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BACKGROUND: Eosinophilic granulomatosis with polyangiitis (EGPA) is often associated with glucocorticoid-dependent asthma and/or ear, nose and throat (ENT) manifestations. When immunosuppressants and/or mepolizumab are ineffective, dupilumab could be an option. We describe the safety and efficacy of off-label use of dupilumab in relapsing and/or refractory EGPA. PATIENTS AND METHODS: We conducted an observational multicentre study of EGPA patients treated with dupilumab. Complete response was defined by Birmingham Vasculitis Activity Score (BVAS)=0 and prednisone dose ≤4 mg/day, and partial response by BVAS=0 and prednisone dose >4 mg/day. Eosinophilia was defined as an eosinophil count >500/mm3. RESULTS: Fifty-one patients were included. The primary indication for dupilumab was disabling ENT symptoms in 92%. After a median follow-up of 13.1 months, 18 patients (35%) reported adverse events (AEs), including two serious AEs. Eosinophilia was reported in 34 patients (67%), with a peak of 2195/mm3 (IQR 1268-4501) occurring at 13 weeks (IQR 4-36) and was associated with relapse in 41%. Twenty-one patients (41%) achieved a complete response and 12 (24%) a partial response. Sixteen (31%) patients experienced an EGPA relapse while on dupilumab, which was associated with blood eosinophilia in 14/16 (88%) patients. The median eosinophil count at the start of dupilumab was significantly lower in relapsers than in non-relapsers, as was the median time between stopping anti-IL-5/IL-5R and switching to dupilumab. CONCLUSION: These results suggest that dupilumab may be effective in treating patients with EGPA-related ENT manifestations. However, EGPA flares occurred in one-third of patients and were preceded by eosinophilia in 88%, suggesting that caution is required.
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Asma , Síndrome de Churg-Strauss , Eosinofilia , Granulomatose com Poliangiite , Humanos , Granulomatose com Poliangiite/complicações , Granulomatose com Poliangiite/tratamento farmacológico , Granulomatose com Poliangiite/diagnóstico , Síndrome de Churg-Strauss/complicações , Síndrome de Churg-Strauss/tratamento farmacológico , Estudos Retrospectivos , Prednisona/uso terapêutico , Resultado do Tratamento , Asma/tratamento farmacológico , Asma/complicações , Eosinofilia/tratamento farmacológico , Eosinofilia/complicações , RecidivaRESUMO
The long-term outcome of connective tissue diseases is associated with the time from symptom onset to diagnosis. To understand gaps in care, we determine whether the length of time between symptom onset and first presentation to a rheumatologist has changed in Germany in recent decades. We analyzed data on patients diagnosed with connective tissue diseases (n = 19,662) collected from the German National Database of the Regional Cooperative Rheumatology Centers. We reviewed the onset of relevant symptoms listed at first presentations from 1993 to 2018 and performed a quantitative analysis of the intervals until first presentation to a rheumatologist. We compared time intervals and performed a linear mixed regression model with random effects to identify associated factors. Although the interval between the onset of symptoms and first presentation to a rheumatologist has diminished since 1980 for all connective tissue diseases, there has been no relevant improvement during the past 2 decades. The interval between symptoms and presentation increases with patients age for all connective tissue diseases (e.g., Systemic sclerosis; for each 10-year-increment of patients age: ß 0.41, CI 0.38; 0.44). Among those diagnosed with systemic sclerosis, the mean interval was 1.5 years (95% CI 1.1; 1.8) for male patients and 2.6 years (95% CI 2.4; 2.8) for females. Patients presenting with different degrees of disease severity on their first visits and with different educational levels had similar mean intervals between symptoms and first presentation regardless of their final diagnoses. Over the past 2 decades, the time to first consultation with a rheumatologist has not continued to improve in Germany, but has stagnated at the same level. Selected patient subgroups, such as older patients with suspected connective tissue diseases and female patients with suspected systemic sclerosis, are at risk to present late and may in particular benefit from an earlier referral to a rheumatologist.
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Artrite , Doenças do Tecido Conjuntivo , Reumatologia , Escleroderma Sistêmico , Humanos , Masculino , Feminino , Reumatologistas , Doenças do Tecido Conjuntivo/diagnósticoRESUMO
INTRODUCTION: In order to successfully integrate telemedicine into the daily routine of rheumatology, both the patient's and the physician's perspective are important. For this purpose, a detailed study by means of a web-based survey was conducted by the Working Group Young Rheumatology (AGJR) of the German Society for Rheumatology (DGRh) and the German Rheumatism League National Association. By means of subgroup analysis of the data regarding video consultation, the aim was now to find out which requirements and wishes patients and physicians have for video consultations. METHODS: The prospective survey was distributed via social media, QR code and email. Descriptive statistics and regression analysis related to video consultation were performed and correlations were shown. RESULTS: The data indicated positive attitudes toward video consultation on the part of both patients (nâ¯= 299) and rheumatologists (nâ¯= 129). A correlation between age and positive opinion of the video consultation was found among the patients (râ¯= 0.161, pâ¯= 0.006), especially among female patients a positive approval of the video consultation was found with increasing age (râ¯= 0.244, pâ¯< 0.001 to male patients: râ¯= -0.190, pâ¯= 0.145). Regarding the travelling time to the treating rheumatologist, male patients found the video consultation more attractive with increasing travelling time (râ¯= 0.229, pâ¯= 0.078). With respect to the wishes of patients and physicians, video consultation should be used primarily for follow-up or emergency appointments. Video consultation for initial appointments, on the other hand, was very rarely mentioned. CONCLUSION: During the COVID 19 pandemic, video consultation was increasingly popular among rheumatology patients as well as among rheumatologists.
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COVID-19 , Doenças Reumáticas , Febre Reumática , Reumatologia , Telemedicina , Humanos , Masculino , Feminino , Estudos Prospectivos , Reumatologia/métodos , Doenças Reumáticas/diagnóstico , Doenças Reumáticas/terapia , ReumatologistasRESUMO
OBJECTIVE: Despite increased physician's awareness and improved diagnostic and serological testing in the recent years, the interval between the initial symptoms and the diagnosis of Systemic lupus erythematosus (SLE) is still very long. Our aim was to study this delay and its association to the outcome of the disease. METHODS: Information on demographics, onset of first symptoms, first physicians visit and time of diagnosis was assessed by self-reported questionnaires among SLE patients in Germany (LuLa cohort, n = 585) in the year 2012. Disease activity (Systemic Lupus Activity Questionnaire; SLAQ), disease related damage (Brief Index of Lupus Damage; BILD), health related quality of life (Short Form 12) and fatigue (FSS) were chosen as proxies for outcome. Linear regression analysis was used to analyze the association of the delay in diagnosis to the outcome, adjusted for age, disease duration and sex. RESULTS: Mean duration between the onset of symptoms and the diagnosis of SLE was 47 months (SD 73). The longer the time to diagnosis, the higher the disease activity (ß = 0.199, p < 0.0001), the disease-related damage (ß = 0.137, p = 0.002) and fatigue (ß 0.145, p = 0.003) and the lower the health-related quality of life (physical ß = -0.136, p = 0.004, mental ß = -0.143, p = 0.004). CONCLUSION: In systemic lupus erythematosus, longer time to diagnosis was associated with worse outcome. Concepts in care with the intention to shorten the time to diagnosis are needed to improve the long-term outcome of the disease.
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Diagnóstico Tardio/efeitos adversos , Lúpus Eritematoso Sistêmico/diagnóstico , Medidas de Resultados Relatados pelo Paciente , Qualidade de Vida , Adulto , Idoso , Estudos de Coortes , Estudos Transversais , Progressão da Doença , Feminino , Alemanha , Humanos , Lúpus Eritematoso Sistêmico/psicologia , Masculino , Pessoa de Meia-Idade , Índice de Gravidade de DoençaRESUMO
OBJECTIVE: The aim of this study was to identify factors associated with impaired work productivity and impaired daily activities in patients with systemic lupus erythematosus (SLE). METHODS: The LuLa study is a longitudinal patient-reported study. Beyond sociodemographic data, work productivity, daily activities and fatigue, several other clinical outcome parameters (e.g. mental health-related quality of life and physical functioning, disease activity, damage and pain) were surveyed with validated questionnaires. The effects of confounders on work productivity (WPAI 2) and daily activity domains (WPAI 4) were studied by multivariate regression analysis. RESULTS: A total of 585 patients completed the questionnaire of whom 259 were employed and analysed. The median impairment in work productivity (WPAI 2) was 20% (Q1-3 0-40), and the median impairment in daily activities (WPAI 4) was 30% (Q1-3 10-50%). Multivariate regression analysis revealed that fatigue, pain, disease activity and health-related quality of life affected WPAI 2 and 4. Furthermore, we observed distinct synergistic effects of fatigue, disease activity and pain on both work productivity and daily activities: a higher impact of fatigue was associated with the reported extent of pain or disease activity. CONCLUSION: In employed patients with SLE, impaired work productivity and impaired daily activities were frequently reported. Fatigue, pain, disease activity and health-related quality of life demonstrated a detrimental impact, with a synergistic effect of fatigue, disease activity and pain. Hence, both optimized pain management and targeted immunomodulatory therapy are important for preserving active participation in life among patients with fatigue.
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Eficiência , Lúpus Eritematoso Sistêmico/complicações , Qualidade de Vida/psicologia , Desempenho Profissional/estatística & dados numéricos , Atividades Cotidianas , Adulto , Fadiga/epidemiologia , Fadiga/etiologia , Feminino , Alemanha/epidemiologia , Humanos , Lúpus Eritematoso Sistêmico/epidemiologia , Lúpus Eritematoso Sistêmico/psicologia , Masculino , Pessoa de Meia-Idade , Dor , Inquéritos e QuestionáriosRESUMO
A few decades ago, the therapy goal of patients with systemic lupus erythematosus (SLE) was survival and the prevention of organ failure. Today, clinical remission and low disease activity are believed to be the optimal therapeutic targets. These aims are difficult to reach for many patients, but they still do not address the health-related quality of life (QoL) that is significantly impaired in SLE patients. Even in the state of remission, QoL and fatigue are insufficient controlled. Thus, patient-oriented research is essential to design new strategies for the management of lupus patients. The INTEGRATE project analyses the patients' and physicians' perspectives to pave the way to design an innovative therapeutic strategy for lupus and focuses on the multifaceted dimensions of the disease burden. Shared decision making (SDM) could include the patient's perspective of SLE to treatment strategy and consider QoL and the burden of lupus into the process of therapy decision.
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Efeitos Psicossociais da Doença , Lúpus Eritematoso Sistêmico/terapia , Planejamento de Assistência ao Paciente , Qualidade de Vida , Atitude Frente a Saúde , Humanos , Lúpus Eritematoso Sistêmico/psicologia , Indução de RemissãoRESUMO
Breathing and vigilance are regulated by pH and CO2 levels in the central nervous system. The hypocretin/orexin (Hcrt/Orx)- and histamine (HA)-containing hypothalamic neurons synergistically control different aspects of the waking state. Acidification inhibits firing of most neurons but these two groups in the caudal hypothalamus are excited by hypercapnia and protons, similar to the chemosensory neurons in the brain stem. Activation of hypothalamic wake-on neurons in response to hypercapnia, seen with the c-Fos assay, is supported by patch-clamp recordings in rodent brain slices: Hcrt/Orx and HA neurons are excited by acidification in the physiological range (pH from 7.4 to 7.0). Multiple molecular mechanisms mediate wake-promoting effects of protons in HA neurons in the tuberomamillary nucleus (TMN): among them are acid-sensing ion channels, Na(+),K(+)-ATPase, group I metabotropic glutamate receptors (mGluRI). HA neurons are remarkably sensitive to the mGluRI agonist DHPG (threshold concentration 0.5 µM) and mGluRI antagonists abolish proton-induced excitation of HA neurons. Hcrt/Orx neurons are excited through block of a potassium conductance and release glutamate with their peptides in TMN. The two hypothalamic nuclei and the serotonergic dorsal raphe cooperate toward CO2/acid-induced arousal. Their interactions and molecular mechanisms of H(+)/CO2-induced activation are relevant for the understanding and treatment of respiratory and metabolic disorders related to sleep-waking such as obstructive sleep apnea and sudden infant death syndrome.
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Canais Iônicos Sensíveis a Ácido/metabolismo , Potenciais de Ação/fisiologia , Hipotálamo/metabolismo , Neurônios/metabolismo , Animais , Ácido Glutâmico/metabolismo , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Neuropeptídeos/metabolismo , OrexinasRESUMO
Background: Biobanks are essential structures for scientific research. The RHINEVIT biobank is used to recruit biomaterials from rheumatology patients in outpatient care and to conduct clinical research studies (e.g., cohort studies) and basic research. RHINEVIT established Broad Consents (BC) to allow extensive and relevant usage of data and biospecimens without the need for specific project restrictions. For quality assurance, we compared the consent rate of individual items of the BC versions in patients with systemic lupus erythematosus (SLE) in the longitudinal study. Methods: BCs were used for biomaterial donation. Informed consent data from RHINEVIT were analyzed. Due to the content restructuring of the BC items due to changes from the templates of the working group of the Medical Ethics Commissions in the Federal Republic of Germany and GDPR requirements, content mapping of the items was performed for the analysis. Results: From September 2015 to March 2022, 291 SLE outpatients donated biomaterials. In 119 patients, the BC was renewed at least once in a subsequent biomaterial donation. Three biomaterial donations were obtained from 21 patients and four from six patients using the respective BC. However, one consent was later revoked. Consent to the BC topics showed consistently high rates of agreement (range 97.5%-100%), with only some patients disagreeing with individual topics. This remained stable over time (median 526 days [Q1 400, Q3 844]). None of the patients disagreed with a certain topic in two consecutive visits. Conclusion: Modifications to the BC did not result in any relevant changes in the approval rates for SLE patients. RHINEVIT's BC is successfully used for the quality-assured handling of excellently annotated biomaterial. The long-term use of these highly valuable biospecimens for unrestricted research, also in an international context, remains assured.
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Objective: To compare physician and patient assessments of global disease activity in anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) and to identify associated factors. Methods: Global disease activity scores (0-10 points) were retrospectively analyzed from physicians and patients with AAV at each outpatient visit from 2010 to 2020. We compared the scores and performed a linear regression with a random effects to identify associated factors. Results: Patients (n = 143, 1,291 pairs, 52% female) had a mean 64 (±15) years of age and a mean disease duration of 9 (±7) years. Patients and physicians global disease activity assessments showed a moderate correlation (Pearson R 0.31, CI [0.23-0.52], p < 0.001). Linear regression showed a strong association between the physician-documented disease activity scores and serum CRP levels (ß = 0.22, CI [0.18, 0.28]), disease duration (ß = -0.022, CI [-0.04,-0.01]) and patients' assessment of disease activity (ß = 0.08, CI [0.04, 0.12]). By contrast, patient assessments were strongly associated with the degree of pain (ß = 0.30, CI [0.25, 0.35]), functional limitations in daily living (HAQ, ß = 0.49, CI [0.21, 0.78]) and the global physical well-being (NRS, ß = 0.39, CI [0.32, 0.46]). Conclusion: Patients' and physicians' assessments of disease activity correlated. High CRP levels and disease duration were associated with physician-assessed disease activity scores, while subjective limitations were associated with higher patient-assessed disease activity scores. These findings highlight and support the need to develop and evaluate patient-reported outcomes to assess disease activity in patients diagnosed with AAV.
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Objective: To analyze the impact of the COVID-19 pandemic on medical care and vaccination acceptance of vasculitis patients in Germany. Methods: A web-based national survey was developed by rheumatology centers and vasculitis patient advocacy groups. The survey was distributed nationwide by mail and flyers and could be accessed via a QR-code or weblink from December 2021 to April 2022. Descriptive statistics [mean, median, standard derivation (SD), 25%, 75% quantile] were calculated. 95% confidence intervals were presented for responses that were directly related to the impact of COVID-19 on parameters associated with vasculitis patient care. Results: The online survey was completed by 117 patients with small and large vessel vasculitis [granulomatosis with polyangiitis (n = 69), eosinophilic granulomatosis with polyangiitis (n = 16), microscopic polyangiitis (n = 12), giant cell arteritis (n = 17) and Takayasu's arteritis (n = 3)]. Prescheduled rheumatological appointments had been canceled due to the COVID-19 pandemic in 12.6% of the respondents [95% confidence interval (CI), 7.3-20.0%); in 9% (95% CI, 4.5-15.6%)] appointments had been replaced by digital services. Therapeutic regimens were changed (shifted, reduced, or discontinued) due to the pandemic in 15.5% (95% CI 9.5-22.2%). Vaccination coverages were generally high compared to patients with other rheumatic diseases and the general population. Highest vaccination coverage was observed against COVID-19 (98.1% 95% CI 93.9-99.6%). Conclusion: Vasculitis patients experienced changes in medical care during COVID-19 pandemic such as cancelation of prescheduled rheumatology appointments and modifications in therapeutic regimens. The overall acceptance rate for vaccination was comparatively high, particularly for vaccination against COVID-19.
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OBJECTIVE: Mepolizumab proved to be an efficacious treatment for eosinophilic granulomatosis with polyangiitis (EGPA) at a dose of 300 mg every 4 weeks in the randomized, controlled MIRRA trial. In a few recently reported studies, successful real-life experiences with the approved dose for treating severe eosinophilic asthma (100 mg every 4 weeks) were observed. We undertook this study to assess the effectiveness and safety of mepolizumab 100 mg every 4 weeks and 300 mg every 4 weeks in a large European EGPA cohort. METHODS: We included all patients with EGPA treated with mepolizumab at the recruiting centers in 2015-2020. Treatment response was evaluated from 3 months to 24 months after initiation of mepolizumab. Complete response to treatment was defined as no disease activity (Birmingham Vasculitis Activity Score [BVAS] = 0) and a prednisolone or prednisone dose (or equivalent) of ≤4 mg/day. Respiratory outcomes included asthma and ear, nose, and throat (ENT) exacerbations. RESULTS: Two hundred three patients, of whom 191 received a stable dose of mepolizumab (158 received 100 mg every 4 weeks and 33 received 300 mg every 4 weeks) were included. Twenty-five patients (12.3%) had a complete response to treatment at 3 months. Complete response rates increased to 30.4% and 35.7% at 12 months and 24 months, respectively, and rates were comparable between mepolizumab 100 mg every 4 weeks and 300 mg every 4 weeks. Mepolizumab led to a significant reduction in BVAS score, prednisone dose, and eosinophil counts from 3 months to 24 months, with no significant differences observed between 100 mg every 4 weeks and 300 mg every 4 weeks. Eighty-two patients (40.4%) experienced asthma exacerbations (57 of 158 [36%] who received 100 mg every 4 weeks; 17 of 33 [52%] who received 300 mg every 4 weeks), and 31 patients (15.3%) experienced ENT exacerbations. Forty-four patients (21.7%) experienced adverse events (AEs), most of which were nonserious AEs (38 of 44). CONCLUSION: Mepolizumab at both 100 mg every 4 weeks and 300 mg every 4 weeks is effective for the treatment of EGPA. The 2 doses should be compared in the setting of a controlled trial.
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Anticorpos Monoclonais Humanizados/administração & dosagem , Eosinofilia/tratamento farmacológico , Granulomatose com Poliangiite/tratamento farmacológico , Adulto , Esquema de Medicação , Eosinofilia/complicações , Feminino , Granulomatose com Poliangiite/complicações , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Resultado do TratamentoRESUMO
Reasons of mon- and oligoarthritis are heterogeneous. The diagnostic approach includes a detailed medical anamnesis, physical examination and imaging (conventional X-ray, sonography, MRI and, CT). Analysis of the synovial fluid is required in suspected septic arthritis and frequently helps in diagnosis and differential diagnosis of crystal arthropathies. Dual-energy-CT (DECT) detects sodium urate crystals and can replace joint puncture in some cases. In addition to crystal arthropathies and septic arthritis, differential diagnosis of mon-/oligoarthritis includes reactive arthritis, arthrosis and monarthritic courses of SpA/PsA. A rheumatologist should be consulted particularly in the case of persistent monarthritides, in order to initiate a specific therapy to prevent secondary damage.
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Artrite/diagnóstico , Artrite/patologia , Artrite/fisiopatologia , Artropatias por Cristais/diagnóstico , Artropatias por Cristais/patologia , Artropatias por Cristais/fisiopatologia , Diagnóstico Diferencial , Diagnóstico por Imagem , HumanosRESUMO
OBJECTIVE: To analyse the impact of the COVID-19 pandemic on rheumatic patients' and rheumatologists' usage, preferences and perception of digital health applications (DHAs). METHODS: A web-based national survey was developed by the Working Group Young Rheumatology of the German Society for Rheumatology and the German League against Rheumatism. The prospective survey was distributed via social media (Twitter, Instagram and Facebook), QR code and email. Descriptive statistics were calculated, and regression analyses were performed to show correlations. RESULTS: We analysed the responses of 299 patients and 129 rheumatologists. Most patients (74%) and rheumatologists (76%) believed that DHAs are useful in the management of rheumatic and musculoskeletal diseases (RMDs) and felt confident in their own usage thereof (90%; 86%). 38% of patients and 71% of rheumatologists reported that their attitude had changed positively towards DHAs and that their usage had increased due to COVID-19 (29%; 48%). The majority in both groups agreed on implementing virtual visits for follow-up appointments in stable disease conditions. The most reported advantages of DHAs were usage independent of time and place (76.6%; 77.5%). The main barriers were a lack of information on suitable, available DHAs (58.5%; 41.9%), poor usability (42.1% of patients) and a lack of evidence supporting the effectiveness of DHAs (23.2% of rheumatologists). Only a minority (<10% in both groups) believed that digitalisation has a negative impact on the patient-doctor relationship. CONCLUSION: The COVID-19 pandemic instigated an increase in patients' and rheumatologists' acceptance and usage of DHAs, possibly introducing a permanent paradigm shift in the management of RMDs.
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COVID-19 , Doenças Musculoesqueléticas/terapia , Aceitação pelo Paciente de Cuidados de Saúde/estatística & dados numéricos , Reumatologistas/estatística & dados numéricos , Telemedicina , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Conhecimentos, Atitudes e Prática em Saúde , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Inquéritos e Questionários , Adulto JovemRESUMO
Histaminergic (HA) neurons located in the tuberomamillary nucleus (TMN) of the posterior hypothalamus fire exclusively during waking and support many physiological functions. We investigated the role of the endovanilloid N-oleoyldopamine (OLDA) in TMN, where dopamine synthesis and its conjugation with oleic acid likely occur. We show that several known targets of OLDA including TRPV1 and cannabinoid receptors are expressed in HA neurons. In contrast to capsaicin, which failed to increase firing of HA neurons in TRPV1 knockout mice (TRPVI KO), OLDA was still able to induce excitation. This excitation was not sensitive to the blockade of cannabinoid receptors 1 and 2 and could result from OLDA interaction with GPR119, as the ligand of GPR119, oleoylethanolamide (OEA), also increased the firing of HA neurons. However, we ruled out this possibility as OEA- (but not OLDA-) excitation was abolished by the PPAR (peroxisome proliferator activated receptor) alpha antagonist MK886. The dopamine uptake blocker nomifensine blanked OLDA-excitation and dopamine receptor antagonists abolished the OLDA action in TRPV1 KO mice. Therefore OLDA excites HA neurons through multiple targets suggesting a central role of the histaminergic system in the behavioral stimulation seen after systemic OLDA application.
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Dopamina/análogos & derivados , Histamina/metabolismo , Região Hipotalâmica Lateral/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Neurotransmissores/farmacologia , Animais , Dopamina/farmacologia , Região Hipotalâmica Lateral/citologia , Região Hipotalâmica Lateral/crescimento & desenvolvimento , Região Hipotalâmica Lateral/metabolismo , Potenciais da Membrana/efeitos dos fármacos , Potenciais da Membrana/fisiologia , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Neurônios/citologia , Neurônios/metabolismo , Técnicas de Patch-Clamp , Canais de Cátion TRPV/genética , Canais de Cátion TRPV/metabolismo , Técnicas de Cultura de TecidosRESUMO
The histaminergic neurons in the tuberomamillary nucleus (TMN) of the posterior hypothalamus are involved in the control of arousal. These neurons are sensitive to hypercapnia as has been shown in experiments examining c-Fos expression, a marker for increased neuronal activity. We investigated the mechanisms through which TMN neurons respond to changes in extracellular levels of acid/CO(2). Recordings in rat brain slices revealed that acidification within the physiological range (pH from 7.4 to 7.0), as well as ammonium chloride (5 mM), excite histaminergic neurons. This excitation is significantly reduced by antagonists of type I metabotropic glutamate receptors and abolished by benzamil, an antagonist of acid-sensing ion channels (ASICs) and Na(+)/Ca(2+) exchanger, or by ouabain which blocks Na(+)/K(+) ATPase. We detected variable combinations of 4 known types of ASICs in single TMN neurons, and observed activation of ASICs in single dissociated TMN neurons only at pH lower than 7.0. Thus, glutamate, which is known to be released by glial cells and orexinergic neurons, amplifies the acid/CO(2)-induced activation of TMN neurons. This amplification demands the coordinated function of metabotropic glutamate receptors, Na(+)/Ca(2+) exchanger and Na(+)/K(+) ATPase. We also developed a novel HDC-Cre transgenic reporter mouse line in which histaminergic TMN neurons can be visualized. In contrast to the rat, the mouse histaminergic neurons lacked the pH 7.0-induced excitation and displayed only a minimal response to the mGluR I agonist DHPG (0.5 µM). On the other hand, ammonium-induced excitation was similar in mouse and rat. These results are relevant for the understanding of the neuronal mechanisms controlling acid/CO(2)-induced arousal in hepatic encephalopathy and obstructive sleep apnoea. Moreover, the new HDC-Cre mouse model will be a useful tool for studying the physiological and pathophysiological roles of the histaminergic system.