Postnatal maturation of the hyperpolarization-activated cation current, Ih, in trigeminal sensory neurons

2011 ◽  
Vol 106 (4) ◽  
pp. 2045-2056 ◽  
Author(s):  
Hyun-jung Cho ◽  
John B. Furness ◽  
Ernest A. Jennings
Keyword(s):  
Action Potential ◽  
Postnatal Development ◽  
Sensory Neurons ◽  
Neuronal Excitability ◽  
Firing Frequency ◽  
Moderate Intensity ◽  
Hcn Channels ◽  
Action Potential Firing ◽  
Membrane Hyperpolarization ◽  
Postnatal Maturation

Hyperpolarization-activated inward currents ( Ih) contribute to neuronal excitability in sensory neurons. Four subtypes of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels generate Ih, with different activation kinetics and cAMP sensitivities. The aim of the present study was to examine the postnatal development of Ih and HCN channel subunits in trigeminal ganglion (TG) neurons. Ih was investigated in acutely dissociated TG neurons from rats aged between postnatal day (P)1 and P35 with whole cell patch-clamp electrophysiology. In voltage-clamp studies, Ih was activated by a series of hyperpolarizing voltage steps from −40 mV to −120 mV in −10-mV increments. Tail currents from a common voltage step (−100 mV) were used to determine Ih voltage dependence. Ih activation was faster in older rats and occurred at more depolarized potentials; the half-maximal activation voltage ( V1/2) changed from −89.4 mV (P1) to −81.6 mV (P35). In current-clamp studies, blocking Ih with ZD7288 caused membrane hyperpolarization and increases in action potential half-duration at all postnatal ages examined. ZD7288 also reduced the action potential firing frequency in multiple-firing neurons. Western blot analysis of the TG detected immunoreactive bands corresponding to all HCN subtypes. HCN1 and HCN2 band density increased with postnatal age, whereas the low-intensity HCN3 and moderate-intensity HCN4 bands were not changed. This study suggests that functional Ih are activated in rat trigeminal sensory neurons from P1 during postnatal development, have an increasing role with age, and modify neuronal excitability.

scholarly journals Zinc Enhances the Inhibitory Effects of Strychnine-Sensitive Glycine Receptors in Mouse Hippocampal Neurons

2007 ◽  
Vol 98 (6) ◽  
pp. 3666-3676 ◽  
Author(s):  
Hai Xia Zhang ◽  
Liu Lin Thio
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Hippocampal Neurons ◽  
Neuronal Excitability ◽  
Hippocampal Slices ◽  
Glycine Receptors ◽  
Inhibitory Effects ◽  
Action Potential Firing ◽  
Embryonic Mouse ◽  
Potential Firing

Although extracellular Zn2+ is an endogenous biphasic modulator of strychnine-sensitive glycine receptors (GlyRs), the physiological significance of this modulation remains poorly understood. Zn2+ modulation of GlyR may be especially important in the hippocampus where presynaptic Zn2+ is abundant. Using cultured embryonic mouse hippocampal neurons, we examined whether 1 μM Zn2+, a potentiating concentration, enhances the inhibitory effects of GlyRs activated by sustained glycine applications. Sustained 20 μM glycine (EC25) applications alone did not decrease the number of action potentials evoked by depolarizing steps, but they did in 1 μM Zn2+. At least part of this effect resulted from Zn2+ enhancing the GlyR-induced decrease in input resistance. Sustained 20 μM glycine applications alone did not alter neuronal bursting, a form of hyperexcitability induced by omitting extracellular Mg2+. However, sustained 20 μM glycine applications depressed neuronal bursting in 1 μM Zn2+. Zn2+ did not enhance the inhibitory effects of sustained 60 μM glycine (EC70) applications in these paradigms. These results suggest that tonic GlyR activation could decrease neuronal excitability. To test this possibility, we examined the effect of the GlyR antagonist strychnine and the Zn2+ chelator tricine on action potential firing by CA1 pyramidal neurons in mouse hippocampal slices. Co-applying strychnine and tricine slightly but significantly increased the number of action potentials fired during a depolarizing current step and decreased the rheobase for action potential firing. Thus Zn2+ may modulate neuronal excitability normally and in pathological conditions such as seizures by potentiating GlyRs tonically activated by low agonist concentrations.

scholarly journals pigkMutation underliesmachobehavior and affects Rohon-Beard cell excitability

2015 ◽  
Vol 114 (2) ◽  
pp. 1146-1157 ◽  
Author(s):  
V. Carmean ◽  
M. A. Yonkers ◽  
M. B. Tellez ◽  
J. R. Willer ◽  
G. B. Willer ◽  
...  
Keyword(s):  
Action Potential ◽  
Sensory Neurons ◽  
Sodium Current ◽  
Genetic Defect ◽  
Sensory Cells ◽  
Loss Of Function ◽  
Wild Type ◽  
Action Potential Firing ◽  
Potential Firing ◽  
Touch Response

The study of touch-evoked behavior allows investigation of both the cells and circuits that generate a response to tactile stimulation. We investigate a touch-insensitive zebrafish mutant, macho (maco), previously shown to have reduced sodium current amplitude and lack of action potential firing in sensory neurons. In the genomes of mutant but not wild-type embryos, we identify a mutation in the pigk gene. The encoded protein, PigK, functions in attachment of glycophosphatidylinositol anchors to precursor proteins. In wild-type embryos, pigk mRNA is present at times when mutant embryos display behavioral phenotypes. Consistent with the predicted loss of function induced by the mutation, knock-down of PigK phenocopies maco touch insensitivity and leads to reduced sodium current (INa) amplitudes in sensory neurons. We further test whether the genetic defect in pigk underlies the maco phenotype by overexpressing wild-type pigk in mutant embryos. We find that ubiquitous expression of wild-type pigk rescues the touch response in maco mutants. In addition, for maco mutants, expression of wild-type pigk restricted to sensory neurons rescues sodium current amplitudes and action potential firing in sensory neurons. However, expression of wild-type pigk limited to sensory cells of mutant embryos does not allow rescue of the behavioral touch response. Our results demonstrate an essential role for pigk in generation of the touch response beyond that required for maintenance of proper INa density and action potential firing in sensory neurons.

scholarly journals Hyperexcitability precedes motoneuron loss in the Smn2B/− mouse model of spinal muscular atrophy

2019 ◽  
Vol 122 (4) ◽  
pp. 1297-1311 ◽  
Author(s):  
K. A. Quinlan ◽  
E. J. Reedich ◽  
W. D. Arnold ◽  
A. C. Puritz ◽  
C. F. Cavarsan ◽  
...  
Keyword(s):  
Cell Death ◽  
Mouse Model ◽  
Action Potential ◽  
Spinal Muscular Atrophy ◽  
Postnatal Development ◽  
Motor Unit ◽  
Muscular Atrophy ◽  
Action Potential Firing ◽  
Motor Unit Number Estimation ◽  
Potential Firing

Spinal motoneuron dysfunction and loss are pathological hallmarks of the neuromuscular disease spinal muscular atrophy (SMA). Changes in motoneuron physiological function precede cell death, but how these alterations vary with disease severity and motoneuron maturational state is unknown. To address this question, we assessed the electrophysiology and morphology of spinal motoneurons of presymptomatic Smn2B/− mice older than 1 wk of age and tracked the timing of motor unit loss in this model using motor unit number estimation (MUNE). In contrast to other commonly used SMA mouse models, Smn2B/− mice exhibit more typical postnatal development until postnatal day (P)11 or 12 and have longer survival (~3 wk of age). We demonstrate that Smn2B/− motoneuron hyperexcitability, marked by hyperpolarization of the threshold voltage for action potential firing, was present at P9–10 and preceded the loss of motor units. Using MUNE studies, we determined that motor unit loss in this mouse model occurred 2 wk after birth. Smn2B/− motoneurons were also larger in size, which may reflect compensatory changes taking place during postnatal development. This work suggests that motoneuron hyperexcitability, marked by a reduced threshold for action potential firing, is a pathological change preceding motoneuron loss that is common to multiple models of severe SMA with different motoneuron maturational states. Our results indicate voltage-gated sodium channel activity may be altered in the disease process. NEW & NOTEWORTHY Changes in spinal motoneuron physiologic function precede cell death in spinal muscular atrophy (SMA), but how they vary with maturational state and disease severity remains unknown. This study characterized motoneuron and neuromuscular electrophysiology from the Smn2B/− model of SMA. Motoneurons were hyperexcitable at postnatal day (P)9–10, and specific electrophysiological changes in Smn2B/− motoneurons preceded functional motor unit loss at P14, as determined by motor unit number estimation studies.

Brain-derived neurotrophic factor stimulation of T-type Ca2+ channels in sensory neurons contributes to increased peripheral pain sensitivity

2019 ◽  
Vol 12 (600) ◽  
pp. eaaw2300 ◽  
Author(s):  
Hua Wang ◽  
Yuan Wei ◽  
Yichen Pu ◽  
Dongsheng Jiang ◽  
Xinghong Jiang ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Sensory Neurons ◽  
Neurotrophic Factor ◽  
Pain Sensitivity ◽  
Neuronal Excitability ◽  
Brain Derived Neurotrophic Factor ◽  
Mitogen Activated Protein Kinase ◽  
Mechanical Stimuli ◽  
Action Potential Firing ◽  
Stimulation Of

Although brain-derived neurotrophic factor (BDNF) is implicated in the nociceptive signaling of peripheral sensory neurons, the underlying mechanisms remain largely unknown. Here, we elucidated the effects of BDNF on the neuronal excitability of trigeminal ganglion (TG) neurons and the pain sensitivity of rats mediated by T-type Ca2+ channels. BDNF reversibly and dose-dependently enhanced T-type channel currents through the activation of tropomyosin receptor kinase B (TrkB). Antagonism of phosphatidylinositol 3-kinase (PI3K) but not of its downstream target, the kinase AKT, abolished the BDNF-induced T-type channel response. BDNF application activated p38 mitogen-activated protein kinase (MAPK), and this effect was prevented by inhibition of PI3K but not of protein kinase A (PKA). Antagonism of either PI3K or p38 MAPK prevented the BDNF-induced stimulation of PKA activity, whereas PKA inhibition blocked the BDNF-mediated increase in T-type currents. BDNF increased the rate of action potential firing in TG neurons and enhanced the pain sensitivity of rats to mechanical stimuli. Moreover, inhibition of TrkB signaling abolished the increased mechanical sensitivity in a rat model of chronic inflammatory pain, and this effect was attenuated by either T-type channel blockade or knockdown of the channel Cav3.2. Together, our findings indicate that BDNF enhances T-type currents through the stimulation of TrkB coupled to PI3K-p38-PKA signaling, thereby inducing neuronal hyperexcitability of TG neurons and pain hypersensitivity in rats.

Development of hypersynchrony in the cortical network during chemoconvulsant-induced epileptic seizures in vivo

2012 ◽  
Vol 107 (6) ◽  
pp. 1718-1730 ◽  
Author(s):  
Adi Cymerblit-Sabba ◽  
Yitzhak Schiller
Keyword(s):  
Action Potential ◽  
Early Phase ◽  
Epileptic Seizures ◽  
Firing Frequency ◽  
Cortical Network ◽  
Small Subset ◽  
Action Potential Firing ◽  
Neuronal Synchronization ◽  
Potential Firing

The prevailing view of epileptic seizures is that they are caused by increased hypersynchronous activity in the cortical network. However, this view is based mostly on electroencephalography (EEG) recordings that do not directly monitor neuronal synchronization of action potential firing. In this study, we used multielectrode single-unit recordings from the hippocampus to investigate firing of individual CA1 neurons and directly monitor synchronization of action potential firing between neurons during the different ictal phases of chemoconvulsant-induced epileptic seizures in vivo. During the early phase of seizures manifesting as low-amplitude rhythmic β-electrocorticography (ECoG) activity, the firing frequency of most neurons markedly increased. To our surprise, the average overall neuronal synchronization as measured by the cross-correlation function was reduced compared with control conditions with ∼60% of neuronal pairs showing no significant correlated firing. However, correlated firing was not uniform and a minority of neuronal pairs showed a high degree of correlated firing. Moreover, during the early phase of seizures, correlated firing between 9.8 ± 5.1% of all stably recorded pairs increased compared with control conditions. As seizures progressed and high-frequency ECoG polyspikes developed, the firing frequency of neurons further increased and enhanced correlated firing was observed between virtually all neuronal pairs. These findings indicated that epileptic seizures represented a hyperactive state with widespread increase in action potential firing. Hypersynchrony also characterized seizures. However, it initially developed in a small subset of neurons and gradually spread to involve the entire cortical network only in the later more intense ictal phases.

scholarly journals Zonal variations in K+ currents in vestibular crista calyx terminals

2015 ◽  
Vol 113 (1) ◽  
pp. 264-276 ◽  
Author(s):  
Frances L. Meredith ◽  
Katherine J. Rennie
Keyword(s):  
Action Potential ◽  
Ampa Receptors ◽  
Channel Blocker ◽  
Outward Current ◽  
Firing Frequency ◽  
Action Potential Firing ◽  
Regional Variations ◽  
Electrophysiological Properties ◽  
Kcnq Channels ◽  
Potential Firing

We developed a rodent crista slice to investigate regional variations in electrophysiological properties of vestibular afferent terminals. Thin transverse slices of the gerbil crista ampullaris were made and electrical properties of calyx terminals in central zones (CZ) and peripheral zones (PZ) compared with whole cell patch clamp. Spontaneous action potential firing was observed in 25% of current-clamp recordings and was either regular or irregular in both zones. Firing was abolished when extracellular choline replaced Na+ but persisted when hair cell mechanotransduction channels or calyx AMPA receptors were blocked. This suggests that ion channels intrinsic to the calyx can generate spontaneous firing. In response to depolarizing voltage steps, outward K+ currents were observed at potentials above −60 mV. K+ currents in PZ calyces showed significantly more inactivation than currents in CZ calyces. Underlying K+ channel populations contributing to these differences were investigated. The KCNQ channel blocker XE991 dihydrochloride blocked a slowly activating, sustained outward current in both PZ and CZ calyces, indicating the presence of KCNQ channels. Mean reduction was greatest in PZ calyces. XE991 also reduced action potential firing frequency in CZ and PZ calyces and broadened mean action potential width. The K+ channel blocker 4-aminopyridine (10–50 μM) blocked rapidly activating, moderately inactivating currents that were more prevalent in PZ calyces. α-Dendrotoxin, a selective blocker of KV1 channels, reduced outward currents in CZ calyces but not in PZ calyces. Regional variations in K+ conductances may contribute to different firing responses in calyx afferents.

scholarly journals Kv1 potassium channels control action potential firing of putative GABAergic deep cerebellar nuclear neurons

2019 ◽  
Author(s):  
Jessica Abigail Feria Pliego ◽  
Christine M. Pedroarena
Keyword(s):  
Potassium Channels ◽  
Action Potential ◽  
Cerebellar Cortex ◽  
Neuronal Excitability ◽  
Inhibitory Synapses ◽  
Channel Blockers ◽  
Action Potential Firing ◽  
Potential Firing ◽  
Low Threshold ◽  
Evoked Activity

ABSTRACTThe Kv1 voltage-gated potassium channels (kv1.1-1.8) display characteristic low-threshold activation ranges what enables their role in regulating diverse aspects of neuronal function, such as the action potential (AP) threshold and waveform, and thereby influence neuronal excitability or synaptic transmission. Kv1 channels are highly expressed in the cerebellar cortex and nuclei and mutations of human Kv1 genes are associated to episodic forms of ataxia (EAT-1). Besides the well-established role of Kv1 channels in regulating the basket-Purkinje cells inhibitory synapses of cerebellar cortex, cerebellar Kv1 channels regulate the principal deep cerebellar nuclear neurons activity (DCNs). DCNs however, include as well different groups of GABAergic cells that project locally to target principal DCNs, or to the inferior-olive or recurrently to the cerebellar cortex, but whether their function is controlled by Kv1 channels remains unclear. Here, using cerebellar slices from the GAD67-GFP line mice to identify putative GABAergic-DCNs and specific Kv1 channel blockers (dendrotoxins-alpha/I/K (DTXs)) we provide evidence that putative GABAergic-DCNs spontaneous and evoked activity is controlled by Kv1 currents. DTXs shifted in the hyperpolarizing direction the voltage threshold of spontaneous APs in GABAergic-DCNs, increased GABAergic-DCNs spontaneous firing rate and decreased these neurons ability to fire repetitively action potentials at high frequency. Moreover, in spontaneously silent putative nucleo-cortical DCNs, DTXs application induced depolarization and tonic firing. These results strongly suggest that Kv1 channels regulate GABAergic-DCNs activity and thereby can control previously unrecognized aspects of cerebellar function.

Inactivation of Voltage-Activated Na+ Currents Contributes to Different Adaptation Properties of Paired Mechanosensory Neurons

2001 ◽  
Vol 85 (4) ◽  
pp. 1595-1602 ◽  
Author(s):  
Päivi H. Torkkeli ◽  
Shin-Ichi Sekizawa ◽  
Andrew S. French
Keyword(s):  
Action Potential ◽  
Sodium Current ◽  
Sense Organ ◽  
Leading Edge ◽  
Type A ◽  
Firing Frequency ◽  
Resting Potential ◽  
Type B ◽  
Action Potential Firing ◽  
Mechanosensory Neurons

Voltage-activated sodium current ( I Na) is primarily responsible for the leading edge of the action potential in many neurons. While I Na generally activates rapidly when a neuron is depolarized, its inactivation properties differ significantly between different neurons and even within one neuron, where I Na often has slowly and rapidly inactivating components. I Nainactivation has been suggested to regulate action potential firing frequency in some cells, but no clear picture of this relationship has emerged. We studied I Na in both members of the paired mechanosensory neurons of a spider slit-sense organ, where one neuron adapts rapidly (type A) and the other slowly (type B) in response to a step depolarization. In both neuron types I Na activated and inactivated with single time constants of 2–3 ms and 5–10 ms, respectively, varying with the stimulus intensity. However, there was a clear difference in the steady-state inactivation properties of the two neuron types, with the half-maximal inactivation ( V 50) being −40.1 mV in type A neurons and −58.1 mV in type B neurons. Therefore I Na inactivated closer to the resting potential in the more slowly adapting neurons. I Na also recovered from inactivation significantly faster in type B than type A neurons, and the recovery was dependent on conditioning voltage. These results suggest that while the rate of I Na inactivation is not responsible for the difference in the adaptation behavior of these two neuron types, the rate of recovery from inactivation may play a major role. Inactivation at lower potentials could therefore be crucial for more rapid recovery.

scholarly journals β3-Adrenergic receptor-dependent modulation of the medium afterhyperpolarization in rat hippocampal CA1 pyramidal neurons

2019 ◽  
Vol 121 (3) ◽  
pp. 773-784 ◽  
Author(s):  
Timothy W. Church ◽  
Jon T. Brown ◽  
Neil V. Marrion
Keyword(s):  
Action Potential ◽  
Adrenergic Receptors ◽  
Adrenergic Receptor ◽  
Neuronal Excitability ◽  
Pyramidal Neurons ◽  
Intracellular Camp ◽  
Action Potential Firing ◽  
Hippocampal Pyramidal Neurons ◽  
Potential Firing ◽  
H Channels

Action potential firing in hippocampal pyramidal neurons is regulated by generation of an afterhyperpolarization (AHP). Three phases of AHP are recognized, with the fast AHP regulating action potential firing at the onset of a burst and the medium and slow AHPs supressing action potential firing over hundreds of milliseconds and seconds, respectively. Activation of β-adrenergic receptors suppresses the slow AHP by a protein kinase A-dependent pathway. However, little is known regarding modulation of the medium AHP. Application of the selective β-adrenergic receptor agonist isoproterenol suppressed both the medium and slow AHPs evoked in rat CA1 hippocampal pyramidal neurons recorded from slices maintained in organotypic culture. Suppression of the slow AHP was mimicked by intracellular application of cAMP, with the suppression of the medium AHP by isoproterenol still being evident in cAMP-dialyzed cells. Suppression of both the medium and slow AHPs was antagonized by the β-adrenergic receptor antagonist propranolol. The effect of isoproterenol to suppress the medium AHP was mimicked by two β3-adrenergic receptor agonists, BRL37344 and SR58611A. The medium AHP was mediated by activation of small-conductance calcium-activated K+ channels and deactivation of H channels at the resting membrane potential. Suppression of the medium AHP by isoproterenol was reduced by pretreating cells with the H-channel blocker ZD7288. These data suggest that activation of β3-adrenergic receptors inhibits H channels, which suppresses the medium AHP in CA1 hippocampal neurons by utilizing a pathway that is independent of a rise in intracellular cAMP. This finding highlights a potential new target in modulating H-channel activity and thereby neuronal excitability. NEW & NOTEWORTHY The noradrenergic input into the hippocampus is involved in modulating long-term synaptic plasticity and is implicated in learning and memory. We demonstrate that activation of functional β3-adrenergic receptors suppresses the medium afterhyperpolarization in hippocampal pyramidal neurons. This finding provides an additional mechanism to increase action potential firing frequency, where neuronal excitability is likely to be crucial in cognition and memory.

scholarly journals Persistent and resurgent Na+ currents in vestibular calyx afferents

2020 ◽  
Vol 124 (2) ◽  
pp. 510-524
Author(s):  
Frances L. Meredith ◽  
Katherine J. Rennie
Keyword(s):  
Action Potential ◽  
Postnatal Development ◽  
Afferent Neurons ◽  
Biophysical Properties ◽  
Action Potential Firing ◽  
Firing Patterns ◽  
Na Currents ◽  
Potential Firing ◽  
New Treatments ◽  
Afferent Terminals

Action potential firing patterns differ between groups of afferent neurons innervating vestibular epithelia. We investigated the biophysical properties of Na+ currents in specialized vestibular calyx afferent terminals during postnatal development. Mature calyces express Na+ currents with transient, persistent, and resurgent components. Nav1.6 channels contribute to resurgent Na+ currents and may enhance firing in peripheral calyx afferents. Understanding Na+ channels that contribute to vestibular nerve responses has implications for developing new treatments for vestibular dysfunction.

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