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.

Opposing roles for medial and central amygdala in the initiation of noradrenergic cell responses to a psychological stressor

Psychological stressors trigger the activation of medullary noradrenergic cells, an effect that has been shown to depend upon yet-to-be-identified structures located higher in the brain. To test whether the amygdala is important in this regard, we examined the effects of amygdala lesions on noradrenergic cell responses to restraint, and also looked at whether any amygdala cells that respond to restraint project directly to the medulla. Ibotenic acid lesions of the medial amygdala completely abolished restraint-induced Fos expression in A1 and A2 noradrenergic cells. In contrast, lesions of the central amygdala actually facilitated noradrenergic cell responses to restraint. Tracer deposits in the dorsomedial (but not ventrolateral) medulla retrogradely labelled many cells in the central nucleus of the amygdala, but none of these cells expressed Fos in response to restraint. These data suggest for the first time that the medial amygdala is critical to the activation of medullary noradrenergic cells by a psychological stressor whereas the central nucleus exerts an opposing, inhibitory influence upon noradrenergic cell recruitment. The initiation of noradrenergic cell responses by the medial amygdala does not involve a direct projection to the medulla. Accordingly, a relay through some other structure, such as the hypothalamic paraventricular nucleus, warrants careful consideration.

Peripheral withdrawal recruits distinct central nuclei in morphine-dependent rats

This study examined if brain pathways in morphine-dependent rats are activated by opioid withdrawal precipitated outside the central nervous system. Withdrawal precipitated with a peripherally acting quaternary opioid antagonist (naloxone methiodide) increased Fos expression but caused a more restricted pattern of neuronal activation than systemic withdrawal (precipitated with naloxone which enters the brain). There was no effect on locus coeruleus and significantly smaller increases in Fos neurons were produced in most other areas. However in the ventrolateral medulla (A1/C1 catecholamine neurons), nucleus of the solitary tract (A2/C2 catecholamine neurons), lateral parabrachial nucleus, supramamillary nucleus, bed nucleus of the stria terminalis, accumbens core and medial prefrontal cortex no differences in the withdrawal treatments were detected. We have shown that peripheral opioid withdrawal can affect central nervous system pathways.

Systemic administration of interleukin-1β activates select populations of central amygdala afferents

The central nucleus of the amygdala (CeA) is activated robustly by an immune challenge such as the systemic administration of the proinflammatory cytokine interleukin-1β (IL-1β). Because IL-1β is not believed to cross the blood-brain barrier in any significant amount, it is likely that IL-1β elicits CeA cell recruitment by means of activation of afferents to the CeA. However, although many studies have investigated the origins of afferent inputs to the CeA, we do not know which of these also respond to IL-1β. Therefore, to identify candidate neurons responsible for the recruitment of CeA cells by an immune challenge, we iontophoretically deposited a retrograde tracer, cholera toxin b-subunit (CTb), into the CeA of rats 7 days before systemic delivery of IL-1β (1 μg/kg, i.a.). By using combined immunohistochemistry, we then quantified the number of Fos-positive CTb cells in six major regions known to innervate the CeA. These included the medial prefrontal cortex, paraventricular thalamus (PVT), ventral tegmental area, parabrachial nucleus (PB), nucleus tractus solitarius, and ventrolateral medulla. Our results show that after deposit of CTb into the CeA, the majority of double-labeled cells were located in the PB and the PVT, suggesting that CeA cell activation by systemic IL-1β is likely to arise predominantly from cell bodies located in these regions. These findings may have significant implications in determining the central pathways involved in generating acute central responses to a systemic immune challenge.

Desenvolvimento do cluster de economia criativa na área central da cidade de São Paulo

A presente dissertação trata da estruturação de um cluster de economia criativa no centro da cidade de São Paulo, voltado à área de tecnologia. A escolha da região central, assim como da economia criativa como impulso para a requalificação econômica e reocupação social da área, tem como objetivo enfrentar o problema do esvaziamento do centro da cidade, impulsionando o empreendedorismo e o posicionamento da região como local de convivência. Para análise da viabilidade e adequabilidade dessa proposta optou-se por uma pesquisa aplicada, cujos procedimentos englobaram uma breve revisão da literatura e também entrevistas com profissionais do setor criativo. Foram realizados estudos de casos internacionais e nacionais; estudo da legislação brasileira; avaliação do nível de desenvolvimento dos setores criativos em São Paulo e reflexão sobre as vocações da cidade. Com essa bagagem, iniciou-se a modelagem do cluster de tecnologia do Distrito Criativo da Sé/República, por meio da qual se objetivou traçar propostas de ações que pudessem ser desenvolvidas em curto, médio e longo prazos. Foram apresentadas ações mais imediatas, como a realização de um branding das atividades já em andamento, medidas realizáveis no médio prazo, como a concretização de parcerias, e outras um tanto mais estruturantes, como a requalificação de espaços e de projetos. Todas essas medidas almejam otimizar a ação municipal na busca pela reocupação da região e, consequentemente, na atração de investimentos para o local, de modo a frear o processo de degradação e alavancar o processo de reposicionamento do centro da cidade de São Paulo como valioso núcleo econômico e cultural para o Município. Com o presente trabalho, chega-se à conclusão de que há exemplos no Brasil e no mundo que podem servir de inspiração para o desenvolvimento da ação proposta e que a possibilidade de se gerar um impacto positivo, mesmo em épocas de dificuldades orçamentárias, é bastante plausível.

Nucleus isthmi and control of breathing in amphibians

Despite recent advances, the mechanisms of neurorespiratory control in amphibians are far from understood. One of the brainstem structures believed to play a key role in the ventilatory control of anuran amphibians is the nucleus isthmi (NI). This nucleus is a mesencephalic structure located between the roof of the midbrain and the cerebellum, which differentiates during metamorphosis; the period when pulmonary ventilation develops in bullfrogs. It has been recently suggested that the NI acts to inhibit hypoxic and hypercarbic drives in breathing by restricting increases in tidal volume. This data is similar to the influence of two pontine structures of mammals, the locus coeruleus and the nucleus raphe magnus. The putative mediators for this response are glutamate and nitric oxide. Microinjection of kynurenic acid (an ionotropic receptor antagonist of excitatory amino acids) and L-NAME (a non-selective NO synthase inhibitor) elicited increases in the ventilatory response to hypoxia and hypercarbia. This article reviews the available data on the role of the NI in the control of ventilation in amphibians. (C) 2004 Elsevier B.V. All rights reserved.

Locus coeruleus is a central chemoreceptive site in toads

The locus coeruleus (LC) has been suggested as a CO2 chemoreceptor site in mammals. This nucleus is a mesencephalic structure of the amphibian brain and is probably homologous to the LC in mammals. There are no data available for the role of LC in the central chemoreception of amphibians. Thus the present study was designed to investigate whether LC of toads (Bufo schneideri) is a CO2/H+ chemoreceptor site. Fos immunoreactivity was used to verify whether the nucleus is activated by hypercarbia (5% CO2 in air). In addition, we assessed the role of noradrenergic LC neurons on respiratory and cardiovascular responses to hypercarbia by using 6-hydroxydopamine lesion. To further explore the role of LC in central chemosensitivity, we examined the effects of microinjection of solutions with different pH values (7.2, 7.4, 7.6, 7.8, and 8.0) into the nucleus. Our main findings were that 1) a marked increase in c-fos-positive cells in the LC was induced after 3 h of breathing a hypercarbic gas mixture; 2) chemical lesions in the LC attenuated the increase of the ventilatory response to hypercarbia but did not affect ventilation under resting conditions; and 3) microinjection with acid solutions (pH = 7.2, 7.4, and 7.6) into the LC elicited an increased ventilation, indicating that the LC of toads participates in the central chemoreception.

CONTROL of THE CENTRAL CHEMOREFLEX BY A5 NORADRENERGIC NEURONS IN RATS

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

Astrócitos imunorreativos à proteína glial fibrilar ácida (GFAP) em sistema nervoso central de equinos normais e de equinos com leucoencefalomalácia

A proteína glial fibrilar ácida (GFAP), subunidade dos filamentos intermediários do citoesqueleto celular, está presente no citoplasma de astrócitos. Técnicas imunohistoquímicas com anticorpos primários anti-GFAP são geralmente empregadas para identificar astrócitos no sistema nervoso, permitindo verificar também sua hipertrofia. Vários estudos mostram a distribuição, a morfologia e a citoarquitetura de astrócitos em várias regiões do SNC do homem e de animais de laboratório. No entanto, em animais domésticos e, especialmente em equinos, poucas informações estão disponíveis. No presente trabalho, verificou-se a densidade e a morfologia de astrócitos imunorreativos à GFAP na substância branca da córtex cerebral de equinos com leucoencefalomalácia (LEM) comparando-se esses aspectos com o de equinos normais. Animais com LEM apresentaram hipertrofia de astrócitos em áreas próximas às lesões, representada pelo aumento do corpo celular, do núcleo e dos prolongamentos citoplasmáticos. O número de astrócitos apresentou-se reduzido e a imunorreatividade foi mais acentuada. Nos animais normais, verificou-se distribuição constante de astrócitos imunorreagentes com características de fibrosos. Alterações vasculares nos animais com LEM, como por exemplo degeneração de endotélio vascular, também foram observadas, podendo estar associadas às alterações astrocíticas.

Bed nucleus of the stria terminalis alpha(1) and alpha(2) adrenoceptors differentially modulate the cardiovascular responses to exercise in rats

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

GABA(A) receptor activation in the lateral parabrachial nucleus induces water and hypertonic NaCl intake

Inhibitory serotonergic and cholecystokinergic mechanisms in the lateral parabrachial nucleus and central GABAergic mechanisms are involved in the regulation of water and NaCl intake. In the present study we investigated if the GABA(A) receptors in the lateral parabrachial nucleus are involved in the control of water, NaCl and food intake in rats. Male Holtzman rats with stainless steel cannulas implanted bilaterally into the lateral parabrachial nucleus were used. Bilateral injections of muscimol (0.2 nmol/0.2 mu l) into the lateral parabrachial nucleus strongly increased 0.3 M NaCl (20.3 +/- 7.2 vs. saline: 2.6 +/- 0.9 ml/180 min) without changing water intake induced by the treatment with the diuretic furosemide combined with low dose of the angiotensin converting enzyme inhibitor captopril s.c. In euhydrated and satiated rats, bilateral lateral parabrachial nucleus injections of muscimol (0.2 and 0.5 nmol/0.2 0) induced 0.3 M NaCl intake (12.1 +/- 6.5 and 32.5 +/- 7.3 ml/180 min, respectively, vs. saline: 0.4 +/- 0.2 ml/180 min) and water intake (5.2 +/- 2.0 and 7.6 +/- 2.8 ml/ 180 min, respectively, vs. saline: 0.8 +/- 0.4 ml/180 min), but no food intake (2 +/- 0.4 g/240 min vs. saline: 1 +/- 0.3 g/240 min). Bilateral lateral parabrachial nucleus injections of the GABAA antagonist bicuculline (1.6 nmol/0.2 mu l) abolished the effects of muscimol (0.5 nmol/0.2 mu l) on 0.3 M NaCl and water intake. Muscimol (0.5 nmol/0.2 mu l) into the lateral parabrachial nucleus also induced a slight ingestion of water (4.2 +/- 1.6 ml/240 min vs. saline: 1.1 +/- 0.3 ml/240 min) when only water was available, a long lasting (for at least 2 h) increase on mean arterial pressure (14 +/- 4 mm Hg, vs. saline: -1 +/- 1 mm Hg) and only a tendency to increase urinary volume and Na+ and K+ renal excretion. Therefore the activation of GABAA receptors in the lateral parabrachial nucleus induces strong NaCl intake, a small ingestion of water and pressor responses, without changes on food intake. (c) 2005 Published by Elsevier Ltd on behalf of IBRO.

Putative antinociceptive action of nitric oxide in the caudal part of the spinal trigeminal nucleus during chronic carrageenan-induced arthritis in the rat temporomandibular joint

In order to investigate a putative role for nitric oxide (NO) in the central nociceptive processing following carrageenan-induced arthritis in the rat temporomandibular joint (TMJ), we analyzed the immunoreactivity, gene expression and activity of nitric oxide synthases (NOS) in the caudal part of the spinal trigeminal nucleus (Sp5C) during the acute (24 h), chronic (15 days) and chronic-active (14 days-24 h) arthritis. In addition, evaluation of head-withdrawal threshold was carried out in all phases of arthritis under chronic inhibition of nNOS with the selective inhibitor 7-nitroindazole (7-NI). Neurons with nNOS-like immunoreactivity (nNOS-LI) were concentrated mainly in the lamina II of the Sp5C, showing no significant statistical difference during arthritis. Only a discrete percentage of nNOS-LI neurons expressed Fos immunoreactivity. The mRNA expression for both nNOS and endothelial nitric oxide synthases (eNOS) presented no noticeable differences among the groups. No expression of inducible nitric oxide synthase (iNOS) was detected in the Sp5C by either immunohistochemistry or reverse-transcription polymerase chain reaction (RTPCR). Ca(2+)-dependent NOS activity in the ipsilateral Sp5C was significantly higher (108.3 +/- 49.2%; P<0.01) in animals during the chronic arthritis. Interestingly, this increased activity was completely abolished 24 h later, in the chronic-active arthritis. Finally, head-withdrawal threshold decreased significantly in the chronic arthritis in animals under 7-NI chronic inhibition. In conclusion, nNOS immunoreactivity and mRNA expression are stable in the Sp5C during TMJ arthritis evolution, but its activity significantly increases in the chronic-phases supporting an antinociceptive role of the nNOS as evidenced by pain threshold experiment. (C) 2009 Elsevier B.V. All rights reserved.

Sodium intake by hyperosmotic rats treated with a GABA(A) receptor agonist into the lateral parabrachial nucleus

Inhibitory mechanisms in the lateral parabrachial nucleus (LPBN) and central GABAergic mechanisms are involved in the regulation of water and NaCl intake. Besides increasing fluid depletion-induced sodium intake, the activation of GABA(A) receptors with muscimol into the LPBN also induces ingestion of 0.3 M NaCl in normonatremic, euhydrated rats. It has been suggested that inhibitory mechanisms activated by osmotic signals are blocked by GABAA receptor activation in the LPBN, thereby increasing hypertonic NaCl intake. Therefore, in the present study we investigated the effects of muscimol injected into the LPBN on water and 0.3 M NaCl intake in hyperosmotic cell-dehydrated rats (rats treated with an intragastric load of 2 M NaCl). Male Wistar rats with stainless steel cannulas implanted bilaterally into the LPBN were used. In euhydrated rats, muscimol (0.5 nmol/0.2 mu l), bilaterally injected into the LPBN, induced ingestion of 0.3 M NaCl (24.6 +/- 7.9 vs. vehicle: 0.5 +/- 0.3 ml/180 min) and water (6.3 +/- 2.1 vs. vehicle: 0.5 +/- 0.3 ml/180 min). One hour after intragastric 2 M NaCl load (2 ml), bilateral injections of muscimol into the LPBN also induced 0.3 M NaCl intake (22.1 +/- 5.2 vs. vehicle: 0.9 +/- 0.8 ml/210 min) and water intake (16.5 +/- 3.6 vs. vehicle: 7.8 +/- 1.8 ml/210 min). The GABAA antagonist bicuculline (0.4 nmol/0.2 mu l) into the LPBN reduced the effect of muscimol on 0.3 M NaCl intake (7.1 +/- 2.1 ml/210 min). Therefore, the activation of GABAA receptors in the LPBN induces ingestion of 0.3 M NaCl by hyperosmotic cell-dehydrated rats, suggesting that plasma levels of renin or osmolarity do not affect sodium intake after the blockade of LPBN inhibitory mechanisms with muscimol. (c) 2007 Elsevier B.V. All rights reserved.

Commissural nucleus of the solitary tract is important for cardiovascular responses to caudal pressor area activation

The nucleus of the solitary tract (NTS) is the site of the first synapse of cardiovascular afferent fibers in the central nervous system. Important mechanisms for cardiovascular regulation are also present in the caudal pressor area (CPA) localized at the caudal end of the ventrolateral medulla. In the present study we sought to investigate the role of the commissural subnucleus of the NTS (commNTS) on pressor and tachycardic responses induced by L-glutamate injected into the CPA. Male Holtzman rats (n=8 rats/group) anesthetized with urethane (1.2 g/kg of body weight, iv) received injections of the GABAA receptor agonist muscimol into the commNTS. Unilateral injection of L-glutamate (10 nmol/ 100 nL) into the CPA increased mean arterial pressure (MAP, 31 4 mm Hg, vs. saline: 3 +/- 2 mm Hg) and heart rate (HR, 44 8 bpm, vs. saline: 10 7 bpm). inhibition of commNTS neurons with muscimol (120 pmol/60 nL) abolished the increase in MAP (9 4 mm Hg) and HR (17 7 bpm) produced by L-glutamate into the CPA. The present results suggest that the pressor and tachycardic responses to CPA activation are dependent on commNTS mechanisms.