Immunohistochemical detection of phosphorylated form of extracellular signal-regulated kinase 1/2 in rat vestibular nuclei following hemorrhagic hypotension.

The purpose of this study was to evaluate the expression of the phosphorylated form of extracellular-regulated protein kinase 1/2 (pERK1/2), which is one of the major regulatory factors for transcription of the c-fos oncogene in neurons, within the vestibular nuclei (VN) of rats following acute arterial hypotension. Following acute arterial hypotension induced by rapid hemorrhage, a significant number of pERK1/2-immunoreactive neurons appeared bilaterally in the caudal aspect of the medial and inferior VN. No labeling of pERK1/2 was observed in the lateral VN. The peak expression of pERK1/2-immunoreactive neurons in these nuclei occurred within 5 min after hemorrhage. In bilaterally labyrinthectomized rats, the appearance of pERK1/2-immunoreactive neurons was eliminated in the VN. These results suggest that, following acute hypotension, afferent signals from the peripheral vestibular receptors are required for activation of extracellular signal-regulated kinase 1/2 in the VN.