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ß-amyloid42 (Aß42) in Alzheimer's disease (AD) and orexin in narcolepsy are considered crucial biomarkers for diagnosis and therapeutic targets. Recently, orexin and Aß cerebral dynamics have been studied in both pathologies, but how they interact with each other remains further to be known. In this study, we investigated the reliability of using the correlation between orexin-A and Aß42 CSF levels as a candidate marker to explain the chain of events leading to narcolepsy or AD pathology. In order to test the correlation between these biomarkers, patients diagnosed with AD (n = 76), narcolepsy type 1 (NT1, n = 17), narcolepsy type 2 (NT2, n = 23) and healthy subjects (n = 91) were examined. Patients and healthy subjects underwent lumbar puncture between 8:00 and 10:00 am at the Neurology Unit of the University Hospital of Rome "Tor Vergata". CSF levels of Aß42, total-tau, phosphorylated-tau, and orexin-A were assessed. The results showed that CSF levels of Aß42 were significantly lower (p < 0.001) in AD (332.28 ± 237.36 pg/mL) compared to NT1 (569.88 ± 187.00 pg/mL), NT2 (691.00 ± 292.63 pg/mL) and healthy subjects (943.68 ± 198.12 pg/mL). CSF orexin-A levels were statistically different (p < 0.001) between AD (148.01 ± 29.49 pg/mL), NT1 (45.94 ± 13.63 pg/mL), NT2 (104.92 ± 25.55 pg/mL) and healthy subjects (145.18 ± 27.01 pg/mL). Moderate-severe AD patients (mini mental state examination < 21) showed the highest CSF orexin-A levels, whereas NT1 patients showed the lowest CSF orexin-A levels. Correlation between CSF levels of Aß42 and orexin-A was found only in healthy subjects (r = 0.26; p = 0.01), and not in narcolepsy or AD patients. This lack of correlation in both diseases may be explained by the pathology itself since the correlation between these two biomarkers is evident only in the healthy subjects. This study adds to the present literature by further documenting the interplay between orexinergic neurotransmission and cerebral Aß dynamics, possibly sustained by sleep.
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Doença de Alzheimer , Peptídeos beta-Amiloides , Biomarcadores , Narcolepsia , Orexinas , Fragmentos de Peptídeos , Humanos , Orexinas/líquido cefalorraquidiano , Peptídeos beta-Amiloides/líquido cefalorraquidiano , Doença de Alzheimer/líquido cefalorraquidiano , Narcolepsia/líquido cefalorraquidiano , Masculino , Feminino , Pessoa de Meia-Idade , Idoso , Fragmentos de Peptídeos/líquido cefalorraquidiano , Biomarcadores/líquido cefalorraquidiano , Adulto , Proteínas tau/líquido cefalorraquidianoRESUMO
The dynorphin peptides are the endogenous ligands for the kappa opioid receptor (KOR) and regulate food intake. Administration of dynorphin-A1-13 (DYN) in the paraventricular hypothalamic nucleus (PVN) increases palatable food intake, and this effect is blocked by co-administration of the orexin-A neuropeptide, which is co-released with DYN in PVN from neurons located in the lateral hypothalamus. While PVN administration of DYN increases palatable food intake, whether it increases food-seeking behaviors has yet to be examined. We tested the effects of DYN and norBNI (a KOR antagonist) on the seeking and consumption of sucrose using a progressive ratio (PR) and demand curve (DC) tasks. In PVN, DYN did not alter the sucrose breaking point (BP) in the PR task nor the elasticity or intensity of demand for sucrose in the DC task. Still, DYN reduced the delay in obtaining sucrose and increased licks during sucrose intake in the PR task, irrespective of the co-administration of orexin-A. In PVN, norBNI increased the delay in obtaining sucrose and reduced licks during sucrose intake in the PR task while increasing elasticity without altering intensity of demand in the DC task. However, subcutaneous norBNI reduced the BP for sucrose and increased the delay in obtaining sucrose in the PR task while reducing the elasticity of demand. Together, these data show different effects of systemic and PVN blockade of KOR on food-seeking, consummatory behaviors, and incentive motivation for sucrose and suggest that KOR activity in PVN is necessary but not sufficient to drive seeking behaviors for palatable food.
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Dinorfinas , Motivação , Núcleo Hipotalâmico Paraventricular , Receptores Opioides kappa , Receptores Opioides kappa/metabolismo , Dinorfinas/farmacologia , Dinorfinas/metabolismo , Núcleo Hipotalâmico Paraventricular/metabolismo , Núcleo Hipotalâmico Paraventricular/efeitos dos fármacos , Animais , Masculino , Motivação/efeitos dos fármacos , Orexinas , Ratos , Ratos Sprague-Dawley , Naltrexona/farmacologia , Naltrexona/análogos & derivados , Ingestão de Alimentos/efeitos dos fármacos , Ingestão de Alimentos/fisiologia , Ingestão de Alimentos/psicologia , Sacarose , Comportamento Alimentar/efeitos dos fármacos , Comportamento Alimentar/psicologia , Antagonistas de Entorpecentes/farmacologiaRESUMO
The postpartum period is a demanding time during which mothers experience numerous physiological adaptations that enable them to care for their offspring while maintaining their wellbeing. Hypocretins, also known as orexins, are neuropeptides synthesized by hypothalamic neurons that play a fundamental role in several functions, including the promotion of wakefulness and motivated behaviors, such as maternal care. In this regard, several findings suggest that the activity of the hypocretinergic system increases in the early postpartum period and begins to decline as weaning approaches. In particular, hypocretins within the medial preoptic area, a crucial region during this period, modulate both maternal behavior and sleep. Although further studies are necessary to obtain a comprehensive understanding of the role of hypocretins in lactating females, current research suggests that this system participates in promoting active components of maternal behavior and regulating wakefulness and sleep adjustments during the postpartum period, potentially leading to increased wakefulness during this stage. These adaptive adjustments enable the mother to cope with the continuously changing demands of the pups.
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RATIONALE: In a social context, individuals are able to detect external information from others and coordinate behavioral responses according to the situation, a phenomenon called social decision-making. Social decision-making is multifaceted, influenced by emotional and motivational factors like stress, sickness, and hunger. However, the neurobiological basis for motivational state competition and interaction is not well known. OBJECTIVE: We investigated possible neural mechanisms through which internal states could shape social behavior in a social affective preference (SAP) test. In the SAP test, experimental rats given a choice to interact with naïve or stressed conspecifics exhibit an age-dependent preference to interact with stressed juvenile conspecifics, but avoid stressed adult conspecifics. First, we assessed the effect of food and water deprivation on SAP behavior. Behavior in the SAP test requires the insular cortex, which receives input from the ingestion-related peptides melanin-concentrating hormone (MCH) and orexin neurons of the lateral hypothalamus (LH). This study aimed to evaluate the role of LH and insular MCH and orexin in SAP test. METHODS: SAP tests were conducted in rats that were sated, food and water deprived or allowed 1 h of access to food and water after 14 h of deprivation (relieved condition). Separate cohorts of sated rats received cannula implants for microinjection of drugs to inhibit the LH or to block or stimulate MCH or orexin receptors in the insula prior to SAP tests or social interaction tests. RESULTS: Food and water deprivation prior to SAP tests with juvenile rats caused a shift in preference away from the stressed rat toward the naïve juveniles. Pharmacological inhibition of LH with muscimol (100 ng/side) abolished the preference for the juvenile-stressed conspecific, as well as the preference for the adult naïve conspecific. The blockade of MCH receptor 1or orexin receptors in the insular cortex with SNAP94847 (50 µM) or TCS1102 (1 µM), respectively, also abolished the preference for the stressed juvenile conspecific, but only the antagonism of orexin receptors was able to abolish the preference for the adult naïve conspecific. Microinjection of increasing doses (50 or 500 nM) of MCH or orexin-A in the insular cortex increased the interaction time in the one-on-one social interaction test with juvenile conspecifics; however, only the microinjection of orexin-A increased the interaction time with adult naïve conspecifics. CONCLUSIONS: Taken together, these results suggest that lateral hypothalamus peptides shape the direction of social approach or avoidance via actions MCH and orexin neurotransmission in the insular cortex.
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Abstract Background Several randomized clinical trials (RCTs) have shown that dual orexin receptor antagonists (DORAs) are effective in the treatment of chronic insomnia. However, the superiority of one particular DORA over the others remains unclear. Objective To perform a network meta-analysis to evaluate the efficacy of different DORAs in patients with chronic insomnia. Methods The Medline, Embase, and Cochrane Central databases were searched for RCTs that compared DORA with placebo in patients ≥ 18 years of age with a diagnosis of insomnia disorder. We pooled outcomes for wake time after sleep onset (WASO), latency to persistent sleep (LPS), total sleep time (TST), and adverse events (AEs). Results We included 10 RCTs with 7,806 patients, 4,849 of whom received DORAs as the intervention. Overall, we found that DORAs were associated with the improvement of all analyzed efficacy outcomes. Concerning TST, an apparent dose-dependent pattern was noticed, with higherdoses relating to a longerTST. Lemborexant 10mg provided the largest reduction in WASO (at month 1) in minutes (standardized mean difference [SMD] = −25.40; 95% confidence interval [95%CI] = −40.02- −10.78), followed by suvorexant 20/15mg (SMD = −25.29; 95%CI = −36.42- −14.15), which also appeared to provide the largest decrease in long-term WASO (SMD = −23.70; 95%CI = −35.89- −11.51). The most frequent AEs were somnolence, nasopharyngitis, and headache, with rates of up to 14.8%. Conclusion Our results suggest that DORAs are associated with greater efficacy when compared with placebo in the treatment of insomnia, a complex 24-hour sleep disorder. Additionally, dosing might play an important role in the management of chronic insomnia.
Resumo Antecedentes Inúmeros ensaios clínicos randomizados (ECRs) têm demonstrado que os antagonistas duais do receptor de orexina (dual orexin receptor antagonists, DORAs, em inglês) são eficazes no tratamento da insônia. Contudo, restam dúvidas quanto à superioridade de um DORA com relação aos outros. Objetivo Realizar uma meta-análise em rede para avaliar a eficácia de diferentes DORAs em pacientes com insônia. Métodos Foram feitas buscas nas bases de dados Medline, Embase e Cochrane Central por ECRs que comparassem DORAs e placebo em pacientes ≥ 18 anos de idade com diagnóstico de insônia. Os seguintes desfechos foram selecionados: tempo desperto após o início do sono (wake time after sleep onset, WASO, em inglês), latência para o sono persistente (latency to persistent sleep, LPS, em inglês), tempo total de sono (total sleep time, TST, em inglês), e efeitos adversos (EAs). Resultados Incluímos 10 ensaios clínicos com 7,806 pacientes, 4,849 dos quais receberam DORAs como intervenção. Os DORAs foram associados à melhoria de todos os desfechos de eficácia analisados. Em relação ao TST, um aparente padrão de dependência da dose foi identificado, com doses maiores se associando a um maior TST. Lemborexant 10 mg proporcionou a maior redução em WASO (no primeiro mês) em minutos (diferença padronizada das médias [standardized mean difference, [SMD], em inglês) = −25.40; intervalo de confiança de 95% [IC95%] = −40.02- −10.78), seguido de suvorexant 20/15mg (SMD = −25.29; IC95% = −36.42- −14.15), o qual também proporcionou a maior diminuição em WASO no longo prazo (SMD = −23.70; IC95% = −35.89- −11.51). Os EAs mais frequentes foram sonolência, nasofaringite e cefaleia, com taxas de até 14.8%. Conclusão Nossos resultados sugerem que os DORAs estão associados a uma maior eficácia quando comparados com placebo no tratamento da insónia, um complexo transtorno do sono de 24 horas. Além disso, a dosagem pode desempenhar um papel importante no manejo da insónia crônica.
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PURPOSE: The involvement of the orexin system in the physiopathology of insomnia has been rapidly increasing in understanding. In this sense, daridorexant was the third orexin receptor antagonist approved by the FDA in January 2022. This review aims to summarize the chemistry, pharmacodynamics, pharmacokinetics, efficacy, safety, and tolerability profile of daridorexant for the treatment of insomnia disorder. METHODS: We performed a review of daridorexant for the treatment of insomnia disorder. The search was carried out in Medline via PubMed, Embase, and clinical trials, up to March 2022. RESULTS: Daridorexant 25 and 50 mg had more significant improvement for the wake after sleep onset (WASO), latency to persistent sleep (LPS), and subjective total sleep time (sTST) than placebo. In addition, daridorexant 50 mg was better for Insomnia Daytime Symptoms and Impacts Questionnaire (IDSIQ) than placebo. The most common adverse events were nasopharyngitis and headache. CONCLUSION: Daridorexant was efficacious and safe. Studies that evaluate the long-term safety and compare daridorexant with benzodiazepines, benzodiazepine receptor agonists, sedative antidepressants, and other orexin receptor antagonists are required.
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Distúrbios do Início e da Manutenção do Sono , Antidepressivos/uso terapêutico , Benzodiazepinas , Método Duplo-Cego , Humanos , Hipnóticos e Sedativos/efeitos adversos , Imidazóis , Lipopolissacarídeos , Antagonistas dos Receptores de Orexina/efeitos adversos , Orexinas , Pirrolidinas , Receptores de GABA-A , Distúrbios do Início e da Manutenção do Sono/tratamento farmacológicoRESUMO
The medial preoptic area (mPOA) undergoes through neuroanatomical changes across the postpartum period, during which its neurons play a critical role in the regulation of maternal behavior. In addition, this area is also crucial for sleep-wake regulation. We have previously shown that hypocretins (HCRT) within the mPOA facilitate active maternal behaviors in postpartum rats, while the blockade of endogenous HCRT in this area promotes nursing and sleep. To explore the mechanisms behind these HCRT actions, we aimed to evaluate the effects of juxta-cellular HCRT-1 administration on mPOA neurons in urethane-anesthetized postpartum and virgin female rats. We recorded mPOA single units and the electroencephalogram (EEG) and applied HCRT-1 juxta-cellular by pressure pulses. Our main results show that the electrophysiological characteristics of the mPOA neurons and their relationship with the EEG of postpartum rats did not differ from virgin rats. Additionally, neurons that respond to HCRT-1 had a slower firing rate than those that did not. In addition, administration of HCRT increased the activity in one group of neurons while decreasing it in another, both in postpartum and virgin rats. This study suggests that the mechanisms by which HCRT modulate functions controlled by the mPOA involve different cell populations.
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Lactação , Área Pré-Óptica , Animais , Feminino , Neurônios/fisiologia , Orexinas/farmacologia , Ratos , UretanaRESUMO
Orexin-A, a hormone secreted by orexin neurons, is involved in caloric-intake regulation. Current understanding is based primarily on animal studies. Studies of orexin in humans are scarce, and to our knowledge there are no prior studies in adolescents. We studied fasting Orexin-A levels related to energy intake at breakfast and a subsequent snack in adolescents (n = 668) from a longitudinal study in Chile. Body-Mass Index (BMI), components of the metabolic syndrome and fasting blood levels of leptin, insulin, ghrelin, and orexin-A were measured. Energy intake was calculated based on food weights before and after the standardized breakfast and subsequent snack. High energy intake was defined as ≥ 75th percentile. We assessed the relationship between orexin-A and high energy intake, adjusting for confounders. Higher orexin levels were associated with high breakfast energy intake (OR: 1.21; 95%CI: 0.98-1.49). Conversely, those with higher orexin levels showed a non-significant trend for lower odds of high energy intake for the snack (OR: 0.87; 95%CI: 0.70-1.07). There was a significant interaction between high breakfast energy intake and orexin levels. Those who ate more calories at breakfast displayed a lower inhibitory effect of orexin on eating at the snack (p < 0.05). There was no significant interaction between weight status and orexin. In conclusion, orexin-A levels were associated with breakfast energy intake and inversely related with subsequent snack energy intake in participants whose caloric intake at breakfast was within the normal range. Based on these findings, it appears that the association of orexin-A with energy intake depends on eating behavior.
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Desjejum , Jejum , Orexinas , Adolescente , Animais , Chile , Ingestão de Energia/fisiologia , Comportamento Alimentar/fisiologia , Humanos , Estudos Longitudinais , LanchesRESUMO
Orexin-A, a hormone secreted by orexin neurons, is involved in caloric-intake regulation. Current understanding is based primarily on animal studies. Studies of orexin in humans are scarce, and to our knowledge there are no prior studies in adolescents. We studied fasting Orexin-A levels related to energy intake at breakfast and a subsequent snack in adolescents (n = 668) from a longitudinal study in Chile. Body-Mass Index (BMI), components of the metabolic syndrome and fasting blood levels of leptin, insulin, ghrelin, and orexin-A were measured. Energy intake was calculated based on food weights before and after the standardized breakfast and subsequent snack. High energy intake was defined as ≥ 75th percentile. We assessed the relationship between orexin-A and high energy intake, adjusting for confounders. Higher orexin levels were associated with high breakfast energy intake (OR: 1.21; 95%CI: 0.98-1.49). Conversely, those with higher orexin levels showed a non-significant trend for lower odds of high energy intake for the snack (OR: 0.87; 95%CI: 0.70-1.07). There was a significant interaction between high breakfast energy intake and orexin levels. Those who ate more calories at breakfast displayed a lower inhibitory effect of orexin on eating at the snack (p < 0.05). There was no significant interaction between weight status and orexin. In conclusion, orexin-A levels were associated with breakfast energy intake and inversely related with subsequent snack energy intake in participants whose caloric intake at breakfast was within the normal range. Based on these findings, it appears that the association of orexin-A with energy intake depends on eating behavior.
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Desjejum , Ingestão de Energia , Jejum , Orexinas , Adolescente , Chile , Ingestão de Energia/fisiologia , Comportamento Alimentar/fisiologia , Humanos , Estudos Longitudinais , Orexinas/sangue , LanchesRESUMO
The orexin peptides promote hedonic intake and other reward behaviors through different brain sites. The opioid dynorphin peptides are co-released with orexin peptides but block their effects on reward in the ventral tegmental area (VTA). We previously showed that in the paraventricular hypothalamic nucleus (PVN), dynorphin and not orexin peptides enhance hedonic intake, suggesting they have brain-site-specific effects. Obesity alters the expression of orexin and dynorphin receptors, but whether their expression across different brain sites is important to hedonic intake is unclear. We hypothesized that hedonic intake is regulated by orexin and dynorphin peptides in PVN and that hedonic intake in obesity correlates with expression of their receptors. Here we show that in mice, injection of DYN-A1-13 (an opioid dynorphin peptide) in the PVN enhanced hedonic intake, whereas in the VTA, injection of OXA (orexin-A, an orexin peptide) enhanced hedonic intake. In PVN, OXA blunted the increase in hedonic intake caused by DYN-A1-13. In PVN, injection of norBNI (opioid receptor antagonist) reduced hedonic intake but a subsequent OXA injection failed to increase hedonic intake, suggesting that OXA activity in PVN is not influenced by endogenous opioid activity. In the PVN, DYN-A1-13 increased the intake of the less-preferred food in a two-food choice task. In obese mice fed a cafeteria diet, orexin 1 receptor mRNA across brain sites involved in hedonic intake correlated with fat preference but not caloric intake. Together, these data support that orexin and dynorphin peptides regulate hedonic intake in an opposing manner with brain-site-specific effects.
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Dinorfinas , Núcleo Hipotalâmico Paraventricular , Analgésicos Opioides/metabolismo , Analgésicos Opioides/farmacologia , Animais , Encéfalo/metabolismo , Dinorfinas/metabolismo , Dinorfinas/farmacologia , Camundongos , Obesidade/metabolismo , Orexinas/metabolismoRESUMO
Hypocretins (HCRT), also known as orexins, includes two neuroexcitatory peptides, HCRT-1 and HCRT-2 (orexin A y B, respectively), synthesized by neurons located in the postero-lateral hypothalamus, whose projections and receptors are widely distributed throughout the brain, including the medial preoptic area (mPOA). HCRT have been associated with a wide range of physiological functions including sleep-wake cycle, maternal behavior and body temperature, all regulated by the mPOA. Previously, we showed that HCRT in the mPOA facilitates certain active maternal behaviors, while the blockade of HCRT-R1 increases the time spent in nursing. As mother rats mainly sleep while they nurse, we hypothesize that HCRT in the mPOA of lactating rats reduce sleep and nursing, while intra-mPOA administration of a dual orexin receptor antagonist (DORA) would cause the opposite effect. Therefore, the aim of this study was to determine the role of HCRT within the mPOA, in the regulation and integration of the sleep-wake cycle, maternal behavior and body temperature of lactating rats. For that purpose, we assessed the sleep-wake states, maternal behavior and body temperature of lactating rats following microinjections of HCRT-1 (100 and 200 µM) and DORA (5 mM) into the mPOA. As expected, our data show that HCRT-1 in mPOA promote wakefulness and a slightly increase in body temperature, whereas DORA increases both NREM and REM sleep together with an increment of nursing and milk ejection. Taken together, our results strongly suggest that the endogenous reduction of HCRT within the mPOA contribute to the promotion of sleep, milk ejection and nursing behavior in lactating rats.
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Temperatura Corporal , Área Pré-Óptica , Animais , Feminino , Humanos , Lactação , Comportamento Materno , Orexinas/metabolismo , Área Pré-Óptica/metabolismo , Ratos , SonoRESUMO
ABSTRACT Background: Narcolepsy is a disease resulting from the loss of hypocretin-producing cells or other dysfunctions of the hypocretinergic system. In addition to sleep disorders, affected patients may experience increased weight gain, olfactory changes, and poorer quality of life. Methods: This study aimed to investigate the relationship between narcolepsy and weight gain, years of study, sleep parameters, and olfactory dysfunction in patients with narcolepsy type 1 and narcolepsy type 2. Anthropometric, olfactory, socioeducational, and excessive daytime sleepiness evaluations were performed in 77 patients. Results: Greater weight gain and abdominal obesity were observed in patients with type 1 narcolepsy. Patients with higher education level had lower scores of daytime sleepiness, higher scores on the olfactory function test, and lower rates of abdominal obesity. Discussion: Patients with narcolepsy type 1 showed an increased body weight and abdominal obesity when compared to narcolepsy type 2. The patients with a higher schooling level showed a reduction of the daytime sleepiness scores, lower rates of abdominal obesity, and better scores on the olfactory function test. Conclusion: Among all the patients with narcolepsy, the data indicated that aging and hypocretin deficiency are associated with abdominal obesity, while years of study is the variable that mostly influences olfaction function.
RESUMO Antecedentes: A narcolepsia é resultante da perda de células produtoras de hipocretina ou da disfunção do sistema hipocretinérgico. Além dos distúrbios do sono característicos da doença, os pacientes afetados podem apresentar também aumento de peso, alterações olfatórias e pior qualidade de vida. Métodos: O objetivo do estudo é investigar a relação entre a narcolepsia e o ganho de peso, anos de estudo, parâmetros do sono e a disfunção olfatória em pacientes com narcolepsia tipo 1 e narcolepsia tipo 2. Foram realizadas avaliações antropométricas, do olfato, sociais, educacionais e da sonolência excessiva diurna nos 77 indivíduos participantes da pesquisa. Resultados: Foram observados, nos pacientes com narcolepsia tipo 1, maior ganho de peso e maior frequência de obesidade central. Pacientes com ensino superior apresentaram escores mais baixos de sonolência excessiva diurna, escores mais altos no teste de função olfatória e menores taxas de obesidade central. Discussão: Pacientes com narcolepsia tipo 1 apresentaram maior ganho de peso e obesidade central quando comparados aos com narcolepsia tipo 2. Os pacientes com maior escolaridade apresentaram menores escores de sonolência diurna, de obesidade central e melhores escores no teste da função olfatória. Conclusão: Nos indivíduos com narcolepsia tipo 1 e tipo 2, os dados indicaram que o envelhecimento e a deficiência de hipocretina estão associados à obesidade central, enquanto anos de estudo é a variável que mais influencia na função olfatória.
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Humanos , Neuropeptídeos , Obesidade Abdominal/complicações , Narcolepsia , Qualidade de Vida , Envelhecimento , Peptídeos e Proteínas de Sinalização Intracelular , OrexinasRESUMO
The ability to distinguish between threatening (repulsors), neutral and appetitive stimuli (attractors) stimuli is essential for survival. The orexinergic neurons of hypothalamus send projections to the limbic structures, such as different subregions of the medial prefrontal cortex (mPFC), suggesting that the orexinergic mechanism in the prelimbic cortex (PL) is involved in the processing of fear and anxiety. We investigated the role of orexin receptors type 1 (OX1R) and type 2 (OX2R) in the PL in such processes upon confrontation with an erratically moving robo-beetle in mice. The selective blockade of OX1R and OX2R in the PL with SB 334867 (3, 30, 300 nM) and TCS OX2 29 (3, 30, 300 nM), respectively, did not affect general exploratory behavior or reactive fear such as avoidance, jumping or freezing, but significantly enhances tolerance and approach behavior at the highest dose of each antagonist tested (300 nM). We interpret these findings as evidence for an altered cognitive appraisal of the potential threatening stimulus. Consequently, the orexin system seems to bias the perception of stimuli towards danger or threat via OX1R and OX2R in the PL.
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Córtex Cerebral , Antagonistas dos Receptores de Orexina , Animais , Córtex Cerebral/metabolismo , Hipotálamo/metabolismo , Camundongos , Antagonistas dos Receptores de Orexina/farmacologia , Receptores de Orexina/metabolismo , Orexinas/metabolismoRESUMO
In pre-metamorphic tadpoles, the neural network generating lung ventilation is present but actively inhibited; the mechanisms leading to the onset of air breathing are not well understood. Orexin (ORX) is a hypothalamic neuropeptide that regulates several homeostatic functions, including breathing. While ORX has limited effects on breathing at rest, it potentiates reflexive responses to respiratory stimuli mainly via ORX receptor 1 (OX1R). Here, we tested the hypothesis that OX1Rs facilitate the expression of the motor command associated with air breathing in pre-metamorphic bullfrog tadpoles (Lithobates catesbeianus). To do so, we used an isolated diencephalic brainstem preparation to determine the contributions of OX1Rs to respiratory motor output during baseline breathing, hypercapnia and hypoxia. A selective OX1R antagonist (SB-334867; 5-25â µmol l-1) or agonist (ORX-A; 200â nmolâ l-1 to 1â µmol l-1) was added to the superfusion media. Experiments were performed under basal conditions (media equilibrated with 98.2% O2 and 1.8% CO2), hypercapnia (5% CO2) or hypoxia (5-7% O2). Under resting conditions gill, but not lung, motor output was enhanced by the OX1R antagonist and ORX-A. Hypercapnia alone did not stimulate respiratory motor output, but its combination with SB-334867 increased lung burst frequency and amplitude, lung burst episodes, and the number of bursts per episode. Hypoxia alone increased lung burst frequency and its combination with SB-334867 enhanced this effect. Inactivation of OX1Rs during hypoxia also increased gill burst amplitude, but not frequency. In contrast with our initial hypothesis, we conclude that ORX neurons provide inhibitory modulation of the CO2 and O2 chemoreflexes in pre-metamorphic tadpoles.
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Pulmão , Respiração , Animais , Larva , Orexinas , Rana catesbeianaRESUMO
Allatotropin is a pleiotropic peptide originally characterized in insects. The existence of AT neuropeptide signaling was proposed in other invertebrates. In fact, we previously proposed the presence of an AT-like system regulating feeding behavior in Hydra sp. Even in insects, the information about the AT signaling pathway is incomplete. The aim of this study is to analyze the signaling cascade activated by AT in Hydra plagiodesmica using a pharmacological approach. The results show the involvement of Ca2+ and IP3 signaling in the transduction pathway of the peptide. Furthermore, we confirm the existence of a GPCR system involved in this pathway, that would be coupled to a Gq subfamily of Gα protein, which activates a PLC, inducing an increase in IP3 and cytosolic Ca2+. To the best of our knowledge, this work represents the first in vivo approach to study the overall signaling pathway and intracellular events involved in the myoregulatory effect of AT in Hydra sp.
Assuntos
Sinalização do Cálcio , Hydra/metabolismo , Hormônios de Inseto/metabolismo , Neuropeptídeos/metabolismo , Orexinas/metabolismo , Receptores Acoplados a Proteínas G/metabolismo , Animais , Cálcio/metabolismo , Sinalização do Cálcio/efeitos dos fármacos , Inibidores Enzimáticos/farmacologia , Estrenos/farmacologia , Proteínas de Ligação ao GTP/metabolismo , Indóis/farmacologia , Receptores de Inositol 1,4,5-Trifosfato/metabolismo , Maleimidas/farmacologia , Meliteno/farmacologia , Proteína Quinase C/antagonistas & inibidores , Proteína Quinase C/metabolismo , Pirrolidinonas/farmacologia , Fosfolipases Tipo C/antagonistas & inibidores , Fosfolipases Tipo C/metabolismoRESUMO
Orexins-A (OrxA) and -B (OrxB) neuropeptides are synthesized by a group of neurons located in the lateral hypothalamus and adjacent perifornical area, which send their projections to the mesolimbic dopaminergic (DAergic) system including ventral tegmental area and nucleus accumbens (NAc), where orexin receptors are expressed. NAc plays a central role in reward-seeking behavior and drug abuse. NAc-neurons express dopamine-1 (D1R) and dopamine-2 (D2R) receptors. Orexins bind to their two cognate G-protein-coupled receptors, orexin-receptor type-1 (Orx1R) and type-2 (Orx2R). Orexin receptor signaling is involved in behaviors such as motivation and addiction. Orexin-containing neurons modulate DAergic activity that is key in synaptic plasticity induced by addictive drugs. However, the effect of OrxA on expression and content of DAergic receptors in NAc is unknown. The purpose of this study was to investigate whether OrxA can alter gene expression and protein levels of D1R/D2R in NAc. Gene expression was evaluated by real-time PCR analysis and protein levels by western blot in rats. The results show that intracerebroventricular (i.c.v.) injection of OrxA increases both gene transcription and protein content of D2R but fails to modify D1R. This effect was also confirmed with OrxA infusion in NAc/Shell. Our results demonstrate for the first time that OrxA induces up-regulation of gene and protein of D2R in NAc. These findings support the hypothesis that OrxA modulates the DAergic transmission and this may serve to understand how orexin signaling enhances DA responses at baseline conditions and in response to psychostimulants.
Assuntos
Neurônios Dopaminérgicos/efeitos dos fármacos , Núcleo Accumbens/efeitos dos fármacos , Orexinas/farmacologia , Receptores de Dopamina D1/genética , Receptores de Dopamina D2/genética , Animais , Neurônios Dopaminérgicos/citologia , Neurônios Dopaminérgicos/metabolismo , Regulação da Expressão Gênica , Injeções Intraventriculares , Masculino , Núcleo Accumbens/citologia , Núcleo Accumbens/metabolismo , Orexinas/metabolismo , Ligação Proteica , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ratos , Ratos Wistar , Receptores de Dopamina D1/metabolismo , Receptores de Dopamina D2/metabolismo , Transdução de Sinais , Técnicas EstereotáxicasRESUMO
AIMS: Investigate the involvement of the histaminergic projections from tuberomammillary nucleus (TMN) to the spinal cord in the modulation of nociception and peripheral edema in a model of monoarthritis. MAIN METHODS: Subacute monoarthritis was induced by an intraarticular injection of carrageenan followed by LPS 72 h later. Disability and joint edema were assessed at the 3rd hour after LPS and at every hour up to 6 h. KEY FINDINGS: Intrathecal administration of histamine potentiated joint incapacitation and edema, while the H1R antagonist cetirizine decreased both. The H3R agonist immepip decreased both incapacitation and edema, while the H3R antagonist thioperamide had the opposite effect. The microinjection of glutamate into the ventral TMN (vTMN) caused an increase of incapacitation and articular edema, whereas the blockade of this nucleus by cobalt chloride inhibited both parameters. Intrathecal administration of cetirizine prevented the increase of incapacitation and joint edema caused by glutamate microinjection into the vTMN. Similarly, an intrathecal injection of the NKCC1 cotransporter inhibitor bumetanide prevented the effects of glutamate microinjection into the vTMN, whereas coadministration of histamine with bumetanide only inhibited the potentiation of joint edema. A microinjection of orexin B into the vTMN potentiated incapacitation and joint edema, while coadministration of the OX1/2 receptor antagonist almorexant with orexin B did not. SIGNIFICANCE: These data support the notion that TMN participates in the modulation of a peripheral inflammatory process by means of histaminergic projections to the spinal cord, and the hypothalamus may trigger TMN activation by means of glutamate and orexin.
Assuntos
Artrite Experimental/fisiopatologia , Edema/patologia , Região Hipotalâmica Lateral/metabolismo , Nociceptividade/fisiologia , Medula Espinal/metabolismo , Acetamidas/farmacologia , Animais , Feminino , Histamina/administração & dosagem , Isoquinolinas/farmacologia , Orexinas/administração & dosagem , Ratos , Ratos WistarRESUMO
RATIONALE: Reduced levels of orexin-A (OXA) in the central nervous system (CNS) have been associated with the pathophysiology of depression and its exogenous administration promotes antidepressant-like effect. The mechanisms associated with these effects are, however, not yet known. Herein, we investigated the hypothesis that OXA effects could be associated with orexin 1 receptor (OX1R) and tyrosine receptor kinase B (TrkB) activation, in the ventromedial prefrontal cortex (vmPFC), a brain region that is central to depression neurobiology. OBJECTIVES: 1. To Investigate the effects induced by OXA administration into the vmPFC; 2. Evaluate the participation of OX1R and TrkB in behavioral responses induced by OXA. METHODS: Male Wistar rats received intra-vmPFC injections of OXA (10, 50 and 100 pmol/0.2 µL) and were exposed to the forced swimming test (FST) or the open field test (OFT). Independent groups received an intra-vmPFC injection of SB334867 (OX1R antagonist, 10 nmol/0.2 µL) or K252a (non-selective Trk antagonist, 10 pmol/0.2 µL), before local injection of OXA, and were exposed to the same tests. RESULTS: OXA injection (100 pmol/0.2 µL) into the vmPFC induced antidepressant-like effect, which was prevented by SB334867 and K252a pretreatments. CONCLUSION: OXA signaling in the vmPFC induces antidepressant-like effect in the FST which is dependent on OX1R and Trk receptors.
Assuntos
Depressão/tratamento farmacológico , Orexinas/farmacologia , Córtex Pré-Frontal/metabolismo , Animais , Antidepressivos/farmacologia , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Masculino , Atividade Motora/efeitos dos fármacos , Receptores de Orexina/efeitos dos fármacos , Receptores de Orexina/metabolismo , Orexinas/administração & dosagem , Orexinas/metabolismo , Córtex Pré-Frontal/efeitos dos fármacos , Ratos , Ratos Wistar , Receptor trkB/metabolismo , Transdução de Sinais/efeitos dos fármacos , Estresse PsicológicoRESUMO
It has been widely described that chronic intake of fructose causes metabolic alterations which can be associated with brain function impairment. In this study, we evaluated the effects of fructose intake on the sleepâ»wake cycle, locomotion, and neurochemical parameters in Wistar rats. The experimental group was fed with 10% fructose in drinking water for five weeks. After treatment, metabolic indicators were quantified in blood. Electroencephalographic recordings were used to evaluate the sleep architecture and the spectral power of frequency bands. Likewise, the locomotor activity and the concentrations of orexin A and monoamines were estimated. Our results show that fructose diet significantly increased the blood levels of glucose, cholesterol, and triglycerides. Fructose modified the sleepâ»wake cycle of rats, increasing the waking duration and conversely decreasing the non-rapid eye movement sleep. Furthermore, these effects were accompanied by increases of the spectral power at different frequency bands. Chronic consumption of fructose caused a slight increase in the locomotor activity as well as an increase of orexin A and dopamine levels in the hypothalamus and brainstem. Specifically, immunoreactivity for orexin A was increased in the ventral tegmental area after the intake of fructose. Our study suggests that fructose induces metabolic changes and stimulates the activity of orexinergic and dopaminergic neurons, which may be responsible for alterations of the sleepâ»wake cycle.