scholarly journals Manipulation of the Potassium Channel Kv1.1 and Its Effect on Neuronal Excitability in Rat Sensory Neurons

2007 ◽  
Vol 98 (5) ◽  
pp. 2683-2692 ◽  
Author(s):  
Xian Xuan Chi ◽  
G. D. Nicol
Keyword(s):  
Potassium Channel ◽  
Sensory Neurons ◽  
Neuronal Excitability ◽  
Critical Role ◽  
Small Diameter ◽  
Resting Membrane Potential ◽  
Functional Protein ◽  
Western Blots ◽  
Firing Threshold ◽  
Sirna Treatment

Potassium channels play a critical role in regulating many aspects of action potential (AP) firing. To establish the contribution of the voltage-dependent potassium channel Kv1.1 in regulating excitability, we used the selective blocker dendrotoxin-K (DTX-K) and small interfering RNA (siRNA) targeted to Kv1.1 to determine their effects on AP firing in small-diameter capsaicin-sensitive sensory neurons. A 5-min exposure to 10 nM DTX-K suppressed the total potassium current ( IK) measured at +40 mV by about 33%. DTX-K produced a twofold increase in the number of APs evoked by a ramp of depolarizing current. Associated with increased firing was a decrease in firing threshold and rheobase. DTX-K did not alter the resting membrane potential or the AP duration. A 48-h treatment with siRNA targeted to Kv1.1 reduced the expression of this channel protein by about 60% as measured in Western blots. After treatment with siRNA, IK was no longer sensitive to DTX-K, indicating a loss of functional protein. Similarly, after siRNA treatment exposure to DTX-K had no effect on the number of evoked APs, firing threshold, or rheobase. However, after siRNA treatment, the firing threshold had values similar to those obtained after acute exposure to DTX-K, suggesting that the loss of Kv1.1 plays a critical role in setting this parameter of excitability. These results demonstrate that Kv1.1 plays an important role in limiting AP firing and that siRNA may be a useful approach to establish the role of specific ion channels in the absence of selective antagonists.

Sphingosine-1-Phosphate Via Activation of a G-Protein-Coupled Receptor(s) Enhances the Excitability of Rat Sensory Neurons

2006 ◽  
Vol 96 (3) ◽  
pp. 1042-1052 ◽  
Author(s):  
Y. H. Zhang ◽  
J. C. Fehrenbacher ◽  
M. R. Vasko ◽  
G. D. Nicol
Keyword(s):  
G Protein ◽  
Sensory Neurons ◽  
Small Diameter ◽  
G Protein Coupled Receptors ◽  
External Application ◽  
Nociceptive Neurons ◽  
Firing Threshold ◽  
Current Ramp ◽  
Sphingosine 1 Phosphate ◽  
G Protein Coupled

Sphingosine-1-phosphate (S1P) is released by immune cells and is thought to play a key role in chemotaxis and the onset of the inflammatory response. The question remains whether this lipid mediator also contributes to the enhanced sensitivity of nociceptive neurons that is associated with inflammation. Therefore we examined whether S1P alters the excitability of small diameter, capsaicin-sensitive sensory neurons by measuring action potential (AP) firing and two of the membrane currents critical in regulating the properties of the AP. External application of S1P augments the number of APs evoked by a depolarizing current ramp. The enhanced firing is associated with a decrease in the rheobase and an increase in the resistance at firing threshold although neither the firing threshold nor the resting membrane potential are changed. Treatment with S1P enhanced the tetrodotoxin-resistant sodium current and decreased the total outward potassium current ( IK). When sensory neurons were internally perfused with GDP-β-S, a blocker of G protein activation, the S1P-induced increase in APs was completely blocked and suggests the excitatory actions of S1P are mediated through G-protein-coupled receptors called endothelial differentiation gene or S1PR. In contrast, internal perfusion with GDP-β-S and S1P increased the number of APs evoked by the current ramp. These results and our finding that the mRNAs for S1PRs are expressed in both the intact dorsal root ganglion and cultures of adult sensory neurons supports the notion that S1P acts on S1PRs linked to G proteins. Together these findings demonstrate that S1P can regulate the excitability of small diameter sensory neurons by acting as an external paracrine-type ligand through activation of G-protein-coupled receptors and thus may contribute to the hypersensitivity during inflammation.

scholarly journals Sphingosine 1-phosphate receptor 2 antagonist JTE-013 increases the excitability of sensory neurons independently of the receptor

2012 ◽  
Vol 108 (5) ◽  
pp. 1473-1483 ◽  
Author(s):  
Chao Li ◽  
Xian Xuan Chi ◽  
Wenrui Xie ◽  
J. A. Strong ◽  
J.-M. Zhang ◽  
...  
Keyword(s):  
G Protein ◽  
Sensory Neurons ◽  
Neuronal Excitability ◽  
Small Diameter ◽  
G Protein Coupled Receptors ◽  
Prostaglandin E ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Sphingosine 1 Phosphate ◽  
G Protein Coupled

Previously we demonstrated that sphingosine 1-phosphate receptor 1 (S1PR1) played a prominent, but not exclusive, role in enhancing the excitability of small-diameter sensory neurons, suggesting that other S1PRs can modulate neuronal excitability. To examine the potential role of S1PR2 in regulating neuronal excitability we used the established selective antagonist of S1PR2, JTE-013. Here we report that exposure to JTE-013 alone produced a significant increase in excitability in a time- and concentration-dependent manner in 70–80% of recorded neurons. Internal perfusion of sensory neurons with guanosine 5′- O-(2-thiodiphosphate) (GDP-β-S) via the recording pipette inhibited the sensitization produced by JTE-013 as well as prostaglandin E2. Pretreatment with pertussis toxin or the selective S1PR1 antagonist W146 blocked the sensitization produced by JTE-013. These results indicate that JTE-013 might act as an agonist at other G protein-coupled receptors. In neurons that were sensitized by JTE-013, single-cell RT-PCR studies demonstrated that these neurons did not express the mRNA for S1PR2. In behavioral studies, injection of JTE-013 into the rat's hindpaw produced a significant increase in the mechanical sensitivity in the ipsilateral, but not contralateral, paw. Injection of JTE-013 did not affect the withdrawal latency to thermal stimulation. Thus JTE-013 augments neuronal excitability independently of S1PR2 by unknown mechanisms that may involve activation of other G protein-coupled receptors such as S1PR1. Clearly, further studies are warranted to establish the causal nature of this increased sensitivity, and future studies of neuronal function using JTE-013 should be interpreted with caution.

scholarly journals The Chemokine CXCL1/Growth Related Oncogene Increases Sodium Currents and Neuronal Excitability in Small Diameter Sensory Neurons

2008 ◽  
Vol 4 ◽  
pp. 1744-8069-4-38 ◽  
Author(s):  
Jun-Gang Wang ◽  
Judith A Strong ◽  
Wenrui Xie ◽  
Rui-Hua Yang ◽  
Dennis E Coyle ◽  
...  
Keyword(s):  
Sensory Neurons ◽  
Neuronal Excitability ◽  
Small Diameter ◽  
Sodium Currents

Patch-Clamp Analysis of Gene-Targeted Vomeronasal Neurons Expressing a Defined V1r or V2r Receptor: Ionic Mechanisms Underlying Persistent Firing

2007 ◽  
Vol 98 (4) ◽  
pp. 2357-2369 ◽  
Author(s):  
Kirill Ukhanov ◽  
Trese Leinders-Zufall ◽  
Frank Zufall
Keyword(s):  
Sensory Neurons ◽  
Cell Damage ◽  
Critical Role ◽  
Vomeronasal Organ ◽  
Input Resistance ◽  
Cell Types ◽  
Brain Regions ◽  
Resting Membrane Potential ◽  
Action Potential Firing ◽  
Persistent Firing

Sensory neurons in the mouse vomeronasal organ consist of two major groups, apical and basal, that project to different brain regions, express unique sets of receptors, and serve distinct functions. Electrical properties of these two subpopulations, however, have not been systematically characterized. V1rb2-tau-GFP and V2r1b-tau-GFP tagged vomeronasal sensory neurons (VSNs) were selected as prototypical apical or basal VSNs, respectively, and their biophysical properties were analyzed in acute slices that minimized cell damage. Basal V2r1b-expressing VSNs had voltage-gated conductances, and especially Na+ (Nav) and Ca2+ (Cav) currents, that were substantially larger than those observed in apical V1rb2 VSNs, although the resting membrane potential, input resistance, and membrane capacitance were similar in both cell types. Of several types of Cav currents, T-type and L-type Cav currents contributed to action potential firing, and both currents alone were capable of generating oscillatory Ca2+ spikes. The L-type Cav current was uniquely coupled to a BK large-conductance K+ current, and interplay between these channels played a critical role in repolarizing spikes and maintaining persistent firing in VSNs. Larger Nav and Cav conductances, along with a more positive inactivation voltage of the Nav current in the V2r1b VSNs, contributed to the larger spike amplitude and higher spike frequency induced by depolarizing current in these cells compared with V1rb2 VSNs. Basal GFP-negative VSNs and V2r1b VSNs responded to prolonged depolarization with persistent, but adapting discharge that could be relevant in sensory adaptation. Collectively, these results suggest a novel mechanism for regulating and encoding neuronal activity in the accessory olfactory system.

scholarly journals Expression of sphingosine 1-phosphate receptors in the rat dorsal root ganglia and defined single isolated sensory neurons

2012 ◽  
Vol 44 (18) ◽  
pp. 889-901 ◽  
Author(s):  
J. S. Kays ◽  
Chao Li ◽  
G. D. Nicol
Keyword(s):  
Sensory Neurons ◽  
Dorsal Root ◽  
Neuronal Excitability ◽  
Expression Profiles ◽  
Large Diameter ◽  
Small Diameter ◽  
Positive Control ◽  
Single Neurons ◽  
Sphingosine 1 Phosphate ◽  
S1p Receptor

Previously, we demonstrated that sphingosine 1-phosphate (S1P) increased the excitability of small-diameter sensory neurons, in part, through activation of S1P receptor 1 (S1PR1), suggesting that other S1PRs can modulate neuronal excitability. Therefore, studies were undertaken to establish the expression profiles of S1PRs in the intact dorsal root ganglion (DRG) and in defined single isolated sensory neurons. To determine mRNA expression of S1PRs in the DRG, SYBR green quantitative PCR (qPCR) was used. To determine the expression of S1PR mRNAs in single neurons of defined diameters, a preamplification protocol utilizing Taqman primer and probes was used to enhance the sensitivity of detection. The preamplification protocol also permitted detection of mRNA for two hallmark neuronal receptor/ion channels, TRPV1 and P2X3. Expression profiles of S1PR mRNA isolated from lung and brain were used as positive control tissues. In the intact DRG, the order of expression of S1PRs was S1PR3>>R1≈R2>R5≈R4. In the single neurons, the expression of S1PRs was quite variable with some neurons expressing all five subtypes, whereas some expressing only one subtype. In contrast to the DRG, S1PR1 was the highest expressing subtype in 10 of the 18 small-, medium-, and large-diameter sensory neurons. S1PR1 was the second highest expressor in ∼50% of those remaining neurons. Overall, in the single neurons, the order of expression was S1PR1>>R3≈R5>R4>R2. The results obtained from the single defined neurons are consistent with our previous findings wherein S1PR1 plays a prominent but not exclusive role in the enhancement of neuronal excitability.

scholarly journals Systemic administration of anti-NGF increases A-type potassium currents and decreases pancreatic nociceptor excitability in a rat model of chronic pancreatitis

2012 ◽  
Vol 302 (1) ◽  
pp. G176-G181 ◽  
Author(s):  
Yaohui Zhu ◽  
Kshama Mehta ◽  
Cuiping Li ◽  
Guang-Yin Xu ◽  
Liansheng Liu ◽  
...  
Keyword(s):  
Chronic Pancreatitis ◽  
Sensory Neurons ◽  
Neuronal Excitability ◽  
Potassium Currents ◽  
Input Resistance ◽  
Resting Membrane Potential ◽  
Trinitrobenzene Sulfonic Acid ◽  
Mrna Levels ◽  
Control Serum ◽  
Clamp Condition

We have previously shown that pancreatic sensory neurons in rats with chronic pancreatitis (CP) display increased excitability associated with a decrease in transient inactivating potassium currents ( IA), thus accounting in part for the hyperalgesia associated with this condition. Because of its well known role in somatic hyperalgesia, we hypothesized a role for the nerve growth factor (NGF) in driving these changes. CP was induced by intraductal injection of trinitrobenzene sulfonic acid (TNBS) in rats. After 3 wk, anti-NGF antibody or control serum was injected intra-peritoneally daily for 1 wk. This protocol was repeated in another set of experiments in control rats (receiving intraductal PBS instead of TNBS). Pancreatic nociceptors labeled with the dye Dil were identified, and patch-clamp recordings were made from acutely dissociated DRG neurons. Sensory neurons from anti-NGF-treated rats displayed a lower resting membrane potential, increased rheobase, decreased burst discharges in response to stimulatory current, and decreased input resistance compared with those treated with control serum. Under voltage-clamp condition, neuronal IA density was increased in anti-NGF-treated rats compared with rats treated with control serum. However, anti-NGF treatment had no effect on electrophysiological parameters in neurons from control rats. The expression of Kv-associated channel or ancillary genes Kv1.4, 4.1, 4.2, 4.3, and DPP6, DPP10, and KCHIPs 1–4 in pancreas-specific nociceptors was examined by laser-capture microdissection and real-time PCR quantification of mRNA levels. No significant differences were seen among those. These findings emphasize a key role for NGF in maintaining neuronal excitability in CP specifically via downregulation of IA by as yet unknown mechanisms.

scholarly journals Nerve growth factor enhances the excitability of rat sensory neurons through activation of the atypical protein kinase C isoform, PKMζ

2012 ◽  
Vol 107 (1) ◽  
pp. 315-335 ◽  
Author(s):  
Y. H. Zhang ◽  
J. Kays ◽  
K. E. Hodgdon ◽  
T. C. Sacktor ◽  
G. D. Nicol
Keyword(s):  
Nerve Growth Factor ◽  
Growth Factor ◽  
Sensory Neurons ◽  
Sodium Current ◽  
Small Diameter ◽  
Neurotrophin Receptor ◽  
P75 Neurotrophin Receptor ◽  
Internal Perfusion ◽  
Western Blots ◽  
Nerve Growth

Our previous work showed that nerve growth factor (NGF) increased the excitability of small-diameter capsaicin-sensitive sensory neurons by activating the p75 neurotrophin receptor and releasing sphingolipid-derived second messengers. Whole cell patch-clamp recordings were used to establish the signaling pathways whereby NGF augments action potential (AP) firing (i.e., sensitization). Inhibition of MEK1/2 (PD-98059), PLC (U-73122, neomycin), or conventional/novel isoforms of PKC (bisindolylmaleimide I) had no effect on the sensitization produced by NGF. Pretreatment with a membrane-permeable, myristoylated pseudosubstrate inhibitor of atypical PKCs (aPKCs: PKMζ, PKCζ, and PKCλ/ι) blocked the NGF-induced increase in AP firing. Inhibitors of phosphatidylinositol 3-kinase (PI3K) also blocked the sensitization produced by NGF. Isolated sensory neurons were also treated with small interfering RNA (siRNA) targeted to PKCζ. Both Western blots and quantitative real-time PCR established that PKMζ, but neither full-length PKCζ nor PKCλ/ι, was significantly reduced after siRNA exposure. Treatment with these labeled siRNA prevented the NGF-induced enhancement of excitability. Furthermore, consistent with the high degree of catalytic homology for aPKCs, internal perfusion with active recombinant PKCζ or PKCι augmented excitability, recapitulating the sensitization produced by NGF. Internal perfusion with recombinant PKCζ suppressed the total potassium current and enhanced the tetrodotoxin-resistant sodium current. Pretreatment with the myristoylated pseudosubstrate inhibitor blocked the increased excitability produced by ceramide or internal perfusion with recombinant PKCζ. These results demonstrate that NGF leads to the activation of PKMζ that ultimately enhances the capacity of small-diameter capsaicin-sensitive sensory neurons to fire APs through a PI3K-dependent signaling cascade.

New Insights on KCa3.1 Channel Modulation

2020 ◽  
Vol 26 (18) ◽  
pp. 2096-2101
Author(s):  
Giuseppe Manfroni ◽  
Francesco Ragonese ◽  
Lorenzo Monarca ◽  
Andrea Astolfi ◽  
Loretta Mancinelli ◽  
...  
Keyword(s):  
Potassium Channel ◽  
Critical Role ◽  
Calcium Signalling ◽  
Typical Feature ◽  
Open Probability ◽  
Pharmacological Agents ◽  
Channel Modulation ◽  
Calcium Dependent ◽  
Modelling Techniques ◽  
Calcium Activated Potassium Channel

The human intermediate conductance calcium-activated potassium channel, KCa3.1, is involved in several pathophysiological conditions playing a critical role in cell secretory machinery and calcium signalling. The recent cryo-EM analysis provides new insights for understanding the modulation by both endogenous and pharmacological agents. A typical feature of this channel is the low open probability in saturating calcium concentrations and its modulation by potassium channel openers (KCOs), such as benzo imidazolone 1-EBIO, without changing calcium-dependent activation. In this paper, we proposed a model of KCOs action in the modulation of channel activity. The KCa3.1 channel has a very rich pharmacological profile with several classes of molecules that selectively interact with different binding sites of the channel. Among them, benzo imidazolones can be openers (positive modulators such as 1-EBIO, DC-EBIO) or blockers (negative modulators such as NS1619). Through computation modelling techniques, we identified the 1,4-benzothiazin-3-one as a promising scaffold to develop new KCa3.1 channel modulators. Further studies are needed to explore the potential use of 1-4 benzothiazine- 3-one in KCa3.1 modulation and its pharmacological application.

scholarly journals The NALCN Channel Regulator UNC-80 Functions in a Subset of Interneurons To Regulate Caenorhabditis elegans Reversal Behavior

2019 ◽  
Vol 10 (1) ◽  
pp. 199-210 ◽  
Author(s):  
Chuanman Zhou ◽  
Jintao Luo ◽  
Xiaohui He ◽  
Qian Zhou ◽  
Yunxia He ◽  
...  
Keyword(s):  
Plant Hormone ◽  
Neuronal Excitability ◽  
Resting Membrane Potential ◽  
Loss Of Function ◽  
Wild Type ◽  
C Elegans ◽  
Link Type ◽  
Complex Functions ◽  
And Function ◽  
Multiple Loss

NALCN (Na+leak channel, non-selective) is a conserved, voltage-insensitive cation channel that regulates resting membrane potential and neuronal excitability. UNC79 and UNC80 are key regulators of the channel function. However, the behavioral effects of the channel complex are not entirely clear and the neurons in which the channel functions remain to be identified. In a forward genetic screen for C. elegans mutants with defective avoidance response to the plant hormone methyl salicylate (MeSa), we isolated multiple loss-of-function mutations in unc-80 and unc-79. C. elegans NALCN mutants exhibited similarly defective MeSa avoidance. Interestingly, NALCN, unc-80 and unc-79 mutants all showed wild type-like responses to other attractive or repelling odorants, suggesting that NALCN does not broadly affect odor detection or related forward and reversal behaviors. To understand in which neurons the channel functions, we determined the identities of a subset of unc-80-expressing neurons. We found that unc-79 and unc-80 are expressed and function in overlapping neurons, which verified previous assumptions. Neuron-specific transgene rescue and knockdown experiments suggest that the command interneurons AVA and AVE and the anterior guidepost neuron AVG can play a sufficient role in mediating unc-80 regulation of the MeSa avoidance. Though primarily based on genetic analyses, our results further imply that MeSa might activate NALCN by direct or indirect actions. Altogether, we provide an initial look into the key neurons in which the NALCN channel complex functions and identify a novel function of the channel in regulating C. elegans reversal behavior through command interneurons.

scholarly journals PKA-RIIβ autophosphorylation modulates PKA activity and seizure phenotypes in mice

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Jingliang Zhang ◽  
Chenyu Zhang ◽  
Xiaoling Chen ◽  
Bingwei Wang ◽  
Weining Ma ◽  
...  
Keyword(s):  
Therapeutic Target ◽  
Neurological Disorders ◽  
Neuronal Excitability ◽  
Granule Cells ◽  
Critical Role ◽  
Intrinsic Excitability ◽  
Seizure Susceptibility ◽  
Seizure Onset ◽  
Potential Therapeutic Target ◽  
Seizure Model

AbstractTemporal lobe epilepsy (TLE) is one of the most common and intractable neurological disorders in adults. Dysfunctional PKA signaling is causally linked to the TLE. However, the mechanism underlying PKA involves in epileptogenesis is still poorly understood. In the present study, we found the autophosphorylation level at serine 114 site (serine 112 site in mice) of PKA-RIIβ subunit was robustly decreased in the epileptic foci obtained from both surgical specimens of TLE patients and seizure model mice. The p-RIIβ level was negatively correlated with the activities of PKA. Notably, by using a P-site mutant that cannot be autophosphorylated and thus results in the released catalytic subunit to exert persistent phosphorylation, an increase in PKA activities through transduction with AAV-RIIβ-S112A in hippocampal DG granule cells decreased mIPSC frequency but not mEPSC, enhanced neuronal intrinsic excitability and seizure susceptibility. In contrast, a reduction of PKA activities by RIIβ knockout led to an increased mIPSC frequency, a reduction in neuronal excitability, and mice less prone to experimental seizure onset. Collectively, our data demonstrated that the autophosphorylation of RIIβ subunit plays a critical role in controlling neuronal and network excitabilities by regulating the activities of PKA, providing a potential therapeutic target for TLE.

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