RESUMO
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.
Assuntos
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
Kisspeptin (KISS), a key hormone involved in the regulation of the hypothalamic-pituitary-ovarian (HPO) axis, has been localized in the anteroventral periventricular (AVPV) nucleus and the neighboring rostral periventricular nucleus (PeVN), and in the arcuate (ARC) nucleus of the mammalian hypothalamus. In the ARC, the KISS neurons that co-express neurokinin B (NKB) and dynorphin A (Dyn) are named KNDy cells. The South American plains vizcacha is a rodent with peculiar reproductive traits. Around mid-pregnancy, vizcacha shows the reactivation of its HPO axis with the pulsatile release of gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH), an essential event for the success of gestation. Considering the role of KISS system in GnRH modulation, the aim of this work was to study their neuroanatomical distribution in adult vizcachas. AVPV showed sexual dimorphism with a significant smaller area in males (t-Test, p < 0.05), and KISS immunoreactivity was detected in somas and varicosities homogenously distributed in the AVPV with a concordant sex-related expression pattern. NKB and Dyn expression was also observed in cytoplasm of neurons scattered in the AVPV. Three subpopulations of neurons were detected in the AVPV: neurons expressing Dyn and NKB (DyNK cells), neurons expressing KISS and NKB (KiNK cells), and single NKB expressing neurons. Strikingly, KISS and Dyn were always expressed in different cells. In addition, in the ARC nucleus, KNDy cells were detected. On the other hand, KISS and GnRH expression was detected in different subpopulations of neurons, GnRH cells showed KISS receptor (KISSR or GPR-54) expression, and KISS immunoreactive afferent contacts were detected making close appositions onto somas and dendrites of GnRH cells. These results show similarities and differences between the KISS system in the hypothalamus of the vizcacha and other mammals, and constitute crucial observations about KISS and GnRH relation. Considering the peculiarity of HPO axis regulation in this species, the present work provides a neuroanatomical framework for the further elucidation of molecular mechanisms underlying GnRH expression and secretion.
Assuntos
Hormônio Liberador de Gonadotropina , Kisspeptinas , Animais , Núcleo Arqueado do Hipotálamo/metabolismo , Feminino , Hormônio Liberador de Gonadotropina/metabolismo , Hipotálamo/metabolismo , Kisspeptinas/metabolismo , Masculino , Mamíferos/metabolismo , Neurocinina B/metabolismo , Gravidez , América do SulRESUMO
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.
Assuntos
Dinorfinas , Núcleo Hipotalâmico Paraventricular , Analgésicos Opioides/metabolismo , Analgésicos Opioides/farmacologia , Animais , Encéfalo/metabolismo , Dinorfinas/metabolismo , Dinorfinas/farmacologia , Camundongos , Obesidade/metabolismo , Orexinas/metabolismoRESUMO
ABSTRACT Dynorphin A is an endogenous opioid peptide that is part of the KNDy system in the hypothalamus of mammals. This peptide acts as an inhibitor of the GnRH pulse generation, thus regulating the onset of puberty and reproductive cycles. The PDYN gene encodes the propeptide Prodynorphin, the precursor of Dynorphin A. Despite its physiological relevance, PDYN has not emerged as a candidate gene associated with puberty in genomic association studies conducted in cattle. The present work aimed to search for signatures of selection on the PDYN gene among cattle breeds. To this, the whole genome sequences from 57 samples of ten cattle breeds were used. The samples were grouped based on breed selection history and their productive differences, particularly in terms of sexual precocity. The population structure was analyzed using Principal Component Analyses. To evidence recent selection processes, neutrality tests, such as Tajima's D and Fu & Li's F* and D* were performed in defined functional regions of PDYN. The putative promoter of PDYN showed a population structure that is in agreement with the criteria considered to make the groups. In that region, neutrality tests were consistently negative and resulted in statistically significant for the dairy breeds. Also, these breeds exhibited less variability in the haplotype analyses than the others. The results presented here suggest that regulatory regions of PDYN could be under positive selection, particularly in dairy breeds.
RESUMEN Dinorfina A es un péptido opioide endógeno que forma parte del sistema KNDy en el hipotálamo de mamíferos. Este péptido actúa como inhibidor de la generación de los pulsos de GnRH, regulando así el inicio de la pubertad y los ciclos reproductivos. El gen PDYN codifica el propéptido Prodinorfina, precursor de Dinorfina A. A pesar de su relevancia fisiológica, PDYN no ha surgido como gen candidato asociado a pubertad en estudios de asociación genómicos en bovinos. El presente trabajo tuvo como objetivo buscar huellas de selección en el gen PDYN entre diferentes razas bovinas. Para alcanzarlo se utilizaron secuencias genómicas de 57 muestras de diez razas bovinas. Las muestras fueron agrupadas considerando la historia de selección y las diferencias productivas entre razas, particularmente en términos de precocidad sexual. La estructura poblacional fue analizada usando análisis de componentes principales. Para evidenciar procesos de selección recientes se realizaron pruebas de neutralidad, tales como D de Tajima y F* y D* de Fu & Li, en diferentes regiones funcionales de PDYN. El promotor putativo de PDYN mostró una estructura poblacional que es consistente con los criterios usados para agrupar las razas. En esa región, las pruebas de neutralidad fueron consistentemente negativas y estadísticamente significativas en las razas lecheras. Además, estas razas también exhibieron menor variabilidad en los análisis de haplotipos que las demás razas. Los resultados presentados aquí sugieren que regiones regulatorias de PDYN estarían bajo selección positiva, particularmente en razas bovinas lecheras.
RESUMO
Decreased dopaminergic activity and increased kappa opioid activity in the mesolimbic system underlie the negative emotional states related to chronic pain. However, it is not known whether these changes are just consequence of chronic pain or contribute to the sensorial changes associated with chronic pain. In this study, we asked whether the mesolimbic dopamine and kappa opioid systems contribute to the development and maintenance of chronic hyperalgesia, one of the most common sensorial changes related to chronic pain. The lesion of the dopaminergic cells of the ventral tegmental area prevented the transition from acute to chronic hyperalgesia when performed in pain-free rats, but did not affect the maintenance of chronic hyperalgesia, when performed in chronic pain in rats. As hyperalgesia becomes chronic, the dopamine levels in the nucleus accumbens decrease. The blockade of the kappa opioid receptors in the nucleus accumbens both prevented and reversed the development of chronic hyperalgesia, but did not affect its maintenance. Complementarily, the pharmacological activation of the kappa opioid receptors in the nucleus accumbens facilitated the transition from acute to chronic hyperalgesia. None of these interventions affected acute hyperalgesia. These findings suggest that the mesolimbic dopamine and kappa opioid systems specifically drive the pain chronification process, without affecting acute pain or the maintenance of chronic pain.
Assuntos
Dor Aguda/metabolismo , Dor Crônica/metabolismo , Neurônios Dopaminérgicos/metabolismo , Núcleo Accumbens/metabolismo , Receptores Opioides kappa/metabolismo , Área Tegmentar Ventral/metabolismo , Dor Aguda/induzido quimicamente , Analgésicos Opioides/farmacologia , Animais , Dor Crônica/induzido quimicamente , Dinoprostona/toxicidade , Progressão da Doença , Dopamina/metabolismo , Neurônios Dopaminérgicos/efeitos dos fármacos , Masculino , Núcleo Accumbens/efeitos dos fármacos , Oxidopamina/toxicidade , Ratos , Ratos Wistar , Receptores Opioides kappa/agonistas , Área Tegmentar Ventral/efeitos dos fármacosRESUMO
Hypothalamic paraventricular nucleus (PVN) projections to the spinal dorsal horn (SDH) are related to antinociception. Several neuropeptides from this nucleus could be released to the spinal cord after nociceptive stimuli. Indeed, it has been shown that enkephalins, oxytocin and vasopressin could be released at this level. Although the antinociceptive effects of these neuropeptides are well studied, little is known about the potential interaction between these molecules. In this study, we provide anatomical evidence of the interaction between oxytocin (OT), vasopressin (AVP), dynorphin (DYN) and enkephalin (ENK) along the PVN projections to the spinal dorsal horn at L3 level. A retrograde tracer (True Blue®) microinjected at L3 in the SDH and immunofluorescence with antibodies against OT, AVP, DYN and ENK were used. The experiments showed different levels of peptide immunoreactivity distribution along the rostro-caudal area of the PVN. A high percentage of co-localizations between two of the peptides (OT-AVP, OT-DYN, AVP-ENK, DYN-ENK) were present along the PVN. The following co-localizations occupied 4.76-9.62% of the total PVN area. PVN projections to the SDH at L3 level showed similar results. Our results show that different antinociceptive peptides may be interacting with each other to evoke PVN antinociceptive effects as part of the endogenous system of nociceptive modulation.
Assuntos
Encefalinas/farmacologia , Ocitocina/farmacologia , Núcleo Hipotalâmico Paraventricular/efeitos dos fármacos , Medula Espinal/efeitos dos fármacos , Vasopressinas/farmacologia , Animais , Dinorfinas/farmacologia , Encefalinas/metabolismo , Masculino , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Nociceptividade/efeitos dos fármacos , Núcleo Hipotalâmico Paraventricular/metabolismo , Ratos Wistar , Medula Espinal/metabolismo , Corno Dorsal da Medula Espinal/efeitos dos fármacos , Corno Dorsal da Medula Espinal/metabolismoRESUMO
Animal models have suggested that prenatal ethanol exposure (PEE) alters the κ opioid receptor system. The present study investigated the brain expression of dynorphin and nociceptin/orphanin FQ related genes and assessed anxiety-like behavior in the light-dark box (LDB), shelter-seeking and risk-taking behaviors in the concentric square field (CSF) test, and ethanol-induced locomotion in the open field (OF), in infant or adolescent Wistar rats that were exposed to PEE (0.0 or 2.0â¯g/kg, intragastrically, gestational days 17-20). We measured brain mRNA levels of prodynorphin (PDYN), κ opioid receptors (KOR), the nociceptin/orphanin FQ opioid peptide precursor prepronociceptin (ppN/OFQ) and nociceptine/orphanin FQ receptors (NOR). Prenatal ethanol exposure upregulated PDYN and KOR mRNA levels in the ventral tegmental area (VTA) in infant and adolescent rats and KOR mRNA levels in the prefrontal cortex in infant rats. The changes in gene expression in the VTA were accompanied by a reduction of DNA methylation at the PDYN gene promoter, and by a reduction of DNA methylation at the KOR gene promoter. The PEE-induced upregulation of PDYN/KOR in the VTA was accompanied by lower NOR gene expression in the VTA, and lower PDYN gene expression in the nucleus accumbens. PEE rats exhibited hypolocomotion in the OF, greater avoidance of the white and brightly lit areas in the LDB and CSF, and greater preference for the sheltered area in the CSF test. These results suggest that PEE upregulates the dynorphin system, resulting in an anxiety-prone phenotype and triggering compensatory responses in the nociceptin/orphanin FQ system. These findings may help elucidate the mechanisms that underlie the effects of PEE and suggest that the dynorphin and nociceptin/orphanin FQ systems may be possible targets for the prevention and treatment of PEE-induced alterations.
Assuntos
Ansiedade/metabolismo , Encefalinas/metabolismo , Transtornos do Espectro Alcoólico Fetal/metabolismo , Transtornos do Espectro Alcoólico Fetal/psicologia , Precursores de Proteínas/metabolismo , Receptores Opioides kappa/metabolismo , Receptores Opioides/metabolismo , Animais , Animais não Endogâmicos , Encéfalo/efeitos dos fármacos , Encéfalo/crescimento & desenvolvimento , Encéfalo/metabolismo , Depressores do Sistema Nervoso Central/toxicidade , Metilação de DNA/efeitos dos fármacos , Modelos Animais de Doenças , Etanol/toxicidade , Feminino , Regulação da Expressão Gênica no Desenvolvimento/efeitos dos fármacos , Masculino , Atividade Motora/efeitos dos fármacos , Regiões Promotoras Genéticas , RNA Mensageiro/metabolismo , Distribuição Aleatória , Ratos Wistar , Assunção de Riscos , Receptor de NociceptinaRESUMO
The dynorphin (DYN) peptide family includes opioid and non-opioid peptides, yet the physiological role of the non-opioid DYN peptides remains poorly understood. Recent evidence shows that administering the non-opioid peptide DYN-A2-17 into the paraventricular hypothalamic nucleus (PVN) simultaneously increased short-term intake of standard rodent chow and spontaneous physical activity (SPA). The present studies aimed to expand upon the mechanisms and role of DYN-A2-17 on food intake and energy expenditure. Injection of DYN-A2-17 in PVN increased SPA, energy expenditure and wheel running in the absence of food. Repeated DYN-A2-17 injection in PVN increased short-term chow intake, but this effect habituated over time and failed to alter cumulative food intake, body weight or adiposity. Pre-treatment with a CRF receptor antagonist into PVN blocked the effects of DYN-A2-17 on food intake while injection of DYN-A2-17 in PVN increased plasma ACTH. Finally, as DYN peptides are co-released with orexin peptides, we compared the effects of DYN-A2-17 to orexin-A and the opioid peptide DYN-A1-13 on food choice and intake in PVN when palatable snacks and chow were available. DYN-A1-13 selectively increased intake of palatable snacks. DYN-A2-17 and orexin-A decreased palatable snack intake while orexin-A also increased chow intake. These findings demonstrate that the non-opioid peptide DYN-A2-17 acutely regulates physical activity, energy expenditure and food intake without long-term effects on energy balance. These data also propose different roles of opioid, non-opioid DYN and orexin peptides on food choice and intake when palatable and non-palatable food options are available.
Assuntos
Fármacos do Sistema Nervoso Central/farmacologia , Dinorfinas/farmacologia , Metabolismo Energético/efeitos dos fármacos , Comportamento Alimentar/efeitos dos fármacos , Fragmentos de Peptídeos/farmacologia , Corrida , Adiposidade/efeitos dos fármacos , Adiposidade/fisiologia , Hormônio Adrenocorticotrópico/sangue , Animais , Peso Corporal/efeitos dos fármacos , Peso Corporal/fisiologia , Comportamento de Escolha/efeitos dos fármacos , Comportamento de Escolha/fisiologia , Metabolismo Energético/fisiologia , Comportamento Alimentar/fisiologia , Masculino , Camundongos Endogâmicos BALB C , Orexinas/metabolismo , Núcleo Hipotalâmico Paraventricular/efeitos dos fármacos , Núcleo Hipotalâmico Paraventricular/metabolismo , Receptores de Hormônio Liberador da Corticotropina/antagonistas & inibidores , Receptores de Hormônio Liberador da Corticotropina/metabolismo , Corrida/fisiologiaRESUMO
Food intake and physical activity are regulated by multiple neuropeptides, including orexin and dynorphin (DYN). Orexin-A (OXA) is one of two orexin peptides with robust roles in regulation of food intake and spontaneous physical activity (SPA). DYN collectively refers to several peptides, some of which act through opioid receptors (opioid DYN) and some whose biological effects are not mediated by opioid receptors (non-opioid DYN). While opioid DYN is known to increase food intake, the effects of non-opioid DYN peptides on food intake and SPA are unknown. Neurons that co-express and release OXA and DYN are located within the lateral hypothalamus. Limited evidence suggests that OXA and opioid DYN peptides can interact to modulate some aspects of behaviors classically related to orexin peptide function. The paraventricular hypothalamic nucleus (PVN) is a brain area where OXA and DYN peptides might interact to modulate food intake and SPA. We demonstrate that injection of des-Tyr-dynorphin (DYN-A(2-17), a non opioid DYN peptide) into the PVN increases food intake and SPA in adult mice. Co-injection of DYN-A(2-17) and OXA in the PVN further increases food intake compared to DYN-A(2-17) or OXA alone. This is the first report describing the effects of non-opioid DYN-A(2-17) on food intake and SPA, and suggests that DYN-A(2-17) interacts with OXA in the PVN to modulate food intake. Our data suggest a novel function for non-opioid DYN-A(2-17) on food intake, supporting the concept that some behavioral effects of the orexin neurons result from combined actions of the orexin and DYN peptides.
Assuntos
Dinorfinas/fisiologia , Orexinas/metabolismo , Fragmentos de Peptídeos/fisiologia , Animais , Regulação do Apetite , Ingestão de Energia , Masculino , Camundongos Endogâmicos BALB C , Atividade MotoraRESUMO
BACKGROUND AND PURPOSE: Crotalphine is an antinociceptive peptide that, despite its opioid-like activity, does not induce some of the characteristic side effects of opioids, and its amino acid sequence has no homology to any known opioid peptide. Here, we evaluated the involvement of the peripheral cannabinoid system in the crotalphine effect and its interaction with the opioid system. EXPERIMENTAL APPROACH: Hyperalgesia was evaluated using the rat paw pressure test. Involvement of the cannabinoid system was determined using a selective cannabinoid receptor antagonist. Cannabinoid and opioid receptor activation were evaluated in paw slices by immunofluorescence assays using conformation state-sensitive antibodies. The release of endogenous opioid peptides from skin tissue was measured using a commercial enzyme immunoassay (EIA). KEY RESULTS: Both p.o. (0.008-1.0 µg·kg(-1) ) and intraplantar (0.0006 µg per paw) administration of crotalphine induced antinociception in PGE2 -induced hyperalgesia. Antinociception by p.o. crotalphine (1 µg·kg(-1) ) was blocked by AM630 (50 µg per paw), a CB2 receptor antagonist, and by antiserum anti-dynorphin A (1 µg per paw). Immunoassay studies confirmed that crotalphine increased the activation of both κ-opioid (51.7%) and CB2 (28.5%) receptors in paw tissue. The local release of dynorphin A from paw skin was confirmed by in vitroâ EIA and blocked by AM630. CONCLUSIONS AND IMPLICATIONS: Crotalphine-induced antinociception involves peripheral CB2 cannabinoid receptors and local release of dynorphin A, which is dependent on CB2 receptor activation. These results enhance our understanding of the mechanisms involved in the peripheral effect of crotalphine, as well as the interaction between the opioid and cannabinoid systems.