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Aaron J. Camp - One of the best experts on this subject based on the ideXlab platform.

  • The intrinsic plasticity of Medial Vestibular Nucleus neurons during Vestibular compensation-a systematic review and meta-analysis.
    Systematic reviews, 2020
    Co-Authors: Rajiv Wijesinghe, Aaron J. Camp
    Abstract:

    Vestibular compensation is a homeostatic process that occurs in the central nervous system in response to peripheral Vestibular dysfunction. Experimental studies in rodent models have suggested that unilateral peripheral Vestibular lesions are correlated with an increase in the intrinsic excitability of central Vestibular neurons. This process may be dependent on the intrinsic properties of the neurons themselves. We aimed to conduct a systematic review of the literature to survey the evidence for changes in intrinsic plasticity observed during the acute phase of Vestibular compensation. We systematically reviewed the literature regarding the electrophysiological effect of experimentally induced unilateral Vestibular deafferentation (UVD) on the intrinsic membrane properties of Medial Vestibular Nucleus neurons in animal models. We developed tools to assess the methodological quality (precision, validity and bias) of studies that met pre-determined inclusion and exclusion criteria. We extracted numerical data and performed a meta-analysis of specific quantitative data pooled from these studies. We identified 17 studies that satisfied the inclusion criteria. There is moderate quality evidence to suggest a statistically significant increase in the intrinsic excitability of Medial Vestibular Nucleus neurons following unilateral Vestibular deafferentation. Specifically, the spontaneous discharge rate increases by 4 spikes/s on average and the sensitivity to current stimuli increases. Using this novel approach, we demonstrate that the methodology of systematic review and meta-analysis is a useful tool in the summation of data across experimental animal studies with similar aims.

  • Stochastic Noise Application for the Assessment of Medial Vestibular Nucleus Neuron Sensitivity In Vitro.
    Journal of visualized experiments : JoVE, 2019
    Co-Authors: Sebastian P. Stefani, Paul P. Breen, Jorge M. Serrador, Aaron J. Camp
    Abstract:

    Galvanic Vestibular stimulation (GVS) has been shown to improve balance measures in individuals with balance or Vestibular impairments. This is proposed to be due to the stochastic resonance (SR) phenomenon, which is defined as application of a low-level/subthreshold stimulus to a non-linear system to increase detection of weaker signals. However, it is still unknown how SR exhibits its positive effects on human balance. This is one of the first demonstrations of the effects of sinusoidal and stochastic noise on individual neurons. Using whole-cell patch clamp electrophysiology, sinusoidal and stochastic noise can be applied directly to individual neurons in the Medial Vestibular Nucleus (MVN) of C57BL/6 mice. Here we demonstrate how to determine the threshold of MVN neurons in order to ensure the sinusoidal and stochastic stimuli are subthreshold and from this, determine the effects that each type of noise has on MVN neuronal gain. We show that subthreshold sinusoidal and stochastic noise can modulate the sensitivity of individual neurons in the MVN without affecting basal firing rates.

  • Attenuated glycine receptor function reduces excitability of mouse Medial Vestibular Nucleus neurons
    Neuroscience, 2010
    Co-Authors: Aaron J. Camp, Robert J. Callister, Rebecca Lim, Wayne B. Anderson, Peter R. Schofield, Alan M. Brichta
    Abstract:

    Spontaneous activity in Medial Vestibular Nucleus (MVN) neurons is modulated by synaptic inputs. These inputs are crucial for maintaining gaze and posture and contribute to Vestibular compensation after lesions of peripheral Vestibular organs. We investigated how chronically attenuated glycinergic input affects excitability of MVN neurons. To this end we used three mouse strains (spastic, spasmodic, and oscillator), with well-characterized naturally occurring mutations in the inhibitory glycine receptor (GlyR). First, using whole-cell patch-clamp recordings, we demonstrated that the amplitude of the response to rapidly applied glycine was dramatically reduced by 25 to 90% in MVN neurons from mutant mice. We next determined how reduced GlyR function affected MVN neuron output. Neurons were classified using two schemas: (1) the shape of their action potential afterhyperpolarization (AHP); and (2) responses to hyperpolarizing current injection. In the first schema, neurons were classified as types A, B and C. The prevalence of type C neurons in the mutant strains was significantly increased. In the second schema, the proportion of neurons lacking post inhibitory rebound firing (PRF-deficient) was increased. In both schemas an increase in AHP amplitude was a common feature of the augmented neuron group (type C, PRF-deficient) in the mutant strains. We suggest increased AHP amplitude reduces overall excitability in the MVN and thus maintains network function in an environment of reduced glycinergic input.

  • Inhibitory Synaptic Transmission Differs in Mouse Type A and B Medial Vestibular Nucleus Neurons In Vitro
    Journal of neurophysiology, 2006
    Co-Authors: Aaron J. Camp, Robert J. Callister, Alan M. Brichta
    Abstract:

    Fast inhibitory synaptic transmission in the Medial Vestibular Nucleus (MVN) is mediated by GABAA receptors (GABAARs) and glycine receptors (GlyRs). To assess their relative contribution to inhibit...

Mayank B. Dutia - One of the best experts on this subject based on the ideXlab platform.

  • synaptic plasticity in Medial Vestibular Nucleus neurons comparison with computational requirements of vor adaptation
    PLOS ONE, 2010
    Co-Authors: John Menzies, Mayank B. Dutia, John Porrill, Paul Dean
    Abstract:

    Background: Vestibulo-ocular reflex (VOR) gain adaptation, a longstanding experimental model of cerebellar learning, utilizes sites of plasticity in both cerebellar cortex and brainstem. However, the mechanisms by which the activity of cortical Purkinje cells may guide synaptic plasticity in brainstem Vestibular neurons are unclear. Theoretical analyses indicate that Vestibular plasticity should depend upon the correlation between Purkinje cell and Vestibular afferent inputs, so that, in gain-down learning for example, increased cortical activity should induce long-term depression (LTD) at Vestibular synapses. Methodology/Principal Findings: Here we expressed this correlational learning rule in its simplest form, as an anti-Hebbian, heterosynaptic spike-timing dependent plasticity interaction between excitatory (Vestibular) and inhibitory (floccular) inputs converging on Medial Vestibular Nucleus (MVN) neurons (input-spike-timing dependent plasticity, iSTDP). To test this rule, we stimulated Vestibular afferents to evoke EPSCs in rat MVN neurons in vitro. Control EPSC recordings were followed by an induction protocol where membrane hyperpolarizing pulses, mimicking IPSPs evoked by flocculus inputs, were paired with single Vestibular nerve stimuli. A robust LTD developed at Vestibular synapses when the afferent EPSPs coincided with membrane hyperpolarisation, while EPSPs occurring before or after the simulated IPSPs induced no lasting change. Furthermore, the iSTDP rule also successfully predicted the effects of a complex protocol using EPSP trains designed to mimic classical conditioning. Conclusions: These results, in strong support of theoretical predictions, suggest that the cerebellum alters the strength of Vestibular synapses on MVN neurons through hetero-synaptic, anti-Hebbian iSTDP. Since the iSTDP rule does not depend on post-synaptic firing, it suggests a possible mechanism for VOR adaptation without compromising gaze-holding and VOR performance in vivo.

  • endothelin 1 induced barrel rotation no direct modulation of rat Medial Vestibular Nucleus neurone activity by endothelin 1
    Equilibrium Research, 2007
    Co-Authors: Akio Kawachi, Mayank B. Dutia, Yukari Shibata, Katsushi Yamada, Toshiro Motoya
    Abstract:

    Fourth ventricular injections of endothelin-1 (30-100 ng) induced rotation along the long axis of the body (barrel rotation) in rats. N-methyl-D-aspartate (NMDA, 1-10 μg), an excitatory amino acid, and muscimol (1-10 μg), a GABAA receptor agonist, also evoked barrel rotation. Bath application of NMDA and muscimol on the spontaneous tonic discharge of Medial Vestibular Nucleus (MVN) neurones in rats, showed excitatory and inhibitory responses, respectively. Interestingly, endothelin-1 did not affect the spontaneous discharge rate of MVN neurones when applied either as a 60 s pulse or when the drug was continuously perfused for a period of 5 min. Reciprocal relationship between excitatory and inhibitory inputs, such as glutamate and GABA receptor agonists, for MVN neurones may be crucial in inducing barrel rotation. The results also suggest that the barrel rotation induced by endothelin-1 is mediated by its modulatory effects on indirect pathways to the Vestibular Nucleus.

  • 11β hydroxysteroid dehydrogenase type 1 activity in Medial Vestibular Nucleus and cerebellum after unilateral Vestibular deafferentation in the rat
    Stress, 2004
    Co-Authors: Clare Guilding, Jonathan R. Seckl, Mayank B. Dutia
    Abstract:

    In the early stages of Vestibular compensation (VC) (the behavioural recovery that follows unilateral Vestibular deafferentation), neurons in the Medial Vestibular Nucleus (MVN) on the lesioned side develop a sustained up-regulation of their intrinsic excitability. This plasticity is dependent on the activation of glucocorticoid receptors, which presumably occurs during the acute stress response that accompanies the Vestibular deafferentation symptoms. Recent studies have established that the access of glucocorticoids to their intracellular receptors in brain is potently modulated by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), which catalyses the generation of active glucocorticoids from their inert 11-keto forms. In this study, we investigated the presence of 11β-HSD1 bioactivity, and possible changes in activity in the early stage after Vestibular deafferentation, in the cerebellar nodulus and uvula, the flocculus/paraflocculus (F/PF) complex and the MVN of the rat. 11β-HSD1 activity was found i...

  • long term potentiation and depression after unilateral labyrinthectomy in the Medial Vestibular Nucleus of rats
    Acta Oto-laryngologica, 2003
    Co-Authors: Vito Enrico Pettorossi, Mayank B. Dutia, Adele Frondaroli, Cristina V Dieni, Silvarosa Grassi
    Abstract:

    We previously demonstrated in rat brainstem slices that high-frequency stimulation (HFS) of the Vestibular afferents induces long-term potentiation (LTP) in the ventral part (Vp) of the Medial Vestibular Nucleus (MVN) and long-term depression (LTD) in the dorsal part (Dp). Both LTP and LTD depend on N-methyl-D-aspartate receptor activation, which increases synaptic efficacy; however, in the Dp, LTP reverses to LTD because of the activation of γ-aminobutyric acid-ergic neurons. Here we show that the probability of inducing long-term effects in the MVN of rat brainstem slices is altered after unilateral labyrinthectomy (UL). In fact, LTP occurs less frequently in the ventral contra-lesional side compared with sham-operated rats. In the dorsal ipsi-lesional side, LTD is reduced and LTP enhanced, while the opposite occurs in the dorsal contra-lesional side. These changes in synaptic plasticity may be useful for re-balancing the tonic discharge of the MVN of the two sides during Vestibular compensation, and fo...

  • Tonic activity and GABA responsiveness of Medial Vestibular Nucleus neurons in aged rats.
    Neuroreport, 2001
    Co-Authors: Aydın Him, A R Johnston, Joyce L.w. Yau, Jonathan R. Seckl, Mayank B. Dutia
    Abstract:

    The tonic discharge of rat Medial Vestibular Nucleus (MVN) neurons, and their responsiveness to GABA receptor agonists were investigated in slices prepared from aged rats (24 months old). Aged MVN neurons showed regular spontaneous activity similar to that seen in slices from young adults. However the inhibitory effects of the GABA(A) agonist muscimol on the spontaneous activity of aged MVN neurons were significantly greater than in young MVN neurons. Inhibitory responses to the GABA(B) agonist baclofen also tended to be greater in slices from aged animals, but this difference was not statistically significant. The regular discharge of aged MVN neurons at firing rates similar to those in young animals suggests that the intrinsic excitability of MVN cells is maintained with age. The up-regulation of GABA(A) receptor efficacy in aged MVN neurons may compensate for changes in inhibitory inputs from Vestibular commissures and cerebellum that may occur with neuronal loss in the aged brain.

Y S Chan - One of the best experts on this subject based on the ideXlab platform.

  • 5 ht1a receptor mediated attenuation of synaptic transmission in rat Medial Vestibular Nucleus impacts on Vestibular related motor function
    The Journal of Physiology, 2020
    Co-Authors: Lei Han, Puiyi Kwan, Oscar Wingho Chua, Daisy K Y Shum, Y S Chan
    Abstract:

    KEY POINTS Chemogenetic activation of Medial Vestibular Nucleus-projecting 5-HT neurons resulted in deficits in Vestibular-mediated tasks, including negative geotaxis, balance beam and rota-rod tests. The 5-HT1A receptor mediates the Vestibular-related behavioural effects of 5-HT in the Vestibular Nucleus. 5-HT1A receptor activation attenuated evoked excitatory postsynaptic currents and evoked inhibitory postsynaptic currents via a presynaptic mechanism in the Vestibular Nucleus. ABSTRACT While the anxiolytic effects of serotonergic neuromodulation are well studied, its role in sensorimotor coordination and postural control is unclear. In this study, we show that an increase of serotonin (5-hydroxytryptamine, 5-HT) at the Medial Vestibular Nucleus (MVN), a brainstem centre for vestibulospinal coordination, by either direct cannula administration or chemogenetic stimulation of MVN-projecting serotonergic neurons, adversely affected performance of rats in Vestibular-mediated tasks, including negative geotaxis, balance beam and rota-rod tests. Application of the 5-HT1 and 5-HT7 receptor co-agonist 8-hydroxy-2-(di-n-propylamino) tetralin recapitulated the effect of 5-HT, while co-administration of the specific 5-HT1A receptor antagonist WAY 100135 effectively abolished all 5-HT-induced behavioural deficits. This indicated that 5-HT1A receptors mediated the effects of 5-HT in the rat MVN. Using whole-cell patch-clamp recording, we demonstrated that 5-HT1A receptor activation attenuated both evoked excitatory and evoked inhibitory postsynaptic currents through a presynaptic mechanism in the rat MVN. The results thus highlight the 5-HT1A receptor as the gain controller of Vestibular-related brainstem circuits for posture and balance.

  • 5‐HT 1A receptor‐mediated attenuation of synaptic transmission in rat Medial Vestibular Nucleus impacts on Vestibular‐related motor function
    The Journal of physiology, 2020
    Co-Authors: Lei Han, Puiyi Kwan, Daisy K Y Shum, Oscar Wing‐ho Chua, Y S Chan
    Abstract:

    KEY POINTS Chemogenetic activation of Medial Vestibular Nucleus-projecting 5-HT neurons resulted in deficits in Vestibular-mediated tasks, including negative geotaxis, balance beam and rota-rod tests. The 5-HT1A receptor mediates the Vestibular-related behavioural effects of 5-HT in the Vestibular Nucleus. 5-HT1A receptor activation attenuated evoked excitatory postsynaptic currents and evoked inhibitory postsynaptic currents via a presynaptic mechanism in the Vestibular Nucleus. ABSTRACT While the anxiolytic effects of serotonergic neuromodulation are well studied, its role in sensorimotor coordination and postural control is unclear. In this study, we show that an increase of serotonin (5-hydroxytryptamine, 5-HT) at the Medial Vestibular Nucleus (MVN), a brainstem centre for vestibulospinal coordination, by either direct cannula administration or chemogenetic stimulation of MVN-projecting serotonergic neurons, adversely affected performance of rats in Vestibular-mediated tasks, including negative geotaxis, balance beam and rota-rod tests. Application of the 5-HT1 and 5-HT7 receptor co-agonist 8-hydroxy-2-(di-n-propylamino) tetralin recapitulated the effect of 5-HT, while co-administration of the specific 5-HT1A receptor antagonist WAY 100135 effectively abolished all 5-HT-induced behavioural deficits. This indicated that 5-HT1A receptors mediated the effects of 5-HT in the rat MVN. Using whole-cell patch-clamp recording, we demonstrated that 5-HT1A receptor activation attenuated both evoked excitatory and evoked inhibitory postsynaptic currents through a presynaptic mechanism in the rat MVN. The results thus highlight the 5-HT1A receptor as the gain controller of Vestibular-related brainstem circuits for posture and balance.

Takeshi Kubo - One of the best experts on this subject based on the ideXlab platform.

  • Fos-enkephalin signaling in the rat Medial Vestibular Nucleus facilitates Vestibular compensation.
    Journal of neuroscience research, 2006
    Co-Authors: Tadashi Kitahara, Noriaki Takeda, Takeshi Kaneko, Arata Horii, Munehisa Fukushima, Kaoru Kizawa-okumura, Takeshi Kubo
    Abstract:

    In the present study, we first observed up-regulation in preproenkephalin (PPE)-like immunoreactivity (-LIR), a precursor of Met- and Leu-enkephalin, in the rat ipsilateral Medial Vestibular Nucleus (ipsi-MVN) after unilateral labyrinthectomy (UL). By means of double-staining immunohistochemistry with PPE and Fos, a putative regulator of PPE gene expression, we revealed that some of these PPE-LIR neurons were also Fos immunopositive. The time course of decay of these double-stained neurons was quite parallel to that of UL-induced behavioral deficits. This suggests that these double-labeled neurons could have something to do with development of Vestibular compensation. We next examined correlation between Fos and PPE expression in the ipsi-MVN by means of a 15-min pre-UL application of antisense oligonucleotide probes against c-fos mRNA into the ipsi-MVN. Gel shift assay and Western blotting revealed that elimination of Fos expression significantly reduced both AP-1 DNA binding activity and PPE expression in the ipsi-MVN after UL. C-fos antisense study also revealed that depression of Fos-PPE signaling in the ipsi-MVN caused significantly more severe behavioral deficits during Vestibular compensation. Furthermore, studies with PPE antisense and naloxone, an opioid receptor antagonist, demonstrated that specific depression of enkephalinergic effects in the ipsi-MVN significantly delayed Vestibular compensation. All these findings suggest that, immediately after UL, Fos induced in some of the ipsi-MVN neurons could regulate consequent PPE expression via the AP-1 activation and facilitate the restoration of balance between bilateral MVN activities via the opioid receptor activation, resulting in progress of Vestibular compensation.

  • short communicationn methyl d aspartate receptors contribute to afferent synaptic transmission in the Medial Vestibular Nucleus of young rats
    Brain Research, 1994
    Co-Authors: Yoshifumi Takahashi, Tadaharu Tsumoto, Takeshi Kubo
    Abstract:

    In the Medial Vestibular Nucleus (MVN), the non-N-methyl-d-aspartate (NMDA) subtype of ionotropic glutamate receptors has been reported as operating at synapses between ipsilateral Vestibular afferents and neurons. In the present study, we addressed the question of whether or not NMDA receptors contribute to afferent synaptic transmission in the MVN and if so, to what degree. Using nystatin-perforated or conventional whole-cell patch clamp methods in brainstem slices of young rats (postnatal day 4–6), we found that NMDA receptors contribute to a substantial extent to afferent synaptic transmission in the MVN of young rats.

  • N-methyl-D-aspartate receptors contribute to afferent synaptic transmission in the Medial Vestibular Nucleus of young rats.
    Brain Research, 1994
    Co-Authors: Yoshifumi Takahashi, Tadaharu Tsumoto, Takeshi Kubo
    Abstract:

    Abstract In the Medial Vestibular Nucleus (MVN), the non-N-methyl- d -aspartate (NMDA) subtype of ionotropic glutamate receptors has been reported as operating at synapses between ipsilateral Vestibular afferents and neurons. In the present study, we addressed the question of whether or not NMDA receptors contribute to afferent synaptic transmission in the MVN and if so, to what degree. Using nystatin-perforated or conventional whole-cell patch clamp methods in brainstem slices of young rats (postnatal day 4–6), we found that NMDA receptors contribute to a substantial extent to afferent synaptic transmission in the MVN of young rats.

  • Changes in preproenkephalin mRNA after unilateral and bilateral labyrinthectomy in the rat Medial Vestibular Nucleus
    Molecular Brain Research, 1993
    Co-Authors: Takanori Saika, Takeshi Kubo, Noriaki Takeda, Hiroshi Kiyama, Masaya Tohyama, Toru Matsunaga
    Abstract:

    Abstract We examined the expression of preproenkephalin (PPE) mRNA in the Vestibular nuclei in rats using in situ hybridization histochemistry. In normal rats, PPE mRNA-positive cells were observed in the Medial and spinal Vestibular nuclei. After unilateral labyrinthectomy, PPE mRNA was increased in the Medial Vestibular Nucleus on the operated side from the 1st through the 3rd day after the surgery. It is suggested that the changes in PPE mRNA level after labyrinthectomy are involved in Vestibular compensation.

Cynthia L. Darlington - One of the best experts on this subject based on the ideXlab platform.

  • Immunocytochemical and stereological study of glucocorticoid receptors in rat Medial Vestibular Nucleus neurons and the effects of unilateral Vestibular deafferentation.
    Acta oto-laryngologica, 2005
    Co-Authors: Rong Zhang, P F Smith, Cynthia L. Darlington
    Abstract:

    Conclusion. The results of this study suggest that neither the number of Medial Vestibular Nucleus (MVN) neurons expressing cytosolic glucocorticoid receptors nor blood corticosterone levels change significantly during the development of Vestibular compensation. Objective. Vestibular compensation is a process of partial behavioral recovery that occurs following damage to the Vestibular labyrinth. It has been suggested that this compensation process might be dependent on the release of glucocorticoids such as corticosterone at the time of unilateral Vestibular deafferentation (UVD) and that changes in glucocorticoid receptors in the MVN might contribute to the initiation of the compensation process. Material and methods. We compared the number of MVN neurons expressing cytosolic glucocorticoid receptors in rats at 10 h and 2 weeks following UVD, and in sham and anesthetic control animals; we also measured blood corticosterone levels. Results. Using immunocytochemistry and stereology, we found that the majo...

  • Potent effects of a selective cannabinoid receptor agonist on some guinea pig Medial Vestibular Nucleus neurons
    European journal of pharmacology, 1998
    Co-Authors: David Newsham-west, Cynthia L. Darlington, P F Smith
    Abstract:

    Abstract Binding studies have indicated that the density of the cannabinoid CB1 receptor is very low in the Vestibular Nucleus complex compared to other areas of the central nervous system (CNS), suggesting that CB1 receptors may have little functional significance for the Vestibular Nucleus. However, the dizziness often produced by cannabis suggests that the Vestibular system may be implicated. We investigated the effects of the selective CB1 receptor agonist, CP 55940 (the levorotatory enantiomer of desacetyllevonantradol), on Medial Vestibular Nucleus neurons in guinea pig brainstem slices in vitro. Only 3/18 Medial Vestibular Nucleus neurons tested with 1 μM CP 55940 showed changes in firing rate, however these were decreases with an average magnitude of 72.3%; 3/4 neurons tested with 10 μM CP 55940 showed decreases with an average magnitude of 92.7% (P

  • AN IN VITRO INVESTIGATION OF THE EFFECTS OF THE ACTH/MSH (4-9) ANALOGUE, ORG 2766, ON GUINEA PIG Medial Vestibular Nucleus NEURONS
    Peptides, 1996
    Co-Authors: Darrin P.d. Gilchrist, Cynthia L. Darlington, P F Smith
    Abstract:

    Abstract Vestibular compensation is a process of CNS plasticity that is correlated to a return of resting activity in Medial Vestibular Nucleus (MVN) neurons ipsilateral to a peripheral Vestibular deafferentation. Systemic administration of melanocortin peptides accelerates the compensation process; the ACTH MSH (4–9) analogue, Org 2766, accelerates this process at smaller doses than ACTH MSH (4–10) . The present study investigated the effect of Org 2766 on MVN neurons in vitro using extracellular single-cell recording. Org 2766 was less potent at the neuronal level than ACTH MSH (4–10) . When Org 2766 and ACTH MSH (4–10) were tested consecutively on the same neuron, the response was often different. Org 2766 and ACTH MSH (4–10) may have a different mode and/or site of action.

  • Metabotropic glutamate receptors in the guinea-pig Medial Vestibular Nucleus in vitro.
    Neuroreport, 1995
    Co-Authors: Cynthia L. Darlington, P F Smith
    Abstract:

    Despite the accumulation of a large body of evidence on the function of the kainate/alpha-amino-3-5-methyl-4-iso-xazolepropionic acid (AMPA) and N-methyl-D-aspartate (NMDA) excitatory amino acid (EAA) receptor subtypes within the Vestibular Nucleus, little is known of the metabotropic receptor subtype. The aim of the present study was to examine the response of guinea-pig Medial Vestibular Nucleus (MVN) neurons in brain stem slices to the selective metabotropic receptor agonist, 1S,3R-amino-cyclopentyl-1,3-dicarboxylate (ACPD). Sixty percent (12/20) of MVN neurones responded to 1S,3R-ACPD at a concentration of 10(-6) M, compared with 40% (8/20) and 35% (7/20) of neurones at concentrations of 10(-8) and 10(-10) M. Both increases and decreases in firing rate were observed in different neurones: in general, the magnitude of the responses was large and the duration of the responses was long. Recordings from a slice which contained only the MVN confirmed that these responses were produced by the action of the metabotropic agonist within the MVN itself. These results demonstrate that many MVN neurones have functional metabotropic receptors.

  • Further evidence on the contribution of GABAA receptors to the GABA-mediated inhibition of Medial Vestibular Nucleus neurones in vitro.
    Neuroreport, 1995
    Co-Authors: Mark A. Hutchinson, P F Smith, Cynthia L. Darlington
    Abstract:

    The present study investigated the electrophysiological effects of the selective and potent GABAA receptor agonist, isoguvacine, on guinea-pig Medial Vestibular Nucleus (MVN) neurones in brainstem slices. The results confirm that many MVN neurones have GABAA receptors and that, even at concentrations as low as 10(-8) M, GABA is capable of exerting a powerful inhibitory effect on these neurones via GABAA receptors. The finding that > 50% of neurones did not respond to isoguvacine, even at concentrations of 10(-6) M, suggested that only a specific subset of MVN neurones have GABAA receptors. Since many type I MVN neurones are believed to have postsynaptic GABAA receptors, it is possible that selective agonists such as isoguvacine may be useful in identifying type I neurones in vitro.