RESUMO
Nitric oxide (NO) negatively modulates the secretion of vasopressin (AVP), oxytocin (OT) and atrial natriuretic peptide (ANP) induced by the increase in extracellular osmolality, whereas carbon monoxide (CO) and hydrogen sulphide (H2 S) act to potentiate it; however, little information is available for the osmotic challenge model about whether and how such gaseous systems modulate each other. Therefore, using an acute ex vivo model of hypothalamic and neurohypophyseal explants (obtained from male 6/7-week-old Wistar rats) under conditions of extracellular iso- and hypertonicity, we determined the effects of NO (600 µmol L-1 sodium nitroprusside), CO (100 µmol L-1 tricarbonylchloro[glycinato]ruthenium [II]) and H2 S (10 mmol L-1 sodium sulphide) donors and nitric oxide synthase (NOS) (300 µmol L-1 Nω -methyl-l-arginine [LNMMA]), haeme oxygenase (HO) (200 µmol L-1 Zn(II) deuteroporphyrin IX 2,4-bis-ethylene glycol [ZnDPBG]) and cystathionine ß-synthase (CBS) (100 µmol L-1 aminooxyacetate [AOA]) inhibitors on the release of hypothalamic ANP and hypothalamic and neurohypophyseal AVP and OT, as well as on the activities of NOS, HO and CBS. LNMMA reversed hyperosmolality-induced NOS activity, and enhanced hormonal release by the hypothalamus and neurohypophysis, in addition to increasing CBS and hypothalamic HO activity. AOA decreased hypothalamic and neurohypophyseal CBS activity and hormonal release, whereas ZnDPBG inhibited HO activity and hypothalamic hormone release; however, in both cases, AOA did not modulate NOS and HO activity and ZnDPBG did not affect NOS and CBS activity. Thus, our data indicate that, although endogenous CO and H2 S positively modulate AVP, OT and ANP release, only NO plays a concomitant role of modulator of hormonal release and CBS activity in the hypothalamus and neurohypophysis and that of HO activity in the hypothalamus during an acute osmotic stimulus, which suggests that NO is a key gaseous controller of the neuroendocrine system.
Assuntos
Fator Natriurético Atrial/metabolismo , Monóxido de Carbono/metabolismo , Sulfeto de Hidrogênio/metabolismo , Hipotálamo Médio/metabolismo , Óxido Nítrico/metabolismo , Ocitocina/metabolismo , Vasopressinas/metabolismo , Animais , Cistationina beta-Sintase/metabolismo , Masculino , Óxido Nítrico Sintase/metabolismo , Óxido Nítrico Sintase Tipo I/metabolismo , Ratos Wistar , Sulfurtransferases/metabolismoRESUMO
In a previous study, the administration of corticotrophin-releasing factor (CRF) into the dorsomedial hypothalamus (DMH), a region that modulates defensive reactions, was shown to facilitate elevated T-maze (ETM) avoidance responses, an anxiogenic-like effect. Intra-DMH administration of the CRF type 1 receptor (CRFR1) antagonist antalarmin induced anxiolytic-like effects and counteracted the anxiogenic effects of CRF. The present study further investigates the role played by CRF receptors of the medial hypothalamus in anxiety. For that, male wistar rats were treated with CRFR1 and CRFR2-modulating drugs in the DMH or VMH, another hypothalamic nucleus implicated with defensive and emotional behavior, and tested in the ETM for inhibitory avoidance and escape measurements. In clinical terms, these responses have been respectively related to generalized anxiety and panic disorder. All animals were tested in an open field, immediately after the ETM, for locomotor activity assessment. The results showed that intra-VMH CRF or antalarmin did not alter ETM avoidance or escape performance. Intra-VMH injection of the CRFR2 preferential antagonist antisauvagine-30 or of the selective CRFR2 antagonist astressin 2-B inhibited escape performance, a panicolytic-like effect, without altering avoidance reactions. The CRFR2 agonist urocortin-2 intra-VMH was by itself without effect but blocked the effects of astressin 2-B. None of the drugs administered into the DMH altered ETM measurements. Additionally, none of the compounds altered locomotor activity measurements. These results suggest that VMH CRFR2 modulate a defensive response associated with panic disorder and are of relevance to the better understanding of the neural mechanisms underlying this pathological condition.
Assuntos
Reação de Fuga/fisiologia , Hipotálamo Médio/metabolismo , Aprendizagem em Labirinto/fisiologia , Receptores de Hormônio Liberador da Corticotropina/metabolismo , Análise de Variância , Animais , Hormônio Liberador da Corticotropina/farmacologia , Relação Dose-Resposta a Droga , Reação de Fuga/efeitos dos fármacos , Comportamento Exploratório/efeitos dos fármacos , Antagonistas de Hormônios/farmacologia , Hipotálamo Médio/diagnóstico por imagem , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , Microinjeções , Fragmentos de Peptídeos/farmacologia , Ratos , Ratos Wistar , Receptores de Hormônio Liberador da Corticotropina/antagonistas & inibidores , Urocortinas/farmacologiaRESUMO
Estrogen action is necessary for evidencing the stimulatory action of mifepristone and naloxone on prolactin (PRL) secretion during late pregnancy. Our aim is to determine the mechanism mediating this facilitator action of estrogens. To investigate the hypothalamic mechanisms involved in estrogen actions in PRL secretion at the end of pregnancy, we measured the effect of pretreatment with the estrogen antagonist tamoxifen on the expression of tyrosine hydroxylase (TH), hormone receptors (ERα and ß, PRs, PRLR(long)), and µ- and κ- opioid receptors (ORs) at mRNA (by semiquantitative RT-PCR) and protein (by western blot for TH, PRLR(long), ERα, PRs, µ- and ORs) levels in extracts of medial basal hypothalamus (MBH) and serum PRL, E2 and P4 levels (by RIA) in mifepristone- and naloxone-treated rats. Tamoxifen administration partially prevented PRL release induced by the combined treatment. TH expression diminished and ERα expression increased in mifepristone-treated rats at mRNA and protein levels and tamoxifen partially prevented these changes with no effect on PRs expression. Mifepristone increased PRLR(long) mRNA levels; this increase was blocked by tamoxifen. Combined tamoxifen and mifepristone treatment decreased µ- and k-ORs mRNA but not protein levels. In conclusion, E2 induces neuroadaptive mechanisms necessary to facilitate PRL release preceding delivery. Acting through ERα, E2 modulates hypothalamic dopaminergic neurons activity, regulating TH, µ- and κ-ORs and PRLR(long) expression, and is necessary for evidencing the effects of P4 withdrawal. Its presence on days 14 and 15 of pregnancy is crucial to facilitate the opioid system modulation of PRL secretion at the end of pregnancy in the rat.
Assuntos
Estradiol/metabolismo , Prenhez/fisiologia , Prolactina/metabolismo , Animais , Receptor alfa de Estrogênio/metabolismo , Receptor beta de Estrogênio/metabolismo , Feminino , Hipotálamo Médio/metabolismo , Mifepristona/farmacologia , Naloxona/farmacologia , Gravidez , Prenhez/efeitos dos fármacos , Progesterona/metabolismo , Ratos Wistar , Receptores Opioides kappa/metabolismo , Receptores Opioides mu/metabolismo , Receptores de Progesterona/metabolismo , Receptores da Prolactina/metabolismo , Tirosina 3-Mono-Oxigenase/metabolismoRESUMO
Substance P (SP) was recently reported to be expressed in human kisspeptin/neurokinin B/dynorphin (KNDy) neurons and to enhance KNDy neuron excitability in the mouse hypothalamus. We therefore examined (1) interactions of SP and kisspeptin in the mediobasal hypothalamus of adult male rhesus monkeys using immunofluorescence, and (2) the ability of SP to induce LH release in GnRH-primed, agonadal juvenile male monkeys. SP cell bodies were observed only occasionally in the arcuate nucleus (Arc), but more frequently dorsal to the Arc in the region of the premammillary nucleus. Castration resulted in an increase in the number of SP cell bodies in the Arc but not in the other regions. SP fibers innervated the Arc, where they were found in close apposition with kisspeptin perikarya in the periphery of this nucleus. Beaded SP axons projected to the median eminence, where they terminated in the external layer and intermingled with beaded kisspeptin axons. Colocalization of the two peptides, however, was not observed. Although close apposition between SP fibers and kisspeptin neurons suggest a role for SP in modulating GnRH pulse generator activity, i.v. injections of SP failed to elicit release of GnRH (as reflected by LH) in the juvenile monkey. Although the finding of structural interactions between SP and kisspeptin neurons is consistent with the notion that this tachykinin may be involved in regulating pulsatile GnRH release, the apparent absence of expression of SP in KNDy neurons suggests that this peptide is unlikely to be a fundamental component of the primate GnRH pulse generator.
Assuntos
Hormônio Liberador de Gonadotropina/metabolismo , Hipotálamo Médio , Kisspeptinas/metabolismo , Hormônio Luteinizante/metabolismo , Peptídeos/administração & dosagem , Substância P/metabolismo , Administração Intravenosa , Animais , Castração , Relação Dose-Resposta a Droga , Hipotálamo Médio/citologia , Hipotálamo Médio/efeitos dos fármacos , Hipotálamo Médio/metabolismo , Macaca mulatta , Masculino , Neurônios/efeitos dos fármacos , Neurônios/metabolismoRESUMO
Thyrotropin-releasing hormone (TRH) synthesized in hypothalamic paraventricular nucleus directs hypothalamus-pituitary-thyroid (HPT) axis function, regulating thyrotropin release from adenohypophysis and thyroid hormones serum concentration. Pyroglutamyl aminopeptidase II (PPII), a Zn-dependent metallopeptidase located in adenohypophysis and medial-basal-hypothalamus degrades TRH released from the median eminence and participates in HPT axis function by regulating TRH-induced thyrotropin release from adenohypophysis. It is unknown whether dietary Zn deficiency down-regulates PPII. Our aim was to compare adenohypohyseal and medial-basal-hypothalamic PPII activity and expression of adult rats fed a Zn-deficient diet (2ppm) throughout their lifespan (DD), prenatally (DC) or after weaning (CD) vs. that of animals fed a control diet (20ppm:CC). Female rats consumed a Zn-deficient or control diet from two weeks before gestation and up to the end of lactation. We analyzed adenohypophyseal and medial-basal-hypothalamic PPII activity of dams and male offspring when adults; its relation to median eminence TRH, serum thyrotropin, leptin and thyroid hormones concentration. Offspring ate the same diet as their dams (CC, DD) or were switched from dietary regime after weaning (CD, DC) and until 2.5 months of age. DD males showed decreased adenohypophyseal and medial-basal-hypothalamic PPII activity, along with high thyrotropin serum concentration. Post-weaning Zn-deficiency (CD) decreased PPII activity only in adenohypophysis and increased thyrotropin circulating levels. Zn-replenishment (DC) normalized PPII activity in both regions and serum thyrotropin concentration. Adenohypophyseal PPII activity decreased and prolactin levels increased in Zn-deficient dams. We concluded that long-term changes in dietary Zn down-regulate PPII activity independently of T3, increasing thyrotropin serum concentration, overall resembling sub-clinical hypothyroidism.
Assuntos
Regulação para Baixo/fisiologia , Hipotálamo Médio/metabolismo , Zinco/deficiência , Fatores Etários , Aminopeptidases/deficiência , Aminopeptidases/genética , Análise de Variância , Animais , Regulação para Baixo/efeitos dos fármacos , Feminino , Lactação/efeitos dos fármacos , Masculino , Gravidez , Prolactina/metabolismo , Ácido Pirrolidonocarboxílico/análogos & derivados , RNA Mensageiro/metabolismo , Radioimunoensaio , Ratos , Ratos Wistar , Fatores Sexuais , Tireotropina/metabolismo , Hormônio Liberador de Tireotropina/genética , Hormônio Liberador de Tireotropina/metabolismo , Zinco/administração & dosagem , Zinco/sangueRESUMO
BACKGROUND/AIMS: Adult mice lacking functional GABAB receptors (GABAB1KO) show altered Gnrh1 and Gad1 expressions in the preoptic area-anterior hypothalamus (POA-AH) and females display disruption of cyclicity and fertility. Here we addressed whether sexual differentiation of the brain and the proper wiring of the GnRH and kisspeptin systems were already disturbed in postnatal day 4 (PND4) GABAB1KO mice. METHODS: PND4 wild-type (WT) and GABAB1KO mice of both sexes were sacrificed; tissues were collected to determine mRNA expression (qPCR), amino acids (HPLC), and hormones (RIA and/or IHC). RESULTS: GnRH neuron number (IHC) did not differ among groups in olfactory bulbs or OVLT-POA. Gnrh1 mRNA (qPCR) in POA-AH was similar among groups. Gnrh1 mRNA in medial basal hypothalamus (MBH) was similar in WTs but was increased in GABAB1KO females compared to GABAB1KO males. Hypothalamic GnRH (RIA) was sexually different in WTs (males > females), but this sex difference was lost in GABAB1KOs; the same pattern was observed when analyzing only the MBH, but not in the POA-AH. Arcuate nucleus Kiss1 mRNA (micropunch-qPCR) was higher in WT females than in WT males and GABAB1KO females. Gad1 mRNA in MBH was increased in GABAB1KO females compared to GABAB1KO males. Serum LH and gonadal estradiol content were also increased in GABAB1KOs. CONCLUSION: We demonstrate that GABABRs participate in the sexual differentiation of the ARC/MBH, because sex differences in several reproductive genes, such as Gad1, Kiss1 and Gnrh1, are critically disturbed in GABAB1KO mice at PND4, probably altering the organization and development of neural circuits governing the reproductive axis.
Assuntos
Glutamato Descarboxilase/deficiência , Hormônio Liberador de Gonadotropina/deficiência , Hipotálamo Médio/metabolismo , Kisspeptinas/deficiência , Precursores de Proteínas/deficiência , Receptores de GABA-B/deficiência , Diferenciação Sexual/genética , Animais , Animais Recém-Nascidos , Núcleo Arqueado do Hipotálamo/crescimento & desenvolvimento , Núcleo Arqueado do Hipotálamo/metabolismo , Feminino , Regulação da Expressão Gênica no Desenvolvimento , Glutamato Descarboxilase/genética , Hormônio Liberador de Gonadotropina/genética , Hipotálamo Médio/crescimento & desenvolvimento , Kisspeptinas/genética , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Knockout , Precursores de Proteínas/genética , RNA Mensageiro/biossíntese , RNA Mensageiro/genética , Receptores de GABA-B/genéticaRESUMO
Tanycytes are bipolar cells bridging the cerebrospinal fluid (CSF) to the portal capillaries and may link the CSF to neuroendocrine events. During the perinatal period a subpopulation of radial glial cells differentiates into tanycytes, a cell lineage sharing some properties with astrocytes and the radial glia, but displaying unique and distinct morphological, molecular, and functional characteristics. Four populations of tanycytes, alpha(1,2) and beta(1,2), can be distinguished. These subtypes express differentially important functional molecules, such as glucose and glutamate transporters; a series of receptors for neuropeptide and peripheral hormones; secretory molecules such as transforming growth factors, prostaglandin E(2), and the specific protein P85; and proteins of the endocytic pathways. This results in functional differences between the four subtypes of tanycytes. Thus, alpha(1,2) tanycytes do not have barrier properties, whereas beta(1,2) tanycytes do. Different types of tanycytes use different mechanisms to internalize and transport cargo molecules; compounds internalized via a clathrin-dependent endocytosis would only enter tanycytes from the CSF. There are also differences in the neuron-tanycyte relationships; beta(1,2) tanycytes are innervated by peptidergic and aminergic neurons, but alpha(1,2) tanycytes are not. Important aspects of the neuron-beta(1) tanycyte relationships have been elucidated. Tanycytes can participate in the release of gonadotropin-releasing hormone (GnRH) to the portal blood by expressing estrogen receptors, absorbing molecules from the CSF, and providing signal(s) to the GnRH neurons. Removal of tanycytes prevents the pulse of GnRH release into the portal blood, the peak of luteinizing hormone, and ovulation. The discovery in tanycytes of new functional molecules is opening a new field of research. Thus, thyroxine deiodinase type II, an enzyme generating triiodothyronine (T(3)) from thyroxine, appears to be exclusively expressed by tanycytes, suggesting that these cells are the main source of brain T(3). Glucose transporter-2 (GLUT-2), a low-affinity transporter of glucose and fructose, and ATP-sensitive K(+) channels are expressed by tanycytes, suggesting that they may sense CSF glucose concentrations.
Assuntos
Hipotálamo Médio/citologia , Hipotálamo Médio/fisiologia , Sistemas Neurossecretores/fisiologia , Animais , Astrócitos/citologia , Astrócitos/metabolismo , Astrócitos/fisiologia , Barreira Hematoencefálica/citologia , Barreira Hematoencefálica/fisiologia , Encéfalo/citologia , Encéfalo/fisiologia , Líquido Cefalorraquidiano/fisiologia , Glândulas Endócrinas/citologia , Glândulas Endócrinas/fisiologia , Endocitose/fisiologia , Epêndima/química , Epêndima/citologia , Feminino , Hormônio Liberador de Gonadotropina/sangue , Hormônio Liberador de Gonadotropina/líquido cefalorraquidiano , Hipotálamo Médio/metabolismo , Masculino , Neuroglia/citologia , Neuroglia/metabolismo , Neuroglia/fisiologia , Neurônios/fisiologia , Sistemas Neurossecretores/citologia , Ratos , Células-Tronco/citologia , Células-Tronco/fisiologiaRESUMO
A secondary surge of prolactin has been recently characterised on the afternoon of oestrus. Because the noradrenergic nucleus locus coeruleus participates in the genesis of the pro-oestrous and steroid-induced surges of prolactin, the aim of the present study was to investigate the importance of locus coeruleus norepinephrine in the generation of the prolactin surge of oestrus. For this purpose, we initially re-evaluated the profile of prolactin secretion during the oestrous cycle to verify whether this surge of prolactin was physiological and specific to the day of oestrus. Thereafter, the following were evaluated: (i) the effect of locus coeruleus lesion on the secondary surge of prolactin and on norepinephrine concentration in the medial preoptic area (MPOA), medial basal hypothalamus (MBH) and paraventricular nucleus (PVN) during the day of oestrus and (ii) locus coeruleus neurones activity during the same day by Fos immunoreactivity. Locus coeruleus lesion completely blocked the prolactin surge of oestrus in all rats studied and also significantly reduced norepinephrine concentration in the MPOA, MBH and PVN during the day of oestrus. The number of double-labelled tyrosine hydroxylase/Fos immunoreactive neurones in locus coeruleus was significantly higher at 14.00 h of oestrus, suggesting an increase in its activity preceding the prolactin surge that generally occurs at 15.00 h. Therefore, the increase in locus coeruleus activity on the afternoon of oestrus supports the data obtained with bilateral lesion of this nucleus, suggesting a stimulatory role of locus coeruleus norepinephrine in the genesis of the secondary surge of prolactin.
Assuntos
Estro/sangue , Hipotálamo/metabolismo , Locus Cerúleo/metabolismo , Norepinefrina/metabolismo , Prolactina/sangue , Animais , Estro/fisiologia , Feminino , Hipotálamo Médio/metabolismo , Imuno-Histoquímica , Locus Cerúleo/citologia , Neurônios/metabolismo , Núcleo Hipotalâmico Paraventricular/metabolismo , Área Pré-Óptica/metabolismo , Prolactina/metabolismo , Proteínas Proto-Oncogênicas c-fos/metabolismo , Ratos , Ratos Wistar , Tirosina 3-Mono-Oxigenase/metabolismoRESUMO
We hypothesized that ethanol (EtOH) might act through the endocannabinoid system to inhibit luteinizing hormone-releasing hormone (LHRH) release. Therefore, we examined the mechanism by which EtOH and anandamide (AEA), an endogenous cannabinoid, inhibit LHRH release from incubated medial basal hypothalamic explants. In previous work, we demonstrated that EtOH inhibits the N-methyl-D-aspartic acid-stimulated release of LHRH by increasing the release of two neurotransmitters: beta-endorphin and gamma-aminobutyric acid (GABA). In the present work, bicuculline, a GABAergic antagonist, completely prevented the inhibition of AEA (10(-9)M) on N-methyl-D-aspartic acid-induced LHRH release, but naltrexone, a micro-opioid receptor antagonist, had no effect. AEA also significantly increased GABA release but had no effect on beta-endorphin release. Therefore, AEA could inhibit LHRH release by increasing GABA but not beta-endorphin release. Because EtOH and AEA acted similarly to inhibit LHRH release, we investigated whether both substances would affect the adenylate cyclase activity acting through the same GTP-coupled receptors, the cannabinoid receptors 1 (CB1-rs). AEA and EtOH (10(-1)M) reduced the forskolin-stimulated accumulation of cAMP, but AM251, a specific antagonist of CB1-r, significantly blocked that inhibition. Additionally we investigated whether CB1-r is involved in the inhibition of LHRH by EtOH and AEA. AEA and EtOH reduced forskolin-stimulated LHRH release, but AM251 significantly blocked that inhibition. Also, we demonstrated that EtOH did not act by increasing AEA synthase activity to inhibit LHRH release in our experimental conditions. Therefore, our results indicate that EtOH inhibits the release of LHRH acting through the endocannabinoid system.
Assuntos
Moduladores de Receptores de Canabinoides/metabolismo , Endocanabinoides , Etanol/farmacologia , Hormônio Liberador de Gonadotropina/metabolismo , Animais , Ácidos Araquidônicos/farmacologia , Bicuculina/farmacologia , Colforsina/farmacologia , AMP Cíclico/metabolismo , Hormônio Liberador de Gonadotropina/sangue , Hipotálamo Médio/efeitos dos fármacos , Hipotálamo Médio/metabolismo , Cinética , Masculino , N-Metilaspartato/farmacologia , Naltrexona/farmacologia , Alcamidas Poli-Insaturadas , Radioimunoensaio , Ratos , Ratos WistarRESUMO
The aim of present study is the analysis of monoamines concentrations changes in the anterior, medium and posterior hypothalamus, as well as changes in serum gonadotropins levels, ovarian steroids and follicular growth during the prepubertal development of the female rat. Noradrenergic activity in the anterior, medium and posterior hypothalamus reached highest level at day 13 after birth, followed by a subsequent decrease from day 15 to 19 and an increase on days 22 and 27 postnatal. At day 1, neural activity in the medium hypothalamus was higher than the activity in the anterior and posterior hypothalamus. Serotoninergic activity in three portions of the hypothalamus was higher throughout the prepubertal development. Follicle-stimulating hormone and luteinizing hormone serum levels increased between days 11 and 17 and decreased from day 19 to 36. The concentration of 17beta-estradiol was consistently low throughout the prepubertal development and increased at day 39 after birth. These results indicate that during the prepubertal development of the rat, the three regions of the hypothalamus show significant changes in the monoaminergic neural activity. There is an inverse relationship between the noradrenergic activity on the anterior and medium hypothalamus and serotoninergic activity in the posterior hypothalamus with ovarian steroids during sexual maturation. These changes may be linked to the development of the neuroendocrine processes that modulate gonadotropin secretion and ovarian function.