[The changes of NT-4 expression in spared root ganglion and spinal cord following partial dorsal root rhizotomy]

This study was conducted to detect the expression levels of NT-4 in the spared dorsal root ganglia (DRG, L6) on the operated side and un-operated side, in the spinal lamina II (L3, L5, L6) and Clarke's nucleus (L3) of the normal adult cats and the cats submitted to partial dorsal rhizotomy. The aim was to illuminate the temporospatial changes of NT-4 expression and its possible relation to spinal cord plasticity.

Fifteen male adult cats were divided into three groups. The cats of two groups were submitted to unilateral partial dorsal root rhizotomy (L1-L5, L7-S2 DRG were sectioned, but L6 was spared) and animals were sacrificed at survived 7 days and 14 days after operation. The sections were stained by the immunohistochemistry ABC method under the same condition, using NT-4 (1:200, Santa Cruz) antibody. The distribution and the number of NT-4 positive neurons in bilateral spared DRG (L6) in the operated/un-operated side, spinal lamina II (L3, L5, L6) and Clarke's nucleus (L3) of each animal were observed and counted. All data were analyzed by one-way ANOVA, SNK-q test and paired-t test.

(1) Seven days after partial dorsal root rhizotomy, the number of NT-4 positive neurons in spared DRG in the operated side was significantly less than that of normal group (P<0.05), but significantly more than that of L6 DRG in the unoperated side (P<0.05); the number of NT-4 positive neurons of L6 DRG on the 14th day after partial dorsal root rhizotomy was also less than that of normal group, 7-day group, and the un-operated side (P<0.05). (2) There was no difference in respect to the number of NT-4 positive neuron in L3, L5, L6 spinal lamina II and L3 Clarke's nucleus in the operated side between the normal group, 7-day operation group and 14-day operation group (P>0.05).

Our results suggest that partial dorsal root rhizotomy can mainly lead to the change of NT-4 expression in the spared root ganglion, and NT-4 in the unoperated side DRG are involved in spinal cord plasticity.