Methods: The 0.4mm crowns were fabricated and bonded to the first molar in maxillary of male Sprague-Dawley rats. At 1d, 3d, 5d, 10d, 14d, 21d, and 28d after occlusal alteration treatment, the rats were euthanized by transcardiac perfusion after deep anesthetization. Brain stem sections were obtained and processed for immunofluorescence staining for phospho-p38, phospho-ERK and phospho-JNK, and the numbers of positive cells were counted. Double immunofluorescence staining with NeuN (neuron marker), OX-42 (microglia marker), and glial fibrillary acidic protein (GFAP, astrocyte marker) were also performed.
Results: (1) The increase of phospho-p38 positive cells was detectable after occlusal interference on day1, became significant from day 3 to day 14, and was maintained until day 28 (p<0.01). (2) The expression of phospho-ERK emerged on day 1 and maintained at a moderate level from day 3 to day 28 (p<0.01). (3) No phospho-JNK positive cells were observed at each time point. (4) Both phospho-p38 and phospho-ERK were colocalized with neuron and microglia but not with astrocyte.
Conclusions: p38 and ERK activation are induced in Vsp neuron and microglia for a long time after experimental occlusal interference.