https://nova.newcastle.edu.au/vital/access/ /manager/Index en-au 5 https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:20264 Wed 27 Jul 2022 13:52:56 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:36884 Wed 26 Aug 2020 14:16:44 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:33924 Wed 23 Jan 2019 15:34:09 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:52321 Wed 21 Feb 2024 14:42:46 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:35344 Wed 17 Jul 2019 11:45:17 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:46371 Wed 16 Nov 2022 09:20:48 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:27947 Wed 11 Apr 2018 14:50:35 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:17231 K,L. A similar current was first observed at 15 WG but remained relatively small, even at 18 WG. The presence of a “collapsing” tail current indicates a maturing type I hair cell phenotype and suggests the presence of a surrounding calyx afferent terminal. We were also able to record from calyx afferent terminals in 15–18 WG cristae. In voltage clamp, these terminals exhibited fast inactivating inward as well as slower outward conductances, and in current clamp, discharged a single action potential during depolarizing steps. Together, these data suggest the major functional characteristics of type I and type II hair cells and calyx terminals are present by 18 WG. Our study also describes a new preparation for the functional investigation of key events that occur during maturation of human vestibular organs.]]> Wed 11 Apr 2018 14:41:28 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:17232 2+_ concentration but may influence mitochondrial function as both antioxidant treatments modulated mitochondrial membrane potential. These suggest that the antioxidant-sensitive subpopulations of LC neurons may be more susceptible to oxidative stress (e.g., due to ATP depletion and/or overactivation of Ca²⁺_ dependent pathways). Indeed it may be that this subpopulation of LC neurons is preferentially destroyed in neurological pathologies such as Parkinson’s disease. If this is the case, there may be a protective role for antioxidant therapies.]]> Wed 11 Apr 2018 14:36:25 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:28056 Wed 11 Apr 2018 11:46:32 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:7526 Wed 11 Apr 2018 10:11:50 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:29840 T ≈ 0.25°C per pulse). Afferent spike trains evoked by heat pulse stimuli were diverse and included asynchronous inhibition, asynchronous excitation, and/or phase-locked APs synchronized to each infrared heat pulse. Thermal responses of membrane currents responsible for APs in ganglion neurons were strictly excitatory, with Q₁₀ ≈ 2. In contrast, hair cells responded with a mix of excitatory and inhibitory currents. Excitatory hair cell membrane currents included a thermoelectric capacitive current proportional to the rate of temperature rise (dT/dt) and an inward conduction current driven by ΔT. An iberiotoxin-sensitive inhibitory conduction current was also evoked by ΔT, rising in <3 ms and decaying with a time constant of ∼24 ms. The inhibitory component dominated whole cell currents in 50% of hair cells at −68 mV and in 67% of hair cells at −60 mV. Responses were quantified and described on the basis of first principles of thermodynamics. Results identify key molecular targets underlying heat pulse excitability in vestibular sensory organs and provide quantitative methods for rational application of optical heat pulses to examine protein biophysics and manipulate cellular excitability.]]> Wed 11 Apr 2018 09:55:53 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:51849 Wed 07 Feb 2024 14:24:49 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:34069 in vivo preparation and patch-clamp electrophysiology to test whether the synaptic and intrinsic properties of superficial dorsal horn (SDH) neurons are altered 5 days after the induction of mild colitis in adult male mice (i.e. during acute inflammation of the colon). Whole-cell recordings were made from lumbosacral (L6-S1) superficial dorsal horn neurons (SDH), in animals under isoflurane anesthesia. Noxious colorectal distension (CRD) was used to identify SDH neurons with colonic inputs, while stimulation of the hind paw and tail was employed to assess convergent cutaneous input. Following inflammation, a significantly increased proportion of SDH neurons received both colonic and cutaneous inputs, compared to neurons in naïve animals. In addition, the nature and magnitude of responses to CRD and cutaneous stimulation differed in inflamed animals, as was spontaneous excitatory synaptic drive. Conversely, several measures of intrinsic excitability were altered in a manner that would decrease SDH network excitability following colitis. We propose that during inflammation, sensitization of colonic afferents results in increased signaling to the SDH. This is accompanied by plasticity in SDH neurons whereby their intrinsic properties are changed to compensate for altered afferent activity.]]> Wed 06 Feb 2019 09:51:23 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:36209 c but does not exclude action at intracellular microdomains. Further to this, the incubation of slices with cytochalasin D, an agent that depolymerises the actin cytoskeleton, inhibited the hyperpolarizing response indicating an involvement of the actin cytoskeleton. The data are consistent with the hypothesis that there is a crosstalk between mitochondria and L-type Ca²⁺ channels leading to modulation of noradrenergic neuronal activity mediated by the actin cytoskeleton.]]> Tue 03 Mar 2020 15:35:08 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:39465 Thu 09 Jun 2022 09:22:29 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:9604 Sat 24 Mar 2018 08:39:39 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:1544 Sat 24 Mar 2018 08:30:44 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:12355 Sat 24 Mar 2018 08:18:31 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:12449 40 mV shift of the K⁺ equilibrium potential and a rise in effective K⁺ concentration (>50 mM) in the intercellular space. Together these data suggest K⁺ accumulation in the intercellular space accounts for the different responses in isolated and embedded type I hair cells. To test this notion, we exposed the preparation to hyperosmotic solutions to enlarge the intercellular space. As predicted, the K⁺ accumulation effects were reduced; however, a fit of our data with a classic diffusion model suggested K⁺ permeability, rather than the intercellular space, had been altered by the hyperosmotic change. These results support the notion that under depolarizing conditions Substantial K⁺ accumulation occurs in the space between type I hair cells and calyx. The extent of K⁺ accumulation during normal synaptic transmission, however, remains to be determined.]]> Sat 24 Mar 2018 08:17:49 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:12308 Sat 24 Mar 2018 08:11:38 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:10399 Sat 24 Mar 2018 08:08:45 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:27257 Sat 24 Mar 2018 07:29:11 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:30876 Sat 24 Mar 2018 07:26:39 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:23550 Sat 24 Mar 2018 07:14:09 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:24623 This article is part of a Special Issue entitled 'Annual Reviews 2016'.]]> Sat 24 Mar 2018 07:11:54 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:35649 A receptors (GABA_ARs) and glycine receptors (GlyRs). To assess their relative contribution to inhibition in the MVN, we recorded miniature inhibitory postsynaptic currents (mIPSCs) in physiologically characterized type A and type B MVN neurons. Transverse brain stem slices were prepared from mice (3–8 wk old), and whole cell patch-clamp recordings were obtained from visualized MVN neurons (CsCl internal; V_m = –70 mV; 23°C). In 81 MVN neurons, 69% received exclusively GABA_Aergic inputs, 6% exclusively glycinergic inputs, and 25% received both types of mIPSCs. The mean amplitude of GABA_AR-mediated mIPSCs was smaller than those mediated by GlyRs (22.6 ± 1.8 vs. 35.3 ± 5.3 pA). The rise time and decay time constants of GABAAR- versus GlyR-mediated mIPSCs were slower (1.3 ± 0.1 vs. 0.9 ± 0.1 ms and 10.5 ± 0.3 vs. 4.7 ± 0.3 ms, respectively). Comparison of type A (n = 20) and type B (n = 32) neurons showed that type A neurons received almost exclusively GABA_Aergic inhibitory inputs, whereas type B neurons received GABA_Aergic inputs, glycinergic inputs, or both. Intracellular labeling in a subset of MVN neurons showed that morphology was not related to a MVN neuron's inhibitory profile (n = 15), or whether it was classified as type A or B (n = 29). Together, these findings indicate that both GABA and glycine contribute to inhibitory synaptic processing in MVN neurons, although GABA dominates and there is a difference in the distribution of GABA_A and Gly receptors between type A and type B MVN neurons.]]> Mon 30 Sep 2019 14:53:51 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:11331 Mon 30 Sep 2019 12:33:52 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:377 Mon 24 Sep 2018 16:15:03 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:47328 Mon 22 Apr 2024 12:14:21 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:40675 Mon 18 Jul 2022 09:00:12 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:50959 Mon 14 Aug 2023 15:11:30 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:50760 24 months) mice had impaired performance in a balance beam task compared to young (3-4 months) adult mice. While there was no qualitative loss of cholinergic axon varicosities in the crista ampullaris of old mice, qPCR analysis revealed reduced expression of nicotinic receptor subunit genes Chrna1, Chrna9, and Chrna10 in the cristae of old relative to young mice. Functionally, single-cell patch clamp recordings taken from type II vestibular hair cells exposed to acetylcholine show reduced conductance through alpha9/10 subunit-containing nicotinic receptors in older mice, despite preserved passive membrane properties and voltage-activated conductances. These findings suggest that cholinergic signaling in the peripheral vestibular sensory organs is vulnerable to aging processes, manifesting in dynamic molecular and functional age-related changes. Given the importance of these organs to our everyday activities, and the dramatic increase in fall incidence in the elderly, further investigation into the mechanisms of altered peripheral vestibular function in older humans is warranted.]]> Mon 07 Aug 2023 14:22:26 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:40285 Fri 29 Jul 2022 15:08:02 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:48979 Fri 21 Apr 2023 09:29:59 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:35648 -/-) mice. Immunostaining for choline acetyltransferase revealed there were no obvious gross morphological differences in the peripheral EVS innervation among any of these strains. ACh application onto wt type II hair cells, at resting potentials, produced a fast inward current followed by a slower outward current, resulting in membrane hyperpolarization and decreased membrane resistance. Hyperpolarization and decreased resistance were due to gating of SK channels. Consistent with activation of a9*nAChRs and SK channels, these ACh-sensitive currents were antagonized by the a9*nAChR blocker strychnine and SK blockers apamin and tamapin. Type II hair cells from a9^-/- mice, however, failed to respond to ACh at all. These results confirm the critical importance of a9nAChRs in efferent modulation of mammalian type II vestibular hair cells. Application of exogenous ACh reduces electrical impedance, thereby decreasing type II hair cell sensitivity. NEW & NOTEWORTHY Expression of a9 nicotinic subunit was crucial for fast cholinergic modulation of mammalian vestibular type II hair cells. These findings show a multifaceted efferent mechanism for altering hair cell membrane potential and decreasing membrane resistance that should reduce sensitivity to hair bundle displacements.]]> Fri 18 Aug 2023 10:20:28 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:39731 Fri 17 Jun 2022 17:52:03 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:39675 Fri 17 Jun 2022 15:32:12 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:53582 Fri 08 Dec 2023 15:47:54 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:37045 Fri 07 Aug 2020 14:34:14 AEST ]]>