, and they were not grouped into bundles. In this group some of the myelinated fibers were degenerated and macrophages or in other word, schwann cells contained a large amount of these degenerated sheaths. Semithin section of experimental group (with NGF) showed numerous regenerated axons (myelinated) that were grouped into small bundles. Schwann cells in experimental group were large and eucromatin and some of them were divided. These data indicate that NGF causes myelinated axons, regenerate and making new myelinated sheaths. https://acta.tums.ac.ir/index.php/acta/article/view/2661 https://acta.tums.ac.ir/index.php/acta/article/download/2661/2643