RESUMO
Hypothalamic melanin-concentrating hormone (MCH) neurons participate in many fundamental neuroendocrine processes. While some of their effects can be attributed to MCH itself, others appear to depend on co-released neurotransmitters. Historically, the subject of fast neurotransmitter co-release from MCH neurons has been contentious, with data to support MCH neurons releasing GABA, glutamate, both, and neither. Rather than assuming a position in that debate, this review considers the evidence for all sides and presents an alternative explanation: neurochemical identity, including classical neurotransmitter content, is subject to change. With an emphasis on the variability of experimental details, we posit that MCH neurons may release GABA and/or glutamate at different points according to environmental and contextual factors. Through the lens of the MCH system, we offer evidence that the field of neuroendocrinology would benefit from a more nuanced and dynamic interpretation of neurotransmitter identity.
Assuntos
Hormônios Hipotalâmicos , Hormônios Hipotalâmicos/metabolismo , Hormônios Hipotalâmicos/farmacologia , Hormônios Hipofisários/farmacologia , Hormônios Hipofisários/fisiologia , Neurônios/metabolismo , Melaninas/farmacologia , Melaninas/fisiologia , Hipotálamo/metabolismo , Ácido Glutâmico/farmacologia , Ácido Glutâmico/fisiologia , Neurotransmissores , Ácido gama-AminobutíricoRESUMO
Recent studies have reinforced the view that the lateral hypothalamic area (LHA) regulates food intake and body weight. We identified leptin-sensitive neurons in the arcuate nucleus of the hypothalamus (Arc) that innervate the LHA using retrograde tracing with leptin administration. We found that retrogradely labeled cells in the Arc contained neuropeptide Y (NPY) mRNA or proopiomelanocortin (POMC) mRNA. Following leptin administration, NPY cells in the Arc did not express Fos but expressed suppressor of cytokine signaling-3 (SOCS-3) mRNA. In contrast, leptin induced both Fos and SOCS-3 expression in POMC neurons, many of which also innervated the LHA. These findings suggest that leptin directly and differentially engages NPY and POMC neurons that project to the LHA, linking circulating leptin and neurons that regulate feeding behavior and body weight homeostasis.
Assuntos
Núcleo Arqueado do Hipotálamo/fisiologia , Região Hipotalâmica Lateral/fisiologia , Neurônios/fisiologia , Neuropeptídeo Y/fisiologia , Pró-Opiomelanocortina/fisiologia , Proteínas/fisiologia , Proteínas Repressoras , Fatores de Transcrição , Animais , Núcleo Arqueado do Hipotálamo/citologia , Peso Corporal/fisiologia , Contagem de Células , Ingestão de Alimentos/fisiologia , Homeostase/fisiologia , Região Hipotalâmica Lateral/citologia , Imuno-Histoquímica , Hibridização In Situ , Leptina , Masculino , Vias Neurais/citologia , Vias Neurais/fisiologia , Biossíntese de Proteínas , Proteínas Proto-Oncogênicas c-fos/biossíntese , Proteínas Proto-Oncogênicas c-fos/genética , RNA Mensageiro/biossíntese , RNA Mensageiro/genética , Ratos , Ratos Sprague-Dawley , Transdução de Sinais/fisiologia , Proteína 3 Supressora da Sinalização de Citocinas , Proteínas Supressoras da Sinalização de CitocinaRESUMO
The adipocyte-derived hormone leptin decreases body weight in part by activating the sympathetic nervous system, resulting in increased thermogenesis and energy expenditure. We investigated hypothalamic pathways underlying leptin's effects on stimulating the sympathetic nervous system. We found that leptin activates neurons in the retrochiasmatic area (RCA) and lateral arcuate nucleus (Arc) that innervate the thoracic spinal cord and also contain cocaine- and amphetamine-regulated transcript (CART). We also found that most CART-containing neurons in the RCA and Arc of the hypothalamus also contain proopiomelanocortin (POMC) mRNA. The finding that leptin activates CART/POMC neurons innervating sympathetic preganglionic neurons in the thoracic spinal cord suggests that this pathway may contribute to the increased thermogenesis and energy expenditure and decreased body weight observed following leptin administration.
Assuntos
Hipotálamo/fisiologia , Proteínas do Tecido Nervoso/genética , Neurônios/fisiologia , Pró-Opiomelanocortina/genética , Proteínas/farmacologia , Medula Espinal/fisiologia , Animais , Núcleo Arqueado do Hipotálamo/efeitos dos fármacos , Núcleo Arqueado do Hipotálamo/fisiologia , Regulação da Temperatura Corporal/efeitos dos fármacos , Peso Corporal/efeitos dos fármacos , Metabolismo Energético/efeitos dos fármacos , Hipotálamo/efeitos dos fármacos , Leptina , Masculino , Microinjeções , Vias Neurais/efeitos dos fármacos , Vias Neurais/fisiologia , Neurônios/efeitos dos fármacos , Especificidade de Órgãos , Proteínas/administração & dosagem , RNA Mensageiro/metabolismo , Ratos , Ratos Sprague-Dawley , Medula Espinal/efeitos dos fármacos , Transcrição Gênica/efeitos dos fármacosRESUMO
The lateral hypothalamic area (LHA) participates in the integration of sensory information and somatomotor responses associated with hunger and thirst. Although the LHA is neurochemically heterogeneous, a particularly high number of cells express melanin-concentrating hormone (MCH), which has been reported to play a role in energy homeostasis. Treatment with MCH increases food intake, and MCH mRNA is overexpressed in leptin-deficient (ob/ob) mice. Mice lacking both MCH and leptin present reduced body fat, mainly due to increased resting energy expenditure and locomotor activity. Dense MCH innervation of the cerebral motor cortex (MCx) and the pedunculopontine tegmental nucleus (PPT), both related to motor function, has been reported. Therefore, we postulated that a specific group of MCH neurons project to these areas. To investigate our hypothesis, we injected retrograde tracers into the MCx and the PPT of rats, combined with immunohistochemistry. We found that 25% of the LHA neurons projecting to the PPT were immunoreactive for MCH, and that 75% of the LHA neurons projecting to the MCx also contained MCH. Few MCH neurons were found to send collaterals to both areas. We also found that 15% of the incerto-hypothalamic neurons projecting to the PPT expressed MCH immunoreactivity. Those neurons preferentially innervated the rostral PPT. In addition, we observed that the MCH neurons express glutamic acid decarboxylase mRNA, a gamma-aminobutyric acid (GABA) synthesizing enzyme. We postulate that MCH/GABA neurons are involved in the inhibitory modulation of the innervated areas, decreasing motor activity in states of negative energy balance.
Assuntos
Hormônios Hipotalâmicos/metabolismo , Melaninas/metabolismo , Hormônios Hipofisários/metabolismo , Animais , Transporte Axonal , Ingestão de Energia , Hormônios Hipotalâmicos/deficiência , Hormônios Hipotalâmicos/genética , Imuno-Histoquímica , Hibridização In Situ , Leptina/deficiência , Masculino , Melaninas/deficiência , Melaninas/genética , Melanóforos/metabolismo , Camundongos , Camundongos Obesos , Córtex Motor/metabolismo , Fibras Nervosas/metabolismo , Núcleo Tegmental Pedunculopontino/metabolismo , Hormônios Hipofisários/deficiência , Hormônios Hipofisários/genética , Ratos , Ratos WistarRESUMO
Starvation causes a rapid reduction in thyroid hormone levels in rodents. This adaptive response is caused by a reduction in thyrotropin-releasing hormone (TRH) expression that can be reversed by the administration of leptin. Here we examined hypothalamic signaling pathways engaged by leptin to upregulate TRH gene expression. As assessed by leptin-induced expression of suppressor of cytokine signaling-3 (SOCS-3) in fasted rats, TRH neurons in the paraventricular nucleus are activated directly by leptin. To a greater degree, they also contain melanocortin-4 receptors (MC4Rs), implying that leptin can act directly or indirectly by increasing the production of the MC4R ligand, alpha-melanocyte stimulating hormone (alpha-MSH), to regulate TRH expression. We further demonstrate that both pathways converge on the TRH promoter. The melanocortin system activates the TRH promoter through the phosphorylation and DNA binding of the cAMP response element binding protein (CREB), and leptin signaling directly regulates the TRH promoter through the phosphorylation of signal transducer and activator of transcription 3 (Stat3). Indeed, a novel Stat-response element in the TRH promoter is necessary for leptin's effect. Thus, the TRH promoter is an ideal target for further characterizing the integration of transcriptional pathways through which leptin acts.
Assuntos
Leptina/farmacologia , Receptores de Peptídeos/metabolismo , Proteínas Repressoras , Hormônio Liberador de Tireotropina/genética , Fatores de Transcrição , Animais , Sequência de Bases , Sítios de Ligação/genética , DNA/genética , Jejum/metabolismo , Regulação da Expressão Gênica/efeitos dos fármacos , Humanos , Masculino , Modelos Biológicos , Dados de Sequência Molecular , Núcleo Hipotalâmico Paraventricular/efeitos dos fármacos , Núcleo Hipotalâmico Paraventricular/metabolismo , Regiões Promotoras Genéticas , Proteínas/genética , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ratos , Ratos Sprague-Dawley , Receptor Tipo 4 de Melanocortina , Receptores para Leptina , Receptores de Peptídeos/genética , Transdução de Sinais , Proteína 3 Supressora da Sinalização de Citocinas , Proteínas Supressoras da Sinalização de Citocina , alfa-MSH/metabolismo , alfa-MSH/farmacologiaRESUMO
The incerto-hypothalamic area (IHy) is a poorly defined diencephalic region located at the junction of the medial hypothalamus and zona incerta (ZI). This region is characterized by the presence of the A13 dopaminergic group and also cells expressing melanin-concentrating hormone (MCH) and cocaine- and amphetamine-regulated transcript (CART). The dopaminergic neurons appear to influence luteinizing hormone secretion, but the role of the MCH/CART-expressing cells is unclear. Even though IHy presents a singular neurochemistry, it has long been assumed that it is also part of the zona incerta. By injecting biotinylated dextran amine into the IHy and ZI of adult male Wistar rats, we analyzed the efferent projections from the IHy in comparison to the ZI. We have found that ZI projects mainly to laterally located brain stem structures, whereas the main efferents from the IHy are the reuniens thalamic nucleus, precommissural nucleus, posterior hypothalamic area and dorsolateral periaqueductal gray matter. The IHy projection pattern is quite similar to that of the anterior hypothalamic area and our hodological results suggest that IHy belongs to the medial hypothalamic system and might be part of the defensive behavior system. The IHy could be an integrative area associated with the regulation of neuroendocrine functions related to motivated behaviors, which are mediated by the medial hypothalamus.
Assuntos
Hipotálamo Médio/anatomia & histologia , Vias Neurais/anatomia & histologia , Animais , Biotina/análogos & derivados , Biotina/metabolismo , Dextranos/metabolismo , Dopamina/metabolismo , Hormônios Hipotalâmicos/metabolismo , Masculino , Melaninas/metabolismo , Vias Neurais/metabolismo , Hormônios Hipofisários/metabolismo , Ratos , Ratos Wistar , Estilbamidinas/metabolismoRESUMO
The anteroventral periventricular nucleus (AVPV) is sexually dimorphic, presenting a higher neuronal density in females. The AVPV contains a dense collection of oestrogen and progesterone receptors and has been related to the modulation of gonadotrophin-releasing hormone (GnRH) secretion and gene expression in response to circulating hormonal levels. It has been suggested that cocaine- and amphetamine-regulated transcript (CART) is also related to reproductive control because CART immunoreactive fibres are in close apposition with GnRH neurones. A portion of these fibres originate in the AVPV but its role in mediating hormonal action needs to be better explored. We hypothesised that CART expression in the AVPV would be influenced by the reproductive state and, consequently, by hormonal levels. To test this hypothesis, we analysed CART expression in the AVPV of female rats in different reproductive states (pro-oestrous, pregnancy and lactation). We found that, on the 19th day of pregnancy, female rats presented increased CART expression. Our findings indicate that AVPV CART expression is influenced by the reproductive state and that CART neurones in the AVPV may play a role in the hormonal mechanisms involved in the induction of maternal behaviour.
Assuntos
Ciclo Estral/metabolismo , Núcleos da Linha Média do Tálamo/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Gravidez/metabolismo , Animais , Feminino , Lactação/metabolismo , Proteínas do Tecido Nervoso/genética , Progesterona/fisiologia , RNA Mensageiro/análise , Ratos , Distribuição TecidualRESUMO
Given the current environment in most developed countries, it is a challenge to maintain a good balance between calories consumed and calories burned, although maintenance of metabolic balance is key to good health. Therefore, understanding how metabolic regulation is achieved and how the dysregulation of metabolism affects health is an area of intense research. Most studies focus on the hypothalamus, which is a brain area that acts as a key regulator of metabolism. Among the nuclei that comprise the hypothalamus, the arcuate nucleus is one of the major mediators in the regulation of food intake. The regulation of energy balance is also a key factor ensuring the maintenance of any species as a result of the dependence of reproduction on energy stores. Adequate levels of energy reserves are necessary for the proper functioning of the hypothalamic-pituitary-gonadal axis. This review discusses valuable data presented in the 2015 edition of the International Workshop of Neuroendocrinology concerning the fundamental nature of the hormonal regulation of the hypothalamus and the impact on energy balance and reproduction.
Assuntos
Metabolismo Energético/fisiologia , Hipotálamo/fisiologia , Reprodução/fisiologia , Animais , HumanosRESUMO
Cocaine- and amphetamine-regulated transcript (CART) is a recently described neuropeptide widely expressed in the rat brain. CART mRNA and peptides are found in hypothalamic sites such as the paraventricular nucleus (PVH), the supraoptic nucleus (SON), the lateral hypothalamic area (LHA), the dorsomedial nucleus of the hypothalamus (DMH), the arcuate nucleus (Arc), the periventricular nucleus (Pe), and the ventral premammillary nucleus (PMV). Intracerebroventricular administration of recombinant CART peptide decreases food intake and CART mRNA levels in the Arc are regulated by leptin. Leptin administration induces Fos expression in hypothalamic CART neurons in the PVH, the DMH, the Arc, and the PMV. In the current study, we used double label in situ hybridization histochemistry to investigate the potential direct action of leptin on hypothalamic CART neurons and to define the chemical identity of the hypothalamic CART neurons in the rat brain. We found that CART neurons in the Arc, DMH, and PMV express long form leptin-receptor mRNA, and the suppressor of cytokine signaling-3 (SOCS-3) mRNA after an acute dose of intravenous leptin. We also found that CART neurons in the parvicellular PVH, in the DMH and in the posterior Pe coexpress thyrotropin-releasing hormone (TRH) mRNA. CART neurons in the magnocellular PVH and in the SON coexpress dynorphin (DYN), and CART cell bodies in the LHA and in the posterior Pe coexpress melanin-concentrating hormone (MCH) and glutamic acid decarboxylase (GAD-67) mRNA. In the Arc, a few CART neurons coexpress neurotensin (NT) mRNA. In addition, we examined the distribution of CART immunoreactivity in the human hypothalamus. We found CART cell bodies in the PVH, in the SON, in the LHA, in the Arc (infundibular nucleus) and in the DMH. We also observed CART fibers throughout the hypothalamus, in the bed nucleus of the stria terminalis, and in the amygdala. Our results indicate that leptin directly acts on CART neurons in distinct nuclei of the rat hypothalamus. Furthermore, hypothalamic CART neurons coexpress neuropeptides involved in energy homeostasis, including MCH, TRH, DYN, and NT. The distribution of CART cell bodies and fibers in the human hypothalamus indicates that CART may also play a role in the regulation of energy homeostasis in humans.
Assuntos
Regulação da Expressão Gênica , Hipotálamo/metabolismo , Leptina/farmacologia , Proteínas do Tecido Nervoso/genética , Neurônios/metabolismo , Adulto , Idoso , Animais , Comportamento Alimentar/efeitos dos fármacos , Feminino , Regulação da Expressão Gênica/efeitos dos fármacos , Humanos , Hormônios Hipotalâmicos/genética , Hipotálamo/citologia , Imuno-Histoquímica , Injeções Intraventriculares , Peptídeos e Proteínas de Sinalização Intracelular , Masculino , Melaninas/genética , Pessoa de Meia-Idade , Proteínas do Tecido Nervoso/análise , Proteínas do Tecido Nervoso/farmacologia , Neurônios/citologia , Neuropeptídeos/análise , Neuropeptídeos/genética , Neurotransmissores/análise , Neurotransmissores/genética , Orexinas , Especificidade de Órgãos , Hormônios Hipofisários/genética , Biossíntese de Proteínas , RNA Mensageiro/genética , Ratos , Ratos Sprague-Dawley , Especificidade da Espécie , Transcrição GênicaRESUMO
Leptin has profound effects on food intake, body weight, and neuroendocrine status. The lack of leptin results in hormonal and metabolic alterations and a dramatic increase in body weight. Leptin acts in the brain, especially in the hypothalamus; however, the central nervous system sites that respond to leptin have not been examined comprehensively. In this study, we explored systematically the distribution of leptin-activated neurons throughout the rat brain. Furthermore, we investigated the chemical identity of subsets of these leptin-activated cells. Fos-like immunoreactivity (Fos-IR) was investigated in the rat brain after two different doses of leptin (1.0 mg/kg and 5.0 mg/kg) at 2 hours and 6 hours after injections. The induction of Fos-IR was observed in hypothalamic nuclei, including the paraventricular nucleus (PVH), the retrochiasmatic area (RCA), the ventromedial nucleus (VMH), the dorsomedial nucleus (DMH), the arcuate nucleus (Arc), and the ventral premammillary nucleus (PMV). In addition, leptin-induced Fos-IR was found in several nuclei of the brainstem, including the superior lateral and external lateral subdivisions of the parabrachial nucleus (slPB and elPB, respectively), the supragenual nucleus, and the nucleus of the solitary tract (NTS). By using double-labeling immunohistochemistry or immunohistochemistry coupled with in situ hybridization, leptin-activated neurons were found that contained cocaine- and amphetamine-regulated transcript mRNA in several hypothalamic nuclei, including the RCA, Arc, DMH, and PMV. In the Arc and DMH, leptin-induced Fos-IR was observed in neurons that expressed neurotensin mRNA. Dynorphin neurons in the VMH and in the Arc also expressed Fos-IR. In the brainstem, we found that cholecystokinin neurons in the slPB and glucagon-like peptide-1 neurons in the NTS were activated by leptin. We also investigated the coexpression of Fos-IR and the long form of the leptin receptor (OBRb) mRNA. We found double-labeled neurons surrounding the median eminence and in the RCA, Arc, VMH, DMH, and PMV. However, in brainstem sites, very little OBRb mRNA was found; thus, there were very few double-labeled cells. These results suggest that leptin stimulates brain pathways containing neuropeptides that are involved in the regulation of energy balance, autonomic homeostasis, and neuroendocrine status.
Assuntos
Química Encefálica/fisiologia , Encéfalo/metabolismo , Proteínas de Caenorhabditis elegans , Ingestão de Alimentos/fisiologia , Leptina/metabolismo , Neurônios/química , Ratos Sprague-Dawley/metabolismo , Receptores de Superfície Celular , Animais , Encéfalo/citologia , Proteínas de Transporte/genética , Colecistocinina/genética , Metabolismo Energético/fisiologia , Encefalinas/genética , Homeostase/fisiologia , Imuno-Histoquímica , Hibridização In Situ , Leptina/farmacologia , Masculino , Glicoproteínas de Membrana/genética , Proteínas do Tecido Nervoso/genética , Neurônios/citologia , Neurônios/metabolismo , Neurotensina/genética , Precursores de Proteínas/genética , Proteínas Proto-Oncogênicas c-fos/metabolismo , RNA Mensageiro/metabolismo , Ratos , Ratos Sprague-Dawley/anatomia & histologia , Receptores para Leptina , Receptores Notch , Fatores de TempoRESUMO
Recent studies have identified several neuropeptide systems in the hypothalamus that are critical in the regulation of body weight. The lateral hypothalamic area (LHA) has long been considered essential in regulating food intake and body weight. Two neuropeptides, melanin-concentrating hormone (MCH) and the orexins (ORX), are localized in the LHA and provide diffuse innervation of the neuraxis, including monosynaptic projections to the cerebral cortex and autonomic preganglionic neurons. Therefore, MCH and ORX neurons may regulate both cognitive and autonomic aspects of food intake and body weight regulation. The arcuate nucleus also is critical in the regulation of body weight, because it contains neurons that express leptin receptors, neuropeptide Y (NPY), alpha-melanin-stimulating hormone (alpha-MSH), and agouti-related peptide (AgRP). In this study, we examined the relationships of these peptidergic systems by using dual-label immunohistochemistry or in situ hybridization in rat, mouse, and human brains. In the normal rat, mouse, and human brain, ORX and MCH neurons make up segregated populations. In addition, we found that AgRP- and NPY-immunoreactive neurons are present in the medial division of the human arcuate nucleus, whereas alpha-MSH-immunoreactive neurons are found in the lateral arcuate nucleus. In humans, AgRP projections were widespread in the hypothalamus, but they were especially dense in the paraventricular nucleus and the perifornical area. Moreover, in both rat and human, MCH and ORX neurons receive innervation from NPY-, AgRP-, and alpha-MSH-immunoreactive fibers. Projections from populations of leptin-responsive neurons in the mediobasal hypothalamus to MCH and ORX cells in the LHA may link peripheral metabolic cues with the cortical mantle and may play a critical role in the regulation of feeding behavior and body weight.
Assuntos
Núcleo Arqueado do Hipotálamo/química , Região Hipotalâmica Lateral/química , Hormônios Hipotalâmicos/fisiologia , Melaninas/fisiologia , Neuropeptídeos/fisiologia , Hormônios Hipofisários/fisiologia , Proteína Relacionada com Agouti , Animais , Núcleo Arqueado do Hipotálamo/citologia , Comportamento Alimentar , Humanos , Região Hipotalâmica Lateral/citologia , Imuno-Histoquímica , Peptídeos e Proteínas de Sinalização Intercelular , Masculino , Camundongos , Neuropeptídeo Y/fisiologia , Proteínas/fisiologia , Ratos , Ratos Sprague-Dawley , Organismos Livres de Patógenos EspecíficosRESUMO
Cocaine- and amphetamine-regulated transcript (CART) and CART-derived peptides are widely expressed in the hypothalamus. CART is involved in food intake control and is regulated by circulating leptin, a hormone implicated in a variety of endocrine functions. Lack of leptin (ob/ob mice) is associated with obesity, hypogonadism and infertility. In the arcuate nucleus, dorsomedial nucleus of the hypothalamus, and ventral premammillary nucleus, CART neurons also express leptin receptor long-form splice-variant. Recent studies have suggested that the facilitatory effect of leptin on gonadotropin-releasing hormone (GnRH) secretion is mediated by CART. In the present study, using dual- and triple-label immunohistochemistry, we identified CART fibers in close apposition with GnRH neurons expressing Fos in the afternoon of the proestrous day, as well as with GnRH neurons in male rats. In order to investigate the origin of these fibers, we injected the retrograde tracer Fluorogold into areas containing GnRH cell bodies. In male and female rats, the tracer was injected around the vascular organ of lamina terminalis, median preoptic nucleus and medial preoptic nucleus, as well as in the anteroventral periventricular nucleus. We observed retrogradely labeled neurons in various hypothalamic nuclei, including the arcuate, dorsomedial and ventral premammillary. In these areas, dual-label immunohistochemistry/in situ hybridization revealed that part of the retrogradely labeled neurons also express CART mRNA. As a control, we injected the anterograde tracer biotinylated dextran amine into the ventral premammillary nucleus of both males and females. Most projections targeted brain areas related to reproductive behavior and few fibers were closely associated with GnRH neurons. Our findings indicate that ventral premammillary nucleus CART neurons intermingle with brain circuitry involved in reproduction. Therefore, these neurons are well positioned to mediate leptin effect on reproductive control.
Assuntos
Biotina/análogos & derivados , Hormônio Liberador de Gonadotropina/metabolismo , Hipotálamo/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Vias Neurais/metabolismo , Neurônios/metabolismo , Reprodução/fisiologia , Animais , Núcleo Arqueado do Hipotálamo/citologia , Núcleo Arqueado do Hipotálamo/metabolismo , Dextranos , Ciclo Estral/fisiologia , Feminino , Corantes Fluorescentes , Hipotálamo/citologia , Leptina/metabolismo , Masculino , Proteínas do Tecido Nervoso/genética , Vias Neurais/citologia , Neurônios/citologia , Área Pré-Óptica/citologia , Área Pré-Óptica/metabolismo , Terminações Pré-Sinápticas/metabolismo , Terminações Pré-Sinápticas/ultraestrutura , Proteínas Proto-Oncogênicas c-fos/metabolismo , RNA Mensageiro/metabolismo , Ratos , Ratos Sprague-Dawley , Caracteres Sexuais , EstilbamidinasRESUMO
The melanin-concentrating hormone and neuropeptide glutamic acid-isoleucine are expressed in neurons located mainly in the hypothalamus that project widely throughout the CNS. One of the melanin-concentrating hormone main targets is the medial mammillary nucleus, but the exact origin of these fibers is unknown. We observed melanin-concentrating hormone and neuropeptide glutamic acid-isoleucine immunoreactive fibers coursing throughout the mammillary complex, showing higher density in the pars lateralis of the medial mammillary nucleus, while the lateral mammillary nucleus showed sparse melanin-concentrating hormone innervation. The origins of these afferents were determined by using implant of the retrograde tracer True Blue in the medial mammillary nucleus. Double-labeled neurons were observed in the lateral hypothalamic area, rostromedial zona incerta and dorsal tuberomammillary nucleus. A considerable population of retrogradely labeled melanin-concentrating hormone perikaryal profiles was also immunoreactive to neuropeptide glutamic acid-isoleucine (74+/-15% to 85+/-15%). The afferents from the lateral hypothalamic area, rostromedial zona incerta and dorsal tuberomammillary nucleus to the medial mammillary nucleus were confirmed using implant of the anterograde tracer Phaseolus vulgaris leucoagglutinin. In addition, using double-labeled immunohistochemistry, we found no co-localization between neurons expressing melanin-concentrating hormone and adenosine deaminase (histaminergic marker) in the dorsal tuberomammillary nucleus. We hypothesize that these melanin-concentrating hormone projections participate in spatial memory process mediated by the medial mammillary nucleus. These pathways would enable the animal to look for food during the initial moments of appetite stimulation.
Assuntos
Axônios/metabolismo , Região Hipotalâmica Lateral/metabolismo , Hormônios Hipotalâmicos/metabolismo , Corpos Mamilares/metabolismo , Melaninas/metabolismo , Vias Neurais/metabolismo , Hormônios Hipofisários/metabolismo , Subtálamo/metabolismo , Animais , Axônios/ultraestrutura , Comportamento Alimentar/fisiologia , Corantes Fluorescentes , Região Hipotalâmica Lateral/citologia , Imuno-Histoquímica , Masculino , Corpos Mamilares/citologia , Memória/fisiologia , Vias Neurais/citologia , Fito-Hemaglutininas , Ratos , Ratos Wistar , Percepção Espacial/fisiologia , Subtálamo/citologiaRESUMO
Previous studies have described the distribution of melanin-concentrating hormone (MCH) and neuropeptide EI (NEI) in the rat central nervous system (CNS), and revealed this peptidergic system to be primarily localized in neurons within the lateral hypothalamic area (LHA) and zona incerta (ZI). Moreover, an extensive MCH- and NEI-immunoreactive (ir) fiber distribution has been described throughout the CNS, including a dense innervation within the periaqueductal gray matter (PAG). MCH and NEI have become important markers for the LHA, which harbors a variety of neuronal types as well as the medial forebrain bundle, a complex system of fibers which extends rostrocaudally throughout this area. In the present study, the projection patterns of MCH- and NEI-ir fibers within the PAG were characterized using a diamino benzidine immunoperoxidase procedure to localize each of these peptides in normal rat brain sections. MCH- and NEI-ir fibers were seen coursing through all of its subdivisions the entire length of the PAG, with a more condensed number of fibers in the periaqueductal medial zone. The primary origin(s) of these PAG afferents were determined in combined retrograde tracing immunofluorescent studies in which true blue (TB) was injected into various subdivisions of the PAG. TB-filled MCH-ir neurons were identified mainly in the rostral portion of the medial ZI (ZIm) and in the tuberal LHA (LHAt). Studies confirming this MCH-ir projection in which anterograde tracer (Phaseolus vulgaris leucoagglutinin) was injected into various regions in and around the LHA and ZI revealed a distinction in the PAG projections arising from these nuclei. ZIm injections resulted in labeled fibers mainly within the rostral dorsomedial and dorsolateral regions of the PAG, whereas injections in the LHAt revealed an innervation at intermediate and caudal levels in the ventrolateral region. Since the MCH and NEI fiber distribution patterns in the PAG are identical, this would suggest that these peptides are colocalized within the hypothalamus. Sequential immunofluorescent staining for MCH and NEI on tissue from rats who had received TB injections into the PAG confirmed this, and revealed that approximately 15% of all tracer-filled neurons in the LHA and ZI were both MCH- and NEI-ir. In fact, the vast majority of MCH-ir neurons within these regions also colocalize with NEI. Therefore, the MCH/NEI projection patterns within the PAG arise from two major sources: the ZIm which supplies afferents via a medial pathway that enters the PAG dorsally at rostral levels, and a pathway originating in the LHA that enters the PAG ventrally at more caudal levels. The ZIm and LHA are believed to be the primary, if not the only, sources of MCH and NEI projections to the PAG.
Assuntos
Hormônios Hipotalâmicos/análise , Melaninas/análise , Melanóforos , Neuropeptídeos/análise , Substância Cinzenta Periaquedutal/química , Hormônios Hipofisários/análise , Animais , Imunofluorescência , Imuno-Histoquímica , Masculino , Ratos , Ratos WistarRESUMO
The projection pathways of neurons containing melanin-concentrating hormone (MCH) and neuropeptide EI (NEI), two peptides colocalized in the lateral hypothalamic area (LHA) of the rat, were mapped using the retrogradely transported fluorescent dyes, true blue (TB) and diamidino yellow (DY). TB and DY were injected into the medial septum/diagonal band complex (MS/DBC) and the thoracic level of the spinal cord (SpCd), respectively. Brains from rats receiving only one or both tracer injections were immunohistochemically stained for MCH in the spinal cord and NEI in the forebrain. In the MS/DBC, NEI-immunoreactive (-ir) fibers are concentrated in the MS and in the vertical and horizontal limbs of the DBC. In the SpCd, MCH-ir fibers are concentrated primarily in lamina X. Of the diencephalic NEI-ir neurons, 37.15% project to the MS/DBC and reside in the rostromedial zona incerta (ZIm), in the LHAt and LHAp, and in the perifornical region. Of the diencephalic MCH-ir neurons, 20.2% project to the SpCd and reside in the LHAt and LHAp. In addition, 2. 2% of the MCH-ir cells and 8.7% of the NEI-ir cells in the hypothalamus were labeled with both retrograde tracers and thus project to both the MS/DBC and SpCd. These dual projection neurons are located mainly in the LHAt and LHAp. Anterograde injections of the tracer Phaseolus vulgaris leucoagglutinin into the LHAt and ZIm corroborated our findings in the retrograde studies. Potential autonomic and behavioral roles of the NEI and MCH systems in the MS/DBC and the SpCd are discussed.
Assuntos
Encéfalo/fisiologia , Hormônios Hipotalâmicos/metabolismo , Melaninas/metabolismo , Oligopeptídeos/metabolismo , Hormônios Hipofisários/metabolismo , Medula Espinal/fisiologia , Transmissão Sináptica/fisiologia , Amidinas , Animais , Benzofuranos , Diencéfalo/fisiologia , Corantes Fluorescentes , Região Hipotalâmica Lateral/fisiologia , Imuno-Histoquímica , Masculino , Neurônios/metabolismo , Neurônios/fisiologia , Ratos , Ratos Wistar , Núcleos Septais/fisiologia , Distribuição TecidualRESUMO
The control of pregnant cancer patients is difficult because it involves both mother and fetus, and the metabolic alterations in the cancer host induce a massive mobilization of nutrients diverted to the neoplastic cells. The purpose of the present study was to determine the evolution of the Walker 256 carcinoma in pregnant rats and its consequences on fetal development. The results showed that the tumors displayed a very rapid rate of growth and induced a reduction in fetal weights in the pregnant tumor-bearing rats. The tumor-bearing and pregnant tumor-bearing groups showed a decrease in blood glucose and total serum protein, suggesting an increase in energy utilization of these substrates and synthetic activity by the tumoral cells. An imbalance between protein synthesis and catabolism may occur in the tumor-bearing rats which may be related to the degree of nutritional depletion.
Assuntos
Glicemia/metabolismo , Carcinoma 256 de Walker/metabolismo , Desenvolvimento Embrionário e Fetal/fisiologia , Ingestão de Energia , Complicações Neoplásicas na Gravidez/metabolismo , Animais , Peso Corporal , Feminino , Gravidez , Ratos , Ratos EndogâmicosRESUMO
The present study investigated the involvement of the oxytocinergic neurones that project into the central amygdala (CeA) in the control of electrolyte excretion and hormone secretion in unanaesthetised rats subjected to acute hypertonic blood volume expansion (BVE; 0.3 M NaCl, 2 ml/100 g of body weight over 1 min). Oxytocin and vasopressin mRNA expression in the paraventricular (Pa) and supraoptic nucleus (SON) of the hypothalamus were also determined using the real time-polymerase chain reaction and in situ hybridisation. Male Wistar rats with unilaterally implanted stainless steel cannulas in the CeA were used. Oxytocin (1 µg/0.2 µl), vasotocin, an oxytocin antagonist (1 µg/0.2 µl) or vehicle was injected into the CeA 20 min before the BVE. In rats treated with vehicle in the CeA, hypertonic BVE increased urinary volume, sodium excretion, plasma oxytocin (OT), vasopressin (AVP) and atrial natriuretic peptide (ANP) levels and also increased the expression of OT and AVP mRNA in the Pa and SON. In rats pre-treated with OT in the CeA, previously to the hypertonic BVE, there were further significant increases in plasma AVP, OT and ANP levels, urinary sodium and urine output, as well as in gene expression (AVP and OT mRNA) in the Pa and SON compared to BVE alone. Vasotocin reduced sodium, urine output and ANP levels, although no changes were observed in plasma AVP and OT levels or in the expression of the AVP and OT genes in both hypothalamic nuclei. The results of the present study suggest that oxytocin in the CeA exerts a facilitatory role in the maintenance of hydroelectrolyte balance in response to changes in extracellular volume and osmolality.
Assuntos
Tonsila do Cerebelo/fisiologia , Ocitocina/fisiologia , Equilíbrio Hidroeletrolítico , Animais , Arginina Vasopressina/genética , Arginina Vasopressina/metabolismo , Masculino , Ocitocina/genética , RNA Mensageiro/genética , Ratos , Ratos Wistar , Reação em Cadeia da Polimerase em Tempo RealRESUMO
The physiological effects of melanocortin-4 receptor (MC4-R) on metabolism have been hypothesized to be mediated individually or collectively by neuronal groups innervating the paraventricular nucleus of the hypothalamus (PVH). The present study was designed to identify MC4-R-expressing neurons that innervate the PVH using retrograde tract tracing techniques in the MC4-R-GFP reporter mice. Our initial mapping identified very limited projections from MC4-R-expressing neurons to the PVH. This included a defined population of MC4-R-positive neurons located in the ventral premmamillary nucleus (PMv). Anterograde tracing experiments confirmed projections from PMv neurons to the medial parvicellular subdivision of the PVH, in close proximity to oxytocin neurons and ß-endorphin-containing fibers. Given the known stimulatory effects of leptin and sexual odorants exposure on many PMv neurons, it was expected that MC4-R-expressing neurons in the PMv might be responsive to leptin and activated by odors exposure. Contrary to expectation, MC4-R-GFP neurons in the PMv do not respond to leptin as demonstrated by double labeling for GFP and leptin-induced phosphorylated STAT3. However, we found that Fos expression is induced in a large subset of MC4-R-GFP neurons in the PMv in response to opposite sex odors. Collectively, these results provide evidence for a previous unrecognized role of MC4-R expressed by neurons innervating the PVH that are also sensitive to reproductive cues.
Assuntos
Corpos Mamilares/citologia , Vias Neurais/fisiologia , Neurônios/fisiologia , Animais , Biotina/análogos & derivados , Biotina/metabolismo , Toxina da Cólera/metabolismo , Dextranos/metabolismo , Feminino , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Leptina/administração & dosagem , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Modelos Neurológicos , Neurônios/citologia , Odorantes , Condutos Olfatórios/fisiologia , Proteínas Oncogênicas v-fos/metabolismo , Núcleo Hipotalâmico Paraventricular , Receptor Tipo 4 de Melanocortina/genética , Receptor Tipo 4 de Melanocortina/metabolismo , Fator de Transcrição STAT3/metabolismo , beta-Endorfina/metabolismoRESUMO
We have recently demonstrated that the ventral premammillary nucleus (PMV) plays a key role in the metabolic control of the female reproductive axis. However, whether PMV neurons modulate the reproductive neural circuitry and/or the expression of sexual behaviors has not been determined. Here, we showed that the expression of estrogen and progesterone receptors in the PMV is modulated by changing levels of sex steroids across the estrous cycle. We also showed that sexual behavior, not the high physiologic levels of sex steroids, induces Fos in PMV neurons. Bilateral lesions of the PMV caused no significant changes in proceptive behavior but a high percentage of PMV-lesioned rats failed to exhibit lordosis behavior when exposed to a sexually experienced male rat (50% vs. 18% in the control group). Notably, lesions of the PMV disrupted the physiologic fluctuations of Kiss1 and GnRH mRNA expression characteristic of the proestrus-to-estrus transition. This neurochemical imbalance may ultimately alter female reproductive behavior. Our findings suggest that the PMV is a component of the neural circuitry that modulates the physiologic fluctuations of key neuroendocrine players (i.e., Kiss1 and GnRH) in the control of the female reproductive physiology.