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Rocha JR, Passetto MDF, Maldonado-Menetti JDS, Cabral ALB, Toledo CABD, Koike M. Pigeon as a model to study peripheral projections from the horizontal semicircular canal vestibular apparatus to a brainstem target immunoreactive for AMPA. Acta Cir Bras 2022; 36:e361206. [PMID: 35019066 PMCID: PMC8734960 DOI: 10.1590/acb361206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2021] [Accepted: 11/20/2021] [Indexed: 11/26/2022] Open
Abstract
Purpose: To evaluate whether the pigeon (Columba livia) is a good
model for evaluating the vestibular system involved with postural
maintenance during movement. Methods: This study maps the brainstem targets of the horizontal ampullary inputs from
the vestibular periphery of the pigeon. We used biotin dextran amine (BDA)
injection in horizontal semicircular canal (HSCC), immunohistochemistry for
GluR2/3 and GluR4 AMPA and computerized histomorphology reconstruction. Results: Our results show the same distribution pattern with ipsilateral projections
to vestibular nuclear complex (VNC) from the HSCC, with the majority of
labeled fibers being, long, thin, with few varicosities and many
ramifications. Horizontal semicircular canal projections achieve neurons
belonging to all nuclei of the VNC with exception of dorsal portion of
lateral vestibular nucleus and this area express GluR2/3 and GluR4 AMPA
receptors reinforcing the idea of glutamate participation in these
connections. Conclusions: Pigeon is an appropriated experimental model to study of projections of HSCC
and reinforcing the information that the vestibular system has strong
relation with the fast responses necessary for postural control. Moreover,
its phylogenetic organization apparently conservation, also seems to be a
fundamental characteristic for vertebrates.
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Affiliation(s)
- João Roberto Rocha
- Instituto de Assistência Médica ao Servidor Público Estadual de São Paulo, Brazil
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2
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Holstein GR, Friedrich VLJ, Martinelli GP. Glutamate and GABA in Vestibulo-Sympathetic Pathway Neurons. Front Neuroanat 2016; 10:7. [PMID: 26903817 PMCID: PMC4744852 DOI: 10.3389/fnana.2016.00007] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 01/25/2016] [Indexed: 12/19/2022] Open
Abstract
The vestibulo-sympathetic reflex (VSR) actively modulates blood pressure during changes in posture. This reflex allows humans to stand up and quadrupeds to rear or climb without a precipitous decline in cerebral perfusion. The VSR pathway conveys signals from the vestibular end organs to the caudal vestibular nuclei. These cells, in turn, project to pre-sympathetic neurons in the rostral and caudal ventrolateral medulla (RVLM and CVLM, respectively). The present study assessed glutamate- and GABA-related immunofluorescence associated with central vestibular neurons of the VSR pathway in rats. Retrograde FluoroGold tract tracing was used to label vestibular neurons with projections to RVLM or CVLM, and sinusoidal galvanic vestibular stimulation (GVS) was employed to activate these pathways. Central vestibular neurons of the VSR were identified by co-localization of FluoroGold and cFos protein, which accumulates in some vestibular neurons following galvanic stimulation. Triple-label immunofluorescence was used to co-localize glutamate- or GABA- labeling in the identified VSR pathway neurons. Most activated projection neurons displayed intense glutamate immunofluorescence, suggestive of glutamatergic neurotransmission. To support this, anterograde tracer was injected into the caudal vestibular nuclei. Vestibular axons and terminals in RVLM and CVLM co-localized the anterograde tracer and vesicular glutamate transporter-2 signals. Other retrogradely-labeled cFos-positive neurons displayed intense GABA immunofluorescence. VSR pathway neurons of both phenotypes were present in the caudal medial and spinal vestibular nuclei, and projected to both RVLM and CVLM. As a group, however, triple-labeled vestibular cells with intense glutamate immunofluorescence were located more rostrally in the vestibular nuclei than the GABAergic neurons. Only the GABAergic VSR pathway neurons showed a target preference, projecting predominantly to CVLM. These data provide the first demonstration of two disparate chemoanatomic VSR pathways.
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Affiliation(s)
- Gay R. Holstein
- Department of Neurology, Icahn School of Medicine at Mount SinaiNew York, NY, USA
- Department of Neuroscience, Icahn School of Medicine at Mount SinaiNew York, NY, USA
- Department of Anatomy/Functional Morphology, Icahn School of Medicine at Mount SinaiNew York, NY, USA
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3
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Holstein GR, Friedrich VL, Martinelli GP. Projection neurons of the vestibulo-sympathetic reflex pathway. J Comp Neurol 2015; 522:2053-74. [PMID: 24323841 DOI: 10.1002/cne.23517] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2013] [Revised: 11/19/2013] [Accepted: 12/04/2013] [Indexed: 12/20/2022]
Abstract
Changes in head position and posture are detected by the vestibular system and are normally followed by rapid modifications in blood pressure. These compensatory adjustments, which allow humans to stand up without fainting, are mediated by integration of vestibular system pathways with blood pressure control centers in the ventrolateral medulla. Orthostatic hypotension can reflect altered activity of this neural circuitry. Vestibular sensory input to the vestibulo-sympathetic pathway terminates on cells in the vestibular nuclear complex, which in turn project to brainstem sites involved in the regulation of cardiovascular activity, including the rostral and caudal ventrolateral medullary regions (RVLM and CVLM, respectively). In the present study, sinusoidal galvanic vestibular stimulation was used to activate this pathway, and activated neurons were identified through detection of c-Fos protein. The retrograde tracer Fluoro-Gold was injected into the RVLM or CVLM of these animals, and immunofluorescence studies of vestibular neurons were conducted to visualize c-Fos protein and Fluoro-Gold concomitantly. We observed activated projection neurons of the vestibulo-sympathetic reflex pathway in the caudal half of the spinal, medial, and parvocellular medial vestibular nuclei. Approximately two-thirds of the cells were ipsilateral to Fluoro-Gold injection sites in both the RVLM and CVLM, and the remainder were contralateral. As a group, cells projecting to the RVLM were located slightly rostral to those with terminals in the CVLM. Individual activated projection neurons were multipolar, globular, or fusiform in shape. This study provides the first direct demonstration of the central vestibular neurons that mediate the vestibulo-sympathetic reflex.
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Affiliation(s)
- Gay R Holstein
- Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, New York, 10029; Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, New York, 10029
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Exocytotic machineries of vestibular type I and cochlear ribbon synapses display similar intrinsic otoferlin-dependent Ca2+ sensitivity but a different coupling to Ca2+ channels. J Neurosci 2014; 34:10853-69. [PMID: 25122888 DOI: 10.1523/jneurosci.0947-14.2014] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The hair cell ribbon synapses of the mammalian auditory and vestibular systems differ greatly in their anatomical organization and firing properties. Notably, vestibular Type I hair cells (VHC-I) are surrounded by a single calyx-type afferent terminal that receives input from several ribbons, whereas cochlear inner hair cells (IHCs) are contacted by several individual afferent boutons, each facing a single ribbon. The specificity of the presynaptic molecular mechanisms regulating transmitter release at these different sensory ribbon synapses is not well understood. Here, we found that exocytosis during voltage activation of Ca(2+) channels displayed higher Ca(2+) sensitivity, 10 mV more negative half-maximum activation, and a smaller dynamic range in VHC-I than in IHCs. VHC-I had a larger number of Ca(2+) channels per ribbon (158 vs 110 in IHCs), but their Ca(2+) current density was twofold smaller because of a smaller open probability and unitary conductance. Using confocal and stimulated emission depletion immunofluorescence microscopy, we showed that VHC-I had fewer synaptic ribbons (7 vs 17 in IHCs) to which Cav1.3 channels are more tightly organized than in IHCs. Gradual intracellular Ca(2+) uncaging experiments revealed that exocytosis had a similar intrinsic Ca(2+) sensitivity in both VHC-I and IHCs (KD of 3.3 ± 0.6 μM and 4.0 ± 0.7 μM, respectively). In otoferlin-deficient mice, exocytosis was largely reduced in VHC-I and IHCs. We conclude that VHC-I and IHCs use a similar micromolar-sensitive otoferlin Ca(2+) sensor and that their sensory encoding specificity is essentially determined by a different functional organization of Ca(2+) channels at their synaptic ribbons.
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5
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Maturation of glutamatergic transmission in the vestibulo-olivary pathway impacts on the registration of head rotational signals in the brainstem of rats. Brain Struct Funct 2014; 221:217-38. [DOI: 10.1007/s00429-014-0903-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Accepted: 09/23/2014] [Indexed: 12/19/2022]
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6
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Talaei SA, Salami M. Sensory experience differentially underlies developmental alterations of LTP in CA1 area and dentate gyrus. Brain Res 2013; 1537:1-8. [DOI: 10.1016/j.brainres.2013.08.060] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Revised: 07/31/2013] [Accepted: 08/30/2013] [Indexed: 11/28/2022]
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7
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Li C, Han L, Ma CW, Lai SK, Lai CH, Shum DKY, Chan YS. Maturation profile of inferior olivary neurons expressing ionotropic glutamate receptors in rats: role in coding linear accelerations. Brain Struct Funct 2013; 218:833-50. [PMID: 22706760 PMCID: PMC3695329 DOI: 10.1007/s00429-012-0432-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2012] [Accepted: 05/17/2012] [Indexed: 11/30/2022]
Abstract
Using sinusoidal oscillations of linear acceleration along both the horizontal and vertical planes to stimulate otolith organs in the inner ear, we charted the postnatal time at which responsive neurons in the rat inferior olive (IO) first showed Fos expression, an indicator of neuronal recruitment into the otolith circuit. Neurons in subnucleus dorsomedial cell column (DMCC) were activated by vertical stimulation as early as P9 and by horizontal (interaural) stimulation as early as P11. By P13, neurons in the β subnucleus of IO (IOβ) became responsive to horizontal stimulation along the interaural and antero-posterior directions. By P21, neurons in the rostral IOβ became also responsive to vertical stimulation, but those in the caudal IOβ remained responsive only to horizontal stimulation. Nearly all functionally activated neurons in DMCC and IOβ were immunopositive for the NR1 subunit of the NMDA receptor and the GluR2/3 subunit of the AMPA receptor. In situ hybridization studies further indicated abundant mRNA signals of the glutamate receptor subunits by the end of the second postnatal week. This is reinforced by whole-cell patch-clamp data in which glutamate receptor-mediated miniature excitatory postsynaptic currents of rostral IOβ neurons showed postnatal increase in amplitude, reaching the adult level by P14. Further, these neurons exhibited subthreshold oscillations in membrane potential as from P14. Taken together, our results support that ionotropic glutamate receptors in the IO enable postnatal coding of gravity-related information and that the rostral IOβ is the only IO subnucleus that encodes spatial orientations in 3-D.
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Affiliation(s)
- Chuan Li
- Department of Physiology, LKS Faculty of Medicine, The University of Hong Kong, 21 Sassoon Road, Hong Kong, People’s Republic of China
- Department of Biochemistry, LKS Faculty of Medicine, The University of Hong Kong, 21 Sassoon Road, Hong Kong, People’s Republic of China
- Present Address: Department of Medical Science, Tung Wah College, Wyile Road, Kowloon Hong Kong, People’s Republic of China
| | - Lei Han
- Department of Physiology, LKS Faculty of Medicine, The University of Hong Kong, 21 Sassoon Road, Hong Kong, People’s Republic of China
- Department of Biochemistry, LKS Faculty of Medicine, The University of Hong Kong, 21 Sassoon Road, Hong Kong, People’s Republic of China
| | - Chun-Wai Ma
- Department of Physiology, LKS Faculty of Medicine, The University of Hong Kong, 21 Sassoon Road, Hong Kong, People’s Republic of China
- Department of Biochemistry, LKS Faculty of Medicine, The University of Hong Kong, 21 Sassoon Road, Hong Kong, People’s Republic of China
| | - Suk-King Lai
- Department of Physiology, LKS Faculty of Medicine, The University of Hong Kong, 21 Sassoon Road, Hong Kong, People’s Republic of China
- Department of Biochemistry, LKS Faculty of Medicine, The University of Hong Kong, 21 Sassoon Road, Hong Kong, People’s Republic of China
| | - Chun-Hong Lai
- Department of Physiology, LKS Faculty of Medicine, The University of Hong Kong, 21 Sassoon Road, Hong Kong, People’s Republic of China
| | - Daisy Kwok Yan Shum
- Department of Biochemistry, LKS Faculty of Medicine, The University of Hong Kong, 21 Sassoon Road, Hong Kong, People’s Republic of China
- Research Centre of Heart, Brain, Hormone and Healthy Aging, LKS Faculty of Medicine, The University of Hong Kong, 21 Sassoon Road, Hong Kong, People’s Republic of China
| | - Ying-Shing Chan
- Department of Physiology, LKS Faculty of Medicine, The University of Hong Kong, 21 Sassoon Road, Hong Kong, People’s Republic of China
- Research Centre of Heart, Brain, Hormone and Healthy Aging, LKS Faculty of Medicine, The University of Hong Kong, 21 Sassoon Road, Hong Kong, People’s Republic of China
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Ma CW, Zhang FX, Lai CH, Lai SK, Yung KKL, Shum DKY, Chan YS. Postnatal expression of TrkB receptor in rat vestibular nuclear neurons responsive to horizontal and vertical linear accelerations. J Comp Neurol 2013; 521:612-25. [PMID: 22806574 DOI: 10.1002/cne.23193] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Revised: 10/17/2011] [Accepted: 07/09/2012] [Indexed: 11/05/2022]
Abstract
We examined the maturation expression profile of tyrosine kinase B (TrkB) receptor in rat vestibular nuclear neurons that were activated by sinusoidal linear acceleration along the horizontal or vertical axis. The otolithic origin of Fos expression in these neurons was confirmed with labyrinthectomized controls and normal controls, which showed only sporadically scattered Fos-labeled neurons in the vestibular nucleus. In P4-6 test rats, no Fos-labeled neurons were found in the vestibular nucleus, but the medial and spinal vestibular neurons showed weak immunoreactivity for TrkB. The intensity of TrkB immunoreactivity in vestibular nuclear neurons progressively increased in the second postnatal week but remained low in adults. From P7 onward, TrkB-expressing neurons responded to horizontal or vertical otolithic stimulation with Fos expression. The number of Fos-labeled vestibular nuclear neurons expressing TrkB increased with age, from 13-43% in P7 rats to 85-90% in adult rats. Our results therefore suggest that TrkB/neurotrophin signaling plays a dominant role in modulating vestibular nuclear neurons for the coding of gravity-related horizontal head movements and for the regulation of vestibular-related behavior during postnatal development.
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Affiliation(s)
- Chun-Wai Ma
- Department of Physiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, People's Republic of China
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Holstein GR, Friedrich Jr. VL, Martinelli GP, Ogorodnikov D, Yakushin SB, Cohen B. Fos expression in neurons of the rat vestibulo-autonomic pathway activated by sinusoidal galvanic vestibular stimulation. Front Neurol 2012; 3:4. [PMID: 22403566 PMCID: PMC3289126 DOI: 10.3389/fneur.2012.00004] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Accepted: 01/04/2012] [Indexed: 12/12/2022] Open
Abstract
The vestibular system sends projections to brainstem autonomic nuclei that modulate heart rate and blood pressure in response to changes in head and body position with regard to gravity. Consistent with this, binaural sinusoidally modulated galvanic vestibular stimulation (sGVS) in humans causes vasoconstriction in the legs, while low frequency (0.02-0.04 Hz) sGVS causes a rapid drop in heart rate and blood pressure in anesthetized rats. We have hypothesized that these responses occur through activation of vestibulo-sympathetic pathways. In the present study, c-Fos protein expression was examined in neurons of the vestibular nuclei and rostral ventrolateral medullary region (RVLM) that were activated by low frequency sGVS. We found c-Fos-labeled neurons in the spinal, medial, and superior vestibular nuclei (SpVN, MVN, and SVN, respectively) and the parasolitary nucleus. The highest density of c-Fos-positive vestibular nuclear neurons was observed in MVN, where immunolabeled cells were present throughout the rostro-caudal extent of the nucleus. c-Fos expression was concentrated in the parvocellular region and largely absent from magnocellular MVN. c-Fos-labeled cells were scattered throughout caudal SpVN, and the immunostained neurons in SVN were restricted to a discrete wedge-shaped area immediately lateral to the IVth ventricle. Immunofluorescence localization of c-Fos and glutamate revealed that approximately one third of the c-Fos-labeled vestibular neurons showed intense glutamate-like immunofluorescence, far in excess of the stain reflecting the metabolic pool of cytoplasmic glutamate. In the RVLM, which receives a direct projection from the vestibular nuclei and sends efferents to preganglionic sympathetic neurons in the spinal cord, we observed an approximately threefold increase in c-Fos labeling in the sGVS-activated rats. We conclude that localization of c-Fos protein following sGVS is a reliable marker for sGVS-activated neurons of the vestibulo-sympathetic pathway.
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Affiliation(s)
- Gay R. Holstein
- Department of Neurology, Mount Sinai School of MedicineNew York, NY, USA
- Department of Neuroscience, Mount Sinai School of MedicineNew York, NY, USA
- Department of Anatomy/Functional Morphology, Mount Sinai School of MedicineNew York, NY, USA
| | | | | | - Dmitri Ogorodnikov
- Department of Neurology, Mount Sinai School of MedicineNew York, NY, USA
| | - Sergei B. Yakushin
- Department of Neurology, Mount Sinai School of MedicineNew York, NY, USA
| | - Bernard Cohen
- Department of Neurology, Mount Sinai School of MedicineNew York, NY, USA
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Lo FS, Zhao S. N-methyl-D-aspartate receptor subunit composition in the rat trigeminal principal nucleus remains constant during postnatal development and following neonatal denervation. Neuroscience 2011; 178:240-9. [PMID: 21256193 DOI: 10.1016/j.neuroscience.2011.01.023] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2010] [Revised: 01/06/2011] [Accepted: 01/12/2011] [Indexed: 01/11/2023]
Abstract
N-methyl-D-aspartate receptors (NMDARs) play a major role in various forms of developmental and adult synaptic plasticity (Lopez de Armentia M, Sah P (2003) J Neurosci 23:6876-6883). Activity-dependent shifts in NR2 subunits of the NMDARs have been proposed to be the molecular basis of critical period plasticity. Several supporting examples have been reported; however it is not clear whether the relationship between NMDAR subunit changes and neural plasticity are correlative or causal, nor whether such a relationship is universal across all sensory pathways with developmental plasticity. In the present study, we used voltage-clamp recording techniques to investigate whether subunit composition of NMDARs changes during development and after neonatal denervation in the principal sensory nucleus (PrV) of the trigeminal nerve. Relative AMPA receptor contribution to synaptic transmission increased linearly by the second postnatal week in the normal PrV. Denervation by peripheral nerve damage did not alter this process. We took the weighted decay time constant (τw) of NMDAR-mediated EPSCs as an index for NMDAR subunit composition. The τw measurement and Western blot analysis revealed that NMDARs contained both NR2A and NR2B subunits. The NR2A/NR2B ratio did not change during postnatal development or after neonatal denervation. Thus, critical period plasticity-related pattern formation in the PrV does not depend on changes in subunit composition of NMDARs. The mechanism underlying developmental synaptic plasticity in the PrV differs from those in higher trigeminal centers and other brain structures.
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Affiliation(s)
- F-S Lo
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, 20 Penn Street, Baltimore, MD 21201, USA.
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Lai CH, Yiu CN, Lai SK, Ng KP, Yung KK, Shum DK, Chan YS. Maturation of canal-related brainstem neurons in the detection of horizontal angular acceleration in rats. J Comp Neurol 2010; 518:1742-63. [DOI: 10.1002/cne.22300] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Ma CW, Lai CH, Lai SK, Tse YC, Yung KK, Shum DK, Chan YS. Developmental distribution of vestibular nuclear neurons responsive to different speeds of horizontal translation. Brain Res 2010; 1326:62-7. [DOI: 10.1016/j.brainres.2010.02.032] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2009] [Revised: 02/08/2010] [Accepted: 02/09/2010] [Indexed: 11/17/2022]
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Glutamate responsiveness of medial vestibular nucleus neurons in aged rats. Brain Res Bull 2010; 81:81-4. [PMID: 19616081 DOI: 10.1016/j.brainresbull.2009.07.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2009] [Revised: 07/09/2009] [Accepted: 07/09/2009] [Indexed: 11/21/2022]
Abstract
Disequilibrium, dizziness, vertigo and falls are vestibular system-related problems which are very common especially in older people. In order to clarify these age-related disorders one must understand first the age-related changes in the properties of vestibular neurons that are responsible for equilibrium. The responsiveness of medial vestibular nucleus (MVN) neurons to the NMDA and AMPA/kainate receptor agonists was investigated in slices prepared from young and aged rats using extracellular single cell recording techniques. In both young and aged rats bath application of NMDA and AMPA caused a reversible, dose-dependant increase in the spontaneous discharge of the MVN neurons. The excitatory effects of both NMDA and AMPA on the spontaneous activity of aged MVN neurons were similar to those of young MVN neurons. The spontaneous firing rates of the MVN cells were also similar in young and aged rats. These results suggest that the responsiveness of the NMDA and AMPA/kainate receptors and the excitability of the MVN neurons do not change with age.
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Sun X, Guo YP, Shum DKY, Chan YS, He J. Time course of cortically induced fos expression in auditory thalamus and midbrain after bilateral cochlear ablation. Neuroscience 2009; 160:186-97. [PMID: 19232381 DOI: 10.1016/j.neuroscience.2009.02.020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2008] [Revised: 01/18/2009] [Accepted: 02/10/2009] [Indexed: 11/18/2022]
Abstract
Expression of c-fos in the medial geniculate body (MGB) and the inferior colliculus (IC) in response to bicuculline-induced corticofugal activation was examined in rats at different time points after bilateral cochlear ablation (4 h-30 days). Corticofugal activation was crucial in eliciting Fos expression in the MGB after cochlear ablation. The pars ovoidea (OV) of the medial geniculate body ventral division (MGv) showed dense Fos expression 4 h after cochlear ablation; the expression declined to very low levels at 24 h and thereafter. In turn, strong Fos expression was found in the pars lateralis (LV) of the MGv 24 h after cochlear ablation and dropped dramatically at 14 days. The dorsal division of the MGB (MGd) showed high Fos expression 7 days after cochlear ablation, which persisted for a period of time. Using multi-electrode recordings, neuronal activity of different MGB subnuclei was found to correlate well with Fos expressions. The temporal changes in cortically activated Fos expression in different MGB subnuclei after bilateral cochlear ablation indicate differential denervation hypersensitivities of these MGB neurons and likely point to differential dependence of these nuclei on both auditory ascending and corticofugal descending inputs. After bilateral cochlear ablation, significant increases in Fos-positive neurons were detected unilaterally in all IC subnuclei, ipsilateral to the bicuculline injection.
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Affiliation(s)
- X Sun
- Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
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