Physiological Significances for Expression of Immediate Early Gene Protein by Change of Arterial Pressure in Vestibular Nuclear Complex of Adult Rats

Kim, Young Sun; Park, Kyu Sun; Jang, Se Girl; Yoo, Hong Kyun; Kim, Min Sun; Park, Byung Rim

Abstract

BACKGROUND AND OBJECTIVES
The purpose of this research was to evaluate physiological significances of expression of immediate early gene proteins in the vestibular nuclear complex by change of arterial pressure (AP) in adult Sprague-Dawley rats. MATERIALS AND METHOD: Record AP and inject either sodium nitroprusside (SNP) or phenylnephrine to change AP. Either fast or slow removal of blood from the femoral artery was made to induce different rapidity in reduction of AP. Blood supply to the inner ear was temporally blocked by clamping anterior inferior cerebellar artery (AICA). Immunohistochemical staining and image analysis for cFos, FosB, Krox, and JunB proteins were performed 2, 6, 12 hours after change of AP. RESULTS: The selective expression of cFos protein was observed in the medial vestibular nucleus (MVN) following reduction of AP. The number of cFos positive neurons peaked at 2 hours and then rapidly reduced, returning to the normal value 24 hours after SNP injection. And cFos protein expression was also well correlated with that of AP reduction at 2 hours of SNP injection. The rapid falling of AP caused a significant expression of cFos protein but slow withdrawal of blood did a minimal change of cFos protein expression. In addition, there was a significant expression of cFos protein following the increase of AP by single injection of phenylnephrine. Unilateral occlusion of AICA resulted in the significant expression of cFos protein in bilateral MVN. Furthermore, bilateral ablation of vestibular endorgans resulted in significant reduction of cFos expression by AICA occlusion in MVN. CONCLUSION: These results suggest that cFos protein is a marker for neuronal excitation in vestibular complex in response to rapid changes in the arterial blood pressure and that medial vestibular nuclei plays an important role in signaling the process of cardiovascular information coming from the peripheral vestibular apparatus.