RESUMO
BACKGROUND AND OBJECTIVES: Many expeerimental evidences have beensupported that the vestibulocerebellum involved in recovery of vestibular compensation. The purpose of this study was to investigate effect of unilateral ablation of uvula and nodular lobes on early stage of vestibular compensation. MATERIALS AND METHODS: Adult Sprague-Dawley rats weighing 250~300 g were used and divided into control (CON) group receiving sham operation, unilateral labyrinthectomy (ULX) group, ULX plus left uvulonodulectomy (ULX+Lt-UNLX) group, and ULX plus right uvulonodulectomy (ULX+Rt-UNLX) group. UNLX was performed 1 hour following ULX. Spontaneous nystagmus (SN) and roll head tilt (RHT) were recorded for 3 days following ULX. Temporal change of c-Fos protein expression in the medial vestibular nuclei (MVN) was measured for 2 days following ULX. RESULTS: There were observed SN with contralateral direction to injured labyrinth and RHT toward ipsilateral side with flexion of ipsilateral limb and extenstion of contralateral one just after ULX. There was significant increase in SN frequency of ULX+Rt-UNLX group compared with that of ULX group. In addition, ULX+Rt-UNLX group resulted in severe postural asymmetry. ULX elicited prominent expression of c-Fos protein in contralateral MVN 2 hours but in ipsilateral one 6, 24 hours after ULX, respectively. In contrast, number of c-Fos positive neurons was higher in contralateral MVN. 24 hours after ULX higher expression of c-Fos protein in contralteral MVN was still remained in ULX+Rt-UNLX group but that in ipsilateral MVN was observed in ULX+Lt-UNLX group. CONCLUSION: These results suggest that UNLX have a different effect on the early stage of vestibular compensatory process and the uvulonodulus serves the restoration of balance between intervestibular nuclear activities after ULX by inhibition of vestibular nuclear complex through nhibitory Purkinje system.