Similar Properties of Transient, Persistent, and Resurgent Na Currents in GABAergic and Non-GABAergic Vestibular Nucleus Neurons

2008 ◽  
Vol 99 (5) ◽  
pp. 2060-2065 ◽  
Author(s):  
Aryn H. Gittis ◽  
Sascha du Lac
Keyword(s):  
Transgenic Mice ◽  
Vestibular Nucleus ◽  
Vestibular Nuclei ◽  
Gabaergic Neurons ◽  
Firing Rates ◽  
Na Currents ◽  
Voltage Dependent ◽  
Firing Properties ◽  
K Currents ◽  
Fast Firing

Sodium currents in fast firing neurons are tuned to support sustained firing rates >50–60 Hz. This is typically accomplished with fast channel kinetics and the ability to minimize the accumulation of Na channels into inactivated states. Neurons in the medial vestibular nuclei (MVN) can fire at exceptionally high rates, but their Na currents have never been characterized. In this study, Na current kinetics and voltage-dependent properties were compared in two classes of MVN neurons with distinct firing properties. Non-GABAergic neurons (fluorescently labeled in YFP-16 transgenic mice) have action potentials with faster rise and fall kinetics and sustain higher firing rates than GABAergic neurons (fluorescently labeled in GIN transgenic mice). A previous study showed that these neurons express a differential balance of K currents. To determine whether the Na currents in these two populations were different, their kinetics and voltage-dependent properties were measured in acutely dissociated neurons from 24- to 40-day-old mice. All neurons expressed persistent Na currents and large transient Na currents with resurgent kinetics tuned for fast firing. No differences were found between the Na currents expressed in GABAergic and non-GABAergic MVN neurons, suggesting that differences in properties of these neurons are tuned by their K currents.

scholarly journals Mechanisms of Sustained High Firing Rates in Two Classes of Vestibular Nucleus Neurons: Differential Contributions of Resurgent Na, Kv3, and BK Currents

2010 ◽  
Vol 104 (3) ◽  
pp. 1625-1634 ◽  
Author(s):  
Aryn H. Gittis ◽  
Setareh H. Moghadam ◽  
Sascha du Lac
Keyword(s):  
Action Potential ◽  
Vestibular Nucleus ◽  
Ionic Currents ◽  
Na Channel ◽  
Firing Rates ◽  
Neuronal Populations ◽  
Firing Range ◽  
Na Currents ◽  
The Difference ◽  
Firing Properties

To fire at high rates, neurons express ionic currents that work together to minimize refractory periods by ensuring that sodium channels are available for activation shortly after each action potential. Vestibular nucleus neurons operate around high baseline firing rates and encode information with bidirectional modulation of firing rates up to several hundred Hz. To determine the mechanisms that enable these neurons to sustain firing at high rates, ionic currents were measured during firing by using the action potential clamp technique in vestibular nucleus neurons acutely dissociated from transgenic mice. Although neurons from the YFP-16 line fire at rates higher than those from the GIN line, both classes of neurons express Kv3 and BK currents as well as both transient and resurgent Na currents. In the fastest firing neurons, Kv3 currents dominated repolarization at all firing rates and minimized Na channel inactivation by rapidly transitioning Na channels from the open to the closed state. In slower firing neurons, BK currents dominated repolarization at the highest firing rates and sodium channel availability was protected by a resurgent blocking mechanism. Quantitative differences in Kv3 current density across neurons and qualitative differences in immunohistochemically detected expression of Kv3 subunits could account for the difference in firing range within and across cell classes. These results demonstrate how divergent firing properties of two neuronal populations arise through the interplay of at least three ionic currents.

Firing Properties of GABAergic Versus Non-GABAergic Vestibular Nucleus Neurons Conferred by a Differential Balance of Potassium Currents

2007 ◽  
Vol 97 (6) ◽  
pp. 3986-3996 ◽  
Author(s):  
Aryn H. Gittis ◽  
Sascha du Lac
Keyword(s):  
Vestibular Nucleus ◽  
Brain Slices ◽  
Ionic Currents ◽  
Vestibular Nuclei ◽  
Cell Types ◽  
Delayed Rectifier ◽  
Charge Densities ◽  
Outward Currents ◽  
Firing Properties ◽  
Kinetics Of

Neural circuits are composed of diverse cell types, the firing properties of which reflect their intrinsic ionic currents. GABAergic and non-GABAergic neurons in the medial vestibular nuclei, identified in GIN and YFP-16 lines of transgenic mice, respectively, exhibit different firing properties in brain slices. The intrinsic ionic currents of these cell types were investigated in acutely dissociated neurons from 3- to 4-wk-old mice, where differences in spontaneous firing and action potential parameters observed in slice preparations are preserved. Both GIN and YFP-16 neurons express a combination of four major outward currents: Ca2+-dependent K+ currents ( IKCa), 1 mM TEA-sensitive delayed rectifier K+ currents ( I1TEA), 10 mM TEA-sensitive delayed rectifier K+ currents ( I10TEA), and A-type K+ currents ( IA). The balance of these currents varied across cells, with GIN neurons tending to express proportionately more IKCa and IA, and YFP-16 neurons tending to express proportionately more I1TEA and I10TEA. Correlations in charge densities suggested that several currents were coregulated. Variations in the kinetics and density of I1TEA could account for differences in repolarization rates observed both within and between cell types. These data indicate that diversity in the firing properties of GABAergic and non-GABAergic vestibular nucleus neurons arises from graded differences in the balance and kinetics of ionic currents.

scholarly journals Voltage-dependent and odorant-regulated currents in isolated olfactory receptor neurons of the channel catfish.

1992 ◽  
Vol 99 (4) ◽  
pp. 505-529 ◽  
Author(s):  
T Miyamoto ◽  
D Restrepo ◽  
J H Teeter
Keyword(s):  
Action Potentials ◽  
Olfactory Receptor Neurons ◽  
Olfactory Neurons ◽  
Outward Currents ◽  
Na Currents ◽  
Voltage Dependent ◽  
Inward Currents ◽  
K Current ◽  
Receptor Neurons ◽  
K Currents

The electrical properties of olfactory receptor neurons, enzymatically dissociated from the channel catfish (Ictalurus punctatus), were studied using the whole-cell patch-clamp technique. Six voltage-dependent ionic currents were isolated. Transient inward currents (0.1-1.7 nA) were observed in response to depolarizing voltage steps from a holding potential of -80 mV in all neurons examined. They activated between -70 and -50 mV and were blocked by addition of 1 microM tetrodotoxin (TTX) to the bath or by replacing Na+ in the bath with N-methyl-D-glucamine and were classified as Na+ currents. Sustained inward currents, observed in most neurons examined when Na+ inward currents were blocked with TTX and outward currents were blocked by replacing K+ in the pipette solution with Cs+ and by addition of 10 mM Ba2+ to the bath, activated between -40 and -30 mV, reached a peak at 0 mV, and were blocked by 5 microM nimodipine. These currents were classified as L-type Ca2+ currents. Large, slowly activating outward currents that were blocked by simultaneous replacement of K+ in the pipette with Cs+ and addition of Ba2+ to the bath were observed in all olfactory neurons examined. The outward K+ currents activated over approximately the same range as the Na+ currents (-60 to -50 mV), but the Na+ currents were larger at the normal resting potential of the neurons (-45 +/- 11 mV, mean +/- SD, n = 52). Four different types of K+ currents could be differentiated: a Ca(2+)-activated K+ current, a transient K+ current, a delayed rectifier K+ current, and an inward rectifier K+ current. Spontaneous action potentials of varying amplitude were sometimes observed in the cell-attached recording configuration. Action potentials were not observed in whole-cell recordings with normal internal solution (K+ = 100 mM) in the pipette, but frequently appeared when K+ was reduced to 85 mM. These observations suggest that the membrane potential and action potential amplitude of catfish olfactory neurons are significantly affected by the activity of single channels due to the high input resistance (6.6 +/- 5.2 G omega, n = 20) and low membrane capacitance (2.1 +/- 1.1 pF, n = 46) of the cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Sodium- and Calcium-Dependent Excitability of Embryonic Leech Ganglion Cells in Culture

1991 ◽  
Vol 155 (1) ◽  
pp. 435-453
Author(s):  
KARIN SCHIRRMACHER ◽  
JOACHIM W. DEITMER
Keyword(s):  
Cultured Cells ◽  
Ganglion Cells ◽  
Na Current ◽  
Calcium Dependent ◽  
Na Currents ◽  
Voltage Dependent ◽  
Inward Currents ◽  
Cell Current ◽  
K Currents

Voltage-dependent Na+ and Ca2+ inward currents underlying the action potential in cultured embryonic ganglion cells of the leech Hirudo medicinalis have been investigated using the gigaseal whole-cell current or voltage-clamp technique. Dissociated ganglion cells were isolated from 7- to 14-day-old embryos, and maintained in primary culture for up to 5 days. More than 95% of the cultured cells had voltage-dependent K+ currents and about 75% of the cells had voltagedependent inward currents. Action potentials of 60mV amplitude and 4 ms duration, similar to those in embryonic nerve cells in vivo, could be recorded. Three types of inward currents occurred in these cells: (1) an initial Na+ current, which activated and inactivated rapidly; (2) a second Na+ current, which activated slowly and persisted during membrane depolarization, showing very little inactivation, and (3) a Ca2+-dependent inward current. Both types of Na+ currents were resistant to tetrodotoxin (TTX, 0.2-5 μmol l−1). The Ca+ current was also carried by Ba2+, and was blocked by cobalt and cadmium. The fast Na+ current was first expressed in cells from 8-day-old embryos, 1 day earlier than the Ca2+ current. Between days 8 and 14 the density of the fast Na+ current increased from 22±3 to 51±6 μA cm−2 (±S.D., N=11), while the Ca2+ current grew from 10 μA cm−1 (N=2) to 15±4 μA cm−2 (N=10) during this time.

scholarly journals Functional and molecular analysis of transient voltage‐dependent K + currents in rat hippocampal granule cells

2001 ◽  
Vol 537 (2) ◽  
pp. 391-406 ◽  
Author(s):  
Vladimir Riazanski ◽  
Albert Becker ◽  
Jian Chen ◽  
Dmitry Sochivko ◽  
Ailing Lie ◽  
...  
Keyword(s):  
Molecular Analysis ◽  
Granule Cells ◽  
Voltage Dependent ◽  
Transient Voltage ◽  
K Currents

scholarly journals Gonadotropin-Releasing Hormone Inhibits Ether-à-Go-Go-Related Gene K+ Currents in Mouse Gonadotropes

Endocrinology ◽  
2010 ◽  
Vol 151 (3) ◽  
pp. 1079-1088 ◽  
Author(s):  
Wiebke Hirdes ◽  
Crenguta Dinu ◽  
Christiane K. Bauer ◽  
Ulrich Boehm ◽  
Jürgen R. Schwarz
Keyword(s):  
Resting Potential ◽  
Related Gene ◽  
Activation Curve ◽  
Signal Cascade ◽  
Primary Mouse ◽  
Voltage Dependent ◽  
K Current ◽  
Unknown Signal ◽  
Ca2 Channels ◽  
K Currents

Secretion of LH from gonadotropes is initiated by a GnRH-induced increase in intracellular Ca2+ concentration ([Ca2+]i). This increase in [Ca2+]i is the result of Ca2+ release from intracellular stores and Ca2+ influx through voltage-dependent Ca2+ channels. Here we describe an ether-à-go-go-related gene (erg) K+ current in primary mouse gonadotropes and its possible function in the control of Ca2+ influx. To detect gonadotropes, we used a knock-in mouse strain, in which GnRH receptor-expressing cells are fluorescently labeled. Erg K+ currents were recorded in 80–90% of gonadotropes. Blockage of erg currents by E-4031 depolarized the resting potential by 5–8 mV and led to an increase in [Ca2+]i, which was abolished by nifedipine. GnRH inhibited erg currents by a reduction of the maximal erg current and in some cells additionally by a shift of the activation curve to more positive potentials. In conclusion, the erg current contributes to the maintenance of the resting potential in gonadotropes, thereby securing a low [Ca2+]i by restricting Ca2+ influx. In addition, the erg channels are modulated by GnRH by an as-yet unknown signal cascade.

Inputs from regularly and irregularly discharging vestibular nerve afferents to secondary neurons in squirrel monkey vestibular nuclei. III. Correlation with vestibulospinal and vestibuloocular output pathways

1992 ◽  
Vol 68 (2) ◽  
pp. 471-484 ◽  
Author(s):  
R. Boyle ◽  
J. M. Goldberg ◽  
S. M. Highstein
Keyword(s):  
Spinal Cord ◽  
Transition Zone ◽  
Vestibular Nucleus ◽  
Vestibular Nuclei ◽  
Vestibular Nerve ◽  
Descending Pathways ◽  
Relative Contribution ◽  
Antidromic Stimulation ◽  
Vestibulospinal Tract ◽  
Irregular Afferents

1. A previous study measured the relative contributions made by regularly and irregularly discharging afferents to the monosynaptic vestibular nerve (Vi) input of individual secondary neurons located in and around the superior vestibular nucleus of barbiturate-anesthetized squirrel monkeys. Here, the analysis is extended to more caudal regions of the vestibular nuclei, which are a major source of both vestibuloocular and vestibulospinal pathways. As in the previous study, antidromic stimulation techniques are used to classify secondary neurons as oculomotor or spinal projecting. In addition, spinal-projecting neurons are distinguished by their descending pathways, their termination levels in the spinal cord, and their collateral projections to the IIIrd nucleus. 2. Monosynaptic excitatory postsynaptic potentials (EPSPs) were recorded intracellularly from secondary neurons as shocks of increasing strength were applied to Vi. Shocks were normalized in terms of the threshold (T) required to evoke field potentials in the vestibular nuclei. As shown previously, the relative contribution of irregular afferents to the total monosynaptic Vi input of each secondary neuron can be expressed as a %I index, the ratio (x100) of the relative sizes of the EPSPs evoked by shocks of 4 x T and 16 x T. 3. Antidromic stimulation was used to type secondary neurons as 1) medial vestibulospinal tract (MVST) cells projecting to spinal segments C1 or C6; 2) lateral vestibulospinal tract (LVST) cells projecting to C1, C6; or L1; 3) vestibulooculo-collic (VOC) cells projecting both to the IIIrd nucleus and by way of the MVST to C1 or C6; and 4) vestibuloocular (VOR) neurons projecting to the IIIrd nucleus but not to the spinal cord. Most of the neurons were located in the lateral vestibular nucleus (LV), including its dorsal (dLV) and ventral (vLV) divisions, and adjacent parts of the medial (MV) and descending nuclei (DV). Cells receiving quite different proportions of their direct inputs from regular and irregular afferents were intermingled in all regions explored. 4. LVST neurons are restricted to LV and DV and show a somatotopic organization. Those destined for the cervical and thoracic cord come from vLV, from a transition zone between vLV and DV, and to a lesser extent from dLV. Lumbar-projecting neurons are located more dorsally in dLV and more caudally in DV. MVST neurons reside in MV and in the vLV-DV transition zone.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Segmental differences in firing properties and potassium currents in Drosophila larval motoneurons

2012 ◽  
Vol 107 (5) ◽  
pp. 1356-1365 ◽  
Author(s):  
Subhashini Srinivasan ◽  
Kimberley Lance ◽  
Richard B. Levine
Keyword(s):  
Patch Clamp ◽  
Abdominal Segment ◽  
Body Wall ◽  
Potassium Currents ◽  
Whole Cell Patch Clamp ◽  
Voltage Dependent ◽  
Body Wall Muscles ◽  
Motoneuron Activity ◽  
Firing Properties ◽  
Thoracic And Abdominal

Potassium currents play key roles in regulating motoneuron activity, including functional specializations that are important for locomotion. The thoracic and abdominal segments in the Drosophila larval ganglion have repeated arrays of motoneurons that innervate body-wall muscles used for peristaltic movements during crawling. Although abdominal motoneurons and their muscle targets have been studied in detail, owing, in part, to their involvement in locomotion, little is known about the cellular properties of motoneurons in thoracic segments. The goal of this study was to compare firing properties among thoracic motoneurons and the potassium currents that influence them. Whole-cell, patch-clamp recordings performed from motoneurons in two thoracic and one abdominal segment revealed both transient and sustained voltage-activated K+ currents, each with Ca++-sensitive and Ca++-insensitive [A-type, voltage-dependent transient K+ current (IAv)] components. Segmental differences in the expression of voltage-activated K+ currents were observed. In addition, we demonstrate that Shal contributes to IAv currents in the motoneurons of the first thoracic segment.

Sign in / Sign up

Export Citation Format

Share Document