https://ogma.newcastle.edu.au/vital/access/ /manager/Index ${session.getAttribute("locale")} 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:36884 Wed 26 Aug 2020 14:16:44 AEST ]]> https://ogma.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://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:16911 Tue 24 Aug 2021 14:24:51 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:45974 Tue 08 Nov 2022 14:19:06 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:45859 Thu 08 Dec 2022 10:04:37 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:6928 41%). In older animals (P11–P25) this changed, with AP discharge consisting of brief bursts at current onset (~46% of neurons). Investigation of major subthreshold whole cell currents showed the rapid A-type potassium current (IAr) dominated at all ages examined (90% of neurons at E15–E17, decreasing to >50% after P10). IAr expression levels, based on peak current amplitude, increased during development. Steady-state inactivation and activation for IAr were slightly less potent in E15–E17 versus P21–P25 neurons at potentials near RMP (-55 mV). Together, our data indicate that intrinsic properties and IAr expression change dramatically in SDH neurons during development, with the greatest alterations occurring on either side of a critical period, P6–P10.]]> Sat 24 Mar 2018 08:40:23 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:993 Sat 24 Mar 2018 08:29:51 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:1219 Sat 24 Mar 2018 08:28:33 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:5804 Sat 24 Mar 2018 07:44:54 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:4459 Sat 24 Mar 2018 07:18:30 AEDT ]]> https://ogma.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://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:11331 Mon 30 Sep 2019 12:33:52 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:16907 A miniature inhibitory postsynaptic current (mIPSC) amplitude was increased in spa and ot but not spd, suggesting diminished glycinergic drive leads to compensatory adjustments in the other major fast inhibitory synaptic transmitter system in these mutants. Overall, our data suggest long-term reduction in glycinergic drive to HMs results in changes in intrinsic and synaptic properties that are consistent with homeostatic plasticity in spa and ot but not in spd. We propose such plasticity is an attempt to stabilize HM output, which succeeds in spa but fails in ot.]]> Mon 30 Sep 2019 12:26:58 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:22855 Mon 30 Sep 2019 12:19:51 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:25370 Mon 30 Sep 2019 12:12:52 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:52855 92%). Short-term plasticity was studied by examining discharge rate modulation following release from hyperpolarization [postinhibitory rebound firing (PRF)] and depolarization [firing rate adaptation (FRA)]. PRF and FRA gain were similar in Deiters’ and non-Deiters’ neurons (PRF 24.9 vs. 20.2 Hz and FRA gain 231.5 vs. 287.8 spikes/s/nA, respectively). Inhibitory synaptic input to both populations showed that GABAergic rather than glycinergic inhibition dominated. However, GABAA miniature inhibitory postsynaptic current (mIPSC) frequency was much higher in Deiters’ neurons compared with non-Deiters’ neurons (∼15.9 vs. 1.4 Hz, respectively). Our data suggest that Deiters’ neurons can be reliably identified by their intrinsic membrane and synaptic properties. They are tonically active and glutamatergic, have low sensitivity or “gain,” exhibit little adaptation, and receive strong GABAergic input. Deiters’ neurons also have minimal short-term plasticity, and together these features suggest they are well suited to a role in encoding tonic signals for the vestibulospinal reflex. New & Noteworthy: Deiters’ neurons within the lateral vestibular nucleus project the length of the spinal cord and activate antigravity extensor muscles. Deiters’ neurons were characterized anatomically and physiologically in mice. Deiters’ neurons are tonically active, have homogeneous intrinsic membrane properties, including low input resistance, and receive significant GABAAergic synaptic inputs. Deiters’ neurons show little modulation in response to current injection. These features are consistent with Deiters’ neurons responding to perturbations to maintain posture and balance.]]> Mon 30 Oct 2023 09:54:00 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:38353 Mon 30 Aug 2021 16:06:38 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:47532 0.05) different from that of cardiac and respiratory modulation at rest (47.1%, 18.7–56.3% and 48.6%, 28.4–59.3%, respectively) or during sinusoidal displacement (10.3%, 6.2–32.1% and 26.9%, 13.6–43.3%, respectively). Respiratory frequency was entrained above its resting rate (0.26 Hz, 0.2–0.29 Hz) during sinusoidal neck displacement; there was no significant difference (P > 0.05) between respiratory frequency (0.38 Hz, 0.25–0.49 Hz) and sinusoidal displacement frequency (0.39 Hz, 0.35–0.42 Hz). This study provides evidence that SSNA is modulated during neck movement, raising the possibility that neck mechanoreceptors may contribute to the cutaneous vasoconstriction and sweat release associated with motion sickness. New & Noteworthy: This study demonstrates that dynamic, but not static, stretching of the neck modulates skin sympathetic nerve activity in the lower limbs.]]> Mon 23 Jan 2023 12:22:52 AEDT ]]> https://ogma.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 ]]>