The dynamical changes of GDNF and the gene expression of GDNF mRNA after traumatic brain injury in rats

Objective To investigate the pathology of TBI and to understand the relationship between the expression of GDNF and the timing of traumatic brain injury ( TBI). Methods Immunohistochemical staining, double-labeled with the anti-GDNF antibody and with either the neuron-specific antibody NeuN or the astrogli-al-specific marker GFAP, and in situ hybridization were performed and computer image analysis were used. Results GDNF mRNA and GDNF were faintly expressed in mostly neurons at the cerebral cortex of control group, the staining intensity was increased 15 min post-injury, and peaked at Id and 2d after injury, respectively. Significant differences in GDNF protein were present between control and 2d post-injury (P 0. 05). The intensely stained cells persisted in a high level after 2 days, and significant differences (P 0. 05 ) even presented between control and 7d post-injury. The GDNF mRNA was expressed faintly in the cerebral cortex in the control group, expressed increasingly since 1h after TBI and reached the maximum (P 0. 05) at 1d post-injury with a high level till 7d post-injury (P 0. 05). Conclusion The results indicated that the expression of GDNF mRNA and GDNF protein had a possible relationship with the extending time after TBI. The cells expressing GDNF were mostly neurons before 1 d post-injury, with astroglias after 2d post-injury.