Chronic pain is a severe burden affecting 20% of the population worldwide. To develop novel analgesics, in vivo preclinical assessment of the pain threshold is inevitable. Investigation of the nociception in rodents is still challenging, since most of the currently available methods are manually operated. So, the results highly depend on the experience of the examiner and can be significantly biased by subjective human factors. To improve this translational research paradigm, advanced tools are needed in this field. Therefore, the aim of the present study was to develop a new generation automated pain assessment device. In collaboration with Z-Elektronika Ltd., Pécs, Hungary we have designed and validated high-precision automated dynamic plantar aesthesiometer (ADPA) that is suitable for the assessment of mechanonociceptive threshold in rats and mice. It utilizes artificial intelligence (AI) to automatically recognize the animals investigated. The system’s software controls the mechanical stimulation of the hindpaws with simultaneous video recording of the nocifensive reaction and analysis of the pain thresholds. The main advantage of ADPA is the automated, computer-controlled induction and evaluation of the pain threshold, increasing the quality, comparability, reproducibility, and objectivity of the results. This device may significantly enhance the accuracy of pain assessment in animal models and contribute to improved preclinical pain research.

IntroductionThe treatment of neuropathic pain with traditional and adjuvant analgesics is limited in efficacy and associated with severe adverse effects. Our group has previously shown that somatostatin, released from capsaicin-sensitive peptidergic sensory nerve terminals, mediates analgesic and anti-inflammatory effects at the peripheral and central levels via the somatostatin receptor subtype 4 (SST4). The therapeutic use of native somatostatin is limited by its numerous biological actions mediated by the five somatostatin receptors and its short elimination half-life. Therefore, the development of SST4-selective agonists may be an effective approach for treating neuropathic pain.MethodsIn this comparative study, the receptor binding and activation properties of four small molecules were compared with those of somatostatin and the SST4 receptor superagonist, J-2156, through in silico drug-likeness investigation, pharmacokinetic prediction, molecular docking calculations, in vitro cAMP accumulation assays, and in vivo assessment of their antihyperalgesic effects in the partial sciatic nerve ligation mouse model of traumatic neuropathy.Results and DiscussionDocking calculations showed that all compounds interact with the conserved Asp126 of SST4, which is suggested to play a key role in ligand binding. cAMP assays confirmed that all molecules activate the SST4 receptor with comparable potency to that of J-2156. All examined compounds reversed PSNL-induced mechanical hyperalgesia. Their antihyperalgesic effects ranged from 20% to 70% and depended on both the time and the applied dose. These results suggest that the tested compounds could be potentially effective in the treatment of neuropathic pain.

Introduction Stress maladaptation and dysregulated conditioned fear are hallmarks of trauma- and stressor-related disorders. The centrally projecting Edinger-Westphal nucleus (EWcp) is involved in stress adaptation. As the urocortin 1/cocaine- and amphetamine-regulated transcript (UCN1/CART)-positive neurons of mouse and human EWcp express transient receptor potential ankyrin 1 (TRPA1) mRNA, which reacts to stress, we hypothesized their role in stress adaptation and conditioned fear responses. Methods Male Trpa1 wild-type (WT) and knockout (KO) mice underwent footshock-induced fear conditioning. Behavioural analyses included evaluating freezing/jumping responses and extinction to trauma-related context/cues, and a social interaction test (SIT). Plasma corticosterone (CORT), changes in EWcp/TRPA1/UCN1/CART neurons (RNAscope combined with immunohistochemistry), glial markers and tumor necrosis factor-α (TNF-α) immunoreactivity in the EWcp, hippocampus, central amygdala and medial prefrontal cortex (mPFC) were assessed. Results Stress increased freezing in both genotypes with significantly higher jumping rate in KOs during conditioned fear. Both shocked groups displayed reduced social interest, with higher freezing in KOs than WTs. Fear extinction developed upon repeated introduction to trauma context/cues but was delayed in KOs. Additionally, relapse occurred in KOs only, accompanied by lower CORT levels. In WTs, stress downregulated Trpa1 and increased Ucn1 mRNA expression with enhanced astrocyte responses (except mPFC). In KOs, trauma elevated Cart mRNA and CART peptide levels with higher microglia scores and increased TNF-α immunoreactivity (except EWcp). Conclusion In the EWcp, TRPA1 may modulate trauma-induced neuropeptide cocktail composition. Through influencing astrocyte-microglia interaction, TRPA1 may regulate neuroinflammation in stress-responsive brain areas. Moreover, TRPA1 may diminish fear generalization and promote durable fear extinction.

Acute pancreatitis (AP) is a common gastroenterological disorder characterized by severe abdominal pain and inflammation. Despite its high mortality rate, the pathomechanism of AP remains incompletely understood, although neurogenic inflammation - where nerve-derived mediators trigger or amplify inflammatory responses - also appears to contribute to its pathogenesis. The aim of this study was to further investigate the role of neurogenic inflammation in AP and the impact of sensory nerve desensitisation on disease severity. Sensory afferent neurons were ablated using resiniferatoxin (RTX) prior to AP induction in four distinct rat and mouse models. Additionally, TRPV1 knock-out mice were employed to assess the contribution of this ion channel to AP development. Our findings reveal that RTX-induced sensory nerve desensitisation exacerbates the severity of necrotising AP induced by L-ornithine (L-Orn) and sodium taurocholate (NaTc) in rats, as evidenced by increased tissue damage, leukocyte infiltration or serum amylase activity. Conversely, in the cerulein (Cer)-induced oedematous AP rat model, RTX treatment significantly reduced leukocyte infiltration without affecting tissue oedema. In mice, RTX administration worsened the severity of Cer-induced AP, while TRPV1 gene deletion led to a modest reduction in disease severity. These results suggest that the impact of sensory nerve disruption on AP varies depending on the model and type of AP. The study underscores the important role of sensory neurons and TRPV1 ion channels in the pathogenesis and progression of AP, highlighting the potential for targeted therapies that modulate neurogenic inflammation.

Abstract Cholinergic neurons of the preganglionic Edinger–Westphal nucleus (EW) are involved in Alzheimer’s disease (AD), however, the role of urocortin 1 (UCN1) positive peptidergic neurons of the centrally projecting EW (EWcp) remains unclear. EWcp cells exclusively express transient receptor potential ankyrin 1 (TRPA1) ion channels, implicated in neurodegenerative disorders. We hypothesized that the EWcp/UCN1/Trpa1 neurons may be involved in AD-related pathologies. Age-dependent (2, 6, 9, 12 and 18 months) Trpa1 mRNA expression (RNAscope in situ hybridization) and UCN1 peptide (immunostaining) content of the EWcp were examined in male triple transgenic mouse (3xTg-AD) model of AD. 1H-MRI spectroscopy was performed in the hippocampus at 6, 12 and 18 months to evaluate the taurine and N-acetylaspartate levels, metabolites reflecting neuroprotection and neuronal integrity as AD prognostic markers. Trpa1 expression was lower in 2 and 6-months-old 3xTg-AD than controls. Later the genotype differences disappeared due to the progressive, age-related reduction of Trpa1 mRNA transcripts in the controls. In contrast, the Trpa1 expression of transgenic mice remained persistently low. Similarly, the UCN1 peptide content was also lower in the 2 and 6-months-old 3xTg-AD compared to controls. However, UCN1 level increased with age, which was more pronounced in 3xTg-AD than controls abolishing the genotype differences. Age-dependent decrease in taurine level was detected in transgenic animals leading to significantly lower taurine/creatine ratio in 12 and 18-months-old 3xTg-AD animals compared to the controls. This age-related dynamics of Trpa1 and UCN1 expression of 3xTg-AD mice suggests that altered UCN1 signaling may contribute to AD-associated mood disorders and memory decline.

BACKGROUND AND PURPOSE:Allergic contact dermatitis (ACD) is a frequent inflammatory skin disease with limited therapeutic options. While neuronal Transient Receptor Potential Ankyrin 1 (TRPA1) has been implicated in ACD, the role of keratinocyte TRPA1 remains unclear. We investigated whether allergen binding to keratinocyte TRPA1 drives cytotoxicity, cytokine release and inflammatory amplification. EXPERIMENTAL APPROACH:We combined in vivo oxazolone-induced hypersensitivity in wild-type and Trpa1 knockout mice with pharmacological inhibition by HC-030031, in vitro assays using TRPA1-expressing Chinese hamster ovary (CHO) cells and primary keratinocytes, RNAscope localisation in human and murine skin, cytokine profiling and in silico docking analyses of allergen-TRPA1 interactions. KEY RESULTS:TRPA1 deletion or antagonism markedly reduced oxazolone-induced ear swelling, vascular responses and histopathology. Strong contact sensitisers (2,4-dinitrochlorobenzene [DNCB], 2,4-dinitrofluorobenzene [DNFB], oxazolone and formaldehyde) activated TRPA1, inducing Ca2+ influx, cytotoxicity and IL-1α release, effects absent in Trpa1-deficient cells and inhibited by HC-030031. RNAscope confirmed keratinocyte TRPA1 expression in human and mouse skin. Docking revealed allergen-specific binding modes, where covalent cysteine modification and A-loop stabilisation correlated with potency. Consistent with these observations allergen-induced ROS, which also target the cysteine cluster of TRPA1, may further lower the channel's activation threshold and thereby amplify allergen-driven cytotoxicity. CONCLUSION AND IMPLICATIONS:Keratinocyte TRPA1 integrates direct allergen binding with ROS-mediated sensitisation to drive cytotoxicity and IL-1α release. This dual mechanism helps explain sensitiser potency and positions TRPA1 antagonism as a promising therapeutic approach in ACD, while providing a framework for chemical risk assessment.

Background: Posttraumatic stress disorder (PTSD) is a mental illness in which central stress-regulating regions, including locus coeruleus (LC) and paraventricular nucleus of hypothalamus (PVN), play key roles. Clonidine, a central sympatholytic drug, can inhibit LC activity and reduce PTSD-related symptoms, suggesting noradrenergic involvement. Glia-driven immune mechanisms may link LC activity to PVN responses. Since TRPA1 ion channel is implicated in both neuroinflammation and stress adaptation, we aimed to determine whether its presence modulates the function of brain structures contributing to PTSD-related alteration in central stress adaptation. Methods: Foot shock PTSD model was applied to Trpa1 wild-type (WT) and knockout (KO) mice, and outcomes were assessed four weeks later. Immunohistochemistry was used to evaluate tyrosine hydroxylase (TH) levels in the LC and glial activation in the PVN. Behavioral effects of clonidine and circulating corticosterone levels were also examined. Results: Stress increased LC/TH immunoreactivity and PVN glial activation. Trpa1 deletion exaggerated LC/TH responses but reduced PVN astrocyte activation. Clonidine increased freezing and decreased jumping (a hyperarousal marker). KO mice showed enhanced jumping and did not respond to clonidine. Corticosterone levels remained unchanged. Conclusions: TRPA1 may support stress adaptation in PTSD by regulating LC noradrenergic output and PVN neuroinflammation, independently of α2-adrenergic signaling.

Ethanol disrupts gastric mucosal integrity and induces inflammation. Transient receptor potential ankyrin 1 (TRPA1) and transient receptor potential vanilloid 1 (TRPV1) are receptors expressed in the gastrointestinal tract, but their role in gastric protection against ethanol-induced injury remains unclear. This study investigated the contribution of TRPA1 and TRPV1 to gastric responses following ethanol exposure. Wild-type mice and mice lacking TRPA1, TRPV1, or both receptors were subjected to intragastric ethanol administration. Gastric injury was evaluated by macroscopic and histologic analysis. Messenger RNA expression of selected proinflammatory cytokines and receptor transcripts was quantified using quantitative polymerase chain reaction. Receptor localization was examined by double immunofluorescence and confocal microscopy. Ethanol administration induced pronounced gastric mucosal injury in receptor-deficient mice, whereas only minimal changes were observed in wild-type animals. The protective effect was gradational, with weaker protection associated with TRPV1, greater protection with TRPA1, and the strongest protection when both receptors were present, suggesting a combined contribution of both receptors. In wild-type animals, ethanol exposure induced time-dependent changes in receptor expression, suggesting adaptive regulation. Immunofluorescence revealed localization of both receptors in neuronal and non-neuronal structures of the gastric wall. These findings demonstrate the distinct roles of TRPA1 and TRPV1 in protecting the gastric mucosa against ethanol-induced injury.

Az orvostudomány előtt álló egyik legjelentősebb kihívás agyunk szerveződésének és működésének megértése, és zavarainak, kórképeinek hatékony kezelése. A magyarországi orvostudományi kutatások elmúlt évtizedeiben az egyik legeredményesebb és legnagyobb nemzetközi visszhangot kiváltó területe az agykutatás, amely számos iskolateremtő tudományos műhelyben valósult meg. Jelen munkánkban a hazai agykutatók három világszerte elismert, áttörést jelentő eredményeket elérő egyéniségének, Palkovits Miklós, Vizi E. Szilveszter és Szolcsányi János tudományos munkássága előtt tisztelegve, azok alapvetéseiről adunk egy teljességre nem törekvő összefoglalót, felvillantva legnagyobb hatású felfedezéseiket, szakmai életútjuk meghatározó mérföldköveit.

BACKGROUND AND PURPOSE:Psoriasis is a chronic, relapsing, immune-mediated inflammatory skin disease. The transient receptor potential ankyrin 1 (TRPA1) ion channel plays a protective role in the formation of psoriasiform skin reactions. Here, we investigated the pharmacological activation and blockade of TRPA1 in human skin (patho)physiology. EXPERIMENTAL APPROACH:Six-millimetre full-thickness biopsies were obtained from psoriatic lesional and non-lesional skin of four patients with psoriasis, and from normal skin of four healthy volunteers. Each biopsy was quartered: One segment was untreated, and the other three were cultured with vehicle (DMSO), TRPA1 agonist mustard oil (MO), or TRPA1 antagonist (HC030031), respectively. Global gene expression was measured by RNA sequencing, followed by differential expression and functional enrichment analyses, to identify TRPA1-modulated genes. KEY RESULTS:Pre-evaluation of data with ordination assessment showed clear cluster formation according to treatments and condition of the skin. In healthy skin, TRPA1 activation down-regulated genes associated with interferon signalling, antimicrobial responses, and inflammation/oxidative stress. In lesional psoriatic skin, the genes of interleukin-4 (IL-4), IL-10 and IL-13 cytokine signalling-related proteins, circadian gene expression, and senescence-associated secretory phenotype (SASP) genes were down-regulated by MO treatment. Antagonist treatment did not cause significant gene expression changes, supporting the previous finding that basal TRPA1 activity is low in the skin. DMSO treatment in all three conditions increased expression of several inflammatory genes, which was normalised during data analysis. CONCLUSION AND IMPLICATIONS:Exploration of the interactions between TRPA1 and identified signalling pathways may open new opportunities to target psoriasis, alleviate disease symptoms and optimise therapies.

OBJECTIVE:Pain is one of the major public health burdens worldwide, however, conventional analgesics are often ineffective. Capsaicin-the active compound of Capsicum species, being responsible for their pungency-has been part of traditional medicine long ago. Capsaicin is a natural agonist of the Transient Receptor Potential Vanilloid 1 receptor-localized on capsaicin-sensitive sensory neurons and strongly involved in pain transmission-, and has been in focus of analgesic drug research for many years. In this study, we aimed to develop a sustained release transdermal patch (transdermal therapeutic system, TTS) combining the advantages of low-concentration capsaicin and diclofenac embedded in an innovative structure, as well as to perform complex preclinical investigations of its analgesic effect. METHODS:Drug delivery properties of the TTS were investigated with Franz cell and flow-through cell tests. Analgesic effect of the TTS was examined in in vivo models of acute postoperative and inflammatory, chronic neuropathic and osteoarthritic pain. RESULTS:Modified silicone polymer matrix-based TTS containing low-concentration capsaicin and diclofenac has been developed, releasing both compounds according to zero-order kinetics. Moreover, capsaicin and diclofenac facilitated the liberation of each other. Combined TTS significantly reduced acute postoperative and inflammatory pain, as well as chronic neuropathic and osteoarthritic pain. Interestingly, in acute postoperative and chronic osteoarthritic pain, capsaicin prolonged and potentiated the pain-relieving effect of diclofenac. CONCLUSIONS:New generation combined low-concentration capsaicin-diclofenac containing TTS can be an effective therapeutic tool in acute and chronic pain states involving neuropathic and inflammatory components.

Dysfunction of dopamine receptors and interruption of normal dopaminergic signaling have been linked to severe neuropsychiatric diseases such as schizophrenia, Parkinson's disease and depression. Although these receptors are among the most drug-targeted families of GPCRs, designing compounds with subtype-specific pharmacological profile remains challenging due to the structural similarities among the subtypes of the family. Considering the structural moieties of cariprazine, a prototypic drug with D3 receptor (D3R) preference, we report a library of bitopic analogues to explore how the orthosteric and secondary binding motifs, coupled with different linkers, affect D2R/D3R selectivity and activity. Compounds with promising dopamine receptor selectivities and binding affinities were further characterized on a GPCR panel and in functional assays. Our efforts resulted in an advanced lead compound (20b) with improved D3R and 5-HT2AR, as well as decreased D2R and 5-HT1AR potencies (EC50) compared to cariprazine. The cleaner receptor profile of this compound retained activities for the most important antidepressant mechanisms that were confirmed by reducing the depression-like behavior in mice.

The urocortin 1 (UCN1) and cocaine- and amphetamine-regulated transcript (CART) co-expressing neurons of the centrally projecting Edinger-Westphal nucleus (EWcp), regulate the function of reward- and addiction-related brain areas. EWcp/UCN1/CART neurons highly express the transient receptor potential ankyrin 1 (TRPA1) cation channel. We hypothesized that alcohol and its metabolites may influence TRPA1 ion channels. We also anticipated that 3-months chronic limited-access voluntary alcohol consumption in mice affects EWcp/TRPA1 expression resulting in altered UCN1 and CART dynamics and alcohol consumption. Alcohol preference and serum amylase were assessed to validate the model. In the mouse EWcp, immunofluorescence targeting UCN1 and CART peptides were performed to assess neuronal activation as well as UCN1 and CART peptides content. Mouse Trpa1, Cartpt, and Ucn1 as well as human TRPA1 expression was semi-quantified by RNAscope in situ hybridization. In silico modelling and computational docking were performed to test the ability of alcohol and its metabolites to activate human TRPA1 channels. Alcohol preference gradually declined over the course of the study. Alcohol treatment significantly increased serum amylase level and proportionally decreased Trpa1, Cartpt, and Ucn1 mRNA expression in the EWcp. Moreover, CART but not UCN1 peptide content was also reduced. We demonstrated TRPA1 expression in the human EWcp/UCN1/CART neurons and provided translational evidence that alcohol and its metabolites activate the human TRPA1. We conclude that reduced EWcp/TRPA1 expression may may diminish alcohol preference offering novel potential therapeutic target.

Background/Objectives: Dimethyl trisulfide (DMTS) is a naturally occurring polysulfide with known antioxidant and neuroprotective properties. DMTS is a lipophilic transient receptor potential ankyrin 1 (TRPA1) ligand that reaches the central nervous system (CNS). Its role in the CNS, particularly regarding depression-like behaviour, has yet to be explored. This study investigates the influence of DMTS on stress responses and whether this effect is mediated through the TRPA1 ion channel, known for its role in stress adaptation. Using a mouse model involving three-week exposure, we examined the impact of DMTS on depression-like behaviour and anxiety and identified the involved brain regions. Methods: Our methods involved testing both Trpa1-wild-type and gene-knockout mice under CUMS conditions and DMTS treatment. DMTS was administered intraperitoneally at a dose of 30 mg/kg on days 16 and 20 of the 21-day CUMS protocol-in hourly injections seven times to ensure sustained exposure. Various behavioural assessments-including the open field, marble burying, tail suspension, forced swim, and sucrose preference tests-were performed to evaluate anxiety and depression-like behaviour. Additionally, we measured body weight changes and the relative weights of the thymus and adrenal glands, while serum levels of corticosterone and adrenocorticotropic hormone were quantified via ELISA. FOSB (FBJ murine osteosarcoma viral oncogene homolog B) immunohistochemistry was utilised to assess chronic neuronal activation in stress-relevant brain areas. Results: Results showed that CUMS induces depression-like behaviour, with the response being modulated by the TRPA1 status and that DMTS treatment significantly reduced these effects when TRPA1 channels were functional. DMTS also mitigated thymus involution due to hypothalamic-pituitary-adrenal (HPA) axis dysregulation. Conclusions: Overall, DMTS appears to relieve depressive and anxiety symptoms through TRPA1-mediated pathways, suggesting its potential as a dietary supplement or adjunct therapy for depression and anxiety.

The urocortin 1 (UCN1)-expressing neurons of the centrally projecting Edinger-Westphal nucleus (EWcp) regulate the function of migraine-related brain areas via direct urocortinergic connections. In the central nervous system, EWcp/UCN1 neurons uniquely co-expresses transient receptor potential ankyrin 1 (TRPA1) cation channel, which has also been linked to migraine. Here we aimed to investigate whether central TRPA1 receptors regulate the EWcp/UCN1 neurons' response to migraine. The intraperitoneal calcitonin gene related peptide (CGRP) injection model of migraine was implemented and validated using light-dark box and von Frey assays in wild-type (WT) and TRPA1 knockout (KO) male mice. RNAscope in situ hybridization and immunofluorescence were used to examine the Ucn1, Trpa1 mRNA expression and UCN1 peptide content in the EWcp. FOS immunohistochemistry was performed to assess acute neuronal activation in the EWcp and the antinociceptive lateral periaqueductal gray matter (lPAG). CGRP administration induced light aversion, periorbital hyperalgesia and increased FOS immunoreactivity in the lPAG in both genotypes supporting the model validity. Additionally, Trpa1 deficient mice exhibited reduced sensitivity to light, regardless of the treatment conditions. In the EWcp, CGRP treatment increased FOS immunosignal and Ucn1 mRNA expression in both genotypes. Moreover, in WT mice, the treatment increased the EWcp UCN1 peptide and Trpa1 mRNA levels, with no such changes observed in Trpa1 KO animals. These findings suggest a possible role of central TRPA1 in migraine by regulating UCN1 dynamics in the EWcp. Targeting TRPA1 ion channels through pharmacological interventions may offer a new strategy for migraine treatment.

The urocortin 1 (UCN1)-expressing centrally projecting Edinger-Westphal (EWcp) nucleus is influenced by circadian rhythms, hormones, stress, and pain, all known migraine triggers. Our study investigated EWcp's potential involvement in migraine. Using RNAscope in situ hybridization and immunostaining, we examined the expression of calcitonin gene-related peptide (CGRP) receptor components in both mouse and human EWcp and dorsal raphe nucleus (DRN). Tracing study examined connection between EWcp and the spinal trigeminal nucleus (STN). The intraperitoneal CGRP injection model of migraine was applied and validated by light-dark box, and von Frey assays in mice, in situ hybridization combined with immunostaining, were used to assess the functional-morphological changes. The functional connectivity matrix of EW was examined using functional magnetic resonance imaging in control humans and interictal migraineurs. We proved the expression of CGRP receptor components in both murine and human DRN and EWcp. We identified a direct urocortinergic projection from EWcp to the STN. Photophobic behavior, periorbital hyperalgesia, increased c-fos gene-encoded protein immunoreactivity in the lateral periaqueductal gray matter and trigeminal ganglia, and phosphorylated c-AMP-responsive element binding protein in the STN supported the efficacy of CGRP-induced migraine-like state. Calcitonin gene-related peptide administration also increased c-fos gene-encoded protein expression, Ucn1 mRNA, and peptide content in EWcp/UCN1 neurons while reducing serotonin and tryptophan hydroxylase-2 levels in the DRN. Targeted ablation of EWcp/UCN1 neurons induced hyperalgesia. A positive functional connectivity between EW and STN as well as DRN has been identified by functional magnetic resonance imaging. The presented data strongly suggest the regulatory role of EWcp/UCN1 neurons in migraine through the STN and DRN with high translational value.

Aims: Systemic administration of ammonium chloride (NH4Cl), an acidifying agent used in human patients and experimental conditions, causes hypothermia in mice, however, the mechanisms of the thermoregulatory response to NH4Cl and whether it develops in other species remained unknown. Main methods: We studied body temperature (T-b) changes in rats and mice induced by intraperitoneal administration of NH4Cl after blockade of transient receptor potential vanilloid-1 (TRPV1) or ankyrin-1 (TRPA1) channels. Key findings: In rats, NH4Cl decreased T-b by 0.4-0.8 degrees C (p < 0.05). The NH4Cl-induced hypothermia also developed in Trpv1 knockout (Trpv1(-/-)) and wild-type (Trpv1(+/+)) mice, however, the T-b drop was exaggerated in Trpv1(-/-) mice compared to Trpv1(+/+) controls with maximal decreases of 4.0 vs. 2.1 degrees C, respectively (p < 0.05). Pharmacological blockade of TRPV1 channels with AMG 517 augmented the hypothermic response to NH4Cl in genetically unmodified mice and rats (p < 0.05 for both). In contrast, when NH4Cl was infused to mice genetically lacking the TRPA1 channel, the hypothermic response was significantly attenuated compared to wild-type controls with maximal mean T-b difference of 1.0 degrees C between the genotypes (p = 0.008). Pretreatment of rats with a TRPA1 antagonist (A967079) also attenuated the NH4Cl-induced T-b drop with a maximal difference of 0.7 degrees C between the pretreatment groups (p = 0.003). Significance: TRPV1 channels limit, whereas TRPA1 channels exaggerate the development of NH4Cl-induced hypothermia in rats and mice, but other mechanisms are also involved. Our results warrant for regular T-b control and careful consideration of NH4Cl treatment in patients with TRPA1 and TRPV1 channel dysfunctions.

We have previously proven the involvement of transient receptor potential ankyrin 1 (TRPA1) in stress adaptation. A lack of TRPA1 affects both urocortin 1 (member of the corticotropin-releasing hormone (CRH) family) content of the Edinger–Westphal nucleus. The noradrenergic locus ceruleus (LC) is also an important player in mood control. We aimed at investigating whether the TRPA1 is expressed in the LC, and to test if the response to chronic variable mild stress (CVMS) is affected by a lack of TRPA1. The TRPA1 expression was examined via RNAscope in situ hybridization. We investigated TRPA1 knockout and wildtype mice using the CVMS model of depression. Tyrosine hydroxylase (TH) and FOSB double immunofluorescence were used to test the functional neuromorphological changes in the LC. No TRPA1 expression was detected in the LC. The TH content was not affected by CVMS exposure. The CVMS-induced FOSB immunosignal did not co-localize with the TH neurons. TRPA1 is not expressed in the LC. A lack of functional TRPA1 receptor neither directly nor indirectly affects the TH content of LC neurons under CVMS.

Polysulfides are endogenously produced in mammals and generally associated with protective functions. Our aim was to investigate the effect of dimethyl trisulfide (DMTS) in a mouse model of acute stress. DMTS activates transient receptor potential ankyrin 1 (TRPA1) channels and leads to neuropeptide release, potentially that of substance P (SP). We hypothesize that DMTS might inhibit the degrading enzymes of endocannabinoids, so this system was also investigated as another possible pathway for mediating the effects of DMTS. Trpa1 gene wild-type (WT) and knockout (KO) mice were used to confirm the role of the TRPA1 ion channel in mediating the effects of DMTS. C57BL/6J, NK1 gene KO, and Tac1 gene KO mice were used to evaluate the effect of DMTS on the release and expression of SP. Some C57BL/6J animals were treated with AM251, an inhibitor of the cannabinoid CB1 receptor, to elucidate the role of the endocannabinoid system in these processes. Open field test (OFT) and forced swim test (FST) were performed in each mouse strain. A tail suspension test (TST) was performed in Trpa1 WT and KO animals. C-FOS immunohistochemistry was carried out on Trpa1 WT and KO animals. The DMTS treatment increased the number of highly active periods and decreased immobility time in the FST in WT animals, but had no effect on the Trpa1 KO mice. The DMTS administration induced neuronal activation in the Trpa1 WT mice in the stress-related brain areas, such as the locus coeruleus, dorsal raphe nucleus, lateral septum, paraventricular nucleus of the thalamus, and paraventricular nucleus of the hypothalamus. DMTS may have a potential role in the regulation of stress-related processes, and the TRPA1 ion channel may also be involved in mediating the effects of DMTS. DMTS can be an ideal candidate for further study as a potential remedy for stress-related disorders.