THE INTRACELLULAR MECHANISMS FOR GDNF TO PROMOTE THE SURVIVAL AND DIFFERENTIATION OF MIDBRAIN DOPAMINERGIC NEURONS / 解剖学报

ABSTRACT

Objective To explore the possible roles of PI3K pathway and MAPK pathway in mediating the survival and differentiation-promoting effect of glial cell line-derived neurotrophic factor(GDNF) on midbrain dopaminergic neurons.(Methods Midbrain) slices of early postnatal rats were cultured,the slices were divided into four groups according to the different substances added into the culture medium i.e.blank control group,GDNF group,Wortmanin plus GDNF group,and PD98059 plus GDNF group.On the 6th day,some slices were fixed,embedded and sectioned.The sections were processed for tyrosine hydroxylase(TH) immunohistochemistry,and then examined under microscope to determine the morphologic index for statistic analysis(n=6).Meanwhile,some slices were taken for Western blot to examine the expression of TH protein in midbrain slices(n=4). Results GDNF group slices showed the morphologic maturity,the density and the diameter of TH positive neurons,as well as the level of TH expression,were all significantly higher than that of the control groups.The survival effect of GDNF on DA neurons was almost abolished when the PI3K pathway was blocked with Wortmannin;while the MAP kinase and ERK kinase(MEK) inhibitor PD 98059 was added to block the MAPK pathway,the diameter of TH positive neurons was decreased significantly.Conclusion The PI3K pathway might mediate the survival effect of GDNF,while the MAPK pathway seems to be involved in the differentiation process.