Stimulation of peripheral Kappa opioid receptors inhibits inflammatory hyperalgesia via activation of the PI3K gamma/AKT/nNOS/NO signaling pathway

Background: In addition to their central effects, opioids cause peripheral analgesia. There is evidence showing that peripheral activation of kappa opioid receptors (KORs) inhibits inflammatory pain. Moreover, peripheral mu-opioid receptor (MOR) activation are able to direct block PGE(2)-induced ongoing hyperalgesia However, this effect was not tested for KOR selective activation. In the present study, the effect of the peripheral activation of KORs on PGE(2)-induced ongoing hyperalgesia was investigated. The mechanisms involved were also evaluated. Results: Local (paw) administration of U50488 (a selective KOR agonist) directly blocked, PGE(2)-induced mechanical hyperalgesia in both rats and mice. This effect was reversed by treating animals with L-NMMA or N-propyl-L-arginine (a selective inhibitor of neuronal nitric oxide synthase, nNOS), suggesting involvement of the nNOS/NO pathway. U50488 peripheral effect was also dependent on stimulation of PI3K gamma/AKT because inhibitors of these kinases also reduced peripheral antinociception induced by U50488. Furthermore, U50488 lost its peripheral analgesic effect in PI3K gamma null mice. Observations made in vivo were confirmed after incubation of dorsal root ganglion cultured neurons with U50488 produced an increase in the activation of AKT as evaluated by western blot analyses of its phosphorylated form. Finally, immunofluorescence of DRG neurons revealed that KOR-expressing neurons also express PI3K gamma (congruent to 43%). Conclusions: The present study indicates that activation of peripheral KORs directly blocks inflammatory hyperalgesia through stimulation of the nNOS/NO signaling pathway which is probably stimulated by PI3K gamma/AKT signaling. This study extends a previously study of our group suggesting that PI3K gamma/AKT/nNOS/NO is an important analgesic pathway in primary nociceptive neurons.

Phenotypic alterations of neuropeptide Y and calcitonin gene-related peptide-containing neurons innervating the rat temporomandibular joint during carrageenan-induced arthritis

The aim of this study was to identify immunoreactive neuropeptide Y (NPY) and calcitonin gene-related peptide (CGRP) neurons in the autonomic and sensory ganglia, specifically neurons that innervate the rat temporomandibular joint (TMJ). A possible variation between the percentages of these neurons in acute and chronic phases of carrageenan-induced arthritis was examined. Retrograde neuronal tracing was combined with indirect immunofluorescence to identify NPY-immuno-reactive (NPY-IR) and CGRP-immunoreactive (CGRP-IR) neurons that send nerve fibers to the normal and arthritic temporomandibular joint. In normal joints, NPY-IR neurons constitute 78 +/- 3%, 77 +/- 6% and 10 +/- 4% of double-labeled nucleated neuronal profile originated from the superior cervical, stellate and otic ganglia, respectively. These percentages in the sympathetic ganglia were significantly decreased in acute (58 +/- 2% for superior cervical ganglion and 58 +/- 8% for stellate ganglion) and chronic (60 +/- 2% for superior cervical ganglion and 59 +/- 15% for stellate ganglion) phases of arthritis, while in the otic ganglion these percentages were significantly increased to 19 +/- 5% and 13 +/- 3%, respectively. In the trigeminal ganglion, CGRP-IR neurons innervating the joint significantly increased from 31 +/- 3% in normal animals to 54 +/- 2% and 49 +/- 3% in the acute and chronic phases of arthritis, respectively. It can be concluded that NPY neurons that send nerve fibers to the rat temporomandibular joint are located mainly in the superior cervical, stellate and otic ganglia. Acute and chronic phases of carrageenan-induced arthritis lead to an increase in the percentage of NPY-IR parasympathetic and CGRP-IR sensory neurons and to a decrease in the percentage of NPY-IR sympathetic neurons related to TMJ innervation.

SCG postnatal remodelling - hypertrophy and neuron number stability - in Spix's Yellow-toothed Cavies (Galea spixii)

Whilst a fall in neuron numbers seems a common pattern during postnatal development, several authors have nonetheless reported an increase in neuron number, which may be associated with any one of a number of possible processes encapsulating either neurogenesis or late maturation and incomplete differentiation. Recent publications have thus added further fuel to the notion that a postnatal neurogenesis may indeed exist in sympathetic ganglia. In the light of these uncertainties surrounding the effects exerted by postnatal development on the number of superior cervical ganglion (SCG) neurons, we have used state-of-the-art design-based stereology to investigate the quantitative structure of SCG at four distinct timepoints after birth, viz., 1-3 days, 1 month, 12 months and 36 months. The main effects exerted by ageing on the SCG structure were: (i) a 77% increase in ganglion volume; (ii) stability in the total number of the whole population of SCG nerve cells (no change - either increase or decrease) during post-natal development; (iii) a higher proportion of uninucleate neurons to binucleate neurons only in newborn animals; (iv) a 130% increase in the volume of uninucleate cell bodies; and (v) the presence of BrdU positive neurons in animals at all ages. At the time of writing our results support the idea that neurogenesis takes place in the SCG of preas, albeit it warrants confirmation by further markers. We also hypothesise that a portfolio of other mechanisms: cell repair, maturation, differentiation and death may be equally intertwined and implicated in the numerical stability of SCG neurons during postnatal development. (C) 2011 ISDN. Published by Elsevier Ltd. All rights reserved.

NADPH- Diaphorase positive cardiac neurons in the atria of mice. A morphoquantitative study

Abstract Background The present study was conducted to determine the location, the morphology and distribution of NADPH-diaphorase positive neurons in the cardiac nerve plexus of the atria of mice (ASn). This plexus lies over the muscular layer of the atria, dorsal to the muscle itself, in the connective tissue of the subepicardium. NADPH- diaphorase staining was performed on whole-mount preparations of the atria mice. For descriptive purposes, all data are presented as means ± SEM. Results The majority of the NADPH-diaphorase positive neurons were observed in the ganglia of the plexus. A few single neurons were also observed. The number of NADPH-d positive neurons was 57 ± 4 (ranging from 39 to 79 neurons). The ganglion neurons were located in 3 distinct groups: (1) in the region situated cranial to the pulmonary veins, (2) caudally to the pulmonary veins, and (3) in the atrial groove. The largest group of neurons was located cranially to the pulmonary veins (66.7%). Three morphological types of NADPH-diaphorase neurons could be distinguished on the basis of their shape: unipolar cells, bipolar cells and cells with three processes (multipolar cells). The unipolar neurons predominated (78.9%), whereas the multipolar were encountered less frequently (5,3%). The sizes (area of maximal cell profile) of the neurons ranged from about 90 μm2to about 220 μm2. Morphometrically, the three types of neurons were similar and there were no significant differences in their sizes. The total number of cardiac neurons (obtained by staining the neurons with NADH-diaphorase method) was 530 ± 23. Therefore, the NADPH-diaphorase positive neurons of the heart represent 10% of the number of cardiac neurons stained by NADH. Conclusion The obtained data have shown that the NADPH-d positive neurons in the cardiac plexus of the atria of mice are morphologically different, and therefore, it is possible that the function of the neurons may also be different.

Stimulation of peripheral Kappa opioid receptors inhibits inflammatory hyperalgesia via activation of the PI3Kγ/AKT/nNOS/NO signaling pathway

Abstract Background In addition to their central effects, opioids cause peripheral analgesia. There is evidence showing that peripheral activation of kappa opioid receptors (KORs) inhibits inflammatory pain. Moreover, peripheral μ-opioid receptor (MOR) activation are able to direct block PGE2-induced ongoing hyperalgesia However, this effect was not tested for KOR selective activation. In the present study, the effect of the peripheral activation of KORs on PGE2-induced ongoing hyperalgesia was investigated. The mechanisms involved were also evaluated. Results Local (paw) administration of U50488 (a selective KOR agonist) directly blocked, PGE2-induced mechanical hyperalgesia in both rats and mice. This effect was reversed by treating animals with L-NMMA or N-propyl-L-arginine (a selective inhibitor of neuronal nitric oxide synthase, nNOS), suggesting involvement of the nNOS/NO pathway. U50488 peripheral effect was also dependent on stimulation of PI3Kγ/AKT because inhibitors of these kinases also reduced peripheral antinociception induced by U50488. Furthermore, U50488 lost its peripheral analgesic effect in PI3Kγ null mice. Observations made in vivo were confirmed after incubation of dorsal root ganglion cultured neurons with U50488 produced an increase in the activation of AKT as evaluated by western blot analyses of its phosphorylated form. Finally, immunofluorescence of DRG neurons revealed that KOR-expressing neurons also express PI3Kγ (≅ 43%). Conclusions The present study indicates that activation of peripheral KORs directly blocks inflammatory hyperalgesia through stimulation of the nNOS/NO signaling pathway which is probably stimulated by PI3Kγ/AKT signaling. This study extends a previously study of our group suggesting that PI3Kγ/AKT/nNOS/NO is an important analgesic pathway in primary nociceptive neurons.

Caratterizzazione morfologica e neurochimica dei neuroni sensitivi e motori del trigono vescicale e del muscolo uretrale di maiale

Il trigono della vescica urinaria (UBT) è un'area limitata attraverso la quale penetrano nella vescica la maggior parte dei vasi e fibre e in cui le fibre nervose e neuroni intramurali sono più concentrati. Mediante l’utilizzo combinato di un tracciante retrogrado(FB) e dell’immunoistochimica sono stati valutati il fenotipo e l’area del soma dei neuroni dei gangli spinali (DRG), dei neuroni post-gangliari, il fenotipo dei gangli della catena simpatica (STG) e i gangli mesenterici caudali (CMG) innervanti l’UBT. - Caratterizzazione dei neuroni dei DRG con: peptide correlato al gene della calcitonina (CGRP)(30±3%, 29±3%, rispettivamente), sostanza P(SP)(26±8%, 27±12%), ossido nitrico sintasi neuronale (nNOS)(21±4%; 26±7%), neurofilamento 200kDa (NF200)(75±14%, 81±7% ) , transient receptor potential vanilloid1 (TRPV1)(48±13%, 43±6%) e isolectina-B4-positivi (IB4) (56±6%;43±10%). I neuroni sensoriali, distribuiti da L2 a Ca1 (DRG), hanno presentato una localizzazione segmentale, mostrando maggior densità nei DRG L4-L5 e S2-S4. I neuroni sensoriali lombari sono risultati significativamente più grandi di quelle sacrali (1.112±624μm2 vs716±421μm2). Complessivamente, questi dati indicano che le vie lombari e sacrali probabilmente svolgono ruoli diversi nella trasmissione sensitiva del trigono della vescica urinaria. -I neuroni FB+ della STG e dei CMG sono risultati immunoreattivi per la tirosina idrossilasi (TH)(66±10,1%, 53±8,2%, rispettivamente), la dopamina beta-idrossilasi (DβH)(62±6,2%, 52±6,2%), neuropeptideY (NPY)(59±8%; 66±7%), CGRP(24±3%, 22±3%), SP(22±2%; 38±8%), polipeptide intestinale vasoattivo (VIP)(19±2%; 35±4%), nNOS(15±2%; 33±8%), trasportatore vescicolare dell'acetilcolina (VAChT)(15±2%; 35±5%), leu-encefalina (LENK)(14±7%; 26±9%), e somatostatina (SOM)(12±3%;32±7%).Il numero medio di neuroni FB+ (1845,1±259,3) era nella STG in L1-S3, con i pirenofori più piccoli (465,6±82.7μm2). Un gran numero (4287,5±1450,6) di neuroni FB+ di piccole dimensioni (476,1±103,9μm2) sono stati localizzati lungo il margine dei CMG. Il maggior numero (4793,3±1990,8) di neuroni FB + è stato osservato nel plesso pelvico, dove i neuroni marcati erano raggruppati in micro-gangli e con pirenoforo ancora più piccolo (374,9±85,4 μm2).

Glial cell line-derived neurotrophic factor (GDNF) induces neuritogenesis in the cochlear spiral ganglion via neural cell adhesion molecule (NCAM)

Glial cell line-derived neurotrophic factor (GDNF) increases survival and neurite extension of spiral ganglion neurons (SGNs), the primary neurons of the auditory system, via yet unknown signaling mechanisms. In other cell types, signaling is achieved by the GPI-linked GDNF family receptor α1 (GFRα1) via recruitment of transmembrane receptors: Ret (re-arranged during transformation) and/or NCAM (neural cell adhesion molecule). Here we show that GDNF enhances neuritogenesis in organotypic cultures of spiral ganglia from 5-day-old rats and mice. Addition of GFRα1-Fc increases this effect. GDNF/GFRα1-Fc stimulation activates intracellular PI3K/Akt and MEK/Erk signaling cascades as detected by Western blot analysis of cultures prepared from rats at postnatal days 5 (P5, before the onset of hearing) and 20 (P20, after the onset of hearing). Both cascades mediate GDNF stimulation of neuritogenesis, since application of the Akt inhibitor Wortmannin or the Erk inhibitor U0126 abolished GDNF/GFRα1-Fc stimulated neuritogenesis in P5 rats. Since cultures of P5 NCAM-deficient mice failed to respond by neuritogenesis to GDNF/GFRα1-Fc, we conclude that NCAM serves as a receptor for GDNF signaling responsible for neuritogenesis in early postnatal spiral ganglion.

LIF promotes neurogenesis and maintains neural precursors in cell populations derived from spiral ganglion stem cells

BACKGROUND: Stem cells with the ability to form clonal floating colonies (spheres) were recently isolated from the neonatal murine spiral ganglion. To further examine the features of inner ear-derived neural stem cells and their derivatives, we investigated the effects of leukemia inhibitory factor (LIF), a neurokine that has been shown to promote self-renewal of other neural stem cells and to affect neural and glial cell differentiation. RESULTS: LIF-treatment led to a dose-dependent increase of the number of neurons and glial cells in cultures of sphere-derived cells. Based on the detection of developmental and progenitor cell markers that are maintained in LIF-treated cultures and the increase of cycling nestin-positive progenitors, we propose that LIF maintains a pool of neural progenitor cells. We further provide evidence that LIF increases the number of nestin-positive progenitor cells directly in a cell cycle-independent fashion, which we interpret as an acceleration of neurogenesis in sphere-derived progenitors. This effect is further enhanced by an anti-apoptotic action of LIF. Finally, LIF and the neurotrophins BDNF and NT3 additively promote survival of stem cell-derived neurons. CONCLUSION: Our results implicate LIF as a powerful tool to control neural differentiation and maintenance of stem cell-derived murine spiral ganglion neuron precursors. This finding could be relevant in cell replacement studies with animal models featuring spiral ganglion neuron degeneration. The additive effect of the combination of LIF and BDNF/NT3 on stem cell-derived neuronal survival is similar to their effect on primary spiral ganglion neurons, which puts forward spiral ganglion-derived neurospheres as an in vitro model system to study aspects of auditory neuron development.

Dysregulation of voltage-gated sodium channels by ubiquitin ligase NEDD4-2 in neuropathic pain

Peripheral neuropathic pain is a disabling condition resulting from nerve injury. It is characterized by the dysregulation of voltage-gated sodium channels (Navs) expressed in dorsal root ganglion (DRG) sensory neurons. The mechanisms underlying the altered expression of Na(v)s remain unknown. This study investigated the role of the E3 ubiquitin ligase NEDD4-2, which is known to ubiquitylate Navs, in the pathogenesis of neuropathic pain in mice. The spared nerve injury (SNI) model of traumatic nerve injury-induced neuropathic pain was used, and an Na(v)1.7-specific inhibitor, ProTxII, allowed the isolation of Na(v)1.7-mediated currents. SNI decreased NEDD4-2 expression in DRG cells and increased the amplitude of Na(v)1.7 and Na(v)1.8 currents. The redistribution of Na(v)1.7 channels toward peripheral axons was also observed. Similar changes were observed in the nociceptive DRG neurons of Nedd4L knockout mice (SNS-Nedd4L(-/-)). SNS-Nedd4L(-/-) mice exhibited thermal hypersensitivity and an enhanced second pain phase after formalin injection. Restoration of NEDD4-2 expression in DRG neurons using recombinant adenoassociated virus (rAAV2/6) not only reduced Na(v)1.7 and Na(v)1.8 current amplitudes, but also alleviated SNI-induced mechanical allodynia. These findings demonstrate that NEDD4-2 is a potent posttranslational regulator of Na(v)s and that downregulation of NEDD4-2 leads to the hyperexcitability of DRG neurons and contributes to the genesis of pathological pain.

Ubiquitylation of voltage-gated sodium channels.

Ion channel proteins are regulated by different types of posttranslational modifications. The focus of this review is the regulation of voltage-gated sodium channels (Navs) upon their ubiquitylation. The amiloride-sensitive epithelial sodium channel (ENaC) was the first ion channel shown to be regulated upon ubiquitylation. This modification results from the binding of ubiquitin ligase from the Nedd4 family to a protein-protein interaction domain, known as the PY motif, in the ENaC subunits. Many of the Navs have similar PY motifs, which have been demonstrated to be targets of Nedd4-dependent ubiquitylation, tagging them for internalization from the cell surface. The role of Nedd4-dependent regulation of the Nav membrane density in physiology and disease remains poorly understood. Two recent studies have provided evidence that Nedd4-2 is downregulated in dorsal root ganglion (DRG) neurons in both rat and mouse models of nerve injury-induced neuropathic pain. Using two different mouse models, one with a specific knockout of Nedd4-2 in sensory neurons and another where Nedd4-2 was overexpressed with the use of viral vectors, it was demonstrated that the neuropathy-linked neuronal hyperexcitability was the result of Nav1.7 and Nav1.8 overexpression due to Nedd4-2 downregulation. These studies provided the first in vivo evidence of the role of Nedd4-2-dependent regulation of Nav channels in a disease state. This ubiquitylation pathway may be involved in the development of symptoms and diseases linked to Nav-dependent hyperexcitability, such as pain, cardiac arrhythmias, epilepsy, migraine, and myotonias.

TRPV1 Channels Contribute to Behavioral Hypersensitivity and Spontaneous Activity in Nociceptors After Spinal Cord Injury

A majority of persons who have sustained spinal cord injury (SCI) develop chronic pain. While most investigators have assumed that the critical mechanisms underlying neuropathic pain after SCI are restricted to the central nervous system (CNS), recent studies showed that contusive SCI results in a large increase in spontaneous activity in primary nociceptors, which is correlated significantly with mechanical allodynia and thermal hyperalgesia. Upregulation of ion channel transient receptor vanilloid 1 (TRPV1) has been observed in the dorsal horn of the spinal cord after SCI, and reduction of SCI-induced hyperalgesia by a TRPV1 antagonist has been claimed. However, the possibility that SCI enhances TRPV1 expression and function in nociceptors has not been tested. I produced contusive SCI at thoracic level T10 in adult, male rats and harvested lumbar (L4/L5) dorsal root ganglia (DRG) from sham-treated and SCI rats 3 days and 1 month after injury, as well as from age-matched naive control rats. Whole-cell patch clamp recordings were made from small (soma diameter <30 >μm) DRG neurons 18 hours after dissociation. Capsaicin-induced currents were significantly increased 1 month, but not 3 days, after SCI compared to neurons from control animals. In addition, Ca2+ transients imaged during capsaicin application were significantly greater 1 month after SCI. Western blot experiments indicated that expression of TRPV1 protein in DRG is also increased 1 month after SCI. A major role for TRPV1 channels in pain-related behavior was indicated by the ability of a specific TRPV1 antagonist, AMG9810, to reverse SCI-induced hypersensitivity of hindlimb withdrawal responses to heat and mechanical stimuli. Similar reversal of behavioral hypersensitivity was induced by intrathecal delivery of oligodeoxynucleotides antisense to TRPV1, which knocked down TRPV1 protein and reduced capsaicin-evoked currents. TRPV1 knockdown also decreased the incidence of spontaneous activity in dissociated nociceptors after SCI. Limited activation of TRPV1 was found to induce prolonged repetitive firing without accommodation or desensitization, and this effect was enhanced by SCI. These data suggest that SCI enhances TRPV1 expression and function in primary nociceptors, increasing the excitability and spontaneous activity of these neurons, thus contributing to chronic pain after SCI.

Bradykinin inhibits M current via phospholipase C and Ca2+ release from IP3-sensitive Ca2+ stores in rat sympathetic neurons

A variety of intracellular signaling pathways can modulate the properties of voltage-gated ion channels. Some of them are well characterized. However, the diffusible second messenger mediating suppression of M current via G protein-coupled receptors has not been identified. In superior cervical ganglion neurons, we find that the signaling pathways underlying M current inhibition by B2 bradykinin and M1 muscarinic receptors respond very differently to inhibitors. The bradykinin pathway was suppressed by the phospholipase C inhibitor U-73122, by blocking the IP3 receptor with pentosan polysulfate or heparin, and by buffering intracellular calcium, and it was occluded by allowing IP3 to diffuse into the cytoplasm via a patch pipette. By contrast, the muscarinic pathway was not disrupted by any of these treatments. The addition of bradykinin was accompanied by a [Ca2+]i rise with a similar onset and time to peak as the inhibition of M current. The M current inhibition and the rise of [Ca2+]i were blocked by depletion of Ca2+ internal stores by thapsigargin. We conclude that bradykinin receptors inhibit M current of sympathetic neurons by activating phospholipase C and releasing Ca2+ from IP3-sensitive Ca2+ stores, whereas muscarinic receptors do not use the phospholipase C pathway to inhibit M current channels.

β-Neuregulin-1 is required for the in vivo development of functional Ca2+-activated K+ channels in parasympathetic neurons

The development of functional Ca2+-activated K+ channels (KCa) in chick ciliary ganglion (CG) neurons requires interactions with afferent preganglionic nerve terminals. Here we show that the essential preganglionic differentiation factor is an isoform of β-neuregulin-1. β-Neuregulin-1 transcripts are expressed in the midbrain preganglionic Edinger–Westphal nucleus at developmental stages that coincide with or precede the normal onset of macroscopic KCa in CG neurons. Injection of β-neuregulin-1 peptide into the brains of developing embryos evoked a robust stimulation of functional KCa channels at stages before the normal appearance of these channels in CG neurons developing in vivo. Conversely, injection of a neutralizing antiserum specific for β-neuregulin-1 inhibited the development of KCa channels in CG neurons. Low concentrations of β-neuregulin-1 evoked a robust increase in whole-cell KCa in CG neurons cocultured with iris target tissues. By contrast, culturing CG neurons with iris cells or low concentrations of β-neuregulin-1 by themselves was insufficient to stimulate KCa. These data suggest that the preganglionic factor required for the development of KCa in ciliary ganglion neurons is an isoform of β-neuregulin-1, and that this factor acts in concert with target-derived trophic molecules to regulate the differentiation of excitability.

β-Amyloid peptide blocks the response of α7-containing nicotinic receptors on hippocampal neurons

Alzheimer's disease produces a devastating decline in mental function, with profound effects on learning and memory. Early consequences of the disease include the specific loss of cholinergic neurons in brain, diminished cholinergic signaling, and the accumulation of β-amyloid peptide in neuritic plaques. Of the nicotinic acetylcholine receptors at risk, the most critical may be those containing the α7 gene product (α7-nAChRs), because they are widespread, have a high relative permeability to calcium, and regulate numerous cellular events in the nervous system. With the use of whole-cell patch–clamp recording we show here that nanomolar concentrations of β-amyloid peptides specifically and reversibly block α7-nAChRs on rat hippocampal neurons in culture. The block is noncompetitive, voltage-independent, and use-independent and is mediated through the N-terminal extracellular domain of the receptor. It does not appear to require either calcium influx or G protein activation. β-Amyloid blockade is likely to be a common feature of α7-nAChRs because it applies to the receptors at both somato-dendritic and presynaptic locations on rat hippocampal neurons and extends to homologous receptors on chick ciliary ganglion neurons as well. Because α7-nAChRs in the central nervous system are thought to have numerous functions and recently have been implicated in learning and memory, impaired receptor function in this case may contribute to cognitive deficits associated with Alzheimer's disease.

DEG/ENaC ion channels involved in sensory transduction are modulated by cold temperature

Several DEG/ENaC cation channel subunits are expressed in the tongue and in cutaneous sensory neurons, where they are postulated to function as receptors for salt and sour taste and for touch. Because these tissues are exposed to large temperature variations, we examined how temperature affects DEG/ENaC channel function. We found that cold temperature markedly increased the constitutively active Na+ currents generated by epithelial Na+ channels (ENaC). Half-maximal stimulation occurred at 25°C. Cold temperature did not induce current from other DEG/ENaC family members (BNC1, ASIC, and DRASIC). However, when these channels were activated by acid, cold temperature potentiated the currents by slowing the rate of desensitization. Potentiation was abolished by a “Deg” mutation that alters channel gating. Temperature changes in the physiologic range had prominent effects on current in cells heterologously expressing acid-gated DEG/ENaC channels, as well as in dorsal root ganglion sensory neurons. The finding that cold temperature modulates DEG/ENaC channel function may provide a molecular explanation for the widely recognized ability of temperature to modify taste sensation and mechanosensation.