Objective To investigate the pattern and the role of cytoskeletal genes expression during nerve regeneration. Methods We examined the changes of expression of ? tubulin(? Tub)and three neurofilament(NF)subunits mRNA in rat corticospinal neurons of sensorimotor cortex on the 1st,3rd,5th,7th,10th,14th,21st,28th and 56th days after spinal cord semitransection injury by using in situ hybridization. Results Levels of ? Tub,NF L,NF M and NF H mRNA were dramatically downregulated within large sized pyramidal neurons in layer V of the sensorimotor cortex of side lateral after spinal cord injury.The level of ? Tub mRNA was decreased as early as 1 day postinjury,whereas the levels of NF subunits mRNA were not decreased until later time(on the 3rd days postinjury),and both of them did not return to control levels on the 56th days following the lesion. Conclusion ? Tub gene expression if inhibited in CNS neurons postinjury. The axotomy signeal and the continuance downregulation of NF mRNA expressioon following spinal cord injury may contribute to the ineffective regeneration response of CNS neurons.

Objective In order to explore the mechanisms that regulate the expression of genes coding for cytoskeletal proteins during nerve regeneration. Methods In the present study, in situ hybridization was used to examine the changes of light(NF L),medium(NF M)and heavy (NF H)neurofilament protein subunits mRNA in L 4-6 dosal root ganglion (DRG) sensory neurons during nerve regeneration following a unilateral crush of the sciatic nerve. Results The hybridization signals of each neurofilament subunit mRNA were dramatic decrees in DRG sensory neurons post axotomy by light microscope.The signals of NF\|L and NF\|M mRNA were located in cytoplasm of neurons,whereas NF H mRNA was found in both nucleus and cytoplasm of neurons. Conclusion There are the different mechanisms of regulation of neurofilament subunit genes expression,the reduced neurofilament gene expression may represent a general response to axonal injury and plays an important role in effective nerve regeneration.

Objective To study effects of GDNF and HSV GDNF on apoptosis of spinal cord motoneurons after scratch injury in vitro. Methods In the period of culture cell,motor neurons were periodically observed and counted.Scratch injury was executed on culturing 12th day,in the same time,cultured neurons were divided into 4 groups,and each group was given corresponding medium(medium serum free control group,serum group,HSV GDNF group,GDNF group).On the 4th and 7th day after scratch injury,TUNEL staining was respectively performed,and the number and the mean densities of apoptotic motoneurons were observed. Results The number of living motoneurons was in inverse proportion to time of scratch injury in each group.The number of apoptotic motoneurons from control group,HSV GDNF group to GDNF group was successively decreased as well as the mean densities of apoptotic motoneurons on the 4th and 7th day after scratch injury.Furthermore,the effects of groups with serum were no better than those of medium serum free groups,in the same time,difference was not obviously in HSV GDNF group and GDNF group. Conclusion GDNF and HSV GDNF can decrease apoptosis of injured motoneurons in vitro .It suggests that GDNF and HSV GDNF might play an important role in the growth and development of motor neurons.