Involvement of Activation of Mast Cells via IgE Signaling and Epithelial Cell-Derived Cytokines in the Pathogenesis of Pollen Food Allergy Syndrome in a Murine Model.

Murine models to elucidate the pathogenesis of pollen food allergy syndrome (PFAS), characterized by oral hypersensitivity symptoms induced by specific foods in patients previously sensitized with a pollen, are lacking. The study aimed to examine PFAS pathogenesis in a novel murine model. Birch pollen-immunized mice were orally administered apple extract, and oral symptoms were evaluated based on oral rubbing frequency following the challenge. The birch pollen-immunized mice orally challenged with apple extract exhibited PFAS-like symptoms, including oral rubbing and positive reaction of swelling by the prick test. The apple extract administered with a protease inhibitor reduced the oral rubbing frequency, which was also significantly reduced in the immunized Fcer1a -/- and mast cell-deficient mice compared with the immunized control mice. The oral rubbing frequency, serum IgE levels, and Th2-cytokine production by the cervical lymph node cells were significantly reduced in the immunized Il-33 -/- and thymic stromal lymphopoietin receptor-deficient (Crlf2 -/-) mice as compared with the immunized wild-type mice. IL-33 and thymic stromal lymphopoietin involve the pathogenesis of PFAS. The apple-extract stimulation did not lead to increased Th2-cytokine production in the oral mucosa or number of group 2 innate lymphoid cells or eosinophils. PFAS involves an early-phase response by mast cell degranulation via IgE signaling after the cross-reactivity of Bet v 1-specific IgE and the food allergen, and exacerbation of allergic symptom via proteases in food; PFAS does not involve a late phase with local Th2/eosinophilic inflammation in the oral mucosa. This novel murine model might be used for elucidating the pathogenesis and assessing new therapeutic strategies for PFAS.

Utilization of piperonyl butoxide and 1-aminobenzotriazole for metabolic studies of toxic chemicals in Daphnia magna and Chironomus yoshimatsui.

Daphnids and chironomids have been used to assess the ecological effects of chemicals released into water bodies; however, the toxicity mechanisms in organisms are generally difficult to identify. Here, we developed a system capable of estimating the contribution of cytochrome P450 (CYP) to the metabolism of test substances in Daphnia magna and Chironomus yoshimatsui based on toxicity differences in the absence and presence of the CYP inhibitors piperonyl butoxide (PBO) and 1-aminobenzotriazole (ABT). The optimum concentrations of PBO and ABT that could effectively reduce the toxicity of diazinon, which is toxic after oxidative metabolism in vivo, were determined as 0.5 and 0.6 mg/L for D. magna, and 2.0 and 40.0 mg/L for C. yoshimatsui, respectively. Acute immobilization tests of 15 insecticides were conducted for D. magna and C. yoshimatsui, with and without the optimum concentrations of PBO or ABT. In the presence of either inhibitor, chlorpyrifos and chlorfenapyr toxicity was reduced in both organisms, whereas those of thiocyclam, nereistoxin, and silafluofen were enhanced in C. yoshimatsui. Liquid chromatography-mass spectrometry analysis of D. magna and C. yoshimatsui samples exposed to chlorfenapyr confirmed that the level of the active metabolite produced by CYP was decreased by PBO or ABT in both organisms. The system to which the test substance was co-exposed to PBO or ABT will be valuable for estimating the contribution of CYPs to metabolism and elucidating the toxicity mechanism in daphnids and chironomids.

Epidemiological study of oral allergy syndrome in birch pollen dispersal-free regions.

BACKGROUND: Oral allergy syndrome (OAS) is an immediate allergy caused by a cross-reaction of highly homologous common antigens (pan-allergens) contained in fruits/vegetables and pollen. METHODS: A questionnaire was provided to 6824 outpatient visitors and serum levels of specific IgEs against crude antigens and pan-allergen components were measured to study the relationship between the prevalence of OAS and pollinosis in the Fukui Prefecture where there is almost no dispersal of birch pollen. RESULTS: The prevalence of OAS was 10.8%. The rate of pollinosis complication in the OAS group was 67.4%, and OAS was observed in 16.8% of pollinosis patients. Causative foods in order of frequency were melon, pineapple, kiwi fruit, peach, and apple. A significantly higher number of patients from the OAS group were positive for birch, alder, and timothy grass-specific IgE. The rate of positivity for anti-component IgE corresponding to pollen in OAS group was also significantly higher. Of 34 patients with OAS caused by eating apples, 28 (82.4%) were positive for Mal d1-specific IgE. Of the 52 patients with peach-induced OAS, 41 (78.8%) were positive for Pur p1-specific IgE. The concordance rates between crude antigen-specific IgE and anti-PR-10 component-specific IgE were 87.1% and 93.3% for apple and peach respectively. CONCLUSIONS: In regions where birch pollen is not dispersed, OAS patients have a significant association with the onset of Bet v1-associated allergy. Anti-PR-10 component IgE was useful in diagnosing OAS, and crude antigen-specific IgE was also associated with apple and peach allergies.

Long-term sublingual immunotherapy for Japanese cedar pollinosis and the levels of IL-17A and complement components 3a and 5a.

Allergen-specific immunotherapy is the only treatment that can alter the natural course of allergic disease. We performed long-term sublingual immunotherapy (SLIT) for patients with seasonal allergic rhinitis caused by Japanese cedar pollen (SAR-JCP), screened molecules as candidate biomarkers, and investigated serum IL-17A and complement components 3a (C3a) and C5a in order to evaluate whether these molecules show changes correlated to symptom scores. In this study, we found that the long-term SLIT reduced the serum levels of IL-17A and C3a and C5a. The levels of C3a in the patients significantly decreased from year 1 compared with those at the baseline, and their levels of IL-17A significantly decreased from year 2 compared with those at baseline. The levels of IL-17A, C3a, and C5a at year 4 of SLIT were significantly lower than not only those at baseline, but also those at year 1. A significant positive correlation was found between the symptom medication scores and the levels of IL-17A at year 4. The symptom medication scores in the group in which IL-17A levels decreased at year 4 were significantly lower than those in the group without such a decrease. The serum level of IL-17A might prove useful as a biological parameter to ascertain the effectiveness of SLIT for patients with SAR-JCP. It is necessary to produce new therapeutics for non-responders in whom serum IL-17A levels are still higher against long-term SLIT.

Apolipoprotein A-IV is a candidate target molecule for the treatment of seasonal allergic rhinitis.

BACKGROUND: Allergic rhinitis is a global health problem that causes major illnesses and disability worldwide. Allergen-specific immunotherapy (SIT) is the only available treatment that can alter the natural course of allergic disease. However, the precise mechanism underlying allergen-SIT is not well understood. OBJECTIVE: The aim of the current study was to identify protein expression signatures reflective of allergen-SIT-more specifically, sublingual immunotherapy (SLIT). METHODS: Serum was taken twice from patients with seasonal allergic rhinitis caused by Japanese cedar: once before the pollen season and once during the season. A total of 25 patients was randomly categorized into a placebo-treated group and an active-treatment group. Their serum protein profiles were analyzed by 2-dimensional electrophoresis. RESULTS: Sixteen proteins were found to be differentially expressed during the pollen season. Among the differentially expressed proteins, the serum levels of complement C4A, apolipoprotein A-IV (apoA-IV), and transthyretin were significantly increased in SLIT-treated patients but not in placebo-treated patients. Among these proteins, the serum levels of apoA-IV correlated with the clinical symptom-medication scores (r = -0.635; P < .05) and with quality of life scores (r = -0.516; P < .05) in the case of SLIT-treated patients. The amount of histamine released from the basophils in vitro was greatly reduced after the addition of recombinant apoA-IV in the medium (P < .01). CONCLUSION: Our data will increase the understanding of the mechanism of SLIT and may provide novel insights into the treatment of allergic rhinitis.

Prevalence of allergic rhinitis and sensitization to common aeroallergens in a Japanese population.

BACKGROUND: Allergic rhinitis (AR) is recognized as a major health problem worldwide, and its prevalence depends on the age range of the subjects. The aims of this study were to determine the current prevalence of AR, effects of age on the prevalence of IgE sensitization to inhalant allergens, and serum total IgE levels in Japanese subjects. METHODS: We conducted a survey of 1,540 subjects between 20 and 49 years of age in 2006 and 2007 and examined the prevalence of AR and sensitization to 7 common aeroallergens. We measured serum total IgE and specific IgE to 7 aeroallergens. AR was determined based on symptoms, predominantly in the nose and eyes, caused by aeroallergens as mentioned in a questionnaire and sensitization to any of the 7 aeroallergens as assessed by measurement of serum specific IgE. RESULTS: The prevalence of AR was 44.2% (681 of the 1,540 subjects) and there was no difference among age decades. Of the 1,540 subjects, 1,073 (69.7%) were sensitized to at least 1 of the 7 aeroallergens. The most common allergen in AR was Japanese cedar pollen (89.6%, 610 of the 681 with AR) in all the age decades examined. The sensitization rate to mites was significantly higher in the younger subjects. CONCLUSION: Our data suggest that the prevalence of AR between 20 and 49 years of age has increased by nearly 10% during the last 10 years. Cedar pollen and mites were predominant allergen sources among the 7 aeroallergens in the Japanese population.

Efficacy of oral olopatadine hydrochloride for the treatment of seasonal allergic rhinitis: A randomized, double-blind, placebo-controlled study.

Adequate treatment is critical for maintaining a good level of quality of life (QOL) during the pollen season in patients suffering from seasonal allergic rhinitis (SAR). Olopatadine, a histamine H(1)-receptor antagonist, has been approved in the United States and Europe for the treatment of AR and allergic conjunctivitis as a nasal spray and an ophthalmic solution, respectively. We conducted a randomized, double-blind, placebo-controlled study to determine whether orally administered olopatadine for prophylactic purposes might also be effective for the control of nasal allergy symptoms, especially nasal congestion, in patients with SAR due to Japanese cedar pollen (SAR-JP). A total of 110 patients with SAR caused by JP were randomized to the treatment. The subjects recorded their nasal and ocular allergic symptom scores in a diary, and their QOL was assessed by the Japanese version of the Rhinoconjunctivity Quality of Life Questionnaire. Treatment with oral olopatadine significantly suppressed sneezing (p < 0.001), rhinorrhea (p < 0.001), and nasal congestion (p < 0.05). The total QOL score during the peak JP season was superior in the olopatadine group than in the placebo group (p < 0.05). However, orally administered olopatadine did not exert any significant effect against eye itching and watering of the eyes, unlike olopatadine nasal spray. Treatment with olopatadine tablets yielded superior QOL scores in the domains of usual daily activities and outdoor activities when compared with placebo. No serious adverse effects of the treatment were reported during the study period. These results suggest that oral olopatadine treatment may be a useful alternative treatment strategy for AR.

Comparative effects of ultra-short-acting beta1-blockers on voltage-gated tetrodotoxin-resistant Na+ channels in rat sensory neurons.

BACKGROUND AND OBJECTIVE: To examine a possible mechanism for their antinociceptive actions, we compared the effects of two clinically used ultra-short-acting beta1-blockers, landiolol and esmolol, on tetrodotoxin-resistant sodium (TTX-r Na) channels in rat dorsal root ganglion neurons, which are important for nociception. METHODS: In small (<30 microm) dorsal root ganglion neurons from Sprague-Dawley rats, recordings of whole-cell membrane currents were made using the patch-clamp technique. To examine the effects of landiolol and esmolol on TTX-r Na currents, whole-cell membrane Na currents were evoked every 10 s by stepping for 50 ms from a holding potential of -70 to -10 mV. Each drug was applied at stepwise-increased concentrations every 2 min. The voltage dependence of the steady-state inactivation of the TTX-r Na current was investigated by using a conventional double-pulse protocol. To test for use-dependent blockade of TTX-r Na channels by beta-blockers, trains of depolarizing pulses (to -10 from a holding potential of -70 mV) were applied at one of three frequencies (0.2, 5 or 20 Hz) in the absence or presence of drug (landiolol 8 mmol l, esmolol 140 micromol l). RESULTS: Esmolol blocked TTX-r Na currents in a dose-dependent and use-dependent manner, but a very high concentration of landiolol was required to block TTX-r Na channel activities. The half-maximal inhibitory concentrations (IC50) for the TTX-r Na current were (holding potential, -70 mV) landiolol 7.66 +/- 0.62 mmol l (n = 6) and esmolol 145 +/- 7.5 micromol l (n = 6), and the Hill coefficients were landiolol 1.06 +/- 0.09 (n = 6) and esmolol 0.96 +/- 0.05 (n = 6). CONCLUSION: Esmolol, but not landiolol, may have useful effects against pain related to TTX-r Na channel activity.

Functional expression of GABAB receptors in airway epithelium.

Gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the mammalian central nervous system and exerts its actions via both ionotropic (GABA(A)) and metabotropic (GABA(B)) receptors. The GABA(B) receptor is a dimer composed of R1 and R2 components and classically couples to the heterotrimeric G(i) protein. In addition to their location on neurons, GABA and functional GABA(B) receptors have been detected in peripheral tissue such as airway smooth muscle. We questioned whether airway epithelium expresses receptors that could respond to GABA. We detected the mRNA encoding multiple-splice variants of the GABA(B)R1 and GABA(B)R2 in total RNA isolated from native human and guinea pig airway epithelium and human airway epithelial cell lines (BEAS-2B and H441). Immunoblots identified the GABA(B)R1 and GABA(B)R2 proteins in both guinea pig airway epithelium and BEAS-2B cells. The expression of GABA(B)R1 protein was immunohistochemically localized to basal mucin-secreting and ciliated columnar epithelial cells in guinea pig trachea. Baclofen inhibited adenylyl cyclase activity, induced ERK phosphorylation and cross-regulated phospholipase C, leading to increased inositol phosphates in BEAS-2B cells in a pertussis toxin-sensitive manner, implicating G(i) protein coupling. Thus, these receptors couple to G(i) and cross-regulate the phospholipase C/inositol phosphate pathway. The second messengers of these pathways, cyclic AMP and calcium, play pivotal roles in airway epithelial cell primary functions of mucus clearance. Furthermore, the enzyme that synthesizes GABA, glutamic acid decarboxylase (GAD65/67), was also localized to airway epithelium. GABA may modulate an uncharacterized signaling cascade via GABA(B) receptors coupled to G(i) protein in airway epithelium.

Posterior Reversible Encephalopathy Syndrome after Lenvatinib Therapy in a Patient with Anaplastic Thyroid Carcinoma.

Posterior reversible encephalopathy syndrome (PRES) is a rare reversible neurological syndrome that causes subcortical vasogenic brain edema and which is associated with the use of target-specific agents. Lenvatinib is a target-specific agent that was recently approved for inoperable thyroid cancer. We herein describe the case of a 66-year-old woman with anaplastic thyroid cancer (ATC) who was treated with lenvatinib and who subsequently developed PRES. The clinical and radiological findings improved after suspending therapy for 1 week, and there was no recurrence with intermittent lower-dose lenvatinib treatment. Lenvatinib may prolong survival in patients with ATC and can be administered intermittently, even after PRES onset.

Factors associated with the development and remission of allergic diseases in an epidemiological survey of high school students in Japan.

BACKGROUND: Allergic diseases are an important health problem for children and adults. It is important to know how allergic diseases develop and remit from infancy to adolescence. Early intervention is effective in treating allergic diseases. OBJECTIVE: We performed a large-scale questionnaire survey of high school students in Fukui Prefecture, Japan, and analyzed the factors associated with the development and remission of allergic diseases. METHODS: A total of 21,802 students participated in the epidemiologic survey, and the valid response rate was 89.3% (19,461). We applied an inverse probability weighting method with propensity scores. RESULTS: The present prevalence rate of allergic rhinitis (AR) was 19.2%. The remission rate of AR was 15.3%. Only children and firstborns had a significantly higher risk of developing symptoms of allergic diseases [only child: AR, 1.37; bronchial asthma (BA), 1.30; food allergy (FA), 1.33 and firstborn: AR, 1.38; BA, 1.10]. Constipation was an associated factor for development of atopic dermatitis (AD) (1.17) and AR (1.17), regular intake of lactic acid bacteria was not an associated factor for development of allergic diseases but was a factor for remission of AD (1.22). Hypohidrosis was an associated factor for development of AD (1.25). High academic performance was an associated factor for development of AR (1.20) but was a negative factor for development of BA (0.89). The values in parentheses are significant adjusted odds ratios. CONCLUSION: This epidemiologic survey showed that the hygiene hypothesis and intestinal bacterial flora might influence the development of symptoms and remission of allergic diseases.

Predictor of rehabilitation outcome for dysphagia.

OBJECTIVE: Predicting whether dysphagia will resolve is very difficult, but is obviously important for patients and their families as well as for physicians. This study retrospectively evaluated potential prognostic indicators for dysphagia in order to examine the feasibility of predicting the outcome. METHODS: Data on 123 patients who received initial treatment for dysphagia between April 2008 and March 2010 were reviewed. The patient population included 63 men and 60 women, with a mean age of 81.4 years. All the patients underwent physical examination and video-endoscopy (VE) at the initial assessment, and video-fluorography (VF) was also done if necessary. We used the "Food Intake Level Scale" (FILS) to classify the severity of dysphagia as follows: "no oral intake" (FILS score: 1-3), "oral intake and alternative nutrition" (FILS score: 4-6), and "oral intake alone" (FILS score: 7-10). The patient's age, primary disease, cognitive ability, and general condition were evaluated as potential factors associated with the severity of dysphagia. Each patient underwent assessment at every 2 weeks to evaluate the progress of their dysphagia. RESULTS: Forty-six patients were classified as "no oral intake" (FILS score: 1-3) at the initial examination and subsequently showed improvement to "oral intake and alternative nutrition" (FILS score: 4-6) or "oral intake alone" (FILS score: 7-10). They were compared with 43 patients who were also "no oral intake" at the second examination after training in swallowing. The combination of stroke and cognitive dysfunction showed a sensitivity of 75.9% (22/29) and specificity of 78.3% (18/23) for predicting no improvement of dysphagia, and was a statistically significant parameter. The presence of disuse syndrome showed a sensitivity of 66.0% (31/47) and specificity of 71.4% (30/42) for predicting no improvement of dysphagia, and this was also a significant parameter. CONCLUSION: The results of this study suggest that a combination of factors other than stroke, including cognitive dysfunction and a decrease in activity of daily living (ADL) influence the outcome of dysphagia. It is not rare for patients who resume oral intake to be readmitted within a year for symptoms such as fever. Therefore, effective rehabilitation programs should be developed for the impairments of elderly patients and common disabilities such as dysphagia.

Prevalence of inhaled antigen sensitization and nasal eosinophils in Japanese children under two years old.

OBJECTIVE: The increasingly younger age of onset of allergic rhinitis (AR) has recently become a problem. This study examined the prevalence of inhaled antigen sensitization and nasal eosinophils in children younger than two years old, with measurement of the serum concentrations of aeroallergen-specific IgE antibodies to house dust mites, cat fur, and Japanese cedar pollen, measurement of nasal eosinophil counts, and a questionnaire administered to the children's parents. METHODS: The subjects were a group of healthy children undergoing 18-month infant health checks provided by the local government, and sick children younger than two years old at the pediatric hospital. RESULTS: Among 408 healthy infants, 44 (10.7%) had antigen-specific IgE antibodies, 29 (7.1%) had nasal eosinophils, and eight (2.0%) had both specific IgE antibodies and nasal eosinophils. Nasal assessment revealed that 125 children had rhinorrhea. Of the infants who showed both sensitization to antigens and nasal eosinophils, six (1.5%) had confirmed rhinorrhea. Among 186 sick children younger than two years old at the pediatric hospital, aeroallergen-specific IgE antibodies were detected in five (2.6%). The presence of nasal eosinophils was confirmed in six children (3.2%), which percentage was smaller than that of the healthy group. No infant had either sensitization to antigens or nasal eosinophils. CONCLUSION: The findings described above indicate that the minimum prevalence of AR might be 1.5% in 18-month-old children and that around 10% of affected children have aeroallergen-specific IgE antibodies in Japan. The incidence of AR in young children might increase further.

Human impacts on large benthic foraminifers near a densely populated area of Majuro Atoll, Marshall Islands.

Human impacts on sand-producing, large benthic foraminifers were investigated on ocean reef flats at the northeast Majuro Atoll, Marshall Islands, along a human population gradient. The densities of dominant foraminifers Calcarina and Amphistegina declined with distance from densely populated islands. Macrophyte composition on ocean reef flats differed between locations near sparsely or densely populated islands. Nutrient concentrations in reef-flat seawater and groundwater were high near or on densely populated islands. delta(15)N values in macroalgal tissues indicated that macroalgae in nearshore lagoons assimilate wastewater-derived nitrogen, whereas those on nearshore ocean reef flats assimilate nitrogen from other sources. These results suggest that increases in the human population result in high nutrient loading in groundwater and possibly into nearshore waters. High nutrient inputs into ambient seawater may have both direct and indirect negative effects on sand-producing foraminifers through habitat changes and/or the collapse of algal symbiosis.

Raf-1 kinase mediates adenylyl cyclase sensitization by TNF-alpha in human airway smooth muscle cells.

Tumor necrosis factor (TNF)-alpha is a potent inflammatory cytokine implicated in the exacerbation of asthma. Chronic exposure to TNF-alpha has been reported to induce G protein-coupled receptor desensitization, but adenylyl cyclase sensitization, in airway smooth muscle cells by an unknown mechanism. Cyclic AMP, which is synthesized by adenylyl cyclases in response to G protein-coupled receptor signals, is an important second messenger involved in the regulation of the airway muscle proliferation, migration, and tone. In other cell types, TNF-alpha receptors transactivate the EGF receptor, which activates raf-1 kinase. Further studies in transfected cells show that raf-1 kinase can phosphorylate and activate some isoforms of adenylyl cyclase. Cultured human airway smooth muscle cells were treated with TNF-alpha in the presence or absence of inhibitors of prostaglandin signaling, protein kinases, or G(i) proteins. TNF-alpha caused a significant dose- (1-10 ng/ml) and time-dependent (24 and 48 h) increase in forskolin-stimulated adenylyl cyclase activity, which was abrogated by pretreatment with GW5074 (a raf-1 kinase inhibitor), was partially inhibited by an EGF receptor inhibitor, but was unaffected by pertussis toxin. TNF-alpha also increased phosphorylation of Ser(338) on raf-1 kinase, indicative of activation. IL-1beta and EGF sensitization of adenylyl cyclase activity was also sensitive to raf-1 kinase inhibition by GW5074. Taken together, these studies link two signaling pathways not previously characterized in human airway smooth muscle cells: TNF-alpha transactivation of the EGF receptor, with subsequent raf-1 kinase-mediated activation of adenylyl cyclase.

Functional expression of the GABAB receptor in human airway smooth muscle.

gamma-Aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the mammalian central nervous system and exerts its actions via both ionotropic (GABA(A)/GABA(C)) and metabotropic (GABA(B)) receptors (R). In addition to their location on neurons, GABA and functional GABA(B) receptors have been detected in nonneuronal cells in peripheral tissue. Although the GABA(B)R has been shown to function as a prejunctional inhibitory receptor on parasympathetic nerves in the lung, the expression and functional coupling of GABA(B) receptors to G(i) in airway smooth muscle itself have never been described. We detected the mRNA encoding multiple-splice variants of the GABA(B)R1 and GABA(B)R2 in total RNA isolated from native human and guinea pig airway smooth muscle and from RNA isolated from cultured human airway smooth muscle (HASM) cells. Immunoblots identified the GABA(B)R1 and GABA(B)R2 proteins in human native and cultured airway smooth muscle. The GABA(B)R1 protein was immunohistochemically localized to airway smooth muscle in guinea pig tracheal rings. Baclofen, a GABA(B)R agonist, elicited a concentration-dependent stimulation of [(35)S]GTPgammaS binding in HASM homogenates that was abrogated by the GABA(B)R antagonist CGP-35348. Baclofen also inhibited adenylyl cyclase activity and induced ERK phosphorylation in HASM. Another GABA(B)R agonist, SKF-97541, mimicked while pertussis toxin blocked baclofen's effect on ERK phosphorylation, implicating G(i) protein coupling. Functional GABA(B) receptors are expressed in HASM. GABA may modulate an uncharacterized signaling cascade via GABA(B) receptors coupled to the G(i) protein in airway smooth muscle.

The effects of class Ic antiarrhythmics on tetrodotoxin-resistant Na+ currents in rat sensory neurons.

IV or oral administration of antiarrhythmics has been reported to be effective for relieving neuropathic pain. Recent reports have indicated that tetrodotoxin-resistant (TTX-R) Na(+) channels play important roles in the nerve conduction of nociceptive sensation. In the present study, we investigated the effects of flecainide, pilsicainide (class Ic antiarrhythmics), and lidocaine (a class Ib drug) on TTX-R Na(+) currents in rat dorsal root ganglion neurons using the whole-cell patch-clamp method. Flecainide, pilsicainide, and lidocaine reversibly blocked the peak amplitude of TTX-R Na(+) currents in a concentration-dependent manner with half-maximum inhibitory concentration values of 8.5 +/- 6.6 microM (n = 7), 78 +/- 6.9 microM (n = 7), and 73 +/- 6.8 microM (n = 7), respectively. Each drug shifted the inactivation curve for the TTX-R Na(+) currents in the hyperpolarizing direction and caused a use-dependent block. We also studied an interaction between these antiarrhythmics on TTX-R Na(+) channels. Additional application of flecainide or pilsicainide to lidocaine resulted in an additive increase of tonic and use-dependent block. These results suggest that the inhibition of TTX-R Na(+) currents of dorsal root ganglion neurons by such antiarrhythmics is attributable, at least partly, to their antinociceptive effects.