Growth Associated Protein-43 mRNA Expression in Nucleus Ambiguus Motoneurons after Recurrent Laryngeal Nerve Injury in the Rat

OBJECTIVE: To investigate the time-dependent differences in growth associated protein-43 (GAP-43) mRNA expression in the nucleus ambiguus (NA) motoneurons after recurrent laryngeal nerve (RLN) transection in the rat. MATERIAL AND METHODS: Animals were sacrificed on Days 1, 7, 14 and 21 after axotomy. The sections were then processed for in situ hybridization of GAP-43 mRNA. RESULTS: GAP-43 mRNA transiently increased after axotomy, reaching a peak on postoperative Day 7, and then decreased gradually at 14 and 21 days after axotomy. The peak period of GAP-43 expression in the NA is different from those in the facial and hypoglossal nuclei after axotomy. CONCLUSION: We have already reported that neuronal nitric oxide synthase (nNOS) is induced in the NA motoneurons after axotomy and reaches a peak on postoperative Day 14. This study shows that the expressions of GAP-43 and nNOS are chronologically different.