RESUMEN
We examined the role of the estrogen receptors alpha (ERα) and beta (ERß) in of the preoptic-anterior hypothalamic area (POA-AHA) in the regulation of ovulation in rats. The number of ERα- and ERß-immunoreactive (-ir) cells was determined at 09:00, 13:00, and 17:00 h of each stage of the estrous cycle in intact rats. Additionally, the effects of blocking ERα and ERß on ovulation rate at 09:00 h on diestrus-2 or proestrus day through the microinjection of methyl-piperidino-pyrazole (MPP) or cyclofenil in either side of POA-AHA were evaluated. The number of ERα-ir and ERß-ir cells in POA-AHA varied in each phase of estrous cycle. Either MPP or cyclofenil in the right side of POA-AHA on diestrus-2 day reduced the ovulation rate, while at proestrus day it was decreased in rats treated in either side with MPP, and in those treated with cyclofenil in the left side. MPP or cyclofenil produced a decrease in the surge of luteinizing hormone levels (LH) and an increase in progesterone and follicle stimulating hormone (FSH). Replacement with synthetic luteinizing hormone-releasing hormone in non-ovulating rats treated with MPP or cyclofenil restored ovulation. These results suggest that activation of estrogen receptors on the morning of diestrus-2 and proestrus day asymmetrically regulates ovulation and appropriately regulates the secretion of FSH and progesterone in the morning and afternoon of proestrus day. This ensures that both, the preovulatory secretion of LH and ovulation, occur at the right time.
Asunto(s)
Núcleo Hipotalámico Anterior/metabolismo , Receptor alfa de Estrógeno/metabolismo , Receptor beta de Estrógeno/metabolismo , Ovulación , Área Preóptica/metabolismo , Animales , Núcleo Hipotalámico Anterior/efectos de los fármacos , Estradiol/sangre , Receptor alfa de Estrógeno/antagonistas & inhibidores , Receptor beta de Estrógeno/antagonistas & inhibidores , Ciclo Estral/efectos de los fármacos , Femenino , Hormona Folículo Estimulante/sangre , Hormona Liberadora de Gonadotropina/farmacología , Neuronas/efectos de los fármacos , Neuronas/metabolismo , Ovulación/efectos de los fármacos , Óvulo/efectos de los fármacos , Óvulo/metabolismo , Área Preóptica/efectos de los fármacos , Progesterona/sangre , RatasRESUMEN
BACKGROUND: Muscarinic receptors (mAChRs) of the preoptic and anterior hypothalamus areas (POA-AHA) regulate ovulation in an asymmetric manner during the estrous cycle. The aims of the present study were to analyze the effects of a temporal blockade of mAChRs on either side of the POA-AHA performed in diestrus-2 rats on ovulation, the levels of estradiol, follicle stimulating hormone (FSH) and luteinizing hormone (LH) and the mechanisms involved in changes in ovulation. METHODS: Cyclic rats on diestrus-2 day were anesthetized and randomly assigned to the following groups: 1) microinjection of 1 µl of saline or atropine solution (62.5 ng) in the left or right POA-AHA; 2) removal (unilateral ovariectomty, ULO) of the left (L-ULO) or right (R-ULO) ovary, and 3) rats microinjected with atropine into the left or right POA-AHA plus L-ULO or R-ULO. The ovulation rate and the number of ova shed were measured during the predicted estrus, as well as the levels of estradiol, FSH and LH during the predicted proestrus and the effects of injecting synthetic LH-releasing hormone (LHRH) or estradiol benzoate (EB). RESULTS: Atropine in the left POA-AHA decreased both the ovulation rate and estradiol and LH levels on the afternoon of proestrus, also LHRH or EB injection restored ovulation. L- or R-ULO resulted in a lower ovulation rate and smaller number of ova shed, and only injection of LHRH restored ovulation. EB injection at diestrus-2 restored ovulation in animals with L-ULO only. The levels of estradiol, FSH and LH in rats with L-ULO were higher than in animals with unilateral laparotomy. In the group microinjected with atropine in the left POA-AHA, ovulation was similar to that in ULO rats. In contrast, atropine in the right POA-AHA of ULO rats blocked ovulation, an action that was restored by either LHRH or EB injection. CONCLUSIONS: These results indicated that the removal of a single ovary at noon on diestrus-2 day perturbed the neuronal pathways regulating LH secretion, which was mediated by the muscarinic system connecting the right POA-AHA and the ovaries.
Asunto(s)
Núcleo Hipotalámico Anterior/metabolismo , Diestro/metabolismo , Estradiol/metabolismo , Hormona Folículo Estimulante/metabolismo , Hormona Luteinizante/metabolismo , Ovulación/metabolismo , Área Preóptica/metabolismo , Receptores Muscarínicos/metabolismo , Animales , Núcleo Hipotalámico Anterior/efectos de los fármacos , Atropina/farmacología , Anticonceptivos/farmacología , Diestro/efectos de los fármacos , Estradiol/análogos & derivados , Estradiol/farmacología , Femenino , Hormona Liberadora de Gonadotropina/farmacología , Hormona Luteinizante/efectos de los fármacos , Antagonistas Muscarínicos/farmacología , Ovariectomía , Ovario/efectos de los fármacos , Ovulación/efectos de los fármacos , Área Preóptica/efectos de los fármacos , Proestro/efectos de los fármacos , Proestro/metabolismo , Ratas , Receptores Muscarínicos/efectos de los fármacosRESUMEN
BACKGROUND: Intragastric or intraperitoneal ethanol (EtOH) treatment inhibits reproductive functions in females and male rats. The area of the hypothalamus where these effects take place is unknown. As the participations of the preoptic-anterior hypothalamic area (POA-AHA) in regulating ovulation is asymmetric, this study aims to analyze the effects on 17ß-estradiol(E2 ), progesterone, luteinizing hormone (LH), follicle-stimulating hormone (FSH) serum levels, the messenger ribonucleic acid (mRNA) expression of estrogen receptor alpha (ERα) and beta (ERß), and ovulation resulting from unilaterally microinjecting water or an EtOH solution into either side of the POA-AHA. METHODS: The treatment consisted of microinjecting a 8.6 µM EtOH solution into either side of the POA-AHA. The study was performed on groups of adult cyclic rats at 09.00 hours on diestrus-1, and sacrificed on diestrus-2 at 13.00, on proestrus at 09.00 or 17.00 or on estrus at 09.00 hours. Ovulation rates were assessed in rats sacrificed on estrus. Hormonal serum levels were measured using radioimmunoassay, and as a function of ERα and ERß mRNA expression in each side of the POA-AHA by reverse transcriptase polymerase chain reaction. RESULTS: EtOH treatment blocked ovulation and the preovulatory release of LH, and lowered E2 levels. Irrespective of the treated POA-AHA side, ERα mRNA expression was consistently lower in the left POA-AHA and higher on the right. EtOH treatment in the left POA-AHA decreased FSH serum levels and lowered ERß mRNA expression. In turn, EtOH treatment on the right POA-AHA resulted in higher FSH levels and ERß mRNA expression. CONCLUSIONS: The present results show that EtOH blocks the preovulatory surge of LH on the POA-AHA. The effects of EtOH treatment of preovulatory FSH surge on the POA-AHA are asymmetric (stimulative on the right and inhibiting in the left). The effects of EtOH treatment on preovulatory LH and FSH surge could be explained by the inhibition of ERα and ERß mRNA expression, respectively.
Asunto(s)
Núcleo Hipotalámico Anterior/efectos de los fármacos , Etanol/farmacología , Ovulación/efectos de los fármacos , Área Preóptica/efectos de los fármacos , Animales , Núcleo Hipotalámico Anterior/fisiología , Estradiol/sangre , Receptor alfa de Estrógeno/biosíntesis , Receptor beta de Estrógeno/biosíntesis , Etanol/administración & dosificación , Femenino , Hormona Folículo Estimulante/sangre , Hormona Luteinizante/sangre , Microinyecciones , Área Preóptica/fisiología , Progesterona/sangre , Ratas , Reacción en Cadena de la Polimerasa de Transcriptasa InversaRESUMEN
We investigated whether administration of MOD in rats during the lights-on period into wake-promoting areas, such as anterior hypothalamus (AH) or into the pedunculopontine tegmental nucleus (PPTg) would enhance waking. Results showed that microinjections of 1 microL of MOD (10, 20, or 30 microg) into both brain areas increased the total time of alertness and decreased sleep. Additionally, MOD-treated rats showed an enhancement in alpha power spectra but delta power spectra was diminished. Finally, c-Fos expression was found increased into either AH or the PPTg. Collectively, these results suggest that MOD induces waking via the activity of two wake-related brain areas such as AH and the PPTg.
Asunto(s)
Núcleo Hipotalámico Anterior/efectos de los fármacos , Compuestos de Bencidrilo/farmacología , Estimulantes del Sistema Nervioso Central/farmacología , Núcleo Tegmental Pedunculopontino/efectos de los fármacos , Vigilia/efectos de los fármacos , Análisis de Varianza , Animales , Conducta Animal/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Electroencefalografía/métodos , Masculino , Modafinilo , Proteínas Oncogénicas v-fos/metabolismo , Ratas , Ratas Wistar , Fases del Sueño/efectos de los fármacosRESUMEN
The aim of the present study was to investigate the effects of the alpha2-adrenoceptor antagonist yohimbine on blood pressure and heart rate (HR) regulation, as well as on adrenergic and serotoninergic neurotransmission, in fructose hypertensive (F) rats. The anterior hypothalamic area of control (C) and F rats was perfused with Ringer's solution containing 10 and 100 microg/mL yohimbine through a microdialysis concentric probe. The effects of yohimbine on mean arterial pressure (MAP) and HR, as well as on hypothalamic dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindole acetic acid (5-HIAA) levels, were measured according to perfusion time. Although intrahypothalamic perfusion of yohimbine increased blood pressure in C rats (DeltaMAP 9 +/- 1 and 11 +/- 2 mmHg for 10 and 100 microg/mL yohimbine, respectively; P < 0.05 vs Ringer's perfusion), the alpha-adrenoceptor antagonist did not modify MAP in F. Intrahypothalamic yohimbine had no effect on HR at either concentration tested. Intrahypothalamic perfusion of 10 and 100 microg/mL yohimbine increased DOPAC levels in C rats (135 +/- 6 and 130 +/- 5% of basal levels, respectively; both n = 6; P < 0.05 vs Ringer's perfusion), but not in F animals (115 +/- 6 and 102 +/- 6% of basal levels, respectively; both n = 6). In both C and F rats, yohimbine administration induced an increase in 5-HIAA dialysate levels. The results of the present study support the notion that alpha2-adrenoceptor tone of the anterior hypothalamus of normotensive rats, which contributes to normal blood pressure regulation, is not involved in the control of HR in either normotensive C or hypertensive F rats. The absence of changes in MAP after yohimbine perfusion in F rats suggests that the alpha2-adrenoceptor tone could be decreased in this group of rats and that this may be responsible for the maintenance of hypertension in this model. Intrahypothalamic perfusion of yohimbine increased DOPAC in the dialysate only in C rats, suggesting changes in presynaptic alpha2-adrenoceptor activity in fructose-overloaded rats. Conversely, increased 5-HIAA levels did not differ between C and F groups.
Asunto(s)
Fructosa , Hipertensión/inducido químicamente , Hipotálamo/fisiología , Receptores Adrenérgicos alfa/metabolismo , Receptores Adrenérgicos alfa/fisiología , Ácido 3,4-Dihidroxifenilacético/farmacología , Animales , Núcleo Hipotalámico Anterior/efectos de los fármacos , Formación de Anticuerpos/efectos de los fármacos , Presión Sanguínea/efectos de los fármacos , Peso Corporal/efectos de los fármacos , Corazón/efectos de los fármacos , Frecuencia Cardíaca/efectos de los fármacos , Ácido Hidroxiindolacético/farmacología , Hipotálamo/metabolismo , Masculino , Perfusión/métodos , Ratas , Ratas Sprague-Dawley , Receptores de Serotonina/metabolismo , Transmisión Sináptica/efectos de los fármacos , Yohimbina/administración & dosificación , Yohimbina/farmacologíaRESUMEN
The aim of this work was to demonstrate an alteration of the anterior hypothalamic catecholaminergic system in aortic coarctated (ACo) rats by the perfusion of beta-adrenergic antagonist and the microinfusion of beta-adrenergic agonist. Wistar urethane-chloralose anesthetized rats were used. The carotid artery was cannulated for blood pressure recording and changes in blood pressure were measured. A concentric microdialysis probe was inserted in the anterior hypothalamus. Metoprolol (a beta(1)-adrenoceptor antagonist) perfusion (6 microg ml(-1)) reduced the mean arterial pressure (MAP) in the ACo rats but not in sham operated (SO) animals. The anterior hypothalamic infusion of non-specific beta-adrenergic agonist isoproterenol induced a dose-dependent decrease of blood pressure in both experimental groups, but the depressor response was significantly lower in ACo rats. The pretreatment with atenolol, a selective beta(1)-adrenoceptor antagonist, increased the depressor effect of isoproterenol in ACo rats, but not in SO rats. On the other hand, the hypotensive action of isoproterenol was significantly diminished after the administration of non-specific beta-adrenoceptor antagonist propranolol in SO and ACo rats. The anterior hypothalamic infusion of clenbuterol, a selective beta(2)-adrenergic agonist, induced a dose-dependent decrease of blood pressure in both experimental groups. The depressor response to clenbuterol (1 nmol) was significantly lower in ACo rats than in SO rats. In summary, this study provides the evidence that there is a beta(1)-adrenergic compromise in anaesthetized ACo rats and this compromise may be involved in the maintenance of hypertension. On the other hand, this study also suggests the existence of pressor beta(1)-adrenoceptors in the anterior hypothalamic area of ACo rats but not in SO rats. We also found a diminished depressor beta(2)-adrenergic activity in ACo rats.
Asunto(s)
Núcleo Hipotalámico Anterior/efectos de los fármacos , Coartación Aórtica/fisiopatología , Hipertensión/fisiopatología , Receptores Adrenérgicos beta/efectos de los fármacos , Agonistas Adrenérgicos beta/farmacología , Antagonistas Adrenérgicos beta/farmacología , Animales , Núcleo Hipotalámico Anterior/fisiopatología , Coartación Aórtica/complicaciones , Coartación Aórtica/tratamiento farmacológico , Atenolol/farmacología , Presión Sanguínea/efectos de los fármacos , Clenbuterol/farmacología , Modelos Animales de Enfermedad , Relación Dosis-Respuesta a Droga , Sinergismo Farmacológico , Hipertensión/complicaciones , Hipertensión/tratamiento farmacológico , Hipotensión/inducido químicamente , Isoproterenol/antagonistas & inhibidores , Isoproterenol/farmacología , Masculino , Metoprolol/farmacología , Microinyecciones/métodos , Propranolol/farmacología , Ratas , Ratas Wistar , Receptores Adrenérgicos beta/fisiologíaRESUMEN
The existence of endothelin binding sites on the catecholaminergic neurons of the hypothalamus suggests that endothelins (ETs) participate in the regulation of noradrenergic transmission modulating various hypothalamic-controlled processes such as blood pressure, cardiovascular activity, etc. The effects of ET-1 and ET-3 on the neuronal release of norepinephrine (NE) as well as the receptors and intracellular pathway involved were studied in the rat anterior hypothalamus. ET-1 (10 nM) and ET-3 (10 nM) diminished neuronal NE release and the effect blocked by the selective ET type B receptor antagonist BQ-788 (100 nM). N(omega)-nitro-L-arginine methyl ester (10 microM), methylene blue (10 microM), and KT5823 (2 microM), inhibitors of nitric oxide synthase activity, guanylate cyclase, and protein kinase G, respectively, prevented the inhibitory effects of both ETs on neuronal NE release. In addition, both ETs increased nitric oxide synthase activity. Furthermore, 100 microM picrotoxin, a GABA(A)-receptor antagonist, inhibited ET-1 and ET-3 response. Our results show that ET-1 as well as ET-3 has an inhibitory neuromodulatory effect on NE release in the anterior hypothalamus mediated by the ET type B receptor and the involvement of a nitric oxide-dependent pathway and GABA(A) receptors. ET-1 and ET-3 may thus diminish available NE in the synaptic gap leading to decreased noradrenergic activity.