Change of expression of full-length and truncated TrkBs in the developing monkey central nervous system

We examined the expression of full-length TrkB (TrkB(TK+)) and truncated TrkB (TrkB(TK-)) in the central nervous system (CNS) of the macaque monkey (Macaca fascicularis) using a western blot analysis. Ar the adult stage, the levels of TrkB(TK+) in cerebral cortices were higher than those in other structures of CNS and the expressions of TrkB(TK+) in the association cortices (except area PE) were relatively lower than those in the primary cortices. In contrast, TrkB(TK-) in the hjppocampus and the cerebellum was significantly higher than in other structures. in various developing cerebral cortices, TrkB(TK+) was detected at the same levels from embryonic day 120 (E120) to the adult period. In contrast, the expression of TrkB(TK-) increased remarkably after the newborn stage (NB), reached the maximum level at postnatal day 60 (P60) and maintained the same level into adulthood. The peaks of TrkB(TK-) in the association cortices were more delayed than in the primary cortices. The expression of TrkB(TK-) occurred at a time that correlates with the elimination of axons and the down-regulation of neuropeptides. The present study suggests that TrkB(TK-) plays an important role in the axonal remodelling and that it may act as a negative effector of TrkB(TK+), the primate CNS, reducing responsiveness to BDNF and/or NT-4/5. (C) 1999 Elsevier Science B.V. All rights reserved.