Evidence that the bed nucleus of the stria terminalis contributes to the modulation of hypophysiotropic corticotropin-releasing factor cell responses to systemic interleukin-1β

Systemic infection activates the hypothalamic-pituitary-adrenal (HPA) axis, and brainstem catecholamine cells have been shown to contribute to this response. However, recent work also suggests an important role for the central amygdala (CeA). Because direct connections between the CeA and the hypothalamic apex of the HPA axis are minimal, the present study investigated whether the bed nucleus of the stria terminalis (BNST) might act as a relay between them. This was done by using an animal model of acute systemic infection involving intravascular delivery of the proinflammatory cytokine interleukin-1β (IL-1β, 1 μg/kg). Unilateral ibotenic acid lesions encompassing the ventral BNST significantly reduced both IL-1β-induced increases in Fos immunoreactivity in corticotropin-releasing factor (CRF) cells of the hypothalamic paraventricular nucleus (PVN) and corresponding increases in adrenocorticotropic hormone (ACTH) secretion. Similar lesions had no effect on CRF cell responses to physical restraint, suggesting that the effects of BNST lesions were not due to a nonspecific effect on stress responses. In further studies, we examined the functional connections between PVN, BNST, and CeA by combining retrograde tracing with mapping of IL-1β-induced increases in Fos in BNST and CeA cells. In the case of the BNST, these studies showed that systemic IL-1β administration recruits ventral BNST cells that project directly to the PVN. In the case of the CeA, the results obtained were consistent with an arrangement whereby lateral CeA cells recruited by systemic IL-1β could regulate the activity of medial CeA cells projecting directly to the BNST. In conclusion, the present findings are consistent with the hypothesis that the BNST acts as a relay between the CeA and PVN, thereby contributing to CeA modulation of hypophysiotropic CRF cell responses to systemic administration of IL-1β.

Hypothalamic paraventricular nucleus neurons regulate medullary catecholamine cell responses to restraint stress

Both physical and psychological stressors recruit catecholamine cells (CA) located in the ventrolateral medulla (VLM) and the nucleus of the solitary tract (NTS). In the case of physical stressors, this effect is initiated by signals that first access the central nervous system at or below the level of the medulla. For psychological stressors, however, CA cell recruitment depends on higher structures within the neuraxis. Indeed, we have recently provided evidence of a pivotal role for the medial amygdala (MeA) in this regard, although such a role must involve a relay, as MeA neurons do not project directly to the medulla. However, some of the MeA neurons that respond to psychological stress have been found to project to the hypothalamic paraventricular nucleus (PVN), a structure that provides significant input to the medulla. To determine whether the PVN might regulate medullary CA cell responses to psychological stress, animals were prepared with unilateral injections of the neurotoxin ibotenic acid into the PVN (Experiment 1), or with unilateral injections of the retrograde tracer wheat germ agglutinin-gold (WGA-Au) into the CA cell columns of the VLM or NTS (Experiment 2). Seven days later, animals were subjected to a psychological stressor (restraint; 15 minutes), and their brains were subsequently processed for Fos plus appropriate cytoplasmic markers (Experiment 1), or Fos plus WGA-Au (Experiment 2). PVN lesions significantly suppressed the stress-related induction of Fos in both VLM and NTS CA cells, whereas tracer deposits in the VLM or NTS retrogradely labeled substantial numbers of PVN cells that were also Fos-positive after stress. Considered in concert with previous results, these data suggest that the activation of medullary CA cells in response to psychological stress may involve a critical input from the PVN.

Medial prefrontal cortex control of the paraventricular hypothalamic nucleus response to psychological stress : possible role of the bed nucleus of the stria terminalis

The medial prefrontal cortex (mPFC) has been strongly implicated in control of the paraventricular nucleus of the hypothalamus (PVN) response to stress. Because of the paucity of direct projections from the mPFC to the PVN, we sought to investigate possible brain regions that might act as a relay between the two during psychological stress. Bilateral ibotenic acid lesions of the rat mPFC enhanced the number of Fos-immunoreactive cells seen in the PVN after exposure to the psychological stressor, air puff. Altered neuronal recruitment was seen in only one of the candidate relay populations examined, the ventral bed nucleus of the stria terminalis (vBNST). Furthermore, bilateral ibotenic acid lesions of the BNST caused a significant attenuation of the PVN response to air puff. To better characterize the structural relationships between the mPFC and PVN, retrograde tracing studies were conducted examining Fos expression in cells retrogradely labeled with cholera toxin b subunit (CTb) from the PVN and the BNST. Results obtained were consistent with an important role for both the mPFC and BNST in the mpPVN CRF cell response to air puff. We suggest a set of connections whereby a direct PVN projection from the ipsilateral vBNST is involved in the mpPVN response to air puff and this may, in turn, be modulated by an indirect projection from the mPFC to the BNST.

Peripheral injected cholecystokinin-8S modulates the concentration of serotonin in nerve fibers of the rat brainstem

Serotonin and cholecystokinin (CCK) play a role in the short-term inhibition of food intake. It is known that peripheral injection of CCK increases c-Fos-immunoreactivity (Fos-IR) in the nucleus of the solitary tract (NTS) in rats, and injection of the serotonin antagonist ondansetron decreases the number of c-Fos-IR cells in the NTS. This supports the idea of serotonin contributing to the effects of CCK. The aim of the present study was to elucidate whether peripherally injected CCK-8S modulates the concentration of serotonin in brain feeding-regulatory nuclei. Ad libitum fed male Sprague-Dawley rats received 5.2 and 8.7 nmol/kg CCK-8S (n = 3/group) or 0.15 M NaCl (n = 3-5/group) injected intraperitoneally (ip). The number of c-Fos-IR neurons, and the fluorescence intensity of serotonin in nerve fibers were assessed in the paraventricular nucleus (PVN), arcuate nucleus (ARC), NTS and dorsal motor nucleus of the vagus (DMV). CCK-8S increased the number of c-Fos-ir neurons in the NTS (mean ± SEM: 72 ± 4, and 112 ± 5 neurons/section, respectively) compared to vehicle-treated rats (7 ± 2 neurons/section, P < 0.05), but did not modulate c-Fos expression in the DMV or ARC. Additionally, CCK-8S dose-dependently increased the number of c-Fos-positive neurons in the PVN (218 ± 15 and 128 ± 14, respectively vs. 19 ± 5, P < 0.05). In the NTS and DMV we observed a decrease of serotonin-immunoreactivity 90 min after injection of CCK-8S (46 ± 2 and 49 ± 8 pixel/section, respectively) compared to vehicle (81 ± 8 pixel/section, P < 0.05). No changes of serotonin-immunoreactivity were observed in the PVN and ARC. Our results suggest that serotonin is involved in the mediation of CCK-8's effects in the brainstem. © 2014 Elsevier Inc.

Efeitos da manipulação neonatal sobre a concentração plasmática de hormônios da reprodução e a densidade de receptores de angiotensina II no sistema nervoso central de ratas adultas

A manipulação neonatal é um modelo experimental utilizado para avaliar o modo pelo qual interferências precoces na vida do animal podem alterar funções neuroendócrinas e comportamentos na vida adulta. O procedimento de manipulação neonatal, além de alterar a atividade do eixo hipotálamo-hipófise-adrenal (eixo HPA) em ratos machos e fêmeas, pode causar profundas mudanças na função reprodutiva de ratas adultas. De fato, há evidências de que a manipulação neonatal diminui a atividade do eixo HPA através da redução da síntese e secreção de hormônios que são liberados quando os animais são expostos ao estresse na vida adulta e, além disso, induz à presença de ciclos anovulatórios e diminui a receptividade sexual de ratas. Considerando essas alterações induzidas pela manipulação neonatal que são relacionadas à função reprodutiva de ratas, essa tese teve por objetivo estudar as possíveis causas da alteração no comportamento sexual e ovulação induzidas pela manipulação neonatal. Para isto, além de estudar o perfil hormonal desses animais, o que incluiu os esteróides gonadais, as gonadotrofinas e a prolactina (PRL) em diferentes fases e horários do ciclo estral, o conteúdo do hormônio liberador de gonadotrofinas (LHRH) em algumas regiões do sistema nervoso central (SNC) e na eminência mediana (EM); foi avaliada a possível participação do sistema angiotensinérgico central, através da análise da densidade dos receptores de angiotensina II (Ang II) pela técnica de auto-radiografia, na mediação dos efeitos da manipulação neonatal sobre a função do eixo hipotálamo-hipófise-gônada (eixo HPG) e do eixo HPA. O presente estudo confirmou dados obtidos em nosso laboratório sobre a redução do comportamento sexual e da ovulação em ratas manipuladas no período neonatal. Na tarde do proestro, período no qual ocorrem os eventos necessários para a ovulação na próxima fase do ciclo estral, os resultados mostram que os animais do grupo manipulado têm redução significativa da concentração plasmática de estradiol, de gonadotrofinas e de PRL, assim como um aumento no conteúdo de LHRH na área pré-óptica medial (APOM). A manipulação neonatal também reduziu a concentração plasmática de progesterona analisada após o coito que pode ser decorrente da reduzida estimulação vaginocervical recebida por essas ratas, já que houve uma redução significativa da freqüência de intromissão realizada pelo macho sobre as ratas do grupo manipulado. A densidade de receptores de Ang II na APOM e no núcleo paraventricular do hipotálamo (PVN) também foi alterada pela manipulação neonatal, pois houve redução significativa na densidade desses receptores nessas duas regiões. Em conclusão, a manipulação neonatal reduz profundamente a atividade do eixo HPG e essa alteração é causada por modificações nas concentrações de estradiol no plasma que, por sua vez, pode alterar a secreção de LHRH, de gonadotrofinas e de PRL, comprometendo dessa maneira a ovulação e a receptividade sexual. Contribuindo para os efeitos deletérios da manipulação neonatal sobre a função reprodutiva em ratas, este procedimento pode alterar a implantação do blastocisto devido à redução da secreção de progesterona observada após o coito no grupo manipulado. Alguns dos efeitos da manipulação neonatal parecem ser mediados pelo sistema angiotensinérgico central, como o aumento do conteúdo de LHRH na APOM e a diminuída resposta do eixo HPA observada em animais manipulados submetidos a situações estressantes na vida adulta.

Hypothalamic supraoptic but not paraventricular nucleus is involved in cardiovascular responses to carbachol microinjected into the bed nucleus of stria terminalis of unanesthetized rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Imidazoline receptors of the paraventricular nucleus on the pressor response induced by stimulation of the subfornical organ

In the present experiments we investigated a possible involvement of imidazoline receptors of the paraventricular nucleus (PVN) of the hypothalamus on the presser effects of the angiotensin LI (ANG II) injected into the subfornical organ (SFO), in male Holtzman rats (250-300 g) with a cannula implanted into the third ventricle (3rdV), PVN and SFO. At first we tested the participation of alpha(2) and imidazoline agonist and antagonist compounds on the presser effect of ANG II injected into the 3rdV. Based on the results we may conclude that clonidine associated with rilmenidine was able to block the hypertensive response to ANG IT. The ANG II (20 pmol) injected into SFO induced a robust increase in blood pressure (37 +/- 2 mmHg). Isotonic saline (0.15 M) NaCl did not produce any change in blood pressure (5 +/- 2 mmHg). The injection of rilmenidine (30 mu g/kg/l mu L), an imidazoline agonist agent injected into PVN before ANG II injection into SFO, blocked the presser effect of ANG II (5 +/- 2 mmHg). Also, the injection of idazoxan (60 mu g/kg/mu L) before rilmenidine blocked the inhibitory effect of rilmenidine on blood pressure (39 +/- 4 mmHg). The injection of clonidine (20 nmol/mu L) prior to ANG II into the 3rdV produced a decreased in arterial blood pressure (37 +/- 2 mmHg) to (15 +/- 4 mmHg). The injection of yohimbine (80 nmol/mu L) prior to clonidine blocked the effect of clonidine on the effect of ANG II (27 +/- 2 mmHg). The injection of rilmenidine prior to ANG TI also induced a decrease in arterial blood pressure (10 +/- 3 mmHg). The injection of idazoxan prior to rilmenidine also blocked the inhibitory effect of rilmenidine (24 +/- 3 mmHg). In summary, the present study demonstrated that rilmenidine decreases the hypertensive effect of ANG II, with more potency than clonidine, even when injected into 3rdV or PVN. This study established that the PVN interacts with SFO by imidazoline receptors in order to control the arterial blood pressure. (C) Elsevier, Paris.

Activation of paraventricular nucleus of hypothalamus 5-HT1A receptor on sodium intake

Hypothalamic paraventricular nucleus (PVN) has an important role in the regulation of water and sodium intake. Several researches described the presence of 5-HT1 receptors in the central nervous system. 5-HTIA was one of the prime receptors identified and it is found in the somatodendritic and post-synaptic forms. Therefore, the aim of this study was to investigate the participation of serotonergic 5-HT1A receptors in the PVN on the sodium intake induced by sodium depletion followed by 24 h of deprivation (injection of the diuretic furosemide plus 24 h of sodium-deficient diet). Rats (280-320 g) were submitted to the implant of cannulas bilaterally in the PVN. 5-HT injections (10 and 20 mu g/0.2 mu l) in the PVN reduced NaCl 1.8% intake. 8-OH-DPAT injections (2.5 and 5.0 fig/0.2 mu l) in the PVN also reduced NaCl 1.8% intake. pMPPF bilateral injections (5-HT1A antagonist) previously to 8-OH-DPAT injections have completely blocked the inhibitory effect over NaCl 1.8% intake. 5-HT1A antagonists partially reduced the inhibitory effect of 5-HT on NaCl 1.8% intake induced by sodium depletion. In contrast, the intake of palatable solution (2% sucrose) under body fluid-replete conditions was not changed after bilateral PVN 8-OH-DPTA injections. The results show that 5HT(1A) serotonergic mechanisms in the PVN modulate sodium intake induced by sodium loss. The finding that sucrose intake was not affected by PVN 5-HT1A activation suggests that the effects of the 5-HT1A treatments on the intake of NaCl are not due to mechanisms producing a nonspecific decrease of all ingestive behaviors. (c) 2006 Elsevier B.V. All rights reserved.

Effects of V-1 and angiotensin receptor subtypes of the paraventricular nucleus on the water intake induced by vasopressin injected into the lateral septal area

In this study, we investigated the influence of d(CH2)(5)-Tyr (Me)-AVP (AAVP) an antagonist of V-1 receptors of arginine(8)-vasopressin (AVP) and the effects of losartan and CGP42112A (selective ligands of the AT, and AT, angiotensin receptors, respectively) injections into the paraventricular nucleus (PVN) on the thirst effects of AVP stimulation of the lateral septal area (LSA). AVP injection into the LSA increased the water intake in a dose-dependent manner. AAVP injected into the PVN produced a dose-dependent reduction of the drinking responses elicited by LSA administration of AVP. Both the AT(1) and AT(2) ligands administered into the PVN elicited a concentration-dependent inhibition in the water intake induced by AVP injected into the LSA, but losartan was more effective than CGP42112A the increase in the AVP response. These results indicate that LSA dipsogenic effects induced by AVP are mediated primarily by PVN AT(1) receptors. However, doses of losartan were more effective when combined with CGP42112A than when given alone, suggesting that the thirst induced by AVP injections into LSA may involve activation of multiple angiotensin II (ANG II) receptor subtypes. These results also suggests that facilitatory effects of AVP on water intake into the LSA are mediated through the activation of V-receptors and that the inhibitory effect requires V-receptors. Based on the present findings, we suggest that the administration of AVP into the LSA may play a role in the PVN control of water control. (C) 2003 Elsevier B.V. All rights reserved.

Effects of subtypes of adrenergic and angiotensinergic antagonists on the water and sodium intake induced by adrenaline injected into the paraventricular nucleus

The present experiments were conducted to investigate die role of the alpha(1A)-, alpha(1B)-, beta(1)-, beta(2)-adrenoceptors, and the effects of losartan and CGP42112A (selective ligands of the AT(1) and AT(2) angiotensin receptors, respectively) on the water and sodium intake elicited by paraventricular nucleus (PVN) injection of adrenaline. Male Holtzman rats with a stainless steel cannula implanted into the PVN were used. The ingestion of water and sodium was determined in separate groups submitted to water deprivation or sodium depletion with the diuretic furosemide (20 mg/rat). 5-Methylurapidil (an alpha(1A)-adrenergic antagonist) and ICI-118,551 (a beta(2)-adrenergic antagonist) injected into the PVN produced a dose-dependent increase, whereas cyclazosin (an alpha(1B)-adrenergic antagonist) and atenolol (a beta(1)-adrenergic antagonist) do not affect the inhibitory effect of water intake induced by adrenaline. on the other hand, the PVN administration of adrenaline increased the sodium intake in a dose-dependent manner. Previous injection of the alpha(1A) and beta(1) antagonists decreased, whereas injection of the alpha(1B) and beta(2) antagonists increased the salt intake induced by adrenaline. In rats with several doses of adrenaline into PVN, the previous administration of losartan increased in a dose-dependent manner the inhibitory effect of adrenaline and decreased the salt intake induced by adrenaline, while PVN CGP42112A was without effect. These results indicate that both appetites are mediated primarily by brain AT(1) receptors. However, the doses of losartan were more effective when combined with the doses of CGP42112A than given alone p < 0.05, suggesting that the water and salt intake effects of PVN adrenaline may involve activation of multiple angiotensin II (ANG II) receptors subtypes. (C) 2003 Elsevier B.V. All rights reserved.

Interaction between paraventricular nucleus and medial septal area on the renal effects induced by adrenaline

The aim of the present study was to analyze the role of alpha(1),alpha(2)-adrenoceptors, and the effects of losartan and PD123319 (selective ligands of the AT(1) and AT(2) angiotensin receptors, respectively) injected into the paraventricular nucleus (PVN) on the diuresis, natriuresis, and kaliuresis induced by administration of adrenaline into the medial septal area (MSA). Male Holtzman rats with a stainless steel cannula implanted into the MSA and bilaterally into the PVN were used. The administration of adrenaline into the MSA increased in a dose-dependent manner the urine, sodium, and potassium excretions. The previous administration of prazosin (an alpha(1)-adrenoceptor antagonist) injected into the PVN abolished the above effects of adrenaline, whereas yohimbine (an a-adrenoceptor antagonist) doesn't affect the diuresis, natriuresis, and kaliuresis induced by adrenaline. Pretreatment with losartan into the PVN decreased in a dose-dependent manner the urine, sodium, and potassium excretions induced by MSA administration of adrenaline (50 ng), while PVN PD123319 was without effect. These results indicate that urinary and electrolyte excretion effects induced by adrenaline into the MSA are mediated primarily by PVN AT, receptors. However, the doses of losartan were more effective when combined with the doses of PD123319 than given alone, suggesting that the urinary, natriuretic, and kaliuretic effects of MSA adrenaline may involve activation of multiple angiotensin II receptors subtypes into the PVN. (C) 2004 Elsevier B.V All rights reserved.

Role of the alpha(1)- and alpha(2)-adrenoceptors of the paraventricular nucleus on the water and salt intake, renal excretion, and arterial pressure induced by angiotensin II injection into the medial septal area

In this study we investigated the influence of cu-adrenergic antagonists injections into the paraventricular nucleus (PVN) of the hypothalamus on the thirst and salt appetite, diuresis, natriuresis, and presser effects of angiotensin II (ANG II) stimulation of medial septal area (MSA). ANG II injection into the MSA induced water and sodium intake, diuresis, natriuresis, and presser responses. The previous injection of prazosin (an alpha (1)-adrenergic antagonist) into the PVN abolished, whereas previous administration of yohimbine (an alpha (2)-adrenergic antagonist) into the PVN increased the water and sodium intake, urinary, natriuretic, and presser responses induced by ANG ii injected into the MSA. Previous injection of a nonselective alpha -adrenergic antagonist, regitin, into the PVN blocked the urinary excretion, and reduced the water and sodium intake, sodium intake, and presser responses induced by ANG II injected into the MSA. The present results suggest that alpha -adrenergic pathways involving the PVN are important for the water and sodium excretion, urine and sodium excretion, and presser responses, induced by angiotensinergic activation of the MSA. (C) 2001 Elsevier B.V.

Damage to the central amygdala produces differential encephalic c-fos expression in the water deprivation-partial rehydration protocol

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Activation of the serotonergic 5-HT1A receptor in the paraventricular nucleus of the hypothalamus inhibits water intake and increases urinary excretion in water-deprived rats

The paraventricular nucleus (PVN) may be considered as a dynamic mosaic of chemically-specified subgroups of neurons. 5-HT1A is one of the prime receptors identified and there is expressed throughout all magnocellular regions of the PVN. Several reports have demonstrated that a subpopulation of the magnocellular neurons expressing 5-HT1A receptors are oxytocin (OT) neurons and activation of 5-HT1A receptors in the PVN increases the plasma OT. Increasing evidence shows that OT inhibits water intake and increases urinary excretion in rats. The aim of this study was to investigate the role of serotonergic 5-HT1A receptors in the lateral-medial posterior magnocellular region of the PVN in the water intake and diuresis induced by 24 h of water deprivation. Cannulae were implanted in the PVN of rats. 5-HT injections in the PVN reduced water intake and increased urinary excretion. 8-OH-DPAT (a 5-HT1A agonist) injections blocked the water intake and increased urinary output in all the periods of the observation. pMPPF (a 5-HT1A antagonist) injected bilaterally before the 8-OH-DPAT blocked its inhibitory effect on water intake and its diuretic effect. We suggest that antidipsogenic and diuretic responses seem to be mediated via 5-HT1A receptors of the lateral-medial posterior magnocellular region of the PVN in water-deprived rats. (C) 2008 Elsevier B.V. All rights reserved.

Macrophage Migration Inhibitory Factor in the Paraventricular Nucleus Plays a Major Role in the Sympathoexcitatory Response to Salt

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)