RESUMO
Catecholaminergic C1 cells reside in the rostral and intermediate portions of the ventrolateral medulla (RVLM) and can be activated by hypoxia. These neurons regulate the hypothalamic pituitary axis via direct projections to the hypothalamic paraventricular nucleus (PVH) and regulate the autonomic nervous system via projections to sympathetic and parasympathetic preganglionic neurons. Based on the various effects attributed to the C1 cells and what is currently known of their synaptic inputs, our hypothesis is that acute hypoxia (AH) activates RVLM projecting catecholaminergic neurons to PVH. Anterograde tracer, Phaseolus vulgaris leucoagglutinin (PHA-L) was unilaterally injected into the RVLM and a retrograde tracer Cholera toxin b (CTb) was unilaterally injected into the PVH region. After ten days, male Wistar rats that received CTb injection into the PVH were subjected to AH (8% O2, balanced with N2) or normoxia (21% O2) for 3h. Acute hypoxia significantly increased Fos immunoreactivity in the C1 region (68±2 neurons), and half of the RVLM cells activated are catecholaminergic (35±2 neurons). We observed that 23±4% of the RVLM projecting PVH cells that were activated by AH were also C1 cells. The presence of varicosities containing PHA-L in PVH region was also observed. The present results suggest that catecholaminergic C1-PVH projection is hypoxia-sensitive and the pathway between these two important brain areas can be one more piece in the complex puzzle of neural control of autonomic regulation during hypoxia.
Assuntos
Catecolaminas/metabolismo , Hipóxia/patologia , Bulbo/patologia , Vias Neurais/fisiologia , Neurônios/fisiologia , Análise de Variância , Animais , Pressão Sanguínea/fisiologia , Contagem de Células , Toxina da Cólera/farmacocinética , Modelos Animais de Doenças , Esquema de Medicação , Glutamato Descarboxilase/metabolismo , Frequência Cardíaca/fisiologia , Hipóxia/fisiopatologia , Masculino , Proteínas Oncogênicas v-fos/metabolismo , Núcleo Hipotalâmico Paraventricular , Fito-Hemaglutininas/administração & dosagem , Fito-Hemaglutininas/farmacocinética , Ratos , Ratos Wistar , Tirosina 3-Mono-Oxigenase/metabolismo , Proteína Vesicular 2 de Transporte de Glutamato/metabolismoRESUMO
The prefrontal cortex (PFC) receives strong inputs from monoaminergic cell groups in the brainstem and also sends projections to these nuclei. Recent evidence suggests that the PFC exerts a powerful top-down control over the dorsal raphe nucleus (DR) and that it may be involved in the actions of pharmaceutical drugs and drugs of abuse. In the light of these findings, the precise origin of prefrontal inputs to DR was presently investigated by using the cholera toxin subunit b (CTb) as retrograde tracer. All the injections placed in DR produced retrograde labeling in the medial, orbital, and lateral divisions of the PFC as well as in the medial part of the frontal polar cortex. The labeling was primarily located in layer V. Remarkably, labeling in the medial PFC was denser in its ventral part (infralimbic and ventral prelimbic cortices) than in its dorsal part (dorsal prelimbic, anterior cingulate and medial precentral cortices). After injections in the rostral or caudal DR, the largest number of labeled neurons was observed in the medial PFC, whereas after injections in the mid-rostrocaudal DR, the labeled neurons were more homogeneously distributed in the three main PFC divisions. A cluster of labeled neurons also was observed around the apex of the rostral pole of the accumbens, especially after rostral and mid-rostrocaudal DR injections. Overall, these results confirm the existence of robust prefrontal projections to DR, mainly derived from the ventral part of the medial PFC, and underscore a substantial contribution of the frontal polar cortex.
Assuntos
Vias Aferentes/anatomia & histologia , Vias Neurais/anatomia & histologia , Córtex Pré-Frontal/anatomia & histologia , Núcleos da Rafe/anatomia & histologia , Vias Aferentes/citologia , Vias Aferentes/metabolismo , Animais , Tronco Encefálico/anatomia & histologia , Tronco Encefálico/citologia , Tronco Encefálico/metabolismo , Toxina da Cólera/administração & dosagem , Toxina da Cólera/análise , Toxina da Cólera/farmacocinética , Imuno-Histoquímica , Masculino , Modelos Anatômicos , Vias Neurais/citologia , Vias Neurais/metabolismo , Neurônios/citologia , Neurônios/metabolismo , Córtex Pré-Frontal/citologia , Córtex Pré-Frontal/metabolismo , Núcleos da Rafe/citologia , Núcleos da Rafe/metabolismo , Ratos , Ratos WistarRESUMO
La leishmaniasis comprende un grupo de enfermedades causadas por protozoarios parásitos del género Leishmania. Dado que la piel representa la vía de entrada natural de estos parásitos al organismo y es el sitio de desarrollo de la infección por las especies responsables de las formas cutáneas, en este trabajo se quiso evaluar la efectividad de la vía de inmunización transcutánea (IT) contra la leishmaniasis en un modelo múrido susceptible a la infección. La IT consiste en la aplicación de antígenos y adyuvantes sobre la piel hidratada, y persigue la inducción de respuestas inmunitarias específicas mediante la estimulación local de las células de Langerhans. Para ello, se aplicó un lisado de promastigotes de Leishmania (L.) mexicana (Ag), en presencia de la toxina colérica (Ag+TC), un oligonucleótido contentivo del motivo CpG (Ag+CpG), o una combinación de ambos (Ag+TC+CpG) como adyuvante, a ratones BALB/c. Se pudo demostrar que la inmunización transcutánea con Ag+TC, a través de la piel la de la oreja, induce el desarrollo de una potente respuesta celular contra el parásito, en ausencia de anticuerpos específicos, incapaz de conferir protección frente a la infección. La introducción de CpG, conocido estimulador de respuestas Th1, como segundo adyuvante, si bien mostró un efecto modulador sobre la proliferación inducida por la toxina, no logró mejorar su efecto protector frente a la infección. De manera interesante, la IT con la combinación Ag+CpG confirió cierta protección, aunque moderada y transitoria, contra un reto con el parásito. Este efecto podría estar correlacionado con un aumento en la proporción de los linfocitos T CD8+, mas no parece tener relación con la estimulación de una respuesta linfoproliferativa específica, con la producción de anticuerpos dirigidos contra el parásito, o con alteraciones en el perfil de citocinas en los órganos linfoides, de los animales protegidos con respecto a los no protegidos.
Assuntos
Animais , Camundongos , Imunização , Leishmaniose/imunologia , Oligonucleotídeos , Pele/imunologia , Toxina da Cólera/farmacocinética , Adjuvantes Imunológicos , Alergia e ImunologiaRESUMO
A substantial projection from the retina to the dorsal raphe nucleus (DRN) has been demonstrated in the Chilean degus, a diurnal/crepuscular hystricomorph rodent. Following intraocular injection of cholera toxin subunit B (CTB), immunocytochemically labeled CTB-positive axons and terminals were observed in all major retinorecipient nuclei as well as in the DRN and periaqueductal gray (PAG) of the mesencephalon. Two streams of optic axons to the DRN were observed: one descending from the optic tract at the level of the pretectum and anterior superior colliculus, the other emerging as a small fascicle at the anterior pole of the inferior colliculus and descending bilaterally through the PAG. Contralateral retinal afferents in the DRN appeared to terminate primarily in the dorsomedial and lateral subdivisions of the DRN, and a less extensive ipsilateral component also was observed. Axonal arborizations were characterized by short branches and multiple varicosities, both in the DRN and in the PAG. The extent and density of DRN retinal afferents were not as extensive as previously observed in Mongolian gerbils using identical techniques, but the retinal-DRN projection is considerably larger in degus than in rats. The functional significance of the retinal-DRN pathway remains to be determined, although a variety of evidence indicates that light may directly affect the activity of neurons and serotonin levels in the DRN.
Assuntos
Axônios/ultraestrutura , Mesencéfalo/citologia , Vias Neurais/citologia , Núcleos da Rafe/citologia , Células Ganglionares da Retina/citologia , Roedores/anatomia & histologia , Animais , Axônios/fisiologia , Toxina da Cólera/farmacocinética , Ritmo Circadiano/fisiologia , Feminino , Imuno-Histoquímica , Mesencéfalo/fisiologia , Vias Neurais/fisiologia , Estimulação Luminosa , Núcleos da Rafe/fisiologia , Células Ganglionares da Retina/fisiologia , Roedores/fisiologia , Serotonina/metabolismoRESUMO
In the present work we propose a new phylogenetic hypothesis for the role played by cortical and subcortical afferents to the nucleus of the optical tract, the main visual relay station of the horizontal optokinetic reflex in mammals. The hypothesis is supported by anatomical and physiological data obtained in the South American opossum (Didelphis aurita) using the following experimental approaches: (i) single-unit recordings in the nucleus of the optic tract and simultaneous electrical stimulation of the contralateral nucleus of the optic tract; (ii) single-unit recordings in the nucleus of the optic tract and simultaneous electrical stimulation of the ipsilateral striate cortex; (iii) injection of cholera toxin subunit B into the striate cortex and subsequent immunohistochemical reaction to reveal the presence of the marker in the thalamus and mesencephalon; and (iv) single-unit recordings in the nucleus of the optic tract both before and after ablation of the ipsilateral visual cortex. The main results are: (i) there is a strong inhibitory reciprocal effect upon the nucleus of the optic tract following stimulation of its contralateral counterpart; (ii) electrophysiological and anatomical data imply that the visual cortex does not project directly to the nucleus of the optic tract. Rather, cortical terminals seem to target the nearby anterior and posterior pretectal nuclei and orthodromic latencies in the nucleus of the optic tract following stimulation of the visual cortex were twice as large as in the superior colicullus; and (iii) ablation of the entire visual cortex did not have any effect upon binocularity of cells in the nucleus of the optic tract. These results strengthen the model proposed here for the role of the interactions between the nuclei of the optic tract under optokinetic stimulation. The hypothesis in the present work is that the cortical influences upon the nucleus of the optical tract, in addition to the subcortical ones, appeared only recently in phylogenesis. In more primitive mammals, such as the opossum, subcortical interactions are thought to play a relatively important role. With the emergence of retinal specializations, such as the fovea, one might suppose that there followed the appearance of new ocular movements, such as the smooth pursuit and certain types of saccades, that came to join the pre-existent optokinetic reflex.
Assuntos
Mesencéfalo/fisiologia , Córtex Visual/fisiologia , Vias Visuais/fisiologia , Animais , Toxina da Cólera/farmacocinética , Estimulação Elétrica , Injeções , Masculino , Gambás , Fragmentos de Peptídeos/farmacocinética , Tálamo/metabolismoRESUMO
The development of the facial and hypoglossal motor nuclei were examined in the neonatal Brazilian opossum (Monodelphis domestica), a marsupial in which postnatal central nervous system development has been well characterized. In this study, we utilized postnatal injection of the retrograde tracer cholera toxin subunit B (CtB) to characterize the formation of the facial and hypoglossal motor nuclei in the developing neonatal opossum brainstem. Injections of CtB were made into the cheek/lip region or tongue of opossum pups to retrogradely label the facial or hypoglossal motor nuclei, respectively. Following a 2 h survival time, facial motoneurons in newborn opossum pups (1 PN) exhibited CtB labeling, with their cell bodies localized near the developing cranial abducens nucleus. At 3 and 5 PN, following a 48 h survival time, CtB-labeled facial motoneurons were observed in and migrating to the region of the adult facial motor nucleus in the rostral medulla. Between 7 and 10 PN, almost all facial motoneurons had migrated to their destination within the facial motor nucleus. Hypoglossal motoneurons also exhibited CtB labeling from 1 PN; however, their cell bodies were localized within the hypoglossal motor nucleus at the earliest age examined. Double label studies, to examine guidance of facial motoneurons during migration, demonstrated that CtB-labeled facial motoneurons are in close proximity to vimentin-like immunostained radial glial fibers during migration. These results suggest: (1) migration of facial motoneurons to the facial motor nucleus is a postnatal event, (2) efferent projections from facial and hypoglossal motoneurons project into the peripheral region of their target muscles from the day of birth, and (3) facial motoneurons migrate to their destination in the brainstem thereafter, in close association with radial glial fibers.
Assuntos
Envelhecimento/fisiologia , Animais Recém-Nascidos/crescimento & desenvolvimento , Tronco Encefálico/fisiologia , Nervo Facial/fisiologia , Nervo Hipoglosso/fisiologia , Gambás/fisiologia , Animais , Tronco Encefálico/citologia , Toxina da Cólera/farmacocinética , Nervo Facial/citologia , Nervo Hipoglosso/citologia , Imuno-Histoquímica , Neurônios Motores/fisiologia , Gambás/crescimento & desenvolvimento , Vimentina/metabolismoRESUMO
Many serological reactions using red blood cells (RBC) such as radial immune haemolysis (RIH) and indirect haemagglutination (IH) tests have often been used for the detection of cholera toxin (CT) and heat-labile (LT) enterotoxin produced by porcine and human Escherichia coli strains. In these tests, the enterotoxins bind to sheep, bovine and guinea-pig RBC without any ligand. We studied several factors which might interfere with such binding, as well as the nature of the receptors involved. Treatment of erythrocytes with different enzymes revealed that proteolytic enzymes had no effect on the adsorption of enterotoxins to RBC. Conversely, treatment with neuraminidase increased the adsorption. Experiments carried out with delipidized RBC revealed that none of the enterotoxins under study bound to the cells thus treated. Pre-incubation of ganglioside fractions with the enterotoxins blocked RIH and IH reactions and the biological effect of them on Vero cells. Assaying RBC ganglioside fractions by thin-layer chromatography revealed the presence of GM1. Our results suggest that the receptors for GT and LT enterotoxins in sheep, bovine and guinea pig RBC are gangliosides: mainly GM1.