Effect of sciatic nerve crush on local and target tissue production of neurotrophin-3 transcripts in rats.

The effect of sciatic nerve crush in adult rats on neurotrophin-3 (NT-3) mRNA expression at the site of crush and in ipsilateral foot skin was studied using competitive reverse transcription-polymerase chain reaction (cRT-PCR). Mid-sciatic nerve crush resulted in a significant reduction in the expression of NT-3 mRNA in nerve segments distal to the injury site at 3 and 7 days (approximate 60% decrease; P < 0.01). The reduced NT-3 rnRNA expression started to increase at days 14 post-crush and returned towards control levels at 21 days following the crush. The nerve segment proximal to the crush site showed a similar changed pattern of NT-3 mRNA expression. The effects of denervation on NT-3 mRNA expression in foot skin were also studied. Reduced expression of NT-3 was observed by 7 days post-crush, with a 25% decrease observed by 14 days (P < 0.002). Levels of NT-3 mRNA had returned to normal by 21 days post-crush. The results show that changes in axon-Schwann cell contact do not account for the nerve crush induced loss, or subsequent recovery, of NT-3 mRNA expression in nerve.