The Development Of Telencephalon And Spinal Cord And The Expressions Of TrkA In Rat Embryo

Object: To study the expression of TrkA, the special receptor of NGF,in the telencephalon and spinal cord during the different periods of ratembryo, and to investigate the relationship between TrkA and neuralcell during their development. Method: Using HE, Nissl bodystaining and immunohistochemistry technique to examine thedevelopmental process of neuron in rat telencephalon and spial cord;Using immunohistochemistry technique to detect the expression ofTrkA. Result: (1) The development of the embryonic telencephalon:At E13 stage, the neural tube has closed completely, and formed theprimary brain vesicle. At this age, nissl body has not been detected inthe epithelium. The telencephalon formed at E15 stage. The old braincortex appeared, and consisted of numerous cells layers at the sametime. The wide lateral cerebral ventricle appeared. There was theoriginal corpus striatum at the lateral wall. At this stage, nissl body hasnot been detected yet. At E17 stage, the base shape of telencephalonand the new brain cortex formed. The corpus striatum enlarged step bystep, and partly filled the lateral cerebral ventricle. The boundary ofcells layers of brain cortex was not clear. The nissl bodies could beseen in the cortex neural cells. From E17 to E21 stage, thetelencephalon enlarged and formed the adult shape. The corpusstriatum almost filled the lateral cerebral ventricle. The hippocampwas obvious at the same time. The boundary of the cell layers of thebrain cortex was also obvious step by step. At the same age, a greatquantity of nissls could be seen in the neural cells' body of thehippocamp. (2) The development of the embryonic spinal cord: At E13stage, the spinal cord looked like a block on the T-sect without anynerve fibers and nissl bodies could be seen. At E15 stage, the spinalcord developed gradually and looked like a hairy chestnut seed on theT-sect. No nerve fibers and few nissl bodies could be seen. At E17stage, the spinal cord enlarged more and looked like a butterfly on theT-sect. The central tube looked like a diamond on the T-sect and thenerve fibers was obvious already. From E19 to E21 stage, the spinalcord has the same shape as adult on the T-sect. (3) The expression ofTrkA in the embryonic telencephalon and spinal cord: â‘  Theexpression of TrkA in the different area of the developmentalembryonic telencephalon: At E13 stage, no TrkA positive cell could bedetected. From E15 to E17 stage, the expression of TrkA wasincreased stably in the embryonic telencephalon cortex. At E17 stage,the expression of TrkA reached the peak. At E19 stage, the expressionfelled down, but maintained at a higher level. At E21 stage, the level ofTrkA reached the highest peak. Then, the expression felled downgradually to adult level (3-5 months). The result of the corpus striatumand the hippocamp was the same as the result of the brain cortex.Because of the development of the corpus striatum and the hippocampwas later than the cortex, the TrkA positive cells could be detectedlater. â‘¡ The expression of TrkA in the developmental embryonicspinal cord. There were few TrkA positive cells in the spinal cord atE13 stage. From E15 to E17 stage, the expression of TrkA was stablyincreased in the embryonic spinal cord. At E17 stage, the expressionreached the peak. At E19 stage, the expression felled down, butmaintained at a higher level. At E21 stage, the level reached thehighest peak. Then, the expression felled down gradually to adult level(3-5 months). (4) The expression of Nestin in the embryonictelencephalon and spinal cord: (1) The expression of Nestin in thedifferent areas of the developmental embryonic telencephalon: TheNestin positive cells could be detected in the embryonic telencephalonfrom E13 to E15 stage. With the development, the expression ofNestin was gradually decreased. From E17 to E21 stage, there were nopositive cells could be detected but a few positive nerve fibers at E17stage. â‘¡ The expression of Nestin in the developmental embryonicspinal cord. The result of immunohistochemical staining in the spinalcord is the same as that in the telencephalon. From E17 to E21 stage,there were no positive cells could be detected but a few positive nervefibers at E17 stage. Conclusion: (1) Following the development ofembryonic telencephalon and spinal cord, the expression of Nestindecreased gradually. (2) The neural cells and TrkA developed at theequal pace in the embryonic telencephalon and spinal cord. (3) It is atE15 stage that the TrkA appeared during the development of theembryonic telencephalon and spinal cord. The expression increasedgradually from E15 to E17 stage and felled at E19 stage. While at E21stage the expression of TrkA reached the highest peak. (4) Thedevelopment of the embryonic spinal cord is earlier than theembryonic telencephalon during the CNS formed. The development ofthe embryonic spinal cord formed basically at E19 stage, while thedevelopment of the embryonic telencephalon lasted to E21 stage, evento the post of birth.