See Article History. Learn More in these related Britannica articles:. Such molecular evidence has been crucial in improving the understanding of thermoreception and has led to new approaches in the classification of sensory receptors. For example, today receptors sensitive to temperature and other…. Other than this, very little is known about the molecular details of thermoregulation in fish. History at your fingertips.
Sign up here to see what happened On This Day , every day in your inbox! By signing up, you agree to our Privacy Notice. There are actually only six TRPC channels expressed in humans because TRPC2 is found to be expressed solely in mice and is considered a pseudo-gene in humans; this is partly due to the role of TRPC2 in detecting pheromones, which mice have an increased ability compared to humans. Mutations in TRPC channels have been associated with respiratory diseases along with focal segmental glomerulosclerosis in the kidneys.
TRPV, V for "vanilloid", is named for the vanilloid chemicals that activate this channel, and are some of the most studied TRP channels. These channels have been made famous for their association with molecules such as capsaicin a TRPV1 agonist , and its ability to produce heat sensation and act as a topical ointment for pain relief.
These channels have been shown to be both mechanical receptors for pain and chemosensors activated by various chemical species, including isothiocyanates pungent chemicals in substances such as mustard oil and wasabi , cannabinoids, general and local analgesics, and cinnamaldehyde. TRPM, M for "melastatin", was found during a comparative genetic analysis between benign nevi and malignant nevi melanoma. There is more to be discovered as to what TRPN does, however, it is thought to be mechanically gated. TRPP, P for "polycistin", is named for polycystic kidney disease that is associated with this channel.
Mucolipidosis IV was first discovered in by E. Berman who noticed abnormalities in the eyes of an infant. TRPML is still not highly characterized. TRPY1, Y for "yeast", is highly localized to the yeast vacuole, which is the functional equivalent of a lysosome in a mammalian cell, and acts as a mechanosensor for vacuolar osmotic pressure. Patch clamp techniques and hyperosmotic stimulation have illustrated that TRPY plays a role in intracellular calcium release. Mammalian TRP channels are activated and regulated by a wide variety of stimuli including many post-transcriptional mechanisms like phosphorylation , G-protein receptor coupling , ligand-gating, and ubiquitination.
The receptors are found in almost all cell types and are largely localized in cell and organelle membranes, modulating ion entry. Most TRP channels form homo- or heterotetramers when completely functional. The ion selectivity filter, pore, is formed by the complex combination of p-loops in the tetrameric protein, which are situated in the extracellular domain between the S5 and S6 transmembrane segments.
As with most cation channels, TRP channels have negatively charged residues within the pore to attract the positively charged ions. Each channel in this group is structurally unique, which adds to the diversity of functions that TRP channels possess, however, there are some commonalities that distinguish this group from others.
Starting from the intracellular N-terminus there are varying lengths of ankryin repeats except in TRPM that aid with membrane anchoring and other protein interactions. Group two most distinguishable trait is the long extracellular span between the S1 and S2 transmembrane segments. Members of group two are also lacking in ankryin repeats and a TRP domain. They have been shown, however, to have endoplasmic reticulum ER retention sequences towards on the C-terminal end illustrating possible interactions with the ER.
TRPs have important interactions with other proteins and often form signaling complexes, the exact pathways of which are unknown. In the body, some TRP channels are thought to behave like microscopic thermometers and are used in animals to sense hot or cold. TRPs act as sensors of osmotic pressure , volume , stretch , and vibration.
TRPs have been seen to have complex multidimensional roles in sensory signaling. Many TRPs function as intracellular calcium release channels.
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TRP ion channels convert energy into action potentials in somatosensory nociceptors. There are at least 6 different Thermo-TRP channels and each plays a different role. TRPM5 is involved in taste signaling of sweet , bitter and umami tastes by modulating the signal pathway in type II taste receptor cells.
TRPM5 is activated by the sweet glycosides found in the stevia plant. Several other TRP channels play a significant role in chemosensation through sensory nerve endings in the mouth that are independent from taste buds. The trp -mutant fruit flies, which lack a functional copy of trp gene, are characterized by a transient response to light, unlike wild-type flies that demonstrate a sustained photoreceptor cell activity in response to light.
A mutant fly, trpl , was subsequently isolated. Caterina, Michael J. Macmillan Magazines. Capsaicin, the main pungent ingredient in 'hot' chili peppers, elicits a sensation of burning pain by selectively activating sensory neurons that convey information about noxious stimuli to the central nervous system.
The authors have used an expression cloning strategy based on calcium influx to isolate a functional cDNA encoding a capsaicin receptor from sensory neurons. This receptor is a non-selective cation channel that is structurally related to members of the TRP family of ion channels. The cloned capsaicin receptor is also activated by increases in temp.
Nature , , ISSN: Recent studies suggest that the fly uses the inositol lipid signaling system for visual exitation and that the Drosophila transient receptor potential trp mutation disrupts this process subsequent to the prodn. This paper shows that trp encodes a novel amino acid protein with eight putative transmembrane segments. Immunolocalization indicates that the trp protein is expressed predominantly in the rhabdomeric membranes of the photoreceptor cells.
Story, Gina M. Cell Press. Mammals detect temp. The combined range of temps. Here, we describe the characterization of ANKTM1, a cold-activated channel with a lower activation temp. Consistent with the expression of ANKTM1, we identify noxious cold-sensitive sensory neurons that also respond to capsaicin but not to menthol. Nature Publishing Group. Wasabi, horseradish and mustard owe their pungency to isothiocyanate compds. Topical application of mustard oil allyl isothiocyanate to the skin activates underlying sensory nerve endings, thereby producing pain, inflammation and robust hypersensitivity to thermal and mech.
Despite their widespread use in both the kitchen and the lab. These findings identify a cellular and mol. Peier, Andrea M. A distinct subset of sensory neurons are thought to directly sense changes in thermal energy through their termini in the skin.
Very little is known about the mols. TRPM8 is specifically expressed in a subset of pain- and temp. Cells overexpressing the TRPM8 channel can be activated by cold temps. The identification of a cold-sensing TRP channel in a distinct subpopulation of sensory neurons implicates an expanded role for this family of ion channels in somatic sensory detection. The cellular and mol. Insights into this process have come from the use of pharmacol.
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Here we have characterized and cloned a menthol receptor from trigeminal sensory neurons that is also activated by thermal stimuli in the cool to cold range. This cold- and menthol-sensitive receptor, CMR1, is a member of the TRP family of excitatory ion channels, and we propose that it functions as a transducer of cold stimuli in the somatosensory system.
Transient receptor potential TRP channels are polymodal signal detectors that respond to a wide range of phys. Elucidating how these channels integrate and convert physiol. Here we exploit pharmacol. A domain consisting of transmembrane segments that moves during activation of voltage-gated channels remains stationary in TRPV1, highlighting differences in gating mechanisms for these structurally related channel superfamilies. TRPV1 opening is assocd. Allosteric coupling between upper and lower gates may account for rich physiol.
Transient receptor potential TRP channels are sensors for a wide range of cellular and environmental signals, but elucidating how these channels respond to phys. Here, the authors exploited advances in electron cryo-microscopy to det. Like voltage-gated channels, TRPV1 exhibited 4-fold symmetry around a central ion pathway formed by transmembrane segments S5-S6 and the intervening pore loop, which was flanked by S1-S4 voltage-sensor-like domains.
TRPV1 had a wide extracellular 'mouth' with a short selectivity filter. The conserved 'TRP domain' interacted with the S4-S5 linker, consistent with its contribution to allosteric modulation. Subunit organization was facilitated by interactions among cytoplasmic domains, including N-terminal ankyrin repeats. These observations provide a structural blueprint for understanding unique aspects of TRP channel function. Bikman, Benjamin T. Endocrine Society. Surgical treatments of obesity were shown to induce rapid and prolonged improvements in insulin sensitivity. The aim of the study was to investigate the effects of gastric bypass surgery and the mechanisms that explain the improvement in insulin sensitivity.
The authors performed a cross-sectional, nonrandomized, controlled study. This study was conducted jointly between the Departments of Exercise Science and Physiol. Postsurgery patients were wt. Whole-body insulin sensitivity, muscle glucose transport, and muscle insulin signaling were assessed. Postsurgery subjects had insulin sensitivity index values that were similar to the lean and higher than morbidly obese and wt. Glucose transport was higher in the postsurgery vs. IRS1-pSer in the postsurgery group was lower than morbidly obese and wt.
Insulin sensitivity and glucose transport are greater in the postsurgery patients than predicted from the wt. Corey, David P. Although some protein constituents of the transduction app. Antibodies to TRPA1 label hair bundles, esp.
Inhibition of TRPA1 protein expression in zebrafish and mouse inner ears inhibits receptor cell function, as assessed with elec. TRPA1 is probably a component of the transduction channel itself. Bandell, Michael; Story, Gina M. Six members of the mammalian transient receptor potential TRP ion channels respond to varied temp. The natural compds. The burning and cooling perception of capsaicin and menthol demonstrate that these ion channels mediate thermosensation.
The authors show that, in addn. Bradykinin, an inflammatory peptide acting through its G protein-coupled receptor, also activates TRPA1. The authors further show that phospholipase C is an important signaling component for TRPA1 activation. Cinnamaldehyde, the most specific TRPA1 activator, excites a subset of sensory neurons highly enriched in cold-sensitive neurons and elicits nociceptive behavior in mice.
Collectively, these data demonstrate that TRPA1 activation elicits a painful sensation and provide a potential mol. Bautista, Diana M. National Academy of Sciences. Garlic belongs to the Allium family of plants that produce organosulfur compds. Many health benefits have been ascribed to Allium exts. However, the mol. Intriguingly, allicin and DADS share structural similarities with allyl isothiocyanate, the pungent ingredient in wasabi and other mustard plants that induces pain and inflammation by activating TRPA1, an excitatory ion channel on primary sensory neurons of the pain pathway.
Here we show that allicin and DADS excite an allyl isothiocyanate-sensitive subpopulation of sensory neurons and induce vasodilation by activating capsaicin-sensitive perivascular sensory nerve endings. These and other results suggest that garlic excites sensory neurons primarily through activation of TRPA1. Thus different plant genera, including Allium and Brassica, have developed evolutionary convergent strategies that target TRPA1 channels on sensory nerve endings to achieve chem.
Macpherson, Lindsey J. A review. Summary: Garlic's pungent flavor has made it a popular ingredient in cuisines around the world and throughout history. Garlic's health benefits have been elevated from folklore to clin. Although there is some controversy as to the efficacy of garlic, garlic products are one of the most popular herbal supplements in the U. Raw garlic, when cut and placed on the tongue or lips, elicits painful burning and prickling sensations through unknown mechanisms.
These thermoTRPs are present in the pain-sensing neurons that innervate the mouth. We further show that allicin, an unstable component of fresh garlic, is the chem. Kwan, Kelvin Y. TRPA1, a member of the transient receptor potential TRP family of ion channels, is expressed by dorsal root ganglion neurons and by cells of the inner ear, where it has proposed roles in sensing sound, painful cold, and irritating chems.
To test the in vivo roles of TRPA1, we generated a mouse in which the essential exons required for proper function of the Trpa1 gene were deleted. These mice have a normal startle reflex to loud noise, a normal sense of balance, a normal auditory brainstem response, and normal transduction currents in vestibular hair cells. TRPA1 is apparently not essential for hair-cell transduction but contributes to the transduction of mech.
Society for Neuroscience. Transient receptor potential A1 TRPA1 is expressed in a subset of nociceptive sensory neurons where it acts as a sensor for environmental irritants, including acrolein, and some pungent plant ingredients such as allyl isothiocyanate and cinnamaldehyde. These exogenous compds. We have used electrophysiol. The effect of H2O2 was reversed by treatment with dithiothreitol indicating that H2O2 acts by promoting the formation of disulfide bonds whereas the actions of the alkenyl aldehydes and 15d-PGJ2 were not reversed, suggesting that these agents form Michael adducts.
These data demonstrate that multiple agents produced during episodes of oxidative stress can activate TRPA1 expressed in sensory neurons. Bessac, Bret F. American Society for Clinical Investigation. Sensory neurons in the airways are finely tuned to respond to reactive chems. Nasal trigeminal nerve endings are particularly sensitive to oxidants formed in polluted air and during oxidative stress as well as to chlorine, which is frequently released in industrial and domestic accidents.
Oxidant activation of airway neurons induces respiratory depression, nasal obstruction, sneezing, cough, and pain. While normally protective, chemosensory airway reflexes can provoke severe complications in patients affected by inflammatory airway conditions like rhinitis and asthma. TRPA1 channels were strongly activated by hypochlorite and hydrogen peroxide in primary sensory neurons and heterologous cells. Our results indicate that TRPA1 is an oxidant sensor in sensory neurons, initiating neuronal excitation and subsequent physiol. Public Library of Science. Objective: Several transient receptor potential TRP channels are expressed in pancreatic beta cells and have been proposed to be involved in insulin secretion.
However, the endogenous ligands for these channels are far from clear. Here, we demonstrate the expression of the transient receptor potential ankyrin 1 TRPA1 ion channel in the pancreatic beta cells and its role in insulin release. TRPA1 is an attractive candidate for inducing insulin release because it is calcium permeable and is activated by mols. Methods: Immunohistochem. TRPA1-mediated insulin release was detd. Results: TRPA1 is abundantly expressed in a rat pancreatic beta cell line and freshly isolated rat pancreatic beta cells, but not in pancreatic alpha cells.
TRPA1-mediated insulin release is also obsd. Diabetes-specific microvascular disease is a leading cause of blindness, renal failure and nerve damage, and diabetes-accelerated atherosclerosis leads to increased risk of myocardial infarction, stroke and limb amputation. Four main mol. All seem to reflect a single hyperglycemia-induced process of overprodn.
This integrating paradigm provides a new conceptual framework for future research and drug discovery. Mechanosensory channels of sensory cells mediate the sensations of hearing, touch, and some forms of pain. As shown here and previously, TRPA1 is expressed by hair cells as well as by most nociceptors small neurons of dorsal root, trigeminal, and nodose ganglia and localizes to their sensory terminals mechanosensory stereocilia and peripheral free nerves, resp. Thus, TRPA1 channels are proposed to mediate transduction in both hair cells and nociceptors. Accordingly, we find that heterologously expressed TRPA1 display channel behaviors expected for both auditory and nociceptive transducers.
Second, TRPA1 channels inactivate in hyperpolarized cells but remain open in depolarized cells. This property provides a mechanism for the lack of desensitization, coincidence detection, and allodynia that characterize pain by allowing a sensory neuron to respond constantly to sustained stimulation that is suprathreshold i. Our results support a TRPA1 role in both nociceptor and hair cell transduction.
Cold hyperalgesia is a well-documented symptom of inflammatory and neuropathic pain; however, the underlying mechanisms of this enhanced sensitivity to cold are poorly understood. A subset of transient receptor potential TRP channels mediates thermosensation and is expressed in sensory tissues, such as nociceptors and skin.
Here we report that the pharmacol. Together, these results demonstrate that an NGF-induced TRPA1 increase in sensory neurons via p38 activation is necessary for cold hyperalgesia. Thus, blocking TRPA1 in sensory neurons might provide a fruitful strategy for treating cold hyperalgesia caused by inflammation and nerve damage.
Allyl isothiocyanate, the pungent principle of wasabi and other mustard oils, produces pain by activating TRPA1, an excitatory ion channel on sensory nerve endings. Isothiocyanates are membrane--permeable electrophiles that form adducts with thiols and primary amines, suggesting that covalent modification, rather than classical lock-and-key binding, accounts for their agonist properties. Indeed, we show that the thio1 reactive compds. These findings suggest an unusual paradigm whereby natural products activate a receptor through direct, reversible, and covalent protein modification.
Molecular pain , 2 , 26 ISSN:. PGs do not activate nociceptive ion channels directly, but sensitize them by downstream mechanisms linked to G-protein coupled receptors. Release of these agents from peripheral and central terminals of sensory neurons modulates nociceptive input from the periphery and synaptic transmission at the first sensory synapse, respectively. Heart and blood vessels are densely innervated by sensory nerve endings that express chemo-, mechano-, and thermo-sensitive receptors.
Diabetes care , 26 12 , ISSN: Groups 1, 2, and 3 consumed 1, 3, or 6 g of cinnamon daily, respectively, and groups 4, 5, and 6 were given placebo capsules corresponding to the number of capsules consumed for the three levels of cinnamon. The cinnamon was consumed for 40 days followed by a day washout period. Changes in HDL cholesterol were not significant.
American Society for Nutrition. Background: Previous studies of patients with type 2 diabetes showed that cinnamon lowers fasting serum glucose, triacylglycerol, and LDL- and total cholesterol concns. Objective: We aimed to study the effect of cinnamon on the rate of gastric emptying, the postprandial blood glucose response, and satiety in healthy subjects.
Design: The gastric emptying rate GER was measured by using standardized real-time ultrasonog. Fourteen healthy subjects were assessed by using a crossover trial. The subjects were examd. GER was calcd. The addn. The redn.
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The effect of cinnamon on satiety was not significant. Conclusions: The intake of 6 g cinnamon with rice pudding reduces postprandial blood glucose and delays gastric emptying without affecting satiety. Inclusion of cinnamon in the diet lowers the postprandial glucose response, a change that is at least partially explained by a delayed GER.
Cutler, Ronald R. Oxford University Press. Background Studies have shown the efficacy of intra-partum antibiotics in preventing early-onset group B streptococcal sepsis. This approach results in a high intra-partum antibiotic use. The same antibiotics used in prophylaxis are also first-line treatment for neonatal sepsis, and antibiotic exposure in the peri-natal period has been shown to be a risk factor for late-onset serious bacterial infections and allergic disease.
Antibiotic exposure in the peri-natal period is becoming a major public health issue; alternative strategies are needed. Garlic has been traditionally used to treat vaginal infections. Allicin is the main antibacterial agent isolated from garlic. The aim of the study was to investigate the in vitro activity of a novel allicin ext. Killing kinetics were detd. Agar diffusion tests were compared for allicin liq. Garlic is a popular spice added to several edible prepns. This article focuses on the general chem.
Garlic was shown to metabolized into N-acetyl-S-allyl cysteine, allyl mercaptan, diallyl disulfide, diallyl sulfide, diallyl sulfoxide, diallyl sulfone, and allyl Me sulfide. Garlic was thought to bring about its anticarcinogenic effect through a no. Future research should standardize the dosage of garlic and type, i. The formulation of odorless functional foods with the retention of anticarcinogenic activity should be further studied.
The authors studied the modifying effect of sulfhydryl compd. The present work also describes the inhibitory effect of onion and garlic juices on the nitrosation reactions. Most of these compds. Elsevier B. The authors searched for novel agonists of TRP receptors, esp. They focused attention on garlic compds. Maximum responses of these sulfides were equal to that of AITC. The EC50 values of these compds. Leamy, Andrew W. Elsevier Ireland Ltd. The ion channel TRPA1 is activated by a wide variety of noxious stimuli, such as pollutants, products of oxidative tissue damage, and pungent natural products.
Curcumin, the active principle of turmeric root Curcuma longa , can also form Michael adducts. In order to test the hypothesis that the electrophilic curcumin activates TRPA1, we have performed whole-cell, voltage-clamp anal. In nominally Ca-free extracellular and intracellular solns. In addn. With physiol. Taken together, these results demonstrate that curcumin causes activation and subsequent desensitization of native and recombinant TRPA1 ion channels of multiple mammalian species.
Extensive research over the past half century has shown that curcumin diferuloylmethane , a component of the golden spice turmeric Curcuma longa , can modulate multiple cell signaling pathways. Extensive clin. Some promising effects have been obsd. Curcumin has also shown protection against hepatic conditions, chronic arsenic exposure, and alc.
Curcumin's pleiotropic activities emanate from its ability to modulate numerous signaling mols. In clin. Various formulations of curcumin, including nanoparticles, liposomal encapsulation, emulsions, capsules, tablets, and powder, have been examd. In this review, we discuss in detail the various human diseases in which the effect of curcumin has been investigated.
Song, Yuanlin; Sonawane, N. American Society for Biochemistry and Molecular Biology. Because of the implied potential use of curcumin or similar compds. Nasal potential differences in mice were measured in response to topical perfusion with serial solns. Robust low Cl- and forskolin-induced hyperpolarization of 22 mV was found in wild type mice, with 2. Assay of serum curcumin by Et acetate extn. The results do not support further evaluation of curcumin for cystic fibrosis therapy.
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The purpose of this study is to identify the inhibitory effect of curcumin on renal cyst development and to investigate the inhibitory mechanism. Madin-Darby canine kidney MDCK cyst model and murine embryonic kidney cyst model were used to evaluate inhibitory activity. Curcumin was found to significantly inhibit MDCK cyst development. At max. Curcumin slowed cyst enlargement in both MDCK cyst model and embryonic kidney cyst model with dose-response relationship.
Curcumin failed to affect the chloride transporter CFTR expression and function. Interestingly, curcumin inhibited forskolin-promoted cell proliferation and promoted the tubule formation in MDCK cells, which indicates curcumin promotes MDCK cell differentiation. These results define that curcumin inhibits renal cyst formation and enlargement and suggest that curcumin might be developed as a candidate drug for polycystic kidney disease.
Bentham Science Publishers Ltd. Genistein and curcumin are major components of Asian foods, soybean and curry turmeric resp. These compds. Genistein and curcumin have also been investigated for their potentiation effects on disease-assocd. Recently, we investigated the combined effect of genistein and curcumin on GD-CFTR, which exhibits gating defects without abnormalities in protein synthesis or trafficking using the patch-clamp technique. These results are consistent with the idea that multiple mechanisms are involved in the action of these CFTR potentiators.
In this review, we revisit the pharmacol. The California bay laurel or Umbellularia californica Hook. However, the underlying mechanism of the headache precipitating properties of Umbellularia californica is unknown. The monoterpene ketone umbellulone, the major volatile constituent of the leaves of Umbellularia californica, has irritating properties, and is a reactive molecule that rapidly binds thiols.
Thus, we hypothesized that umbellulone stimulates the transient receptor potential ankyrin 1 channel in a subset of peptidergic, nocioceptive neurons, activating the trigeminovascular system via this mechanism. Umbellulone evoked a calcium-dependent release of calcitonin gene-related peptide from rodent trigeminal nerve terminals in the dura mater. In wild-type mice, umbellulone elicited excitation of trigeminal neurons and released calcitonin gene-related peptide from sensory nerve terminals.
These two responses were absent in transient receptor potential ankyrin 1 deficient mice. Umbellulone caused nocioceptive behaviour after stimulation of trigeminal nerve terminals in wild-type, but not transient receptor potential ankyrin 1 deficient mice. Intranasal application or intravenous injection of umbellulone increased rat meningeal blood flow in a dose-dependent manner; a response selectively inhibited by systemic administration of transient receptor potential ankyrin 1 or calcitonin gene-related peptide receptor antagonists.
These data indicate that umbellulone activates, through a transient receptor potential ankyrin 1-dependent mechanism, the trigeminovascular system, thereby causing nocioceptive responses and calcitonin gene-related peptide release. Pharmacokinetics of umbellulone, given by either intravenous or intranasal administration, suggest that transient receptor potential ankyrin 1 stimulation, which eventually results in meningeal vasodilatation, may be produced via two different pathways, depending on the dose.
Transient receptor potential ankyrin 1 activation may either be caused directly by umbellulone, which diffuses from the nasal mucosa to perivascular nerve terminals in meningeal vessels, or by stimulation of trigeminal endings within the nasal mucosa and activation of reflex pathways. Transient receptor potential ankyrin 1 activation represents a plausible mechanism for Umbellularia californica-induced headache. Present data also strengthen the hypothesis that a series of agents, including chlorine, cigarette smoke, formaldehyde and others that are known to be headache triggers and recently identified as transient receptor potential ankyrin 1 agonists, utilize the activation of this channel on trigeminal nerves to produce head pain.
TRPA1 is activated by electrophilic compds. Here, we demonstrate a bimodal sensitivity of TRPA1 to ligustilide Lig , an electrophilic volatile dihydrophthalide of dietary and medicinal relevance. Aromatization to dehydroligustilide DH-Lig , as occurs during aging of its botanical sources, reversed this profile, enhancing TRPA1 inhibition and reducing activation. Taken together, these observations show that the phthalide structural motif is a versatile platform to investigate the modulation of TRPA1 by small mols.
Finally, the action of Lig on TRPA1 may contribute to the gustatory effects of celery, its major dietary source, and to the pharmacol. Paclitaxel produces a sensory neuropathy, characterized by mech. The transient receptor potential vanilloid 4 TRPV4 channel was reported to contribute to paclitaxel-evoked allodynia in rodents.
Here, we have explored whether TRPA1 activation contributes to paclitaxel-induced mech. Paclitaxel-evoked mech. The reduced paclitaxel-evoked mech. Exposure to paclitaxel of slices of mouse esophagus released the sensory neuropeptide, calcitonin gene-related peptide CGRP. This effect was abolished by capsaicin desensitization and in calcium-free medium indicating neurosecretion from sensory nerve terminals , partially reduced by either HC or HC, and completely abated in the presence of glutathione GSH. Finally, the reduced CGRP release, obsd.
Cold allodynia is, however, entirely dependent on TRPA1. American Society for Pharmacology and Experimental Therapeutics. Furthermore, the endocannabinoid anandamide is known to activate TRPV1 and was recently found to antagonize the menthol- and icilin-sensitive transient receptor potential channels of melastatin type 8 TRPM8. In this study, we investigated the effects of six phytocannabinoids [i. All of the compds. Furthermore, although none of the compds. Our findings suggest that phytocannabinoids and cannabis exts.
Topical application of nicotine, as used in nicotine replacement therapies, causes irritation of the mucosa and skin. This reaction has been attributed to activation of nicotinic acetylcholine receptors nAChRs in chemosensory neurons. In contrast with this view, the chemosensory cation channel transient receptor potential A1 TRPA1 is crucially involved in nicotine-induced irritation.
Micromolar concns. Nicotine acted in a membrane-delimited manner, stabilizing the open state s and destabilizing the closed state s of the channel. In the presence of the general nAChR blocker hexamethonium, nociceptive neurons showed nicotine-induced responses that were strongly reduced in TRPA1-deficient mice. Finally, TRPA1 mediated the mouse airway constriction reflex to nasal instillation of nicotine. The identification of TRPA1 as a nicotine target suggests that existing models of nicotine-induced irritation should be revised and may facilitate the development of smoking cessation therapies with less adverse effects.
Riera, C. Background and purpose: Oily exts.
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Alkylamides and 6-shogaol act on TRPA1 by covalent bonding whereas none of these compds. Conclusions and implications: The pungent nature of components of Sichuan and Melegueta peppers was mediated via interactions with TRPA1 and TRPV1 channels and may explain the aversive properties of these compds.
Vazquez, Guillermo; Wedel, Barbara J. The seven mammalian TRPCs constitute a family of channels which have been proposed to function as store-operated as well as second messenger-operated channels in a variety of cell types. TRPC channels, together with other more distantly related channel families, make up the larger TRP channel superfamily.
This review summarizes recent findings on the structure, regulation and function of the apparently ubiquitous TRPC cation channels. Annual Reviews Inc. The realization that there exists a multimembered family of cation channels with structural similarity to Drosophila's Trp channel emerged during the 2nd half of the s. In mammals, depending on the species, the TRP channel transient receptor potential cation channel family counts 29 or 30 members which has been subdivided into 6 subfamilies on the basis of sequence similarity.
Many members of each of these families, but not all, are involved in sensory signal transduction. John's wort specifically activates TRPC6 channels. Federation of American Societies for Experimental Biology. Hyperforin, a bicyclic polyprenylated acylphloroglucinol deriv. John's wort ext. Hyperforin inhibits the neuronal serotonin and norepinephrine uptake comparable to synthetic antidepressants. In contrast to synthetic antidepressants directly blocking neuronal amine uptake, hyperforin increases synaptic serotonin and norepinephrine concns. Our attempts to identify the mol. Hyperforin induced sodium and calcium entry as well as currents in TRPC6-expressing cells.
Sodium currents and the subsequent breakdown of the membrane sodium gradients may be the rationale for the inhibition of neuronal amine uptake. The hyperforin-induced cation entry was highly specific and related to TRPC6 and was suppressed in cells expressing a dominant neg. Furthermore, hyperforin induces neuronal axonal sprouting like nerve growth factor in a TRPC6-dependent manner. These findings support the role of TRPC channels in neurite extension and identify hyperforin as the first selective pharmacol. Hyperforin integrates inhibition of neurotransmitter uptake and neurotrophic property by specific activation of TRPC6 and represents an interesting lead-structure for a new class of antidepressants.
Blackwell Publishing Ltd. Sensory input from the periphery to the CNS is critically dependent on the strength of synaptic transmission at the first sensory synapse formed between primary afferent dorsal root ganglion DRG and superficial dorsal horn DH neurons of the spinal cord. Transient receptor potential vanilloid 1 TRPV1 expressed on a subset of sensory neurons plays an important role in chronic inflammatory thermal nociception. In this study, the authors have examd.
Capsaicin potently increased the frequency but not the amplitude of mEPSCs in a calcium-dependent manner, suggesting TRPV1-mediated glutamate release from presynaptic terminals of sensory neurons. Continued or repeated applications of capsaicin reduced the frequency of mEPSCs over time.
Transient receptor potential channel
The authors' results indicate that TRPV1 activation can modulate excitatory synaptic transmission at the first sensory synapse and its effects can further be augmented by activation of PKC. Increased gain of sensory input by TRPV1-induced enhancement of glutamate release and its potentiation by various inflammatory mediators may contribute to persistent pain conditions. Selective targeting of TRPV1 expressed on the central terminals of sensory neurons may serve as a strategy to alleviate chronic intractable pain conditions.
Molecular pain , 5 , 5 ISSN:. TRPV1, a non-selective cation channel has been extensively studied and is responsible for inflammatory thermal hypersensitivity. Sensitization of TRPV1 has been shown to be involved in inflammatory pain conditions. TRPV4 is also expressed at the central terminals of sensory neurons. Headache , 52 5 , ISSN:. In dorsal root ganglia, TRPV1-containing nociceptors mediate certain types of inflammatory pain. Neurogenic inflammation of cerebral dura and blood vessels in the trigeminal nociceptive system is thought to be important in migraine pain, but the ion channels important in transducing migraine pain are not known.
Sumatriptan is an agent effective in treatment of migraine and cluster headache. We hypothesized that sumatriptan might modulate activity of TRPV1 channels found in the trigeminal nociceptive system. METHODS: We used immunohistochemistry to detect the presence of TRPV1 channel protein, whole-cell recording in acutely dissociated trigeminal ganglia TG to detect functionality of TRPV1 channels, and whole-cell recording in trigeminal nucleus caudalis TNC to detect effects on release of neurotransmitters from trigeminal neurons onto second order sensory neurons.
Effects specifically on TG neurons that project to cerebral dura were assessed by labeling dural nociceptors with DiI. Capsaicin, a TRPV1 agonist, produced depolarization and repetitive action potential firing in current clamp recordings, and large inward currents in voltage clamp recordings from acutely dissociated TG neurons, demonstrating that TRPV1 channels are functional in trigeminal neurons.
Capsaicin increased spontaneous excitatory postsynaptic currents in neurons of layer II in TNC slices, showing that these channels have a physiological effect on central synaptic transmission. The same effects of capsaicin and sumatriptan were found in acutely dissociated DiI-labeled TG neurons innervating cerebral dura. Our findings that TRPV1 is inhibited by the specific antimigraine drug sumatriptan, and that TRPV1 channels are functional in neurons projecting to cerebral dura suggests a specific role for these channels in migraine or cluster headache.
TRPC6-expressing transgenic animals showed increased nos.