Immunohistochemical Study on beta1- and beta2-Adrenergic Receptors in Rat Vestibular Nuclei / 대한평형의학회지

BACKGROUND AND OBJECTIVES: The aim of this study was to examine the localizations of beta1- and beta2-adrenergic receptors (ARs) in rat vestibular nuclei by immunohistochemical staining procedure. MATERIALS AND METHODS: Twelve male Sprague-Dawley rats were used in this study. Primary antibodies for the beta1- and beta2-ARs were used. The sections were treated with a biotinylated goat anti-rabbit antibody. The sections were then incubated in avidin-biotin-peroxidase reagent and processed with immunoperoxidase using 3.3'-diaminobenzidine tetrahydrochloride. RESULTS: beta1-AR and beta2-AR immunopositive neurons were found to be distributed throughout the four major vestibular nuclei. Both receptors were primarily detected in neuronal somata and their proximal dendrites. beta1-AR and beta2-AR were moderately expressed in the superior vestibular nucleus, lateral vestibular nucleus, medial vestibular nucleus, and spinal vestibular nucleus. CONCLUSION: The present study demonstrates, for the first time, that beta1-AR and beta2-AR receptors are localized in rat vestibular nuclei. Furthermore, this study may provide additional speculation into the role of ARs during vestibular signal processing. Further studies are needed to clarify the roles played by beta1-ARs and beta2-ARs through physiologic and functional studies.

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.

Inhibition of potassium currents in outer hair cells and Deiters' cells from guinea pig cochlea by linopirdine / 生理学报

To study the functional expression of KCNQ gene in outer hair cells (OHCs) and Deiters' cells, the effects of linopirdine on the whole cell K(+) current were investigated by using the whole cell variant of patch clamp technique in the present study. The outward tetraethylammonium (TEA)-sensitive K(+) current and the inward K(+) current (I(Kn)) in OHCs were recorded and measured before and after the administration of linopirdine. Simultaneously, the whole cell currents in Deiters?cells were also observed in normal solution and in the presence of linopirdine. After the application of 100 micromol/L linopirdine to OHCs, the peak K(+) current was reversibly blocked and the late K(+) current was partly reduced. In addition, the decay time constant of the TEA-sensitive K(+) current was prolonged in the presence of 100 micromol/L linopirdine. The inward current in OHCs was totally inhibited after the superfusion of 100 mmol/L and 200 micromol/L linopirdine respectively. The outward rectifier K(+) current (Ik) was the dominant K(+) current in the whole cell currents in Deiters' cells. In the presence of 200 micromol/L linopirdine, the I(K) current was not significantly affected. Our findings demonstrate that the KCNQ heteromeric or homomeric potassium channel is possibly the molecular basis for the peak outward K(+) current and that the inward I(Kn) current is mediated by KCNQ potassium channel. KCNQ potassium channel in OHCs can not only permit the K(+) efflux but also limit the depolarization. In the present study, no expression of KCNQ potassium channel is found in Deiters' cells.

Immunohistochemical Identification of Phosphorylated Extracellular Signal-Regulated Kinase1/2 in Rat Vestibular Nuclei by Unilateral Labyrinthectomy

This study evaluated the expression of phosphorylated signal-regulated kinase1/2 (pERK1/2), which is one of the main factors regulating transcription of the cfos oncogene in neurons, in the vestibular nuclei of Sprague-Dawley rats following unilateral labyrinthectomy (UL). Surgical UL was performed to eliminate afferent signals from the peripheral vestibular receptors in the inner ear, under a surgical microscope, 2 hours after anesthesia. Significant numbers of pERK1/2 immunoreactive neurons were seen in the superior, medial, and inferior vestibular nuclei. There were more pERK1/2 immunoreactive cells in the vestibular nuclei contralateral than in the vestibular nuclei ipsilateral to the injured labyrinth, which resulted in significant asymmetric expression of pERK1/2 immunoreactive cells. Subsequently, the pERK1/2 immunoreactivity decreased rapidly, disappearing 90 min after labyrinthectomy. No pERK1/2 labeling was seen in the lateral vestibular nucleus. These results suggest that intracellular signal pathways for the activation of extracellular signal-regulated kinase in the vestibular nuclei are involved in lesion-neural plasticity in the vestibular system

Characteristics of Motor Evoked Potentials by Pyramidal and Extrapyramidal Systems in Rats / 대한정형외과연구학회지

PURPOSE: Electrophysiologically assess conduction pathways of the pyramidal and extrapyramidal systems in rats and predict the pathways involved in spinal cord injuries. METHOD: The motor area of the cerebral cortex, medullary reticular nucleus, lateral vestibular nucleus, and red nucleus of adult Sprague-Dawley rats were stimulated with microelectrodes. Laminectomies were performed at the C6, T10 and L2 cord level. Field potentials evoked by stimulation of the cerebral cortex and the three motor nuclei were recorded with a glass microelectrode of 1.5~2.5 Mohm filled with 0.2M NaCl. To construct a cross-sectional map of field potentials, recording was made in 7 tracks equally spaced across the spinal cord. In each track, field potentials were recorded at seven equally spaced points from the ventral to dorsal cord. RESULT: Stimulation of the cerebral motor cortex evoked 5 wanes, such as P1, P2, P3, P4, P5. P1 was monitored mainly in the bilateral dorsal half of the spinal cord and other wades mainly in the ventral half of the spinal cord. With lateral vestibular nucleus stimulation, 1 or 2 short duration biphasic waves followed by a longer duration positive wave were monitored mainly in the ipsilateral ventrolateral funiculus of the cord. Field potentials produced by stimulating the medullary reticular nucleus were shown mainly in the ventromedial funiculus, and their latencies were longer than those from the vestibular nucleus stimulation. Field potentials generated by the stimulation of the red nucleus were monitored mainly in the dorsolateral funiculus. CONCLUSION: motor evoked potential is clinically useful to evaluate the descending pathways of the spinal cord.

Role of the vestibular and medullary reticular nuclei for the motor evoked potentials in rats

The motor evoked potentials (MEPs) have been advocated as a method of monitoring the integrity of spinal efferent pathways in various injury models of the central nervous system. However, there were many disputes about origin sites of MEPs generated by transcranial electrical stimulation. The purpose of present study was to investigate the effect of major extrapyramidal motor nuclei such as lateral vestibular nucleus (VN) and medullary reticular nucleus (mRTN) on any components of the MEPs in adult Sprague-Dawley rats. MEPs were evoked by electrical stimulation of the right sensorimotor cortex through a stainless steel screw with 0.5mm in diameter, and recorded epidurally at T9 - T10 spinal cord levels by using a pair of teflon-coated stainless steel wire electrodes with 1mm exposed tip. In order to inject lidocaine and make a lesion, insulated long dental needle with noninsulated tips were placed stereotaxically in VN and mRTN. Lidocaine of 2~3 mul was injected into either VN or mRTN. The normal MEPs were composed of typical four reproducible waves; P1, P2, P3, P4. The first wave (P1) was shown at a mean latency of 1.2 ms, corresponding to a conduction velocity of 67.5 m/sec. The latencies of MEP were shortened and the amplitudes were increased as stimulus intensity was increased. The amplitudes of P1 and P2 were more decreased among 4 waves of MEPs after lidocaine microinjection into mRTN. Especially, the amplitude of P1 was decreased by 50% after lidocaine microinjection into bilateral mRTN. On the other hand, lidocaine microinjection into VN reduced the amplitudes of P3 and P4 than other MEP waves. However, the latencies of MEPs were not changed by lidocaine microinjection into either VN or mRTN. These results suggest that the vestibular and reticular nuclei contribute to partially different role in generation of MEPs elicited by transcranial electrical stimulation.