Inhibition of Rapid Heat Responses in Nociceptive Primary Sensory Neurons of Rats by Vanilloid Receptor Antagonists

1999 ◽  
Vol 82 (6) ◽  
pp. 2853-2860 ◽  
Author(s):  
Timo Kirschstein ◽  
Wolfgang Greffrath ◽  
Dietrich Büsselberg ◽  
Rolf-Detlef Treede
Keyword(s):  
Sensory Neurons ◽  
Reversal Potential ◽  
Vanilloid Receptor ◽  
Maximum Effect ◽  
Dependent Manner ◽  
Primary Sensory Neurons ◽  
Drg Neurons ◽  
Patch Clamp Technique ◽  
Noxious Heat ◽  
Duration Of Action

Recent studies demonstrated that heat-sensitive nociceptive primary sensory neurons respond to the vanilloid receptor (VR) agonist capsaicin, and the first cloned VR is a heat-sensitive ion channel. Therefore we studied to what extent heat-evoked currents in nociceptive dorsal root ganglion (DRG) neurons can be attributed to the activation of native vanilloid receptors. Heat-evoked currents were investigated in 89 neurons acutely dissociated from adult rat DRGs as models for their own terminals using the whole cell patch-clamp technique. Locally applied heated extracellular solution (effective temperature ∼53°C) rapidly activated reversible and reproducible inward currents in 80% (62/80) of small neurons (≤32.5 μm), but in none of nine large neurons ( P < 0.001, χ2 test). Heat and capsaicin sensitivity were significantly coexpressed in this subpopulation of small DRG neurons ( P < 0.001, χ2 test). Heat-evoked currents were accompanied by an increase of membrane conductance (320 ± 115%; mean ± SE, n = 7), had a reversal potential of 5 ± 2 mV ( n = 5), which did not differ from that of capsaicin-induced currents in the same neurons (4 ± 3 mV), and were carried at least by Na+ and Ca2+(pCa2+ > pNa+). These observations are consistent with the opening of temperature-operated nonselective cation channels. The duration of action potentials was significantly higher in heat-sensitive (10–90% decay time: 4.45 ± 0.39 ms, n = 12) compared with heat-insensitive neurons (2.18 ± 0.19 ms, n = 6; P< 0.005, Student's t-test), due to an inflection in the repolarizing phase. This property as well as capsaicin sensitivity and small cell size are characteristics of nociceptive DRG neurons. When coadministered with heat stimuli, the competitive VR antagonist capsazepine (1 μM to 1 mM) significantly reduced heat-evoked currents in a dose-dependent manner (IC50 13 μM, Hill slope −0.58, maximum effect 75%). Preincubation for 12–15 s shifted the IC50 by ∼0.5 log10 units to an estimated IC50 of ∼4 μM. The noncompetitive VR antagonist ruthenium red (5 μM) significantly reduced heat-evoked currents by 33 ± 6%. The effects of both VR antagonists were rapidly reversible. Our results provide evidence for a specific activation of native VRs in nociceptive primary sensory neurons by noxious heat. The major proportion of the rapid heat-evoked currents can be attributed to the activation of these temperature-operated channels, and noxious heat may be the signal detected by VRs under physiological conditions.

scholarly journals Serum From Diabetic BB/W Rats Enhances Calcium Currents in Primary Sensory Neurons

1998 ◽  
Vol 80 (3) ◽  
pp. 1236-1244 ◽  
Author(s):  
Helen Ristic ◽  
Shanthi Srinivasan ◽  
Karen E. Hall ◽  
Anders A. F. Sima ◽  
John W. Wiley
Keyword(s):  
Calcium Channel ◽  
G Protein ◽  
Sensory Neurons ◽  
Calcium Influx ◽  
Surface Membrane ◽  
Calcium Currents ◽  
Primary Sensory Neurons ◽  
Drg Neurons ◽  
Patch Clamp Technique ◽  
Inhibitory G Protein

Ristic, Helen, Shanthi Srinivasan, Karen E. Hall, Anders A. F. Sima, and John W. Wiley. Serum from diabetic BB/W rats enhances calcium currents in primary sensory neurons. J. Neurophysiol. 80: 1236–1244, 1998. We examined the hypothesis that exposure of nondiabetic rat dorsal root ganglion (DRG) neurons to sera from diabetic BB/W rats would produce an increase in calcium currents associated with impaired regulation of the inhibitory G protein–calcium channel complex. Acutely dissociated rat DRGs were incubated for 18–24 h in medium supplemented with sera (10% vol/vol) from either diabetic rats with neuropathy or age-matched, nondiabetic controls. Exposure of DRG neurons to sera from diabetic BB/W rats resulted in a surface membrane immunofluorescence pattern when treated with an anti-rat light-chain antibody that was not observed in neurons exposed to control sera. Calcium current density ( I DCa) was assessed with the use of the whole cell variation of the patch-clamp technique. I DCa in neurons exposed to diabetic sera was significantly increased compared with neurons exposed to control sera. Guanine nucleotide-binding (G) protein regulation of calcium channel function was examined with the use of a two-pulse “facilitation” or I DCa enhancement protocol in the presence of activators [guanosine 5′-O-(3-thiotriphosphate) (GTPγS)] or antagonists [guanosine 5′-O-(2-thiodiphosphate) (GDPβS) and pertussis toxin (PTX)] of G protein function. Facilitation was significantly decreased in neurons exposed to diabetic sera. Intracellular diffusion of neurons with GDPβs blocked facilitation, whereas dialysis with GTPγs increased facilitation to a similar magnitude in neurons exposed to either diabetic or control sera. Treatment with PTX resulted in a significant increase in I DCa and ∼50% decrease in facilitation in neurons treated with control sera but no significant changes in neurons exposed to diabetic sera. We conclude that serum from diabetic BB/W rats with neuropathy contains an autoimmune immunoglobulin that impairs regulation of the inhibitory G protein–calcium channel complex, resulting in enhanced calcium influx. Regulation of the inhibitory G protein–calcium channel complex involves PTX-sensitive and -insensitive G proteins.

scholarly journals Electrophysiological Identification of Tonic and Phasic Neurons in Sensory Dorsal Root Ganglion and Their Distinct Implications in Inflammatory Pain

2014 ◽  
pp. 793-799 ◽  
Author(s):  
Y.-Q. YU ◽  
X.-F. CHEN ◽  
Y. YANG ◽  
F. YANG ◽  
J. CHEN
Keyword(s):  
Sensory Neurons ◽  
Inflammatory Pain ◽  
Action Potentials ◽  
Dorsal Root ◽  
Dependent Manner ◽  
Primary Sensory Neurons ◽  
Drg Neurons ◽  
Fluorescent Tracer ◽  
Firing Patterns ◽  
Venom Toxin

In the mammalian autonomic nervous system, tonic and phasic neurons can be differentiated on firing patterns in response to long depolarizing current pulse. However, the similar firing patterns in the somatic primary sensory neurons and their functional significance are not well investigated. Here, we identified two types of neurons innervating somatic sensory in rat dorsal root ganglia (DRG). Tonic neurons fire action potentials (APs) in an intensity-dependent manner, whereas phasic neurons typically generate only one AP firing at the onset of stimulation regardless of intensity. Combining retrograde labeling of somatic DRG neurons with fluorescent tracer DiI, we further find that these neurons demonstrate distinct changes under inflammatory pain states induced by complete Freund’s adjuvant (CFA) or bee venom toxin melittin. In tonic neurons, CFA and melittin treatments significantly decrease rheobase and AP durations (depolarization and repolarization), enhance amplitudes of overshoot and afterhyperpolarization (AHP), and increase the number of evoked action potentials. In phasic neurons, however, the same inflammation treatments cause fewer changes in these electrophysiological parameters except for the increased overshoot and decreased AP durations. In the present study, we find that tonic neurons are more hyperexcitable than phasic neurons after peripheral noxious inflammatory stimulation. The results indicate the distinct contributions of two types of DRG neurons in inflammatory pain.

Vasoinhibin Suppresses the Neurotrophic Effects of VEGF and NGF in Newborn Rat Primary Sensory Neurons

2017 ◽  
Vol 106 (3) ◽  
pp. 221-233 ◽  
Author(s):  
Ximena Castillo ◽  
Zesergio Melo ◽  
Alfredo Varela-Echavarría ◽  
Elisa Tamariz ◽  
Rodrigo M. Aroña ◽  
...  
Keyword(s):  
Growth Factor ◽  
Neurite Outgrowth ◽  
Sensory Neurons ◽  
Target Cells ◽  
Vascular Endothelial ◽  
Primary Sensory Neurons ◽  
Drg Neurons ◽  
Newborn Rat ◽  
Akt Phosphorylation ◽  
Endothelial Growth Factor

Background/Aims: Studies on the biological actions of vasoinhibins have focused mainly on endothelial cells. However, there is incipient knowledge about how vasoinhibins affect the nervous system, even if the target cells and mechanisms of action involved in these effects are unknown. Methods: In order to determine if neurons are direct targets of vasoinhibins, we examined cellular outcomes and the intracellular pathways involved in the neuronal actions of vasoinhibins using newborn rat dorsal root ganglion (DRG) neurons as a model system. Results: Vascular endothelial growth factor (VEGF) or nerve growth factor (NGF) treatment for 48 h resulted in neurite outgrowth stimulation in both DRG cultured explants and isolated primary sensory neurons. Interestingly, a recombinant vasoinhibin containing the first 123 amino acids of human prolactin antagonized the VEGF- and NGF-induced stimulation of neurite outgrowth. Vasoinhibin significantly reduced the density of neurites in DRG explants and obliterated neuritogenesis in isolated DRG neurons in primary culture, supporting a direct neuronal effect of vasoinhibin. In cultures of isolated DRG cells, virtually all β3-tubulin-labeled cells express TrkA, and the majority of these cells also express VEGFR2. Short-term VEGF or NGF treatment of DRG explants resulted in increased ERK1/2 and AKT phosphorylation, whereas incubation of DRG with the combination of either VEGF or NGF together with vasoinhibin resulted in blunted VEGF- or NGF-induced phosphorylation of both ERK1/2 and AKT. Conclusion: Our results show that primary sensory neurons are direct targets of vasoinhibin, and suggest that vasoinhibin inhibition of neurite outgrowth involves the disruption of ERK and AKT phosphorylation cascades.

Functional Expression of Three P2X2 Receptor Splice Variants From Guinea Pig Cochlea

2000 ◽  
Vol 83 (3) ◽  
pp. 1502-1509 ◽  
Author(s):  
Chu Chen ◽  
Margarett S. Parker ◽  
Anthony P. Barnes ◽  
Prescott Deininger ◽  
Richard P. Bobbin
Keyword(s):  
Guinea Pig ◽  
Splice Variants ◽  
Reversal Potential ◽  
Functional Expression ◽  
Hek293 Cells ◽  
Inward Rectification ◽  
Dependent Manner ◽  
Patch Clamp Technique ◽  
Human Embryonic Kidney Cells ◽  
Guinea Pig Cochlea

ATP has been suggested to act as a neurotransmitter or a neuromodulator in the cochlea. The responses to ATP in different cell types of the cochlea vary in terms of the rate of desensitization and magnitude, suggesting that there may be different subtypes of P2X receptors distributed in the cochlea. Recently three ionotropic P2X2 receptor splice variants, P2X2–1, P2X2–2, and P2X2–3, were isolated and sequenced from a guinea pig cochlear cDNA library. To test the hypothesis that these different splice variants could be expressed as functional homomeric receptors, the three P2X2 receptor variants were individually and transiently expressed in human embryonic kidney cells (HEK293). The biophysical and pharmacological properties of these receptors were characterized using the whole cell patch-clamp technique. Extracellular application of ATP induced an inward current in HEK293 cells containing each of the three splice variants in a dose-dependent manner indicating the expression of homomeric receptors. Current-voltage ( I-V) relationships for the ATP-gated current show that the three subtypes of the P2X2 receptor had a similar reversal potential and an inward rectification index ( I 50 mV/ I −50 mV). However, the ATP-induced currents in cells expressing P2X2–1 and P2X2–2 variants were large and desensitized rapidly whereas the current in those cells expressing the P2X2–3 variant was much smaller and desensitized slower. The order of potency to ATP agonists was 2-MeSATP > ATP > α,β -MeATP for all three expressed splice variants. The ATP receptor antagonists suramin and PPADS reduced the effects of ATP on all three variants. Results demonstrate that three P2X2splice variants from guinea pig cochlea, P2X2–1, P2X2–2, and P2X2–3, can individually form nonselective cation receptor channels when these subunits are expressed in HEK293 cells. The distinct properties of these P2X2receptor splice variants may contribute to the differences in the response to ATP observed in native cochlear cells.

scholarly journals Propofol Restores Transient Receptor Potential Vanilloid Receptor Subtype-1 Sensitivity via  Activation of Transient Receptor Potential Ankyrin Receptor Subtype-1 in Sensory Neurons

2011 ◽  
Vol 114 (5) ◽  
pp. 1169-1179 ◽  
Author(s):  
Hongyu Zhang ◽  
Peter J. Wickley ◽  
Sayantani Sinha ◽  
Ian N. Bratz ◽  
Derek S. Damron
Keyword(s):  
Sensory Neurons ◽  
Transient Receptor Potential ◽  
Receptor Potential ◽  
Vanilloid Receptor ◽  
Receptor Subtype ◽  
Transient Receptor Potential Vanilloid ◽  
Peripheral Sensitization ◽  
Drg Neurons ◽  
Trpv1 Receptors ◽  
Transient Receptor

Background Cross talk between peripheral nociceptors belonging to the transient receptor potential vanilloid receptor subtype-1 (TRPV1) and ankyrin subtype-1 (TRPA1) family has been demonstrated recently. Moreover, the intravenous anesthetic propofol has directly activates TRPA1 receptors and indirectly restores sensitivity of TRPV1 receptors in dorsal root ganglion (DRG) sensory neurons. Our objective was to determine the extent to which TRPA1 activation is involved in mediating the propofol-induced restoration of TRPV1 sensitivity. Methods Mouse DRG neurons were isolated by enzymatic dissociation and grown for 24 h. F-11 cells were transfected with complementary DNA for both TRPV1 and TRPA1 or TRPV1 only. The intracellular Ca concentration was measured in individual cells via fluorescence microscopy. After TRPV1 desensitization with capsaicin (100 nM), cells were treated with propofol (1, 5, and 10 μM) alone or with propofol in the presence of the TRPA1 antagonist, HC-030031 (0.5 μM), or the TRPA1 agonist, allyl isothiocyanate (AITC; 100 μM); capsaicin was then reapplied. Results In DRG neurons that contain both TRPV1 and TRPA1, propofol and AITC restored TRPV1 sensitivity. However, in DRG neurons containing only TRPV1 receptors, exposure to propofol or AITC after desensitization did not restore capsaicin-induced TRPV1 sensitivity. Similarly, in F-11 cells transfected with both TRPV1 and TRPA1, propofol and AITC restored TRPV1 sensitivity. However, in F-11 cells transfected with TRPV1 only, neither propofol nor AITC was capable of restoring TRPV1 sensitivity. Conclusions These data demonstrate that propofol restores TRPV1 sensitivity in primary DRG neurons and in cultured F-11 cells transfected with both the TRPV1 and TRPA1 receptors via a TRPA1-dependent process. Propofol's effects on sensory neurons may be clinically important and may contribute to peripheral sensitization to nociceptive stimuli in traumatized tissue.

scholarly journals Bilateral Neuropathy of Primary Sensory Neurons by the Chronic Compression of Multiple Unilateral DRGs

2016 ◽  
Vol 2016 ◽  
pp. 1-16 ◽  
Author(s):  
Ya-Bin Xie ◽  
Huan Zhao ◽  
Ying Wang ◽  
Kai Song ◽  
Ming Zhang ◽  
...  
Keyword(s):  
Sensory Neurons ◽  
Spontaneous Pain ◽  
Activating Transcription Factor 3 ◽  
Thermal Preference ◽  
Primary Sensory Neurons ◽  
Nerve Root Compression ◽  
Drg Neurons ◽  
Cold Allodynia ◽  
Activating Transcription Factor ◽  
Intervertebral Foramina

To mimic multilevel nerve root compression and intervertebral foramina stenosis in human, we established a new animal model of the chronic compression of unilateral multiple lumbar DRGs (mCCD) in the rat. A higher occurrence of signs of spontaneous pain behaviors, such as wet-dog shaking and spontaneous hind paw shrinking behaviors, was firstly observed from day 1 onward. In the meantime, the unilateral mCCD rat exhibited significant bilateral hind paw mechanical and cold allodynia and hyperalgesia, as well as a thermal preference to 30°C plate between 30 and 35°C. The expression of activating transcription factor 3 (ATF3) was significantly increased in the ipsilateral and contralateral all-sized DRG neurons after the mCCD. And the expression of CGRP was significantly increased in the ipsilateral and contralateral large- and medium-sized DRG neurons. ATF3 and CGRP expressions correlated to evoked pain hypersensitivities such as mechanical and cold allodynia on postoperative day 1. The results suggested that bilateral neuropathy of primary sensory neurons might contribute to bilateral hypersensitivity in the mCCD rat.

scholarly journals Bradykinin Lowers the Threshold Temperature for Heat Activation of Vanilloid Receptor 1

2002 ◽  
Vol 88 (1) ◽  
pp. 544-548 ◽  
Author(s):  
Takeshi Sugiura ◽  
Makoto Tominaga ◽  
Hirotada Katsuya ◽  
Kazue Mizumura
Keyword(s):  
Hek293 Cells ◽  
Threshold Temperature ◽  
Dependent Manner ◽  
Patch Clamp Technique ◽  
Noxious Heat ◽  
Concentration Dependent Manner ◽  
Kinase C ◽  
Vanilloid Receptor 1 ◽  
Heat Activation ◽  
Pkc Activation

Bradykinin (BK) is an inflammatory mediator that plays a pivotal role in pain and hyperalgesia to heat in inflamed tissues by exciting nociceptors and sensitizing them to heat through activation of protein kinase C (PKC). It has been suggested that the capsaicin receptor (VR1), a nociceptor-specific cation channel sensitive to noxious heat, protons, and capsaicin, is a channel that is modified by BK in these effects. In this study, we examined how BK modulates the activity of VR1. We measured VR1 currents using the patch-clamp technique in human embryonic kidney-derived (HEK293) cells expressing VR1 and B2 BK receptor. We found that BK lowered the threshold temperature for activation of VR1 currents in HEK cells down to well below the physiological body temperature in a concentration-dependent manner through PKC activation. We also demonstrated that in capsaicin-sensitive dorsal root ganglion (DRG) neurons the activation threshold of heat-induced current, which is considered to be VR-1 mediated, was lowered by BK and that this effect was also mediated by PKC. These data further support the supposition that modulation of VR1 is a mechanism for the BK-induced excitation of nociceptors and their sensitization to heat.

scholarly journals Sustained morphine treatment augments basal CGRP release from cultured primary sensory neurons in a Raf-1 dependent manner

2008 ◽  
Vol 584 (2-3) ◽  
pp. 272-277 ◽  
Author(s):  
Xu Yue ◽  
Suneeta Tumati ◽  
Edita Navratilova ◽  
Dagmar Strop ◽  
Paul A. St John ◽  
...  
Keyword(s):  
Sensory Neurons ◽  
Dependent Manner ◽  
Primary Sensory Neurons ◽  
Morphine Treatment ◽  
Cgrp Release
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