RESUMO
The aim of this study is to verify the impact of Leptin in blood pressure (BP) regulation and Leptin-resistance in metabolic/neurogenic hypertension through baroreflex afferents and dysregulation. Artery BP/heart rate (HR) were measured while nodose (NG) microinjection of Leptin, membrane depolarization/inward current were obtained by whole-cell patch from NG neurons isolated from adult female rats. Baroreflex sensitivity (BRS) tested with PE/SNP, distribution/expression of Leptin/receptors in the NG/nucleus tractus solitary (NTS) examined using immumostaining and qRT-PCR, and serum concentrations of Leptin/NE measured by ELISA were observed in control and high fructose-drinking induced hypertension (HTN-HFD) rats. The results showed that BP was significantly/dose-dependently reduced by Leptin NG microinjection likely through direct excitation of female-specific subpopulation of Ah-type neurons showing a potent membrane depolarization/inward currents. Sex-specific distribution/expression of OB-Ra/OB-Rb in the NG were detected with estrogen-dependent manner, similar observations were also confirmed in the NTS. As expected, BRS was dramatically decreased in the presence of PE/SNP in both male and female rats except for the female with PE at given concentrations. Additionally, serum concentration of Leptin was elevated in HFD-HTN model rats of either sex with more obvious in females. Under hypertensive condition, the mean fluorescent density of OB-R and mRNA expression for OB-Ra/OB-Rb in the NG/NTS were significantly down-regulated. These results have demonstrated that Leptin play a role in dominant parasympathetic drive via baroreflex afferent activation to buffer Leptin-mediated sympathetic activation systemically and Leptin-resistance is an innegligible mechanism for metabolic/neurogenic hypertension through baroreflex afferent dysregulation.
Assuntos
Barorreflexo , Pressão Sanguínea , Hipertensão , Leptina , Animais , Feminino , Masculino , Ratos , Barorreflexo/efeitos dos fármacos , Pressão Sanguínea/efeitos dos fármacos , Frequência Cardíaca/efeitos dos fármacos , Hipertensão/metabolismo , Hipertensão/fisiopatologia , Leptina/farmacologia , Leptina/metabolismo , Leptina/sangue , Neurônios/metabolismo , Neurônios/efeitos dos fármacos , Gânglio Nodoso/metabolismo , Gânglio Nodoso/efeitos dos fármacos , Ratos Sprague-Dawley , Receptores para Leptina/metabolismo , Núcleo Solitário/metabolismo , Núcleo Solitário/efeitos dos fármacosRESUMO
Prostaglandin E2 (PGE2)-induced coughs in vivo and vagal nerve depolarization in vitro are inhibited by systemic and local administration of prostaglandin EP3 receptor (L-798106) and TRPV1 antagonists (JNJ 17203212). These results indicate a modulating effect of TRPV1 on the EP3 receptor-mediated cough responses to PGE2 likely through the vagal sensory nerve. This study aimed to determine whether 1) inhalation of aerosolized JNJ 17203212 and L-798106 affected cough responses to citric acid (CA, mainly stimulating TRPV1) and PGE2; 2) TRPV1 and EP3 receptor morphologically are co-expressed and electrophysiologically functioned in the individual of vagal pulmonary C-neurons (cell bodies of bronchopulmonary C-fibers in the nodose/jugular ganglia); and 3) there was a cross-effect of TRPV1 and EP3 receptor on these neural excitations. To this end, aerosolized CA or PGE2 was inhaled by unanesthetized guinea pigs pretreated without or with each antagonist given in aerosol form. Immunofluorescence was applied to identify the co-expression of TRPV1 and EP3 receptor in vagal pulmonary C-neurons (retrogradely traced by DiI). Whole-cell voltage patch clamp approach was used to detect capsaicin (CAP)- and PGE2-induced currents in individual vagal pulmonary C-neurons and determine the effects of the TRPV1 and EP3 receptor antagonists on the evoked currents. We found that PGE2-induced cough was attenuated by JNJ 17203212 or L-798106 and CA-evoked cough greatly suppressed only by JNJ 17203212. Approximately 1/4 of vagal pulmonary C-neurons co-expressed EP3 with a cell size < 20 µm. Both CAP- and PGE2-induced currents could be recorded in the individuals of some vagal pulmonary C-neurons. The former was largely inhibited only by JNJ 17203212, while the latter was suppressed by JNJ 17203212 or L-798106. The similarity of the cross-effect of both antagonists on cough and vagal pulmonary C-neural activity suggests that a subgroup of vagal pulmonary C-neurons co-expressing TRPV1 and EP3 receptor is, at least in part, responsible for the cough response to PGE2.
Assuntos
Brônquios/metabolismo , Tosse/metabolismo , Fibras Nervosas Amielínicas/metabolismo , Receptores de Prostaglandina E Subtipo EP3/metabolismo , Canais de Cátion TRPV/metabolismo , Aminopiridinas/farmacologia , Animais , Capsaicina , Ácido Cítrico/farmacologia , Proteínas Quinases Dependentes de AMP Cíclico/antagonistas & inibidores , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Dinoprostona , Cobaias , Ativação do Canal Iônico/efeitos dos fármacos , Masculino , Modelos Biológicos , Fibras Nervosas Amielínicas/efeitos dos fármacos , Gânglio Nodoso/efeitos dos fármacos , Piperazinas/farmacologia , Inibidores de Proteínas Quinases/farmacologia , Ventilação Pulmonar/efeitos dos fármacos , Receptores de Prostaglandina E Subtipo EP3/antagonistas & inibidores , Células Receptoras Sensoriais/efeitos dos fármacos , Células Receptoras Sensoriais/metabolismo , Canais de Cátion TRPV/antagonistas & inibidores , Nervo Vago/efeitos dos fármacos , Nervo Vago/metabolismoRESUMO
Hydrogen sulfide (H2S), which is closely related to various cardiovascular disorders, lowers blood pressure (BP), but whether this action is mediated via the modification of baroreflex afferent function has not been elucidated. Therefore, the current study aimed to investigate the role of the baroreflex afferent pathway in H2S-mediated autonomic control of BP regulation. The results showed that baroreflex sensitivity (BRS) was increased by acute intravenous NaHS (a H2S donor) administration to renovascular hypertensive (RVH) and control rats. Molecular expression data also showed that the expression levels of critical enzymes related to H2S were aberrantly downregulated in the nodose ganglion (NG) and nucleus tractus solitarius (NTS) in RVH rats. A clear reduction in BP by the microinjection of NaHS or L-cysteine into the NG was confirmed in both RVH and control rats, and a less dramatic effect was observed in model rats. Furthermore, the beneficial effects of NaHS administered by chronic intraperitoneal infusion on dysregulated systolic blood pressure (SBP), cardiac parameters, and BRS were verified in RVH rats. Moreover, the increase in BRS was attributed to activation and upregulation of the ATP-sensitive potassium (KATP) channels Kir6.2 and SUR1, which are functionally expressed in the NG and NTS. In summary, H2S plays a crucial role in the autonomic control of BP regulation by improving baroreflex afferent function due at least in part to increased KATP channel expression in the baroreflex afferent pathway under physiological and hypertensive conditions.
Assuntos
Vias Aferentes/metabolismo , Barorreflexo/fisiologia , Pressão Sanguínea/fisiologia , Sulfeto de Hidrogênio/metabolismo , Hipertensão/fisiopatologia , Animais , Anti-Hipertensivos/farmacologia , Barorreflexo/efeitos dos fármacos , Pressão Sanguínea/efeitos dos fármacos , Cardiotônicos/farmacologia , Cistationina beta-Sintase/metabolismo , Cistationina gama-Liase/metabolismo , Sulfeto de Hidrogênio/farmacologia , Hipertensão/tratamento farmacológico , Masculino , Gânglio Nodoso/efeitos dos fármacos , Gânglio Nodoso/enzimologia , Gânglio Nodoso/metabolismo , Canais de Potássio Corretores do Fluxo de Internalização/metabolismo , Ratos Sprague-Dawley , Núcleo Solitário/efeitos dos fármacos , Núcleo Solitário/enzimologia , Núcleo Solitário/metabolismo , Sulfetos/farmacologia , Receptores de Sulfonilureias/metabolismo , Sulfurtransferases/metabolismoRESUMO
BACKGROUND: Acetylsalicylic acid (ASA) is a commonly used anti-inflammatory, antipyretic, and analgesic drug, which has many side effects on the gastric mucosal layer. Despite this, knowledge concerning the influence of ASA on neuronal cells supplying the stomach is very scanty. METHODS: This investigation was performed on ten immature gilts of the Large White Polish race divided into two groups (five animals in each): a control group and animals which were treated with ASA. The retrograde neuronal tracer Fast Blue (FB) was injected into the prepyloric region of the stomach in all animals. ASA was then given orally to the experimental (ASA) group of gilts from the seventh day after FB injection to the 27th day of the experiment. After this period, all animals were euthanized. Immediately after euthanasia, nodose ganglia (NG) were collected and subjected to a standard double-labelling immunofluorescence technique using antibodies directed toward substance P (SP) and other selected neuronal factors, such as galanin (GAL), neuronal isoform of nitric oxide synthase (nNOS), vasoactive intestinal polypeptide (VIP), and calcitonin gene-related peptide (CGRP). Key Results. The obtained results show that SP-LI neurons located in NG supplying the porcine stomach were also immunoreactive to all the above-mentioned neuronal factors. Moreover, ASA administration caused an increase in the degree of colocalization of SP with other neuronal active substances, and the most visible changes concerned the number of neurons simultaneously immunoreactive to SP and CGRP. Conclusions and Inferences. These observations indicate that the population of SP-LI neurons supplying the stomach is not homogeneous and may undergo changes after ASA administration. These changes are probably connected with inflammatory processes and/or neuroprotective reactions although their exact mechanisms remain unknown.
Assuntos
Aspirina/farmacologia , Gânglio Nodoso/efeitos dos fármacos , Estômago/inervação , Substância P/metabolismo , Animais , Aspirina/administração & dosagem , Feminino , Neuropeptídeos/metabolismo , Gânglio Nodoso/química , Estômago/química , SuínosRESUMO
The lungs and the immune and nervous systems functionally interact to respond to respiratory environmental exposures and infections. The lungs are innervated by vagal sensory neurons of the jugular and nodose ganglia, fused together in smaller mammals as the jugular-nodose complex (JNC). Whereas the JNC shares properties with the other sensory ganglia, the trigeminal (TG) and dorsal root ganglia (DRG), these sensory structures express differential sets of genes that reflect their unique functionalities. Here, we used RNA sequencing (RNA-seq) in mice to identify the differential transcriptomes of the three sensory ganglia types. Using a fluorescent retrograde tracer and fluorescence-activated cell sorting, we isolated a defined population of airway-innervating JNC neurons and determined their differential transcriptional map after pulmonary exposure to lipopolysaccharide (LPS), a major mediator of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) after infection with gram-negative bacteria or inhalation of organic dust. JNC neurons activated an injury response program, leading to increased expression of gene products such as the G protein-coupled receptor Cckbr, inducing functional changes in neuronal sensitivity to peptides, and Gpr151, also rapidly induced upon neuropathic nerve injury in pain models. Unique JNC-specific transcripts, present at only minimal levels in TG, DRG, and other organs, were identified. These included TMC3, encoding for a putative mechanosensor, and urotensin 2B, a hypertensive peptide. These findings highlight the unique properties of the JNC and reveal that ALI/ARDS rapidly induces a nerve injury-related state, changing vagal excitability.
Assuntos
Gânglio Nodoso/efeitos dos fármacos , Pneumonia/genética , Receptor de Colecistocinina B/genética , Células Receptoras Sensoriais/efeitos dos fármacos , Transcriptoma , Traumatismos do Nervo Vago/genética , Animais , Gânglios Espinais/efeitos dos fármacos , Gânglios Espinais/imunologia , Gânglios Espinais/patologia , Perfilação da Expressão Gênica , Peptídeos e Proteínas de Sinalização Intracelular/genética , Peptídeos e Proteínas de Sinalização Intracelular/imunologia , Lipopolissacarídeos/farmacologia , Pulmão/efeitos dos fármacos , Pulmão/imunologia , Pulmão/patologia , Proteínas de Membrana/genética , Proteínas de Membrana/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Gânglio Nodoso/imunologia , Gânglio Nodoso/patologia , Hormônios Peptídicos/genética , Hormônios Peptídicos/imunologia , Pneumonia/induzido quimicamente , Pneumonia/imunologia , Pneumonia/patologia , Receptor de Colecistocinina B/imunologia , Receptores Acoplados a Proteínas G/genética , Receptores Acoplados a Proteínas G/imunologia , Células Receptoras Sensoriais/imunologia , Células Receptoras Sensoriais/patologia , Análise de Sequência de RNA , Gânglio Trigeminal/efeitos dos fármacos , Gânglio Trigeminal/imunologia , Gânglio Trigeminal/patologia , Traumatismos do Nervo Vago/induzido quimicamente , Traumatismos do Nervo Vago/imunologia , Traumatismos do Nervo Vago/patologiaRESUMO
BACKGROUND: Extracellular adenosine 5'-triphosphate (ATP) plays important mechanistic roles in pulmonary disorders in general and chronic obstructive pulmonary disease (COPD) and cough in particular. The effects of ATP in the lungs are mediated to a large extent by P2X2/3 receptors (P2X2/3R) localized on vagal sensory nerve terminals (both C and Aδ fibers). The activation of these receptors by ATP triggers a pulmonary-pulmonary central reflex, which results in bronchoconstriction and cough, and is also proinflammatory due to the release of neuropeptides from these nerve terminals via the axon reflex. These actions of ATP in the lungs constitute a strong rationale for the development of a new class of drugs targeting P2X2/3R. DT-0111 is a novel, small, water-soluble molecule that acts as an antagonist at P2X2/3R sites. METHODS: Experiments using receptor-binding functional assays, rat nodose ganglionic cells, perfused innervated guinea pig lung preparation ex vivo, and anesthetized and conscious guinea pigs in vivo were performed. RESULTS: DT-0111 acted as a selective and effective antagonist at P2X2/3R, that is, it did not activate or block P2YR; markedly inhibited the activation by ATP of nodose pulmonary vagal afferents in vitro; and, given as an aerosol, inhibited aerosolized ATP-induced bronchoconstriction and cough in vivo. CONCLUSIONS: These results indicate that DT-0111 is an attractive drug-candidate for the treatment of COPD and chronic cough, both of which still constitute major unmet clinical needs. The reviews of this paper are available via the supplementary material section.
Assuntos
Tosse/tratamento farmacológico , Pulmão/inervação , Neurônios/efeitos dos fármacos , Gânglio Nodoso/efeitos dos fármacos , Doença Pulmonar Obstrutiva Crônica/tratamento farmacológico , Antagonistas do Receptor Purinérgico P2X/farmacologia , Receptores Purinérgicos P2X2/efeitos dos fármacos , Receptores Purinérgicos P2X3/efeitos dos fármacos , Potenciais de Ação , Trifosfato de Adenosina/metabolismo , Administração por Inalação , Aerossóis , Animais , Broncoconstrição/efeitos dos fármacos , Tosse/metabolismo , Tosse/fisiopatologia , Cobaias , Masculino , Neurônios/metabolismo , Gânglio Nodoso/metabolismo , Gânglio Nodoso/fisiopatologia , Estudo de Prova de Conceito , Doença Pulmonar Obstrutiva Crônica/metabolismo , Doença Pulmonar Obstrutiva Crônica/fisiopatologia , Antagonistas do Receptor Purinérgico P2X/administração & dosagem , Ratos , Receptores Purinérgicos P2X2/metabolismo , Receptores Purinérgicos P2X3/metabolismo , Transdução de SinaisRESUMO
The nodose ganglion (NG) is the main parasympathetic ganglion conveying sensory signals to the CNS from numerous visceral organs including digestive signals such as gastric distension or the release the gastrointestinal peptides. The response characteristics of NG neurons to ATP and ADP and pharmacological interrogation of purinergic receptor subtypes have been previously investigated but often in NG cells of undetermined visceral origin. In this study, we confirmed the presence of P2X3 and P2Y1 receptors and characterized P2X and P2Y responses in gastric-innervating NG neurons. Application of ATP-evoked large inward currents and cytosolic Ca2+ increases in gastric-innervating NG neurons. Despite the expression of P2Y1 receptors, ADP elicited only minor modulation of voltage-gated Ca2+ channels. Considering the sensitivity of NG neurons to comorbidities associated with disease or neural injury, purinergic modulation of gastric NG neurons in disease- or injury-states is worthy of further investigation.
Assuntos
Gânglio Nodoso/metabolismo , Receptores Purinérgicos/metabolismo , Células Receptoras Sensoriais/metabolismo , Estômago/inervação , Nervo Vago/metabolismo , Trifosfato de Adenosina/farmacologia , Animais , Cálcio/metabolismo , Sinalização do Cálcio/efeitos dos fármacos , Masculino , Gânglio Nodoso/efeitos dos fármacos , Ratos , Ratos Wistar , Células Receptoras Sensoriais/efeitos dos fármacos , Estômago/efeitos dos fármacos , Nervo Vago/efeitos dos fármacosRESUMO
Previous work has shown that cannabinoids increase feeding, while cholecystokinin (CCK) has an anorexigenic effect on food intake. Receptors for these hormones are located on cell bodies of vagal afferent nerves in the nodose ganglia. An interaction between CCK and endocannabinoid receptors has been suggested. The purpose of these studies is to explore the effect of pretreatment with a cannabinoid agonist, CP 55,940, on nodose neuron activation by CCK. To determine the effect of CP 55,940 and CCK on neuron activation, rats were anesthetized and nodose ganglia were excised. The neurons were dissociated and placed in culture on coverslips. The cells were treated with media; CP 55,940; CCK; CP 55,940 followed by CCK; or AM 251, a CB1 receptor antagonist, and CP 55,940 followed by CCK. Immunohistochemistry was performed to stain the cells for cFos as a measure of cell activation. Neurons were identified using neurofilament immunoreactivity. The neurons on each slip were counted using fluorescence imaging, and the number of neurons that were cFos positive was counted in order to calculate the percentage of activated neurons per coverslip. Pretreatment with CP 55,940 decreased the percentage of neurons expressing cFos-immunoreactivity in response to CCK. This observation suggests that cannabinoids inhibit CCK activation of nodose ganglion neurons.
Assuntos
Agonistas de Receptores de Canabinoides/farmacologia , Colecistocinina/farmacologia , Cicloexanóis/farmacologia , Neurônios/efeitos dos fármacos , Gânglio Nodoso/efeitos dos fármacos , Animais , Células Cultivadas , Masculino , Neurônios/metabolismo , Gânglio Nodoso/citologia , Proteínas Proto-Oncogênicas c-fos/genética , Proteínas Proto-Oncogênicas c-fos/metabolismo , Ratos , Ratos Sprague-DawleyRESUMO
We have addressed the hypothesis that the opposing effects of bronchopulmonary C-fiber activation on cough are attributable to the activation of C-fiber subtypes. Coughing was evoked in anesthetized guinea pigs by citric acid (0.001-2 M) applied topically in 100-µl aliquots to the tracheal mucosa. In control preparations, citric acid evoked 10 ± 1 coughs cumulatively. Selective activation of the pulmonary C fibers arising from the nodose ganglia with either aerosols or continuous intravenous infusion of adenosine or the 5-HT3 receptor-selective agonist 2-methyl-5-HT nearly abolished coughing evoked subsequently by topical citric acid challenge. Delivering adenosine or 2-methyl-5-HT directly to the tracheal mucosa (where few if any nodose C fibers terminate) was without effect on citric acid-evoked cough. These actions of pulmonary administration of adenosine and 2-methyl-5-HT were accompanied by an increase in respiratory rate, but it is unlikely that the change in respiratory pattern caused the decrease in coughing, as the rapidly adapting receptor stimulant histamine also produced a marked tachypnea but was without effect on cough. In awake guinea pigs, adenosine failed to evoke coughing but reduced coughing induced by the nonselective C-fiber stimulant capsaicin. We conclude that bronchopulmonary C-fiber subtypes in guinea pigs have opposing effects on cough, with airway C fibers arising from the jugular ganglia initiating and/or sensitizing the cough reflex and the intrapulmonary C fibers arising from the nodose ganglia actively inhibiting cough upon activation.
Assuntos
Tosse/fisiopatologia , Fibras Nervosas Amielínicas/classificação , Gânglio Nodoso/fisiopatologia , Traqueia/inervação , Potenciais de Ação , Adenosina/administração & dosagem , Animais , Bradicinina/administração & dosagem , Ácido Cítrico , Tosse/induzido quimicamente , Tosse/prevenção & controle , Modelos Animais de Doenças , Cobaias , Histamina/administração & dosagem , Masculino , Fibras Nervosas Amielínicas/efeitos dos fármacos , Gânglio Nodoso/efeitos dos fármacos , Agonistas do Receptor Purinérgico P1/administração & dosagem , Reflexo , Taxa Respiratória , Serotonina/administração & dosagem , Serotonina/análogos & derivados , Agonistas do Receptor 5-HT3 de Serotonina/administração & dosagemRESUMO
The nonselective cation channel transient receptor potential ankryn subtype family 1 (TRPA1) is expressed in neurons of dorsal root ganglia and trigeminal ganglia and also in vagal afferent neurons that innervate the lungs and gastrointestinal tract. Many TRPA1 agonists are reactive electrophilic compounds that form covalent adducts with TRPA1. Allyl isothiocyanate (AITC), the common agonist used to identify TRPA1, contains an electrophilic group that covalently binds with cysteine residues of TRPA1 and confers a structural change on the channel. There is scientific motivation to identify additional compounds that can activate TRPA1 with different mechanisms of channel gating. We provide evidence that ethyl vanillin (EVA) is a TRPA1 agonist. Using fluorescent calcium imaging and whole-cell patch-clamp electrophysiology on dissociated rat vagal afferent neurons and TRPA1-transfected COS-7 cells, we discovered that EVA activates cells also activated by AITC. Both agonists display similar current profiles and conductances. Pretreatment with A967079, a selective TRPA1 antagonist, blocks the EVA response as well as the AITC response. Furthermore, EVA does not activate vagal afferent neurons from TRPA1 knockout mice, showing selectivity for TRPA1 in this tissue. Interestingly, EVA appears to be pharmacologically different from AITC as a TRPA1 agonist. When AITC is applied before EVA, the EVA response is occluded. However, they both require intracellular oxidation to activate TRPA1. These findings suggest that EVA activates TRPA1 but via a distinct mechanism that may provide greater ease for study in native systems compared with AITC and may shed light on differential modes of TRPA1 gating by ligand types.
Assuntos
Benzaldeídos/farmacologia , Canais de Cátion TRPC/agonistas , Animais , Células COS , Chlorocebus aethiops , Células HEK293 , Humanos , Isotiocianatos/farmacologia , Masculino , Camundongos , Neurônios Aferentes/efeitos dos fármacos , Neurônios Aferentes/metabolismo , Gânglio Nodoso/citologia , Gânglio Nodoso/efeitos dos fármacos , Oximas/farmacologia , Técnicas de Patch-Clamp , Ratos , Ratos Sprague-Dawley , Canal de Cátion TRPA1 , Canais de Cátion TRPC/antagonistas & inibidores , Canais de Cátion TRPC/genéticaRESUMO
BACKGROUND: Sensory nerves innervating the airways play an important role in regulating various cardiopulmonary functions, maintaining homeostasis under healthy conditions and contributing to pathophysiology in disease states. Hypo-osmotic solutions elicit sensory reflexes, including cough, and are a potent stimulus for airway narrowing in asthmatic patients, but the mechanisms involved are not known. Transient receptor potential cation channel, subfamily V, member 4 (TRPV4) is widely expressed in the respiratory tract, but its role as a peripheral nociceptor has not been explored. OBJECTIVE: We hypothesized that TRPV4 is expressed on airway afferents and is a key osmosensor initiating reflex events in the lung. METHODS: We used guinea pig primary cells, tissue bioassay, in vivo electrophysiology, and a guinea pig conscious cough model to investigate a role for TRPV4 in mediating sensory nerve activation in vagal afferents and the possible downstream signaling mechanisms. Human vagus nerve was used to confirm key observations in animal tissues. RESULTS: Here we show TRPV4-induced activation of guinea pig airway-specific primary nodose ganglion cells. TRPV4 ligands and hypo-osmotic solutions caused depolarization of murine, guinea pig, and human vagus and firing of Aδ-fibers (not C-fibers), which was inhibited by TRPV4 and P2X3 receptor antagonists. Both antagonists blocked TRPV4-induced cough. CONCLUSION: This study identifies the TRPV4-ATP-P2X3 interaction as a key osmosensing pathway involved in airway sensory nerve reflexes. The absence of TRPV4-ATP-mediated effects on C-fibers indicates a distinct neurobiology for this ion channel and implicates TRPV4 as a novel therapeutic target for neuronal hyperresponsiveness in the airways and symptoms, such as cough.
Assuntos
Trifosfato de Adenosina/metabolismo , Neurônios Aferentes/metabolismo , Sistema Respiratório/inervação , Sistema Respiratório/metabolismo , Canais de Cátion TRPV/metabolismo , Animais , Sinalização do Cálcio , Tosse , Relação Dose-Resposta a Droga , Cobaias , Masculino , Camundongos , Camundongos Knockout , Fibras Nervosas Mielinizadas/efeitos dos fármacos , Fibras Nervosas Mielinizadas/metabolismo , Neurônios Aferentes/efeitos dos fármacos , Gânglio Nodoso/citologia , Gânglio Nodoso/efeitos dos fármacos , Gânglio Nodoso/metabolismo , Antagonistas do Receptor Purinérgico P2X/farmacologia , Canais de Cátion TRPV/agonistas , Nervo Vago/efeitos dos fármacos , Nervo Vago/fisiologiaRESUMO
Clinical studies indicate that adenosine contributes to esophageal mechanical hypersensitivity in some patients with pain originating in the esophagus. We have previously reported that the esophageal vagal nodose C fibers express the adenosine A2A receptor. Here we addressed the hypothesis that stimulation of the adenosine A2A receptor induces mechanical sensitization of esophageal C fibers by a mechanism involving transient receptor potential A1 (TRPA1). Extracellular single fiber recordings of activity originating in C-fiber terminals were made in the ex vivo vagally innervated guinea pig esophagus. The adenosine A2A receptor-selective agonist CGS21680 induced robust, reversible sensitization of the response to esophageal distention (10-60 mmHg) in a concentration-dependent fashion (1-100 nM). At the half-maximally effective concentration (EC50: ≈3 nM), CGS21680 induced an approximately twofold increase in the mechanical response without causing an overt activation. This sensitization was abolished by the selective A2A antagonist SCH58261. The adenylyl cyclase activator forskolin mimicked while the nonselective protein kinase inhibitor H89 inhibited mechanical sensitization by CGS21680. CGS21680 did not enhance the response to the purinergic P2X receptor agonist α,ß-methylene-ATP, indicating that CGS21680 does not nonspecifically sensitize to all stimuli. Mechanical sensitization by CGS21680 was abolished by pretreatment with two structurally different TRPA1 antagonists AP18 and HC030031. Single cell RT-PCR and whole cell patch-clamp studies in isolated esophagus-specific nodose neurons revealed the expression of TRPA1 in A2A-positive C-fiber neurons and demonstrated that CGS21682 potentiated TRPA1 currents evoked by allylisothiocyanate. We conclude that stimulation of the adenosine A2A receptor induces mechanical sensitization of nodose C fibers by a mechanism sensitive to TRPA1 antagonists indicating the involvement of TRPA1.
Assuntos
Agonistas do Receptor A2 de Adenosina/farmacologia , Esôfago/efeitos dos fármacos , Esôfago/inervação , Fibras Nervosas Amielínicas/efeitos dos fármacos , Receptor A2A de Adenosina/efeitos dos fármacos , Adenosina/análogos & derivados , Adenosina/farmacologia , Animais , Relação Dose-Resposta a Droga , Cobaias , Técnicas In Vitro , Isoquinolinas/farmacologia , Contração Muscular/efeitos dos fármacos , Terminações Nervosas/efeitos dos fármacos , Fármacos Neuroprotetores/farmacologia , Gânglio Nodoso/citologia , Gânglio Nodoso/efeitos dos fármacos , Técnicas de Patch-Clamp , Fenetilaminas/farmacologia , Inibidores de Proteínas Quinases/farmacologia , Agonistas do Receptor Purinérgico P2X/farmacologia , Pirimidinas/farmacologia , Sulfonamidas/farmacologia , Canais de Potencial de Receptor Transitório/antagonistas & inibidores , Canais de Potencial de Receptor Transitório/efeitos dos fármacos , Triazóis/farmacologia , Nervo Vago/efeitos dos fármacosRESUMO
The α3ß4 nicotinic acetylcholine receptor (nAChR) subtype is widely expressed in the peripheral and central nervous systems, including in airway sensory nerves. The nAChR subtype transduces the irritant effects of nicotine in tobacco smoke and, in certain brain areas, may be involved in nicotine addiction and/or withdrawal. Menthol, a widely used additive in cigarettes, is a potential analgesic and/or counterirritant at sensory nerves and may also influence nicotine's actions in the brain. We examined menthol's effects on recombinant human α3ß4 nAChRs and native nAChRs in mouse sensory neurons. Menthol markedly decreased nAChR activity as assessed by Ca(2+) imaging, (86)Rb(+) efflux, and voltage-clamp measurements. Coapplication of menthol with acetylcholine or nicotine increased desensitization, demonstrated by an increase in the rate and magnitude of the current decay and a reduction of the current integral. These effects increased with agonist concentration. Pretreatment with menthol followed by its washout did not affect agonist-induced desensitization, suggesting that menthol must be present during the application of agonist to augment desensitization. Notably, menthol acted in a voltage-independent manner and reduced the mean open time of single channels without affecting their conductance, arguing against a simple channel-blocking effect. Further, menthol slowed or prevented the recovery of nAChRs from desensitization, indicating that it probably stabilizes a desensitized state. Moreover, menthol at concentrations up to 1 mM did not compete for the orthosteric nAChR binding site labeled by [(3)H]epibatidine. Taken together, these data indicate that menthol promotes desensitization of α3ß4 nAChRs by an allosteric action.
Assuntos
Agonistas Colinérgicos/farmacologia , Mentol/farmacologia , Gânglio Nodoso/fisiologia , Receptores Nicotínicos/metabolismo , Células Receptoras Sensoriais/fisiologia , Acetilcolina/farmacologia , Regulação Alostérica/efeitos dos fármacos , Animais , Compostos Bicíclicos Heterocíclicos com Pontes/farmacologia , Células Cultivadas , Células HEK293 , Humanos , Canais Iônicos/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Nicotina/farmacologia , Gânglio Nodoso/citologia , Gânglio Nodoso/efeitos dos fármacos , Piridinas/farmacologia , Células Receptoras Sensoriais/efeitos dos fármacos , Transdução de Sinais/efeitos dos fármacosRESUMO
The prevalence of obstructive sleep apnea (OSA) in Americans is 9% and increasing. Increased afferent vagal activation may predispose to OSA by reducing upper airway muscle activation/patency and disrupting respiratory rhythmogenesis. Vagal afferent neurons are inhibited by cannabinoid type 1 (CB1) or cannabinoid type 2 (CB2) receptors in animal models of vagally-mediated behaviors. Injections of dronabinol, a non-selective CB1/CB2 receptor agonist, into the nodose ganglia reduced serotonin (5-HT)-induced reflex apneas. It is unknown what role CB1 and/or CB2 receptors play in reflex apnea. Here, to determine the independent and combined effects of activating CB1 and/or CB2 receptors on dronabinol's attenuating effect, rats were pre-treated with CB1 (AM251) and/or CB2 (AM630) receptor antagonists. Adult male Sprague-Dawley rats were anesthetized, instrumented with bilateral electrodes to monitor genioglossus electromyogram (EMGgg) and a piezoelectric strain gauge to monitor respiratory pattern. Following intraperitoneal treatment with AM251 and/or AM630, or with vehicle, serotonin was intravenously infused into a femoral vein to induce reflex apnea. After baseline recordings, the nodose ganglia were exposed and 5-HT-induced reflex apneas were again recorded to confirm that the nerves remained functionally intact. Dronabinol was injected into each nodose ganglion and 5-HT infusion was repeated. Prior to dronabinol injection, there were no significant differences in 5-HT-induced reflex apneas or phasic and tonic EMGgg before or after surgery in the CB1, CB2, combined CB1/CB2 antagonist, and vehicle groups. In the vehicle group, dronabinol injections reduced 5-HT-induced reflex apnea duration. In contrast, dronabinol injections into nodose ganglia of the CB1, CB2, and combined CB1/CB2 groups did not attenuate 5-HT-induced reflex apnea duration. However, the CB1 and CB2 antagonists had no effect on dronabinol's ability to increase phasic EMGgg. These findings underscore the therapeutic potential of dronabinol in the treatment of OSA and implicate participation of both cannabinoid receptors in dronabinol's apnea suppression effect.
Assuntos
Dronabinol/química , Receptor CB1 de Canabinoide/antagonistas & inibidores , Receptor CB2 de Canabinoide/antagonistas & inibidores , Serotonina/química , Animais , Agonistas de Receptores de Canabinoides/química , Eletromiografia , Veia Femoral/patologia , Indóis/química , Masculino , Gânglio Nodoso/efeitos dos fármacos , Piperidinas/química , Pirazóis/química , Ratos , Ratos Sprague-Dawley , Serotonina/administração & dosagem , Apneia Obstrutiva do Sono/induzido quimicamente , Apneia Obstrutiva do Sono/tratamento farmacológico , Resultado do TratamentoRESUMO
Neuronal nitric oxide (NO) plays an important role in gastric motor activity and modulates the mechanosensitivity of gastro-oesophageal vagal afferents. Effects of NO on food intake are dependent on feeding status. We sought to determine the effect of NO on gastro-oesophageal vagal afferent activity in the normally fed and food-restricted states and the second messenger pathways mediating these effects. Eight week old female C56BL/6 mice were fed ad libitum or food restricted for 14 h. An in vitro preparation was used to determine the functional effects of NO and the second messenger pathways involved. Expression of NO signal transduction molecules in vagal afferents was determined by reverse-transcription polymerase chain reaction (RT-PCR). Endogenous NO and the NO donor S-nitroso-N-acetylpenicillamine (SNAP) inhibited vagal mucosal afferent responses to tactile stimuli in mice fed ad libitum. After a 14 h fast endogenous NO and SNAP potentiated tension and mucosal afferent responses to mechanical stimulation. The excitatory effect of NO was blocked by the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor apocynin. After a 14 h fast expression of NADPH oxidase 2 (NOX2) mRNA in whole nodose ganglia was significantly reduced and the excitatory effect of NO on gastro-oesophageal vagal afferents was lost. Under fasting conditions the inhibitory effect of NO was blocked with the hyperpolarisation-activated cyclic nucleotide-gated (HCN) channel blocker ivabradine and mRNA expression of HCN3 in the nodose ganglia was elevated. In conclusion, the role of NO in the peripheral modulation of gastro-oesophageal vagal afferents is dynamic and dependent on feeding status.
Assuntos
Dieta , Esôfago/inervação , Mecanotransdução Celular , Neurônios Aferentes/fisiologia , Óxido Nítrico/metabolismo , Gânglio Nodoso/fisiologia , Acetofenonas/farmacologia , Animais , Benzazepinas/farmacologia , Esôfago/fisiologia , Feminino , Canais Disparados por Nucleotídeos Cíclicos Ativados por Hiperpolarização/antagonistas & inibidores , Canais Disparados por Nucleotídeos Cíclicos Ativados por Hiperpolarização/genética , Canais Disparados por Nucleotídeos Cíclicos Ativados por Hiperpolarização/metabolismo , Ivabradina , Glicoproteínas de Membrana/genética , Glicoproteínas de Membrana/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , NADPH Oxidase 2 , NADPH Oxidases/antagonistas & inibidores , NADPH Oxidases/genética , NADPH Oxidases/metabolismo , Neurônios Aferentes/metabolismo , Gânglio Nodoso/efeitos dos fármacos , Gânglio Nodoso/metabolismo , Canais de Potássio/genética , Canais de Potássio/metabolismoRESUMO
UNLABELLED: Estrogen reportedly facilitates visceral nociception at the spinal or supraspinal level. The present study was aimed to investigate whether estrogen modulates visceral pain through the vagal pathway. Ovariectomized rats received estradiol, which was administered subcutaneously (to act through both the vagal and spinal pathways) or intraduodenally (to preferentially act through the vagal pathway). Luminally applied estradiol induced a rapid and significant decrease in the visceromotor response to colorectal distension, with increased c-Fos expression in nodose ganglion neurons. Systemically injected estradiol increased visceromotor response and c-Fos expression in both nodose and dorsal root ganglion (T6-12) neurons. The antinociceptive effect of estrogen was abolished by surgical vagotomy or chemical denervation of vagal afferents. Both luminally and systemically administered estradiol elicited selective 5-hydroxytryptamine secretion from the duodenum. Granisetron, a 5-hydroxytryptamine 3 receptor antagonist, reversed the antinociceptive effect of estrogen. Intestinal mucosal mast cell stabilizers prevented estradiol-induced antinociception and 5-hydroxytryptamine secretion. Ultrastructural analysis revealed that estradiol caused piecemeal degranulation of intestinal mucosal mast cells. The actions of estradiol were inhibited by an estrogen receptor ß antagonist and mimicked by an estrogen receptor ß agonist. These results suggest that estrogen can trigger vagus-mediated antinociception, which is masked by its spinally mediated pronociception. PERSPECTIVE: This study is the first to show a vagus-mediated estrogenic antinociception, in which the nongenomic estrogen receptor ß-mediated, intestinal mucosal mast cell-derived 5-hydroxytryptamine/5-hydroxytryptamine 3 receptor pathway is involved. This work may provide new insights into the sex hormone modulation of visceral sensitivity related to irritable bowel syndrome and indicate potential therapeutic targets to manage this disease.
Assuntos
Analgésicos/farmacologia , Estradiol/farmacologia , Receptores 5-HT3 de Serotonina/metabolismo , Nervo Vago/efeitos dos fármacos , Dor Visceral/tratamento farmacológico , Dor Visceral/fisiopatologia , Vias Aferentes/efeitos dos fármacos , Vias Aferentes/fisiopatologia , Analgésicos/administração & dosagem , Animais , Duodeno/efeitos dos fármacos , Duodeno/fisiopatologia , Estradiol/administração & dosagem , Estrogênios/administração & dosagem , Estrogênios/farmacologia , Feminino , Gânglios Espinais/efeitos dos fármacos , Gânglios Espinais/fisiopatologia , Mucosa Intestinal/efeitos dos fármacos , Mucosa Intestinal/fisiopatologia , Mucosa Intestinal/ultraestrutura , Mastócitos/efeitos dos fármacos , Mastócitos/fisiologia , Mastócitos/ultraestrutura , Neurônios/efeitos dos fármacos , Neurônios/fisiologia , Gânglio Nodoso/efeitos dos fármacos , Gânglio Nodoso/fisiopatologia , Proteínas Proto-Oncogênicas c-fos/metabolismo , Ratos , Ratos Sprague-Dawley , Receptores de Estrogênio/antagonistas & inibidores , Receptores de Estrogênio/metabolismo , Serotonina/metabolismo , Nervo Vago/fisiopatologiaRESUMO
Hyperpolarization-activated currents (Ih) mediated by hyperpolarization-activated cyclic nucleotide-gated (HCN) channels modulate excitability of myelinated A- and Ah-type visceral ganglion neurons (VGN). Whether alterations in Ih underlie the previously reported reduction of excitability of myelinated Ah-type VGNs following ovariectomy (OVX) has remained unclear. Here we used the intact nodose ganglion preparation in conjunction with electrophysiological approaches to examine the role of Ih remodeling in altering Ah-type neuron excitability following ovariectomy in adult rats. Ah-type neurons were identified based on their afferent conduction velocity. Ah-type neurons in nodose ganglia from non-OVX rats exhibited a voltage 'sag' as well as 'rebound' action potentials immediately following hyperpolarizing current injections, which both were suppressed by the Ih blocker ZD7288. Repetitive spike activity induced afterhyperpolarizations lasting several hundreds of milliseconds (termed post-excitatory membrane hyperpolarizations, PEMHs), which were significantly reduced by ZD7288, suggesting that they resulted from transient deactivation of Ih during the preceding spike trains. Ovariectomy reduced whole-cell Ih density, caused a hyperpolarizing shift of the voltage-dependence of Ih activation, and slowed Ih activation. OVX-induced Ih remodeling was accompanied by a flattening of the stimulus frequency/response curve and loss of PEMHs. Also, HCN1 mRNA levels were reduced by â¼30% in nodose ganglia from OVX rats compared with their non-OVX counterparts. Acute exposure of nodose ganglia to 17beta-estradiol partly restored Ih density and accelerated Ih activation in Ah-type cells. In conclusion, Ih plays a significant role in modulating the excitability of myelinated Ah-type VGNs in adult female rats.
Assuntos
Canais de Cátion Regulados por Nucleotídeos Cíclicos/metabolismo , Potenciais da Membrana/fisiologia , Gânglio Nodoso/fisiologia , Ovariectomia , Células do Corno Posterior/fisiologia , Animais , Estradiol/farmacologia , Potenciais Evocados/efeitos dos fármacos , Potenciais Evocados/fisiologia , Feminino , Potenciais da Membrana/efeitos dos fármacos , Bainha de Mielina/metabolismo , Gânglio Nodoso/efeitos dos fármacos , Técnicas de Patch-Clamp , Células do Corno Posterior/efeitos dos fármacos , Ratos , Nervo Vago/efeitos dos fármacos , Nervo Vago/fisiologiaRESUMO
Clinical studies showed that GABA(B) receptor agonists improve symptoms in patients with gastroesophageal reflux disease. One proposed mechanism of this effect is direct inhibition of the gastroesophageal vagal tension mechanosensors by GABA(B) agonists leading to reduction of reflux. In addition to tension mechanosensors, the vagal nodose ganglion supplies the esophagus with nociceptive C-fibers that likely contribute to impairment of esophageal reflex regulation in diseases. We hypothesized that GABA(B) agonists inhibit mechanically-induced activation of vagal esophageal nodose C-fibers in baseline and/or in sensitized state induced by inflammatory mediators. Ex vivo extracellular recordings were made from the esophageal nodose C-fibers in the isolated vagally-innervated guinea pig esophagus. We found that the selective GABA(B) agonist baclofen (100-300 microM) did not inhibit activation of esophageal nodose C-fibers evoked by esophageal distention (10-60 mmHg). The mechanical response of esophageal nodose C-fibers can be sensitized by different pathways including the stimulation of the histamine H(1) receptor and the stimulation the adenosine A(2A) receptor. Baclofen failed to inhibit mechanical sensitization of esophageal nodose C-fibers induced by histamine (100 microM) or the selective adenosine A(2A) receptor agonist CGS21680 (3 nM). Our data suggest that the direct mechanical inhibition of nodose C-fibers in the esophagus is unlikely to contribute to beneficial effects of GABA(B) agonists in patients with esophageal diseases.
Assuntos
Vias Aferentes/fisiologia , Baclofeno/administração & dosagem , Esôfago/inervação , Esôfago/fisiologia , Agonistas de Receptores de GABA-A/administração & dosagem , Inibição Neural/fisiologia , Gânglio Nodoso/fisiologia , Vias Aferentes/efeitos dos fármacos , Animais , Relação Dose-Resposta a Droga , Esôfago/efeitos dos fármacos , Cobaias , Masculino , Inibição Neural/efeitos dos fármacos , Gânglio Nodoso/efeitos dos fármacosRESUMO
Gastrointestinal mechanisms involved in the suppression of appetite are compromised in obesity. Glucagon-like peptide-1 (GLP-1) is released in response to nutrients, suppresses food intake, and has been shown to play a role in regulation of energy balance. It is not known whether obese-prone (OP) rats exhibit dysfunctional GLP-1 signaling that could contribute to decreased nutrient-induced satiation and hyperphagia. Therefore, we examined the effects of exogenous intraperitoneal administration of the GLP-1R agonist, exendin-4 (Ex-4), on food intake in OP and obese-resistant (OR) rats during chow or high-energy/high-fat (HE/HF) feeding. All doses of Ex-4 effectively suppressed intake in OP and OR rats fed chow; however, during HE/HF-feeding, OP rats suppressed intake significantly less than OR rats at all Ex-4 doses tested. This was associated with downregulation of GLP-1R mRNA expression in the vagal nodose ganglia of OP rats. Furthermore, HE/HF-fed OP rats had significantly lower plasma GLP-1 levels, decreased protein levels of GLP-1 in the intestinal epithelium, and reduced number of L cells in the distal ileum. These results demonstrate that HE/HF-feeding, coupled with OP phenotype, results in reduced endogenous GLP-1 and GLP-1R activation, indicating that impaired GLP-1 signaling during obesity may exacerbate hyperphagia and weight gain.
Assuntos
Dieta Hiperlipídica , Ingestão de Alimentos/efeitos dos fármacos , Hipoglicemiantes/farmacologia , Obesidade/metabolismo , Peptídeos/farmacologia , Receptores de Glucagon/agonistas , Peçonhas/farmacologia , Adiposidade/efeitos dos fármacos , Animais , Peso Corporal/efeitos dos fármacos , Regulação para Baixo/efeitos dos fármacos , Exenatida , Receptor do Peptídeo Semelhante ao Glucagon 1 , Íleo/metabolismo , Mucosa Intestinal/metabolismo , Masculino , Gânglio Nodoso/efeitos dos fármacos , Gânglio Nodoso/metabolismo , Obesidade/genética , Ratos , Receptores de Glucagon/genética , Receptores de Glucagon/metabolismoRESUMO
Peripheral injection of pancreatic polypeptide (PP) and peptide YY(3-36) (PYY(3-36)), the hormones released in response to meals, reduce food intake, in which the rank order of the potency is PP>PYY(3-36). These anorectic effects are abolished in abdominal vagotomized rats, suggesting that PP and PYY(3-36) induce anorexia via vagal afferent nerves. However, it is not clear whether PP and PYY(3-36) directly act on vagal afferent neurons. In this study, we examined the effects of PP and PYY(3-36) on cytosolic Ca(2+) concentration ([Ca(2+)](i)) in isolated nodose ganglion neurons of the mouse vagal afferent nerves. At 10(-11)M, PP but not PYY(3-36) recruited a significant population of nodose ganglion neurons into [Ca(2+)](i) increases. PP at 10(-11) to 10(-7) and PYY(3-36) at 10(-10) to 10(-7)M increased [Ca(2+)](i) in a concentration-dependent manner. At submaximal to maximal concentrations of 10(-10) and 10(-8)M, PP increased [Ca(2+)](i) in approximately twice greater population of nodose ganglion neurons than PYY(3-36). Furthermore, the majority of PP-responsive neurons also exhibited [Ca(2+)](i) responses to cholecystokinin-8, a hormone known to induce satiety through activating nodose ganglion neurons. The results demonstrate that PP and PYY(3-36) directly activate nodose ganglion neurons and suggest that the marked effect of PP on cholecystokinin-8-responsive nodose ganglion neurons could be linked to the regulation of feeding.