This article has Open Peer Review reports available.
Differential expression of the capsaicin receptor TRPV1 and related novel receptors TRPV3, TRPV4 and TRPM8 in normal human tissues and changes in traumatic and diabetic neuropathy
© Facer et al; licensee BioMed Central Ltd. 2007
Received: 07 November 2006
Accepted: 23 May 2007
Published: 23 May 2007
Transient receptor potential (TRP) receptors expressed by primary sensory neurons mediate thermosensitivity, and may play a role in sensory pathophysiology. We previously reported that human dorsal root ganglion (DRG) sensory neurons co-expressed TRPV1 and TRPV3, and that these were increased in injured human DRG. Related receptors TRPV4, activated by warmth and eicosanoids, and TRPM8, activated by cool and menthol, have been characterised in pre-clinical models. However, the role of TRPs in common clinical sensory neuropathies needs to be established.
We have studied TRPV1, TRPV3, TRPV4, and TRPM8 in nerves (n = 14) and skin from patients with nerve injury, avulsed dorsal root ganglia (DRG) (n = 11), injured spinal nerve roots (n = 9), diabetic neuropathy skin (n = 8), non-diabetic neuropathic nerve biopsies (n = 6), their respective control tissues, and human post mortem spinal cord, using immunohistological methods.
TRPV1 and TRPV3 were significantly increased in injured brachial plexus nerves, and TRPV1 in hypersensitive skin after nerve repair, whilst TRPV4 was unchanged. TRPM8 was detected in a few medium diameter DRG neurons, and was unchanged in DRG after avulsion injury, but was reduced in axons and myelin in injured nerves. In diabetic neuropathy skin, TRPV1 expressing sub- and intra-epidermal fibres were decreased, as was expression in surviving fibres. TRPV1 was also decreased in non-diabetic neuropathic nerves. Immunoreactivity for TRPV3 was detected in basal keratinocytes, with a significant decrease of TRPV3 in diabetic skin. TRPV1-immunoreactive nerves were present in injured dorsal spinal roots and dorsal horn of control spinal cord, but not in ventral roots, while TRPV3 and TRPV4 were detected in spinal cord motor neurons.
The accumulation of TRPV1 and TRPV3 in peripheral nerves after injury, in spared axons, matches our previously reported changes in avulsed DRG. Reduction of TRPV1 levels in nerve fibres in diabetic neuropathy skin may result from the known decrease of nerve growth factor (NGF) levels. The role of TRPs in keratinocytes is unknown, but a relationship to changes in NGF levels, which is produced by keratinocytes, deserves investigation. TRPV1 represents a more selective therapeutic target than other TRPs for pain and hypersensitivity, particularly in post-traumatic neuropathy.
The cloning of the vanilloid receptor-1 (TRPV1) [1, 2] has led to greater understanding of the mechanisms of thermosensation and the effects of capsaicin, the noxious component from chilli peppers. TRPV1 is a non-selective, cation channel activated by capsaicin and heat (42°C or greater), and is a member of the transient receptor potential (TRP) family of temperature sensitive ion channels. Thermal sensations and pain are detected via sub-sets of neurons which are activated within distinct temperature ranges, from cool (<25°C – 28°C – TRPM8 ), warm (>27°C – 38°C – TRPV3[4, 5] and TRPV4 [6, 7] to noxious/painful heat (>43°C – 52°C – TRPV2  and TRPV1[1, 2]) and cold (<17°C -TRPA1) sensations[3, 9, 10].
Studies of TRPV1 in animal models have revealed its role in heat and pain mechanisms [11, 12]. Subsequent studies indicated that it may not act as the only receptor for heat  especially since the response of neurons to heat and capsaicin are not always identical . Searches of the GenBank nucleotide databank revealed an unfinished human sequence homologous to TRPV1, which has since been identified as a temperature-sensitive but capsaicin and pH insensitive, vanilloid receptor-like protein nominated as TRPV3 [4, 5]. Although vanilloid receptors are known to exist and function as homomers [15, 16], some evidence has been provided for the biochemical association of TRPV3 and TRPV1 suggesting heteromerization , thus allowing a greater range of receptor characteristics. In addition to its co-localization with TRPV1 in small/medium diameter sensory neurons of the dorsal root ganglion (DRG), the number of both TRPV3- and TRPV1- immunoreactive sensory neurons increased significantly after DRG avulsion injury i.e. central axotomy . In genetically modified mice lacking the TRPV1 receptor, thermal hyperalgesia was impaired . In animal models of nerve injury, TRPV1 mRNA was reported to be down-regulated after axotomy  but up-regulated in spared nerve fibres . Other studies have demonstrated changes in the molecular phenotype of undamaged neurons in neuropathic pain models of nerve ligation. In the Seltzer model, where undamaged afferents may be identified by retrograde labelling, the expression of the neuropeptides substance P and galanin, both known nociceptive mediators, as well as mRNA for the sodium channel SNS, increased in the somata of undamaged fibres [21–23].
Relatively little is known of vanilloid receptors in human nerve injury and skin, and their relationship to pain or hypersensitivity. Nerve injury-induced alterations of sodium channel density and distribution is thought to contribute to pain by generation of ectopic discharges from the neuroma or DRG . Previous studies of injured human nerves have shown that some sodium channel subunits accumulate in proximal nerve stumps  and neuromata  while others can be switched on  thus contributing to changes in membrane excitability and/or pain. Peripheral nerve injury in humans may lead to changes in skin sensitivity depending upon the level at which injury is sustained and its severity. Numbness, hypo- or hyper-algesia and allodynia are common symptoms, sometimes in combination, which may arise over many years following injury or surgical repair. Such variability in sensation is due to processes of nerve regeneration and re-innervation of the skin, and may lead to such phenomena as paradoxical sensation (burning sensation on cooling the skin). Phenotypic change of primary afferents with respect to expression of TRPs may be one possible explanation for some of these symptoms and signs.
TRPV3 and TRPV1 are present not only in DRG sensory neurons but also in various regions of the central nervous system and non-neuronal tissue [5, 27]. TRPV3, for example, has been detected in rodent keratinocytes . In addition, TRPV1-immunoreactivity has been shown to be present in cultured keratinocytes where its activation by capsaicin induces the production of pro-inflammatory mediators such as COX-2, IL-8 and PGE-2 [29, 30]. The presence of vanilloid receptors in keratinocytes thus provides a potential for keratinocyte/nerve interaction , but these findings and their physiological relevance remain controversial. Basal and supra-basal keratinocytes also produce the neurotrophins NGF and NT-3 respectively [31, 32] and TRPV1 is known to be regulated by neurotrophins, i.e. NGF and GDNF [33–38]. Evaluation of epidermal innervation has proven to be helpful for the assessment of diabetic and other small fibre neuropathies, where innervation has been related to sensory changes [31, 39–43]. In an animal model of diabetes, thermal allodynia and hyperalgesia were associated with sensitisation of TRPV1 receptors in spinal cord .
TRPV4 is a nonselective cation channel, first described as an osmosensor , whose opening seems to result from tyrosine kinase-dependent phosphorylation . It is activated at temperatures above 27°C and expressed and functions as an osmosensor in rodent nociceptors . Two further, temperature sensitive, ion channels TRPM8 and TRPA1 are localised in sensory neurons and are sensitive to cool/cold temperatures < 25–28°C for TRPM8 and < 17°C for TRPA1 [3, 5, 9].
The aim of the present study was to investigate the distribution of the vanilloid receptors TRPV1, TRPV3, TRPV4, and TRPM8 in normal and injured human peripheral nerves and spinal nerve roots and in normal and neuropathic (painful neuroma and diabetes) skin and spinal cord,
Specimens of injured nerve (proximal to site of injury) and dorsal root ganglion (DRG) were obtained during surgery for brachial plexus repair. Specimens were sub-divided according to the delay between date of injury and tissue collection at surgery, where acute was defined as less than 3 weeks delay (acute nerves: n = 6; male 5; age range 14 – 34 y; chronic: n = 8; male 5; age range 15 – 43 y; and acute DRG: n = 5; male 4; age range 18 – 50 y; chronic DRG: n = 6; male 6; age range 18 – 30 y). Control nerves (n = 8; male 6; age range 36 – 81 y) were obtained during routine surgery for limb amputation or similar procedures, and control DRG (n = 8; male 3; age range 41 – 98 yr) obtained via the Netherlands Brain Bank with less than 12 h post-mortem delay. Dorsal and ventral pairs of injured (root avulsion) spinal nerve roots were obtained also during brachial plexus repair (n = 9, 4 acute and 5 chronic; male 8; age range 22 – 47 y). Neuropathic, sural nerve biopsies (n = 6; 4 male; age range 49 – 71 yr) were obtained from patients with neuropathies, including demyelinating and polyneuropathies. Control, human spinal cords (n = 2; male 1; age 60 and 64 y), with small attached nerve roots, were obtained after less than 12 h post-mortem delay via the Netherlands Brain Bank. Normal, hyper- and hypo-sensitive skin and painful neuroma samples were collected from the amputated arm of a patient who had a brachial plexus injury with subsequent repair 8 years previously (n = 1; male, age 46 y);. Full thickness, lateral calf skin biopsies were obtained from diabetic patients (n = 8; male 8; age range 36–65 y) under local anaesthetic, and control calf skin biopsies were obtained from patients undergoing harvest of intact sural nerve for brachial plexus repair, or therapeutic elective limb amputation for a non-neurological condition (n = 8; male 5; age range 33–71 y). Skin samples were obtained from excised, supernumerary human digits (n = 2). Fully informed consent was obtained for all tissues collected, with approval of the Local Ethics Committees.
GSK, Harlow, UK.
GSK, Harlow, UK.
GSK, Harlow, UK.
GSK, Harlow, UK.
Phoenix Pharmaceuticals, Belmont, CA, USA
Novocastra, Newcastle, UK
Dako Cytomation, Cambs. UK
Computerized image analysis was used (Seescan Cambridge, UK) to quantify immunoreactive nerve fibres. Images were captured via video link to an Olympus BX50 microscope (x20 objective) and scanned by the computer. Three to five fields from two tissue sections were analysed where positive immunostaining was highlighted by setting grey-level detection limits at threshold and the area of highlighted fibres obtained as percentage area of the field scanned.
The size (small/medium or large diameter) and number of nucleated sensory neurons for each DRG section were assessed using a calibrated microscope eyepiece graticule and the number of positive TRPV4 cells expressed as % of total neurons for each DRG sample.
The intensity of immunoreaction for TRPV3 or TRPV4 in basal keratinocytes was graded by two independent observers on an arbitrary scale from negative (0) to maximum (3). TRPV1-, neurofilament- and PPN- immunoreactive sub-epidermal fibres were counted for each section and the length of epidermis measured using a microscope eyepiece graticule.
All statistical analysis used non-parametric Mann-Whitney t test.
A summary of results obtained in the tissues examined are presented in tabular form (Table 2).
Increased (brachial plexus)
Increased (brachial plexus)
Decreased (see Smith et al 2002)
Decreased (see Smith et al 2002)
Positive Unchanged Co-localise with TRPV1/TRPV3
Decreased fibres Negative keratinocytes
Nerve fibres not detected Trend for decreased keratinocytes
Positive fibres – very few
Positive fibres Decreased
Positive dorsal horn
Positive motor neurones
Positive weak motor neurones
Weak fibres in dorsal horn and roots
Nerve roots and spinal cord
TRPV4 was present in injured roots, both dorsal and ventral (Fig 6B), but was weak in motor neurons and fibres in the ventral horns. There was no significant staining in the dorsal horns.
Four out of 9 samples showed strong TRPV3-immunoreactivity in motor neurones and fibres in the ventral horn of the spinal cord (Fig 6C). In these positive samples, counts of TRPV3 motor neurones were 33% of total. In accord, there was strong TRPV3 immunoreactivity, mostly in large calibre fibres, in ventral (Fig 6D) but not dorsal spinal roots. TRPV3 immunoreactivity in the ventral roots was largely lost three to four weeks following injury.
Diabetic neuropathy skin
TRPV1-immunoreactive fibres were detected in distal peripheral nerve and were present in fine fibres in control skin up to and including the epidermis, whilst TRPV3-immunoreactivity in fibres was relatively weak in the nerve trunk and undetectable at the skin level but was present in basal keratinocytes (see below).
Few TRPV4-immunopositive nerve fibres were detected in skin samples. Positive but patchy immunostaining of TRPV4 basal keratinocytes was observed (Fig 8E). Sub-epidermal fibres were detected using antibodies to peripherin (PPN; Fig 8F)
As described above, antibodies to TRPM8 showed strong large calibre and weak fine calibre fibre bundles up to the sub-epidermal layer. TRPM8 immunoreactivity was not detected in keratinocytes.
The TRP family appears to have differential expression in the peripheral nervous system, and specific changes in peripheral neuropathies.
In this study we have described, to our knowledge for the first time, the presence of TRPV4 and TRPM8 in human sensory neurons. TRPV4 expression was not specific for any neuronal subtype in DRG and did not appear to be affected by injury in either DRG or peripheral nerves. The wide distribution of TRPV4 in both small and large neurons matches observations in mice . The distribution of TRPM8 was confined to a small proportion of small/medium neurons. TRPM8 immunoreactive large calibre fibres with clear nodes of Ranvier were observed, suggesting labelling of Schwann cells-myelin in addition to fine weak fibres, as also observed by us in tooth pulp (unpublished observations). Small dot-like structures in the tissue surrounding the sensory neurons, apparent with antibodies in Figure 1 probably represents immunoreactivity in nerve fibres cut transverse to the plane of the sections. TRPM8 mRNA has been shown to be localised mainly in A- delta fibres/C-fibres in rat primary afferent neurones . In rodents, TRPM8 and the cold activated receptor TRPA1 are also detected in sub-populations of small neurons. In mouse DRG, TRPM8 mRNA does not co-express with many of the classical markers of nociception including TRPV1. However, TRPA1 is found in nociceptive sensory neurons in DRG and colocalises with TRPV1, CGRP and SP but not with TRPM8 in rat [9, 47]. Co-expression of TRPA1 with TRPV1 could explain the paradoxical heat sensation which may be experienced on exposure to a very cold stimulus.
We have shown previously and confirmed in this study that TRPV1 and TRPV3 were present in human DRG neurons, mostly of small/medium diameter, and that the number of positive cells increased after DRG avulsion injury .
Roots and Spinal Cord
There was a clear difference in the distribution of TRPV3 and TRPV1 in spinal nerve roots. TRPV3 was present in ventral but not dorsal roots, in contrast, TRPV1 was present in dorsal but negligible in ventral roots.
The strong immunoreactivity for TRPV3 in adult human motor neurons and ventral roots correlates well with studies in monkeys showing TRPV3 m-RNA in motor neurons and other neuronal elements . Accordingly, we found strong TRPV3 immunoreactivity in motor neurons in adult rat (data not shown). The TRPV3-immunoreactive, large calibre fibres seen in control and acutely injured ventral spinal roots almost disappear after chronic injury. The weak TRPV3 immunoreactivity in dorsal roots is consistent with a preferential transport peripherally rather than centrally. It cannot be excluded that these observations reflect a difference in levels of TRPV3 protein or quality of the antibody.
TRPV1 immunoreactivity was not detected in ventral roots, which may be expected as it was not detected in motor neurons. In rats, TRPV1 has been shown to be transported from the DRG neurons both peripherally and centrally to laminae I and II of the spinal cord via the dorsal root . In accord with this, we have shown that TRPV1 is present in spinal dorsal roots.
Peripheral nerve-brachial plexus injury
In this study we have shown that both TRPV3 and TRPV1 are increased in peripheral nerve proximal to the site of injury in accord with our previous study of human DRG, . The increase in injured nerves indicates that these receptors continue to be exported from the ganglion and/or accumulate in the nerve proximal to injury, despite overall reduced support from peripheral trophic factors e.g. NGF/GDNF. An increased availability of trophic factors to spared nerve fibres may be similar to the finding in an animal model of partial nerve injury. In this model it was suggested that undamaged fibres obtain more neurotrophin made available because of the reduced uptake by damaged fibres . The increased TRPV receptors immunostaining seen in our study, in combination with the presence of regenerating fibres, may be particularly relevant for the development and persistence of pain. In addition, inflammatory mediators and neurotrophins derived from damaged Schwann cells or infiltrating macrophages at the injury site may contribute to enhance the production of vanilloid receptors [51–54].
The abundance of TRPV1 fibres in painful, hypersensitive skin relative to normal skin correlates well with the TRPV1 involvement in mechanisms of pain and hyperalgesia in a similar fashion to that described in injured nerve above. Corroborative evidence for the involvement of TRPV1-immunoreactive nerves in painful skin is shown in our recent work in vulvodynia and breast pain [38, 55]. The lack of detection of TRPV3 immunoreactive fibres in skin may be similar to that described for dorsal roots.
Peripheral neuropathic nerves
There was a clear decrease in the expression of TRPV1 in neuropathic nerves compared to controls. The cases were different, from distal axonal to demyelinating neuropathy. In all cases histology showed a decrease of nerve fibres and/or axonal atrophy.
Skin and diabetic neuropathy
We have shown that TRPV3 is present in human keratinocytes, which is consistent with the report of TRPV3 in rodent keratinocytes . Our report that TRPV1 and TRPV3 co-localize in human DRG suggested co-expression but we were unable to detect TRPV1 in human keratinocytes despite several reports describing TRPV1 in keratinocytes and other non-neuronal cells [29, 30, 56–59]. However these studies were performed in cultured keratinocytes and TRPV1 expression could therefore be a consequence of culture conditions. Alternatively, the lack of TRPV1 immunoreactivity in keratinocytes in the present study could reflect low level of expression or receptor conformational changes preventing antigen-antibody recognition.
Diabetic epidermis is known to be abnormally thin, so the trend we describe for decrease of TRPV3 in keratinocytes, may be related to changes of neurotrophins or other factors controlling skin differentiation and TRPV3 expression. Functional properties of vanilloid receptors in keratinocytes have been suggested to involve novel properties of transduction between the basal keratinocytes and sub-epidermal/epidermal nerve endings  or exocytosis of epidermal lamellar bodies, which is regulated by calcium influx . A functional role for vanilloid receptors in keratinocytes remains unclear.
In the present study, we have demonstrated that TRPV1 is decreased in both intra- and sub-epidermal fibres in diabetes resulting in the hypo-sensitivity typical of diabetic neuropathy. Similar results for intra-epidermal fibres have been shown in human diabetic skin using the pan-neuronal marker PGP-9.5  whilst others have shown no change of TRPV1. The observed decrease of TRPV1 may have been due simply to an overall reduction of innervation, a common feature of diabetes. To address this we used a neuronal marker for quantification of total innervation to normalise values. Ideally, antibodies to the pan-neuronal marker PGP-9.5 would have been used but these are not optimal on post-fixed tissue. Instead, comparisons were made using the nerve markers neurofilament and peripherin, which do not detect epidermal fibres, thus limiting our normalised analysis to sub-epidermal fibres. The density of TRPV1 sub-epidermal fibres was still clearly decreased in diabetic skin after normalisation with either of the above neuronal markers. In addition to a loss of fibres, our results therefore suggest that TRPV1 is down-regulated in remaining fibres.
Vanilloid receptors are differentially regulated after nerve injury and in diabetic neuropathy. A change of expression and regulation of vanilloid receptors may play a role in sensory dysfunction, related to states of hyper/hypo-algesia. TRPV1 represents a more selective target than TRPV3 for pain, particularly for post-traumatic chronic hypersensitivity states.
- Caterina MJ, Schumacher MA, Tominaga M, Rosen TA, Levine JD, Julius D: The capsaicin receptor: a heat-activated ion channel in the pain pathway. Nature. 1997, 389 (6653): 816-824. 10.1038/39807.View ArticlePubMedGoogle Scholar
- Hayes P, Meadows HJ, Gunthorpe MJ, Harries MH, Duckworth DM, Cairns W, Harrison DC, Clarke CE, Ellington K, Prinjha RK, Barton AJ, Medhurst AD, Smith GD, Topp S, Murdock P, Sanger GJ, Terrett J, Jenkins O, Benham CD, Randall AD, Gloger IS, Davis JB: Cloning and functional expression of a human orthologue of rat vanilloid receptor-1. Pain. 2000, 88 (2): 205-215. 10.1016/S0304-3959(00)00353-5.View ArticlePubMedGoogle Scholar
- McKemy DD, Neuhausser WM, Julius D: Identification of a cold receptor reveals a general role for TRP channels in thermosensation. Nature. 2002, 416 (6876): 52-58. 10.1038/nature719.View ArticlePubMedGoogle Scholar
- Smith GD, Gunthorpe MJ, Kelsell RE, Hayes PD, Reilly P, Facer P, Wright JE, Jerman JC, Walhin JP, Ooi L, Egerton J, Charles KJ, Smart D, Randall AD, Anand P, Davis JB: TRPV3 is a temperature-sensitive vanilloid receptor-like protein. Nature. 2002, 418 (6894): 186-190. 10.1038/nature00894.View ArticlePubMedGoogle Scholar
- Xu H, Ramsey IS, Kotecha SA, Moran MM, Chong JA, Lawson D, Ge P, Lilly J, Silos-Santiago I, Xie Y, DiStefano PS, Curtis R, Clapham DE: TRPV3 is a calcium-permeable temperature-sensitive cation channel. Nature. 2002, 418 (6894): 181-186. 10.1038/nature00882.View ArticlePubMedGoogle Scholar
- Liedtke W, Choe Y, Marti-Renom MA, Bell AM, Denis CS, Sali A, Hudspeth AJ, Friedman JM, Heller S: Vanilloid receptor-related osmotically activated channel (VR-OAC), a candidate vertebrate osmoreceptor. Cell. 2000, 103 (3): 525-535. 10.1016/S0092-8674(00)00143-4.View ArticlePubMedPubMed CentralGoogle Scholar
- Strotmann R, Harteneck C, Nunnenmacher K, Schultz G, Plant TD: OTRPC4, a nonselective cation channel that confers sensitivity to extracellular osmolarity. Nat Cell Biol. 2000, 2 (10): 695-702. 10.1038/35036318.View ArticlePubMedGoogle Scholar
- Caterina MJ, Rosen TA, Tominaga M, Brake AJ, Julius D: A capsaicin-receptor homologue with a high threshold for noxious heat. Nature. 1999, 398 (6726): 436-441. 10.1038/18906.View ArticlePubMedGoogle Scholar
- Story GM, Peier AM, Reeve AJ, Eid SR, Mosbacher J, Hricik TR, Earley TJ, Hergarden AC, Andersson DA, Hwang SW, McIntyre P, Jegla T, Bevan S, Patapoutian A: ANKTM1, a TRP-like channel expressed in nociceptive neurons, is activated by cold temperatures. Cell. 2003, 112 (6): 819-829. 10.1016/S0092-8674(03)00158-2.View ArticlePubMedGoogle Scholar
- Tominaga M, Caterina MJ: Thermosensation and pain. J Neurobiol. 2004, 61 (1): 3-12. 10.1002/neu.20079.View ArticlePubMedGoogle Scholar
- Winter J, Bevan S, Campbell EA: Capsaicin and pain mechanisms. Br J Anaesth. 1995, 75 (2): 157-168.View ArticlePubMedGoogle Scholar
- Tominaga M, Caterina MJ, Malmberg AB, Rosen TA, Gilbert H, Skinner K, Raumann BE, Basbaum AI, Julius D: The cloned capsaicin receptor integrates multiple pain-producing stimuli. Neuron. 1998, 21 (3): 531-543. 10.1016/S0896-6273(00)80564-4.View ArticlePubMedGoogle Scholar
- Davis JB, Gray J, Gunthorpe MJ, Hatcher JP, Davey PT, Overend P, Harries MH, Latcham J, Clapham C, Atkinson K, Hughes SA, Rance K, Grau E, Harper AJ, Pugh PL, Rogers DC, Bingham S, Randall A, Sheardown SA: Vanilloid receptor-1 is essential for inflammatory thermal hyperalgesia. Nature. 2000, 405 (6783): 183-187. 10.1038/35012076.View ArticlePubMedGoogle Scholar
- Nagy I, De Mot R: Sequence analysis of the oxidase/reductase genes upstream of the Rhodococcus erythropolis aldehyde dehydrogenase gene thcA reveals a gene organisation different from Mycobacterium tuberculosis. DNA Seq. 1999, 10 (1): 61-66.View ArticlePubMedGoogle Scholar
- Szallasi A, Blumberg PM: Vanilloid (Capsaicin) receptors and mechanisms. Pharmacol Rev. 1999, 51 (2): 159-212.PubMedGoogle Scholar
- Kedei N, Szabo T, Lile JD, Treanor JJ, Olah Z, Iadarola MJ, Blumberg PM: Analysis of the native quaternary structure of vanilloid receptor 1. J Biol Chem. 2001, 276 (30): 28613-28619. 10.1074/jbc.M103272200.View ArticlePubMedGoogle Scholar
- Gunthorpe MJ, Benham CD, Randall A, Davis JB: The diversity in the vanilloid (TRPV) receptor family of ion channels. Trends Pharmacol Sci. 2002, 23 (4): 183-191. 10.1016/S0165-6147(02)01999-5.View ArticlePubMedGoogle Scholar
- Caterina MJ, Leffler A, Malmberg AB, Martin WJ, Trafton J, Petersen-Zeitz KR, Koltzenburg M, Basbaum AI, Julius D: Impaired nociception and pain sensation in mice lacking the capsaicin receptor. Science. 2000, 288 (5464): 306-313. 10.1126/science.288.5464.306.View ArticlePubMedGoogle Scholar
- Michael GJ, Priestley JV: Differential expression of the mRNA for the vanilloid receptor subtype 1 in cells of the adult rat dorsal root and nodose ganglia and its downregulation by axotomy. J Neurosci. 1999, 19 (5): 1844-1854.PubMedGoogle Scholar
- Hudson LJ, Bevan S, Wotherspoon G, Gentry C, Fox A, Winter J: VR1 protein expression increases in undamaged DRG neurons after partial nerve injury. Eur J Neurosci. 2001, 13 (11): 2105-2114. 10.1046/j.0953-816x.2001.01591.x.View ArticlePubMedGoogle Scholar
- Ma W, Bisby MA: Differential expression of galanin immunoreactivities in the primary sensory neurons following partial and complete sciatic nerve injuries. Neuroscience. 1997, 79 (4): 1183-1195. 10.1016/S0306-4522(97)00088-2.View ArticlePubMedGoogle Scholar
- Ma W, Bisby MA: Increase of preprotachykinin mRNA and substance P immunoreactivity in spared dorsal root ganglion neurons following partial sciatic nerve injury. Eur J Neurosci. 1998, 10 (7): 2388-2399. 10.1046/j.1460-9568.1998.00249.x.View ArticlePubMedGoogle Scholar
- Porreca F, Lai J, Bian D, Wegert S, Ossipov MH, Eglen RM, Kassotakis L, Novakovic S, Rabert DK, Sangameswaran L, Hunter JC: A comparison of the potential role of the tetrodotoxin-insensitive sodium channels, PN3/SNS and NaN/SNS2, in rat models of chronic pain. Proc Natl Acad Sci U S A. 1999, 96 (14): 7640-7644. 10.1073/pnas.96.14.7640.View ArticlePubMedPubMed CentralGoogle Scholar
- Waxman SG, Kocsis JD, Black JA: Type III sodium channel mRNA is expressed in embryonic but not adult spinal sensory neurons, and is reexpressed following axotomy. J Neurophysiol. 1994, 72 (1): 466-470.PubMedPubMed CentralGoogle Scholar
- Coward K, Plumpton C, Facer P, Birch R, Carlstedt T, Tate S, Bountra C, Anand P: Immunolocalization of SNS/PN3 and NaN/SNS2 sodium channels in human pain states. Pain. 2000, 85 (1-2): 41-50. 10.1016/S0304-3959(99)00251-1.View ArticlePubMedGoogle Scholar
- England JD, Happel LT, Kline DG, Gamboni F, Thouron CL, Liu ZP, Levinson SR: Sodium channel accumulation in humans with painful neuromas. Neurology. 1996, 47 (1): 272-276.View ArticlePubMedGoogle Scholar
- Mezey E, Toth ZE, Cortright DN, Arzubi MK, Krause JE, Elde R, Guo A, Blumberg PM, Szallasi A: Distribution of mRNA for vanilloid receptor subtype 1 (VR1), and VR1-like immunoreactivity, in the central nervous system of the rat and human. Proc Natl Acad Sci U S A. 2000, 97 (7): 3655-3660. 10.1073/pnas.060496197.View ArticlePubMedPubMed CentralGoogle Scholar
- Peier AM, Reeve AJ, Andersson DA, Moqrich A, Earley TJ, Hergarden AC, Story GM, Colley S, Hogenesch JB, McIntyre P, Bevan S, Patapoutian A: A heat-sensitive TRP channel expressed in keratinocytes. Science. 2002, 296 (5575): 2046-2049. 10.1126/science.1073140.View ArticlePubMedGoogle Scholar
- Inoue K, Koizumi S, Fuziwara S, Denda S, Denda M: Functional vanilloid receptors in cultured normal human epidermal keratinocytes. Biochem Biophys Res Commun. 2002, 291 (1): 124-129. 10.1006/bbrc.2002.6393.View ArticlePubMedGoogle Scholar
- Southall MD, Li T, Gharibova LS, Pei Y, Nicol GD, Travers JB: Activation of epidermal vanilloid receptor-1 induces release of proinflammatory mediators in human keratinocytes. J Pharmacol Exp Ther. 2003, 304 (1): 217-222. 10.1124/jpet.102.040675.View ArticlePubMedGoogle Scholar
- Anand P, Terenghi G, Warner G, Kopelman P, Williams-Chestnut RE, Sinicropi DV: The role of endogenous nerve growth factor in human diabetic neuropathy. Nat Med. 1996, 2 (6): 703-707. 10.1038/nm0696-703.View ArticlePubMedGoogle Scholar
- Kennedy AJ, Wellmer A, Facer P, Saldanha G, Kopelman P, Lindsay RM, Anand P: Neurotrophin-3 is increased in skin in human diabetic neuropathy. J Neurol Neurosurg Psychiatry. 1998, 65 (3): 393-395.View ArticlePubMedPubMed CentralGoogle Scholar
- Winter J, Forbes CA, Sternberg J, Lindsay RM: Nerve growth factor (NGF) regulates adult rat cultured dorsal root ganglion neuron responses to the excitotoxin capsaicin. Neuron. 1988, 1 (10): 973-981. 10.1016/0896-6273(88)90154-7.View ArticlePubMedGoogle Scholar
- Ogun-Muyiwa P, Helliwell R, McIntyre P, Winter J: Glial cell line derived neurotrophic factor (GDNF) regulates VR1 and substance P in cultured sensory neurons. Neuroreport. 1999, 10 (10): 2107-2111. 10.1097/00001756-199907130-00021.View ArticlePubMedGoogle Scholar
- Ramer MS, Priestley JV, McMahon SB: Functional regeneration of sensory axons into the adult spinal cord. Nature. 2000, 403 (6767): 312-316. 10.1038/35002084.View ArticlePubMedGoogle Scholar
- Priestley JV, Michael GJ, Averill S, Liu M, Willmott N: Regulation of nociceptive neurons by nerve growth factor and glial cell line derived neurotrophic factor. Can J Physiol Pharmacol. 2002, 80 (5): 495-505. 10.1139/y02-034.View ArticlePubMedGoogle Scholar
- Anand U, Otto WR, Casula MA, Day NC, Davis JB, Bountra C, Birch R, Anand P: The effect of neurotrophic factors on morphology, TRPV1 expression and capsaicin responses of cultured human DRG sensory neurons. Neurosci Lett. 2006, 399 (1-2): 51-56. 10.1016/j.neulet.2006.01.046.View ArticlePubMedGoogle Scholar
- Tympanidis P, Casula MA, Yiangou Y, Terenghi G, Dowd P, Anand P: Increased vanilloid receptor VR1 innervation in vulvodynia. Eur J Pain. 2004, 8 (2): 129-133. 10.1016/S1090-3801(03)00085-5.View ArticlePubMedGoogle Scholar
- Kennedy WR, Wendelschafer-Crabb G, Johnson T: Quantitation of epidermal nerves in diabetic neuropathy. Neurology. 1996, 47 (4): 1042-1048.View ArticlePubMedGoogle Scholar
- Lauria G, McArthur JC, Hauer PE, Griffin JW, Cornblath DR: Neuropathological alterations in diabetic truncal neuropathy: evaluation by skin biopsy. J Neurol Neurosurg Psychiatry. 1998, 65 (5): 762-766.View ArticlePubMedPubMed CentralGoogle Scholar
- Kennedy WR, Said G: Sensory nerves in skin: answers about painful feet?. Neurology. 1999, 53 (8): 1614-1615.View ArticlePubMedGoogle Scholar
- Periquet MI, Novak V, Collins MP, Nagaraja HN, Erdem S, Nash SM, Freimer ML, Sahenk Z, Kissel JT, Mendell JR: Painful sensory neuropathy: prospective evaluation using skin biopsy. Neurology. 1999, 53 (8): 1641-1647.View ArticlePubMedGoogle Scholar
- Anand P: Nerve growth factor regulates nociception in human health and disease. Br J Anaesth. 1995, 75 (2): 201-208.View ArticlePubMedGoogle Scholar
- Kamei J, Zushida K, Morita K, Sasaki M, Tanaka S: Role of vanilloid VR1 receptor in thermal allodynia and hyperalgesia in diabetic mice. Eur J Pharmacol. 2001, 422 (1-3): 83-86. 10.1016/S0014-2999(01)01059-7.View ArticlePubMedGoogle Scholar
- Alessandri-Haber N, Yeh JJ, Boyd AE, Parada CA, Chen X, Reichling DB, Levine JD: Hypotonicity induces TRPV4-mediated nociception in rat. Neuron. 2003, 39 (3): 497-511. 10.1016/S0896-6273(03)00462-8.View ArticlePubMedGoogle Scholar
- Shu SY, Ju G, Fan LZ: The glucose oxidase-DAB-nickel method in peroxidase histochemistry of the nervous system. Neurosci Lett. 1988, 85 (2): 169-171. 10.1016/0304-3940(88)90346-1.View ArticlePubMedGoogle Scholar
- Suzuki M, Watanabe Y, Oyama Y, Mizuno A, Kusano E, Hirao A, Ookawara S: Localization of mechanosensitive channel TRPV4 in mouse skin. Neurosci Lett. 2003, 353 (3): 189-192. 10.1016/j.neulet.2003.09.041.View ArticlePubMedGoogle Scholar
- Kobayashi K, Fukuoka T, Obata K, Yamanaka H, Dai Y, Tokunaga A, Noguchi K: Distinct expression of TRPM8, TRPA1, and TRPV1 mRNAs in rat primary afferent neurons with adelta/c-fibers and colocalization with trk receptors. J Comp Neurol. 2005, 493 (4): 596-606. 10.1002/cne.20794.View ArticlePubMedGoogle Scholar
- Peier AM, Moqrich A, Hergarden AC, Reeve AJ, Andersson DA, Story GM, Earley TJ, Dragoni I, McIntyre P, Bevan S, Patapoutian A: A TRP channel that senses cold stimuli and menthol. Cell. 2002, 108 (5): 705-715. 10.1016/S0092-8674(02)00652-9.View ArticlePubMedGoogle Scholar
- Valtschanoff JG, Rustioni A, Guo A, Hwang SJ: Vanilloid receptor VR1 is both presynaptic and postsynaptic in the superficial laminae of the rat dorsal horn. J Comp Neurol. 2001, 436 (2): 225-235. 10.1002/cne.1063.View ArticlePubMedGoogle Scholar
- Tracey DJ, Walker JS: Pain due to nerve damage: are inflammatory mediators involved?. Inflamm Res. 1995, 44 (10): 407-411. 10.1007/BF01757696.View ArticlePubMedGoogle Scholar
- Hu-Tsai M, Woolf C, Winter J: Influence of inflammation or disconnection from peripheral target tissue on the capsaicin sensitivity of rat dorsal root ganglion sensory neurones. Neurosci Lett. 1996, 203 (2): 119-122. 10.1016/0304-3940(95)12277-X.View ArticlePubMedGoogle Scholar
- Ramer MS, French GD, Bisby MA: Wallerian degeneration is required for both neuropathic pain and sympathetic sprouting into the DRG. Pain. 1997, 72 (1-2): 71-78. 10.1016/S0304-3959(97)00019-5.View ArticlePubMedGoogle Scholar
- Theodosiou M, Rush RA, Zhou XF, Hu D, Walker JS, Tracey DJ: Hyperalgesia due to nerve damage: role of nerve growth factor. Pain. 1999, 81 (3): 245-255. 10.1016/S0304-3959(99)00018-4.View ArticlePubMedGoogle Scholar
- Gopinath P, Wan E, Holdcroft A, Facer P, Davis JB, Smith GD, Bountra C, Anand P: Increased capsaicin receptor TRPV1 in skin nerve fibres and related vanilloid receptors TRPV3 and TRPV4 in keratinocytes in human breast pain. BMC Womens Health. 2005, 5 (1): 2-10.1186/1472-6874-5-2.View ArticlePubMedPubMed CentralGoogle Scholar
- Veronesi B, Oortgiesen M, Carter JD, Devlin RB: Particulate matter initiates inflammatory cytokine release by activation of capsaicin and acid receptors in a human bronchial epithelial cell line. Toxicol Appl Pharmacol. 1999, 154 (1): 106-115. 10.1006/taap.1998.8567.View ArticlePubMedGoogle Scholar
- Denda M, Fuziwara S, Inoue K, Denda S, Akamatsu H, Tomitaka A, Matsunaga K: Immunoreactivity of VR1 on epidermal keratinocyte of human skin. Biochem Biophys Res Commun. 2001, 285 (5): 1250-1252. 10.1006/bbrc.2001.5299.View ArticlePubMedGoogle Scholar
- Dvorakova M, Kummer W: Transient expression of vanilloid receptor subtype 1 in rat cardiomyocytes during development. Histochem Cell Biol. 2001, 116 (3): 223-225.View ArticlePubMedGoogle Scholar
- Stander S, Moormann C, Schumacher M, Buddenkotte J, Artuc M, Shpacovitch V, Brzoska T, Lippert U, Henz BM, Luger TA, Metze D, Steinhoff M: Expression of vanilloid receptor subtype 1 in cutaneous sensory nerve fibers, mast cells, and epithelial cells of appendage structures. Exp Dermatol. 2004, 13 (3): 129-139. 10.1111/j.0906-6705.2004.0178.x.View ArticlePubMedGoogle Scholar
- Denda M, Fuziwara S, Inoue K: Influx of calcium and chloride ions into epidermal keratinocytes regulates exocytosis of epidermal lamellar bodies and skin permeability barrier homeostasis. J Invest Dermatol. 2003, 121 (2): 362-367. 10.1046/j.1523-1747.2003.12367.x.View ArticlePubMedGoogle Scholar
- The pre-publication history for this paper can be accessed here:http://www.biomedcentral.com/1471-2377/7/11/prepub
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.