Abstract:

Objective To explore the activation of phospho-p38 mitogen activated protein kinases（p-p38MAPK） and to evaluate the possible role of nerve growth factor（NGF） on neuronal protection and regeneration of injured nerve in a model of hypoglossal nerve injury in rats. Methods Sixty healthy adult SD rats were divided randomly into three groups: NC control group, NS control group and NGF treatment group. The rats were allowed to survive for 1, 3, 5, 7 and 14 days after operation respectively. Frozen sections were processed for immunohistochemistry（IHC） to decide the p-p38MAPK expression level in the motoneurons of hypoglossal nucleus. Nissl’s staining was used to evaluate cellular morphological and architectural changes in the hypoglossal nucleus. Transmission electron microscope （TEM） study was employed to investigate the subcellular structural alternations of the hypoglossal nerve distal to the injury site. Results The expression level of p-p38MAPK was low in NC group and elevated in all operated animals. However, p-p38MAPK immunoreactivity in the hypoglossal motoneurons in NGF group was lower than NS control group after injury. The survival rate of motoneurons in hypoglossal nucleus of injured side in NGF group was higher than that in NS group. Ultrastructural study revealed more regenerating myelinated axons which distributed homogenously in the distal site of the lesioned hypoglossal nerve from the NGF group than NS group. Conclusion p-p38MAPK was slightly expression in normal hypoglossal nucleus but intensively expression after injury. NGF candown-regulate p-p38MAPK expression in the motoneurons of hypoglossal nucleus after hypoglossal nerve was crushed. Exogenous NGF can protect damaged neurons and promote nerve regeneration after hypoglossal nerve crush injury in rats.

Key words: nerve growth factor, hypoglossal nerve, crush, regeneration