Expression of Phosphorylated ERK1/2 and cFos Proteins in Vestibular Nuclei by Selective Stimulation of Horizontal Semicircular Canal

BACKGROUND: There is a little information about the effect of selective vestibular stimulation on the expression of activity-dependent metabolic markers in the vestibular nuclei. The purpose of this study was to evaluate effect of afferent excitation of the horizontal semicircular canal on expression of phosphorylated ERK1/2 (pERK1/2) and cFos proteins in the vestibular nuclei. METHODS: The horizontal semicircular canal of Sprague-Dawley rats was selectively stimulated by using the sinusoidal horizontal stimulator with 10-minute duration of stimulation. Conventional immunohistochemical method was used to visualize pERK1/2 or cFos immunoreactive neurons in the vestibular nuclei following rotation. RESULTS: Five minutes after stimulation of the horizontal semicircular canal there was a high expression of pERK1/2 protein in the medial vestibular nucleus among 4 major subnuclei of the central vestibular nuclear complex. On the contrary, immunoreactivity of cFos protein was observed in the medial and inferior vestibular nucleus 2 hours after horizontal sinusoidal rotation. The lateral vestibular nucleus was free from the expression of pERK1/2 and cFos proteins in response to excitation of the horizontal semicircular canal. However, in the vestibular nuclei of unilaterally labyrinthectomized rats expression of pERK and cFos proteins was markedly suppressed in ipsi-lesional side as well as contra-lesional side following stimulation of the horizontal semicircular canal. Furthermore no expression of pERK1/2 and cFos protein in the bilateral vestibular nuclei of bilaterally labyrinthectomized rats was noted after stimulation of the horizontal semicircular canal. CONCLUSIONS: Therefore these results of present study suggest that excitatory afferent signals from the peripheral vestibular receptors are essential for protein translation for pERK1/2 and cFos in response to stimulation of the semicircular canal.

ALTERATION OF PHOSPHORYLATED ERK1/2 IN THE RAT BRAIN INDUCED BY WATER RESTRICTION / 解剖学报

Objective To investigate the effect of stress induced by water restriction on the level of phosphorylated(ERK1/2) in rat brain. Methods Fifty-eight male Wistar rats were used and randomly divided into control group(C,n=4) and three experimental groups: TW(drinking at scheduled time),EB(empty bottle stimulus),WR(restricted water drinking),which were subdivided into three subgroups by time as 3d,7d, 14d(n=6 for each).In C group,water was freely accessed to the animal for one week.In the experimental groups the water supply was restricted following a week of accommodation and the other week for timed water supply training.In TW group,the water was supplied twice a day and 10 min for each in a fixed time. In EB and WR groups,the water was served only once a day for 10 min,and in the other scheduled time for water supply only an empty bottle without water was provided in the EB group and water was limited in the WR group.All the animals were deeply anesthetized 1h after the last stimulus and transcardially infused,then the brains were cut into free-floating sections and processed for immunohistochemical staining of pERKI/2 with ABC method.The expression of pERK1/2 positive staining was measured with image analysis system. Results The area of phosphorylated ERK1/2 was significantly increased in many brain structures,especially in paraventricular hypothalamic nucleus(PVN),supraoptic nucleus(SON),ventrolateral septum(LSV),medial amygdaloid nucleus(MeA),central amygdaloid nucleus(CEA) and nucleus of solitary tract(NTS) in TW,EB and WR group compared with C group.The expression of phosphorylated ERK1/2 in SON,LSV, MeA and CeA in EB and WR group were higher than that in TW group;pERK1/2 expression of LSV,MeA,CeA and NTS in EB group increased and went down more early and quickly than that in WR group.The response of phosphorylated ERK1/2 was dependent on both stimulus methods and time in all the nuclei mentioned above except PVN,in which only the stimulus time was related. Conclusion The level of pERK 1/2 was significantly altered in PVN,SON,LSV,MeA,CeA and NTS following stimulation of water restriction.The results indicate that the activated nuclei in the brain by physical and psychological stressors are different.