RESUMO
In many parts of the nervous system, signals pass across multiple synaptic relays on their way to a destination, but little is known about how these relays form and the function they serve. To get some insight into this question we ask how the connectivity patterns are organized at two successive synaptic relays in a simple, cholinergic efferent pathway. We found that the organization at successive relays in the parasympathetic nervous system strongly resemble each other despite the different embryological origin and physiological properties of the pre- and postsynaptic cells. Additionally, we found a similar developmental synaptic pruning and elaboration strategy is used at both sites to generate their adult organizations. The striking parallels in adult innervation and developmental mechanisms at the relays argue that a general strategy is in operation. We discuss why from a functional standpoint this structural organization may amplify central signals while at the same time maintaining positional targeting.
Assuntos
Vias Eferentes/fisiologia , Plasticidade Neuronal/fisiologia , Neurônios/metabolismo , Sistema Nervoso Parassimpático/fisiologia , Glândula Submandibular/fisiologia , Sinapses/metabolismo , Células Acinares/fisiologia , Células Acinares/ultraestrutura , Animais , Animais Recém-Nascidos , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Biomarcadores/metabolismo , Vias Eferentes/crescimento & desenvolvimento , Vias Eferentes/ultraestrutura , Fluoresceína-5-Isotiocianato , Expressão Gênica , Genes Reporter , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Processamento de Imagem Assistida por Computador , Proteínas Luminescentes/genética , Proteínas Luminescentes/metabolismo , Camundongos , Camundongos Transgênicos , Neurônios/ultraestrutura , Imagem Óptica , Sistema Nervoso Parassimpático/crescimento & desenvolvimento , Sistema Nervoso Parassimpático/ultraestrutura , Glândula Submandibular/crescimento & desenvolvimento , Glândula Submandibular/ultraestrutura , Sinapses/ultraestrutura , Antígenos Thy-1/genética , Antígenos Thy-1/metabolismoRESUMO
The suprachiasmatic nucleus (SCN), which is considered to be the master circadian clock in mammals, establishes biological rhythms of approximately 24 h that several organs exhibit. One aspect relevant to the study of the neurofunctional features of biological rhythmicity is the identification of communication pathways between the SCN and other brain areas. As a result, SCN efferent projections have been investigated in several species, including rodents and a few primates. The fibers originating from the two main intrinsic fiber subpopulations, one producing vasoactive intestinal peptide (VIP) and the other producing arginine vasopressin (AVP), exhibit morphological traits that distinguish them from fibers that originate from other brain areas. This distinction provides a parameter to study SCN efferent projections. In this study, we mapped VIP (VIP-ir) and AVP (AVP-ir) immunoreactive (ir) fibers and endings in the hypothalamus of the primate Sapajus apella via immunohistochemical and morphologic study. Regarding the fiber distribution pattern, AVP-ir and VIP-ir fibers were identified in regions of the tuberal hypothalamic area, retrochiasmatic area, lateral hypothalamic area, and anterior hypothalamic area. VIP-ir and AVP-ir fibers coexisted in several hypothalamic areas; however, AVP-ir fibers were predominant over VIP-ir fibers in the posterior hypothalamus and medial periventricular area. This distribution pattern and the receiving hypothalamic areas of the VIP-ir and AVP-ir fibers, which shared similar morphological features with those found in SCN, were similar to the patterns observed in diurnal and nocturnal animals. This finding supports the conservative nature of this feature among different species. Morphometric analysis of SCN intrinsic neurons indicated homogeneity in the size of VIP-ir neurons in the SCN ventral portion and heterogeneity in the size of two subpopulations of AVP-ir neurons in the SCN dorsal portion. The distribution of fibers and morphometric features of these neuronal populations are described and compared with those of other species in the present study.
Assuntos
Arginina Vasopressina/metabolismo , Vias Eferentes/anatomia & histologia , Hipotálamo/anatomia & histologia , Núcleo Supraquiasmático/anatomia & histologia , Peptídeo Intestinal Vasoativo/metabolismo , Animais , Cebus , Vias Eferentes/metabolismo , Vias Eferentes/ultraestrutura , Hipotálamo/metabolismo , Hipotálamo/ultraestrutura , Imuno-Histoquímica , Masculino , Fibras Nervosas/metabolismo , Fibras Nervosas/fisiologia , Fibras Nervosas/ultraestrutura , Área Pré-Óptica/fisiologia , Área Pré-Óptica/ultraestrutura , Núcleo Supraquiasmático/metabolismo , Núcleo Supraquiasmático/ultraestruturaRESUMO
The pre-Bötzinger complex (preBötC) of the ventrolateral medulla is the kernel for inspiratory rhythm generation. However, it is not fully understood how inspiratory neural activity is generated in the preBötC and propagates to other medullary regions. We analyzed the detailed anatomical connectivity to and from the preBötC and functional aspects of the inspiratory information propagation from the preBötC on the transverse plane of the medulla oblongata. Tract-tracing with immunohistochemistry in young adult rats demonstrated that neurokinin-1 receptor- and somatostatin-immunoreactive neurons in the preBötC, which could be involved in respiratory rhythmogenesis, are embedded in the plexus of axons originating in the contralateral preBötC. By voltage-imaging in rhythmically active slices of neonatal rats, we analyzed origination and propagation of inspiratory neural activity as depolarizing wave dynamics on the entire transverse plane as well as within the preBötC. Novel combination of pharmacological blockade of glutamatergic transmission and mathematical subtraction of the video images under blockade from the control images enabled to extract glutamatergic signal propagations. By ultra-high-speed voltage-imaging we first demonstrated the inter-preBötC conduction process of inspiratory action potentials. Intra-preBötC imaging with high spatiotemporal resolution during a single spontaneous inspiratory cycle unveiled deterministic nonlinearities, i.e., chaos, in the population recruitment. Collectively, we comprehensively elucidated the anatomical pathways to and from the preBötC and dynamics of inspiratory neural information propagation: (1) From the preBötC in one side to the contralateral preBötC, which would synchronize the bilateral rhythmogenic kernels, (2) from the preBötC directly to the bilateral hypoglossal premotor and motor areas as well as to the nuclei tractus solitarius, and (3) from the hypoglossal premotor areas toward the hypoglossal motor nuclei. The coincidence of identified anatomical and functional connectivity between the preBötC and other regions in adult and neonatal rats, respectively, indicates that this fundamental connectivity is already well developed at the time of birth.
Assuntos
Inalação/fisiologia , Bulbo/anatomia & histologia , Bulbo/fisiologia , Neurônios/citologia , Neurônios/fisiologia , Potenciais de Ação , Animais , Relógios Biológicos/fisiologia , Vias Eferentes/anatomia & histologia , Vias Eferentes/fisiologia , Vias Eferentes/ultraestrutura , Ácido Glutâmico/metabolismo , Imuno-Histoquímica , Interneurônios/citologia , Interneurônios/fisiologia , Interneurônios/ultraestrutura , Masculino , Bulbo/ultraestrutura , Microscopia Eletrônica , Técnicas de Rastreamento Neuroanatômico , Neurônios/ultraestrutura , Ratos Wistar , Receptores da Neurocinina-1/metabolismo , Centro Respiratório/anatomia & histologia , Centro Respiratório/fisiologia , Centro Respiratório/ultraestrutura , Núcleo Solitário/anatomia & histologia , Núcleo Solitário/fisiologia , Núcleo Solitário/ultraestrutura , Somatostatina/metabolismo , Técnicas de Cultura de Tecidos , Gravação em Vídeo , Imagens com Corantes Sensíveis à VoltagemRESUMO
This study investigated electrophysiological and histological changes as well as alterations of myelin relevant proteins of descending motor tracts in rat pups. Motor-evoked potentials (MEPs) represent descending conducting responses following stimulation of the motor cortex to responses being elicited from the lower extremities. MEP responses were recorded biweekly from postnatal (PN) week 1 to week 9 (adult). MEP latencies in PN week 1 rats averaged 23.7 ms and became shorter during early maturation, stabilizing at 6.6 ms at PN week 4. During maturation, the conduction velocity (CV) increased from 2.8 ± 0.2 at PN week 1 to 35.2 ± 3.1 mm/ms at PN week 8. Histology of the spinal cord and sciatic nerves revealed progressive axonal myelination. Expression of the oligodendrocyte precursor markers PDGFRα and NG2 were downregulated in spinal cords, and myelin-relevant proteins such as GalC, CNP, and MBP increased during maturation. Oligodendrocyte-lineage markers Olig2 and MOG, expressed in myelinated oligodendrocytes, peaked at PN week 3 and were downregulated thereafter. A similar expression pattern was observed in neurofilament M/H subunits that were extensively phosphorylated in adult spinal cords but not in neonatal spinal cords, suggesting an increase in axon diameter and myelin formation. Ultrastructural morphology in the ventrolateral funiculus (VLF) showed axon myelination of the VLF axons (99.3%) at PN week 2, while 44.6% were sheathed at PN week 1. Increased axon diameter and myelin thickness in the VLF and sciatic nerves were highly correlated to the CV (rs > 0.95). This suggests that MEPs could be a predicator of morphological maturity of myelinated axons in descending motor tracts.
Assuntos
Axônios/ultraestrutura , Vias Eferentes/crescimento & desenvolvimento , Potencial Evocado Motor/fisiologia , Bainha de Mielina/ultraestrutura , Oligodendroglia/metabolismo , Medula Espinal/crescimento & desenvolvimento , Animais , Axônios/fisiologia , Vias Eferentes/fisiologia , Vias Eferentes/ultraestrutura , Feminino , Proteínas da Mielina/metabolismo , Oligodendroglia/citologia , Ratos , Ratos Sprague-Dawley , Nervo Isquiático/fisiologia , Medula Espinal/citologia , Medula Espinal/fisiologia , Estimulação Magnética TranscranianaRESUMO
Sound production that is mediated by intrinsic or extrinsic swim bladder musculature has evolved multiple times in teleost fishes. Sonic muscles must contract rapidly and synchronously to compress the gas-filled bladder with sufficient velocity to produce sound. Muscle modifications that may promote rapid contraction include small fiber diameter, elaborate sarcoplasmic reticulum (SR), triads at the A-I boundary, and cores of sarcoplasm. The diversity of innervation patterns indicate that sonic muscles have independently evolved from different trunk muscle precursors. The analysis of sonic motor pathways in distantly related fishes is required to determine the relationships between sonic muscle evolution and function in acoustic signaling. We examined the ultrastructure of sonic and adjacent hypaxial muscle fibers and the distribution of sonic motor neurons in the coral reef Pyramid Butterflyfish (Chaetodontidae: Hemitaurichthys polylepis) that produces sound by contraction of extrinsic sonic muscles near the anterior swim bladder. Relative to adjacent hypaxial fibers, sonic muscle fibers were sparsely arranged among the endomysium, smaller in cross-section, had longer sarcomeres, a more elaborate SR, wider t-tubules, and more radially arranged myofibrils. Both sonic and non-sonic muscle fibers possessed triads at the Z-line, lacked sarcoplasmic cores, and had mitochondria among the myofibrils and concentrated within the peripheral sarcoplasm. Sonic muscles of this derived eutelost possess features convergent with other distant vocal taxa (other euteleosts and non-euteleosts): small fiber diameter, a well-developed SR, and radial myofibrils. In contrast with some sonic fishes, however, Pyramid Butterflyfish sonic muscles lack sarcoplasmic cores and A-I triads. Retrograde nerve label experiments show that sonic muscle is innervated by central and ventrolateral motor neurons associated with spinal nerves 1-3. This restricted distribution of sonic motor neurons in the spinal cord differs from many euteleosts and likely reflects the embryological origin of sonic muscles from hypaxial trunk precursors rather than occipital somites.
Assuntos
Neurônios Motores/ultraestrutura , Músculo Esquelético/inervação , Músculo Esquelético/ultraestrutura , Perciformes/fisiologia , Vocalização Animal , Sacos Aéreos/inervação , Sacos Aéreos/ultraestrutura , Animais , Recifes de Corais , Vias Eferentes/ultraestrutura , Fibras Musculares Esqueléticas/ultraestrutura , Perciformes/anatomia & histologia , Sarcômeros/ultraestrutura , Nervos Espinhais/ultraestruturaRESUMO
The periaqueductal gray (PAG) is a critical brain region involved in opioid analgesia and provides efferents to descending pathways that modulate nociception. In addition, the PAG contains ascending pathways to regions involved in the regulation of reward, including the substantia nigra (SN) and the ventral tegmental area (VTA). SN and VTA contain dopaminergic neurons that are critical for the maintenance of positive reinforcement. Interestingly, the PAG is also reported to contain a population of dopaminergic neurons. In this study, the distribution of catecholaminergic neurons within the ventrolateral (vl) PAG was examined using immunocytochemical methods. In addition, the catecholaminergic PAG neurons were examined to determine whether these neurons are integrated into ascending (VTA, SN) and descending rostral ventral medulla (RVM) efferent pathways from this region. The immunocytochemical analysis determined that catecholaminergic neurons in the PAG are both dopaminergic and noradrenergic and these neurons have a distinct rostrocaudal distribution within the ventrolateral column of PAG. Dopaminergic neurons were concentrated rostrally and were significantly smaller than noradrenergic neurons. Combined immunocytochemistry and tract tracing methods revealed that catecholaminergic neurons are distinct from, but closely associated with, both ascending and descending efferent projection neurons. Finally, by electron microscopy, catecholaminergic neurons showed close dendritic appositions with other neurons in PAG, suggesting a possible nonsynaptic mechanism for regulation of PAG output by these neurons. In conclusion, our data indicate that there are two populations of catecholaminergic neurons in the vlPAG that form dendritic associations with both ascending and descending efferents suggesting a possible nonsynaptic modulation of vlPAG neurons.
Assuntos
Catecolaminas/metabolismo , Vias Eferentes/metabolismo , Neurônios/metabolismo , Substância Cinzenta Periaquedutal/metabolismo , Animais , Vias Eferentes/ultraestrutura , Masculino , Bulbo/metabolismo , Bulbo/ultraestrutura , Neurônios/ultraestrutura , Substância Cinzenta Periaquedutal/ultraestrutura , Ratos , Ratos Sprague-Dawley , Área Tegmentar Ventral/metabolismo , Área Tegmentar Ventral/ultraestruturaRESUMO
We reported pharmacological data suggesting that stimulation of a vago-vagal reflex activates GABAergic neurons in the hindbrain that inhibit dorsal motor nucleus of the vagus (DMV) neurons projecting to the antrum, but not to the fundus (Ferreira et al., 2002). The purpose of this study was to use an ultrastructural approach to test the hypothesis that GABAergic terminals form synapses with DMV antrum-projecting neurons, but not with DMV fundus-projecting neurons. A retrograde tracer, CTB-HRP, was injected into the gastric smooth muscle of either the fundus or the antrum of anesthetized rats. Animals were re-anesthetized 48 h later and perfusion-fixed with acrolein and paraformaldehyde. Brainstems were processed histochemically for CTB-HRP, and immunocytochemically for glutamic acid decarboxylase isoenzyme 67 immunoreactivity (GAD67-IR) by dual-labeling electron microscopic methods. Most cell bodies and dendrites of neurons that were retrogradely labeled from the stomach occurred at the level of the area postrema. Examination of 214 synapses on 195 neurons that projected to the antrum revealed that 23.0+/-3.6% (n = 4) of synaptic contacts were with GAD67-IR terminals. The examination of 220 synapses on 203 fundus-projecting neurons revealed that only 7.9+/-3.1% (n = 4) of synaptic contacts were with GAD67-IR terminals. The difference between GAD67-IR synaptic contacts with antrum- and fundus-projecting neurons was statistically significant (p<0.05). These data suggest that brainstem circuitry controlling the antrum involves GABAergic transmission.
Assuntos
Vias Eferentes/metabolismo , Antro Pilórico/inervação , Nervo Vago/metabolismo , Ácido gama-Aminobutírico/metabolismo , Animais , Vias Eferentes/ultraestrutura , Glutamato Descarboxilase/metabolismo , Imuno-Histoquímica , Microscopia Eletrônica de Transmissão , Antro Pilórico/metabolismo , Ratos , Nervo Vago/ultraestruturaRESUMO
The olfactory bulb receives a large number of centrifugal fibers whose functions remain unclear. To gain insight into the function of the bulbar centrifugal system, the morphology of individual centrifugal axons from olfactory cortical areas was examined in detail. An anterograde tracer, Phaseolus vulgaris leucoagglutinin, was injected into rat olfactory cortical areas, including the pars lateralis of the anterior olfactory nucleus (lAON) and the anterior part of the piriform cortex (aPC). Reconstruction from serial sections revealed that the extrabulbar segments of centrifugal axons from the lAON and those from the aPC had distinct trajectories: the former tended to innervate the pars externa of the AON before entering the olfactory bulb, while the latter had extrabulbar collaterals that extended to a variety of targets. In contrast to the extrabulbar segments, no clear differences were found between the intrabulbar segments of axons from the lAON and from the aPC. The intrabulbar segments of centrifugal axons were mainly found in the granule cell layer but a few axons extended into the external plexiform and glomerular layer. Approximately 40% of centrifugal axons innervated both the medial and lateral aspects of the olfactory bulb. The number of boutons found on single intrabulbar segments was typically less than 1000. Boutons tended to aggregate and form complex terminal tufts with short axonal branches. Terminal tufts, no more than 10 in single axons from ipsilateral cortical areas, were localized to the granule cell layer with varying intervals; some tufts formed patchy clusters and others were scattered over areas that extended for a few millimeters. The patchy, widespread distribution of terminals suggests that the centrifugal axons are able to couple the activity of specific subsets of bulbar neurons even when the subsets are spatially separated.
Assuntos
Axônios/ultraestrutura , Bulbo Olfatório/citologia , Condutos Olfatórios/citologia , Animais , Transporte Axonal , Vias Eferentes/ultraestrutura , Masculino , Fito-Hemaglutininas , Ratos , Ratos WistarRESUMO
Aging is associated with many functional and morphological central nervous system changes. It is important to distinguish between changes created by normal aging and those caused by disease. In the present study we characterized myelin changes within the murine rubrospinal tract and found that internode lengths significantly decrease as a function of age which suggests active remyelination. We also analyzed the proliferation, distribution and phenotypic fate of dividing cells with Bromodeoxyuridine (5-bromo-2-deoxyuridine, BrdU). The data reveal a decrease in glial cell proliferation from 1 to 6, 14 and 21 months of age in gray matter 4 weeks post-BrdU injections. However, we found an increase in gliogenesis at 21st month in white matter of the spinal cord. Half of newly generated cells expressed NG2. Most cells were positive for the early oligodendrocyte marker Olig2 and a few also expressed CC1. Very few cells ever became positive for the astrocytic markers S100beta or GFAP. These data demonstrate ongoing oligodendrogenesis and myelinogenesis as a function of age in the spinal cord.
Assuntos
Envelhecimento/metabolismo , Bainha de Mielina/metabolismo , Fibras Nervosas Mielinizadas/metabolismo , Oligodendroglia/metabolismo , Nós Neurofibrosos/metabolismo , Medula Espinal/metabolismo , Envelhecimento/patologia , Animais , Proteínas Relacionadas à Autofagia , Fatores de Transcrição Hélice-Alça-Hélice Básicos/análise , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Biomarcadores/análise , Biomarcadores/metabolismo , Bromodesoxiuridina , Proliferação de Células , Vias Eferentes/metabolismo , Vias Eferentes/ultraestrutura , Feminino , Peptídeos e Proteínas de Sinalização Intracelular/análise , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Bainha de Mielina/ultraestrutura , Fibras Nervosas Mielinizadas/ultraestrutura , Regeneração Nervosa/fisiologia , Proteínas do Tecido Nervoso/análise , Proteínas do Tecido Nervoso/metabolismo , Fator de Transcrição 2 de Oligodendrócitos , Oligodendroglia/ultraestrutura , Nós Neurofibrosos/ultraestrutura , Núcleo Rubro/metabolismo , Núcleo Rubro/ultraestrutura , Medula Espinal/ultraestruturaRESUMO
We have examined the ultrastructure of the myenteric ganglion of the subdiaphragmatic esophagus and determined whether the ganglion neurons receive direct projections from the dorsal motor nucleus of the vagus (DMV) using wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) as an anterograde tracer. The neurons (22.2 microm x 13.3 microm) of myenteric ganglion in the esophagus contained dark cytoplasm having many free ribosomes, mitochondria, and an oval nucleus, and received only a few axon terminals contacting somata. All axon terminals formed asymmetric synaptic contacts with dendrites or somata. Approximately 85% of the axon terminals contacting dendrites and about 50% of the axon terminals contacting somata contained pleomorphic vesicles, while the rest contained round synaptic vesicles. When WGA-HRP was injected into the DMV, anterogradely labeled fibers and terminals were found in the myenteric ganglia. The WGA-HRP labeled terminals were large (1.97 microm) and contained round clear vesicles and small granular vesicles. These labeled terminals contacted exclusively the small dendrites, but not the somata. These results suggest that the DMV neurons project directly to the myenteric ganglion neurons and regulate the esophageal muscles via the ganglion neurons.
Assuntos
Vias Eferentes/fisiologia , Gânglios Parassimpáticos/fisiologia , Bulbo/fisiologia , Sinapses/fisiologia , Nervo Vago/fisiologia , Animais , Vias Eferentes/ultraestrutura , Gânglios Parassimpáticos/ultraestrutura , Masculino , Bulbo/ultraestrutura , Microscopia Eletrônica de Transmissão/métodos , Neurônios/fisiologia , Neurônios/ultraestrutura , Ratos , Ratos Sprague-Dawley , Sinapses/ultraestrutura , Conjugado Aglutinina do Germe de Trigo-Peroxidase do Rábano Silvestre/metabolismoRESUMO
The baroreflex control of heart rate (HR) is reduced following chronic intermittent hypoxia (CIH). Since the nucleus ambiguus (NA) plays a key role in baroreflex control of HR, we examined whether CIH remodels vagal efferent projections to cardiac ganglia. C57BL/6J mice (3-4 months of age) were exposed to either room air (RA) or CIH for 3 months. Confocal microscopy was used to examine NA axons and terminals in cardiac ganglia following Fluoro-Gold (FG) injections to label cardiac ganglia, and microinjections of tracer DiI into the left NA to anterogradely label vagal efferents. We found that: 1) Cardiac ganglia were widely distributed on the dorsal surface of the atria. Although the total number of cardiac ganglia did not differ between RA and CIH mice, the size of ganglia and the somatic area of cardiac principal neurons (PNs) were significantly decreased (P < 0.01), and the size of the PN nuclei was increased following CIH (P < 0.01). 2) NA axons entered cardiac ganglia and innervated PNs with dense basket endings in both RA and CIH mice, and the percentage of innervated PNs was similar (RA: 50 +/- 1.0%; CIH: 49 +/- 1.0%; P > 0.10). In CIH mice, however, swollen cardiac axons and terminals without close contacts to PNs were found. Furthermore, varicose endings around PNs appeared swollen and the axonal varicose area around PNs was almost doubled in size (CIH: 163.1 +/- 6.4 microm(2); RA: 88 +/- 3.9 microm(2), P < 0.01). Thus, CIH significantly altered the structure of cardiac ganglia and resulted in reorganized vagal efferent projections to cardiac ganglia. Such remodeling of cardiac ganglia and vagal efferent projections provides new insight into the effects of CIH on the brain-heart circuitry of C57BL/6J mice.
Assuntos
Gânglios Simpáticos/fisiologia , Gânglios Simpáticos/ultraestrutura , Hipóxia/patologia , Animais , Barorreflexo/fisiologia , Doença Crônica , Vias Eferentes/fisiologia , Vias Eferentes/ultraestrutura , Frequência Cardíaca/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Fatores de TempoRESUMO
Cochlear root neurons (CRNs) are involved in the acoustic startle reflex, which is widely used in behavioral models of sensorimotor integration. A short-latency component of this reflex, the auricular reflex, promotes pinna movements in response to unexpected loud sounds. However, the pathway involved in the auricular component of the startle reflex is not well understood. We hypothesized that the auricular reflex is mediated by direct and indirect inputs from CRNs to the motoneurons responsible for pinna movement, which are located in the medial subnucleus of the facial motor nucleus (Mot7). To assess whether there is a direct connection between CRNs and auricular motoneurons in the rat, two neuronal tracers were used in conjunction: biotinylated dextran amine, which was injected into the cochlear nerve root, and Fluoro-Gold, which was injected into the levator auris longus muscle. Under light microscopy, close appositions were observed between axon terminals of CRNs and auricular motoneurons. The presence of direct synaptic contact was confirmed at the ultrastructural level. To confirm the indirect connection, biotinylated dextran amine was injected into the auditory-responsive portion of the caudal pontine reticular nucleus, which receives direct input from CRNs. The results confirm that the caudal pontine reticular nucleus also targets the Mot7 and that its terminals are concentrated in the medial subnucleus. Therefore, it is likely that CRNs innervate auricular motoneurons both directly and indirectly, suggesting that these connections participate in the rapid auricular reflex that accompanies the acoustic startle reflex.
Assuntos
Nervo Coclear/ultraestrutura , Pavilhão Auricular/inervação , Vias Eferentes/ultraestrutura , Neurônios Motores/ultraestrutura , Neurônios/ultraestrutura , Reflexo Acústico/fisiologia , Animais , Feminino , Córtex Motor/ultraestrutura , Ratos , Ratos Wistar , Reflexo de Sobressalto/fisiologiaRESUMO
The ventral posterior nucleus of the thalamus (VP) receives two major sets of excitatory inputs, one from the ascending somatosensory pathways originating in the dorsal horn, dorsal column nuclei, and trigeminal nuclei, and the other originating from the cerebral cortex. Both systems use glutamate as neurotransmitter, as do the thalamocortical axons relaying somatosensory information from the VP to the primary somatosensory cortex (SI). The synapses formed by these projection systems differ anatomically, physiologically, and in their capacity for short-term synaptic plasticity. Glutamate uptake into synaptic vesicles and its release at central synapses depend on two isoforms of vesicular glutamate transporters, VGluT1 and VGluT2. Despite ample evidence of their complementary distribution, some instances exist of co-localization in the same brain areas or at the same synapses. In the thalamus, the two transcripts coexist in cells of the VP and other nuclei but not in the posterior or intralaminar nuclei. We show that the two isoforms are completely segregated at VP synapses, despite their widespread expression throughout the dorsal and ventral thalamus. We present immunocytochemical, ultrastructural, gene expression, and connectional evidence that VGluT1 in the VP is only found at corticothalamic synapses, whereas VGluT2 is only found at terminals made by axons originating in the spinal cord and brainstem. By contrast, the two VGluT isoforms are co-localized in thalamocortical axon terminals targeting layer IV, but not in those targeting layer I, suggesting the presence of two distinct projection systems related to the core/matrix pattern of organization of thalamocortical connectivity described in other mammals.
Assuntos
Ácido Glutâmico/metabolismo , Terminações Pré-Sinápticas/metabolismo , Núcleos Ventrais do Tálamo/metabolismo , Proteína Vesicular 1 de Transporte de Glutamato/metabolismo , Proteína Vesicular 2 de Transporte de Glutamato/metabolismo , Vias Aferentes/metabolismo , Vias Aferentes/ultraestrutura , Animais , Biomarcadores/análise , Biomarcadores/metabolismo , Mapeamento Encefálico/métodos , Tronco Encefálico/metabolismo , Tronco Encefálico/ultraestrutura , Vias Eferentes/metabolismo , Vias Eferentes/ultraestrutura , Expressão Gênica/fisiologia , Hibridização In Situ , Camundongos , Microscopia Confocal , Microscopia Imunoeletrônica , Terminações Pré-Sinápticas/ultraestrutura , RNA Mensageiro/análise , RNA Mensageiro/metabolismo , Córtex Somatossensorial/metabolismo , Córtex Somatossensorial/ultraestrutura , Medula Espinal/metabolismo , Medula Espinal/ultraestrutura , Transmissão Sináptica/fisiologia , Núcleos Ventrais do Tálamo/ultraestrutura , Proteína Vesicular 1 de Transporte de Glutamato/genética , Proteína Vesicular 2 de Transporte de Glutamato/genéticaRESUMO
Kappa opioid receptor (KOR) ligands alter nociceptive responses when applied to the rostral ventromedial medulla (RVM). However, the effects of kappa opioid receptor ligands are distinct in males and females. The present study examined the distribution of kappa opioid receptor immunoreactivity in the RVM of male and female rats. KOR immunoreactivity was found at pre- and postsynaptic sites within the RVM of both sexes. The most common KOR-immunoreactive (KOR-ir) neuronal structures were unmyelinated axons, followed by axon terminals, dendrites, and somata. Different proportions of KOR-ir axon terminals and dendrites were found in females at different estrous stages. Specifically, dendrites containing KOR immunoreactivity were less abundant in proestrus females compared with estrus females and showed a trend toward being less abundant in males, suggesting that KOR ligands applied to the RVM may be less potent in proestrus females. These findings suggest that the distribution of KORs in the RVM may be influenced by reproductive hormone levels. We also found KOR immunoreactivity in many spinally projecting neurons within the RVM of female rats. These findings are consistent with the hypothesis that KOR ligands influence nociceptive behaviors by altering the activity of specific populations of neurons within the RVM. The abundance of KOR in axons and axon terminals in RVM indicates a substantial role for presynaptic effects of KOR ligands through pathways that have not been clearly delineated. Altering the balance between pre- and postsynaptic receptive sites may underlie differences in the effects of KOR agonists on nociceptive responses in males and females.
Assuntos
Bulbo/metabolismo , Neurônios/metabolismo , Receptores Opioides kappa/metabolismo , Reprodução/fisiologia , Formação Reticular/metabolismo , Caracteres Sexuais , Animais , Dendritos/metabolismo , Dendritos/ultraestrutura , Vias Eferentes/metabolismo , Vias Eferentes/ultraestrutura , Ciclo Estral/fisiologia , Feminino , Hormônios Esteroides Gonadais/metabolismo , Imuno-Histoquímica , Masculino , Bulbo/ultraestrutura , Microscopia Eletrônica de Transmissão , Fibras Nervosas Amielínicas/metabolismo , Fibras Nervosas Amielínicas/ultraestrutura , Neurônios/ultraestrutura , Peptídeos Opioides/metabolismo , Terminações Pré-Sinápticas/metabolismo , Terminações Pré-Sinápticas/ultraestrutura , Ratos , Formação Reticular/ultraestrutura , Membranas Sinápticas/metabolismo , Membranas Sinápticas/ultraestrutura , Transmissão Sináptica/fisiologiaRESUMO
The causative gene for the reeler mouse is reelin which encodes Reelin protein, an extracellular molecule. In the present study, we have examined the cytoarchitecture, myeloarchitecture, and afferent/efferent systems of the superior colliculus (SC) of the reeler mouse. In the reeler, the laminar structures of the superficial three layers of the SC were disorganized and intermingled into a single layer, i.e., the superficial fused layer (SuF), as previously reported in the reelin-deficient SRK rat (Sakakibara et al., Develop. Brain Res. 141:1-13). Next, we have investigated the course and terminals of visual corticotectal and retinotectal projections with an injection of biocytin into the visual cortex or an injection of cholera toxin subunit B into the retina, respectively. In the reeler, anterogradely labeled visual corticotectal and retinotectal fibers took an aberrant course within the SuF, resulting in abnormal myeloarchitecture of the superficial SC of the reeler. Retrograde labeling of tectospinal tract neurons could not show any differences between the normal and reeler mice, suggesting that the deep layers of the reeler SC are cytoarchitectually normal. In situ hybridization and immunohistochemical studies have shown that reelin mRNA and Reelin protein were both recognized in the normal SC. These results suggest that Reelin protein plays some roles in histogenesis of the superficial layers of the SC.
Assuntos
Camundongos Mutantes Neurológicos/anatomia & histologia , Proteína Básica da Mielina/metabolismo , Colículos Superiores/metabolismo , Colículos Superiores/ultraestrutura , Animais , Moléculas de Adesão Celular Neuronais/genética , Moléculas de Adesão Celular Neuronais/metabolismo , Toxina da Cólera/metabolismo , Vias Eferentes/metabolismo , Vias Eferentes/ultraestrutura , Proteínas da Matriz Extracelular/genética , Proteínas da Matriz Extracelular/metabolismo , Peroxidase do Rábano Silvestre/metabolismo , Hibridização In Situ/métodos , Lisina/análogos & derivados , Lisina/metabolismo , Camundongos , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Proteína Reelina , Retina/metabolismo , Serina Endopeptidases/genética , Serina Endopeptidases/metabolismo , Córtex Visual/metabolismo , Vias Visuais/metabolismo , Vias Visuais/ultraestruturaRESUMO
Age-related changes in the number and size of large cholinergic terminals immunoreactive for vesicular acetylcholine transporter (VAChT), were documented for the dorsolateral nucleus (DLN), retrodorsolateral nucleus (RDLN) and spinal nucleus of the bulbospongiosus (SNB) of the lumbosacral spinal cord of male rats. The most significant changes were a large increase in the number and size of cholinergic terminals within the DLN of aged animals, together with a small decrease in terminal number within the RDLN. No significant age-associated differences in VAChT labeling were seen within the SNB. In both age groups, SNB motoneurons projecting to the levator ani muscle received about 9 to 10 contacts from large cholinergic terminals. Ultrastructural examination of the terminals revealed structures likely to be postsynaptic subsurface cisterns that are characteristic of type C terminal boutons. Since both the DLN and SNB contain motoneurons innervating pelvic muscles and sphincters, these findings provide further evidence for a central cholinergic influence on micturition and sexual reflexes and suggest that this may remain robust in the face of ageing.
Assuntos
Envelhecimento , Vias Eferentes/metabolismo , Neurônios Motores/metabolismo , Pelve/inervação , Medula Espinal/fisiologia , Proteínas Vesiculares de Transporte de Acetilcolina/metabolismo , Análise de Variância , Animais , Toxina da Cólera/metabolismo , Vias Eferentes/ultraestrutura , Imuno-Histoquímica , Região Lombossacral , Masculino , Microscopia Imunoeletrônica/métodos , Neurônios Motores/ultraestrutura , Ratos , Ratos WistarAssuntos
Drosophila/fisiologia , Vias Eferentes/fisiologia , Junção Neuromuscular/fisiologia , Animais , Vias Eferentes/crescimento & desenvolvimento , Vias Eferentes/ultraestrutura , Junção Neuromuscular/ultraestrutura , Terminações Pré-Sinápticas/fisiologia , Terminações Pré-Sinápticas/ultraestrutura , Sinapses/fisiologia , Sinapses/ultraestruturaRESUMO
The myenteric ganglia regulate not only gastric motility but also secretion, because a submucous plexus is sparsely developed in the rodent stomach. We have examined whether the neurons of the dorsal motor nucleus of the vagus (DMV) have direct synaptic contacts on the myenteric ganglia and the ultrastructure of the vagal efferent terminals by using wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP). The myenteric ganglia of the rat were composed of four types of neurons, i.e., small, medium-sized, large, and elongated neurons. The average numbers of axosomatic terminals per profile were 2.0 on the small neurons, 3.1 on the medium-sized neurons, 1.2 on the large neurons, and 4.2 on the elongated neuron. More than half of the axosomatic terminals contained round vesicles and formed asymmetric synaptic contacts on the small, medium-sized, and large neurons. About 80% of the axosomatic terminals on the elongated neurons contained pleomorphic vesicles and formed asymmetric synaptic contacts. When WGA-HRP was injected into the DMV, many anterogradely labeled terminals were found around the myenteric neurons. The labeled terminals were large (3.16 +/- 0.10 microm) and contacted exclusively the somata. Most of them (about 90%) contained round vesicles and formed asymmetric synaptic contacts. Serial ultrathin sections revealed that almost all neurons in a ganglion received projections from the DMV. The vagal axon terminals generally contacted the medium-sized or the elongated neurons, whereas a few labeled terminals contacted the small and the large neurons. The present results indicate that the DMV projects to all types of neurons and that their axon terminals contain mostly round synaptic vesicles and form asymmetric synaptic contacts.
Assuntos
Vias Eferentes/ultraestrutura , Gânglios Parassimpáticos/ultraestrutura , Bulbo/ultraestrutura , Plexo Mientérico/ultraestrutura , Sinapses/ultraestrutura , Nervo Vago/ultraestrutura , Animais , Vias Eferentes/fisiologia , Gânglios Parassimpáticos/fisiologia , Masculino , Bulbo/fisiologia , Microscopia Eletrônica de Transmissão , Músculo Liso/inervação , Músculo Liso/ultraestrutura , Plexo Mientérico/fisiologia , Peristaltismo/fisiologia , Terminações Pré-Sinápticas/fisiologia , Terminações Pré-Sinápticas/ultraestrutura , Ratos , Ratos Sprague-Dawley , Estômago/inervação , Estômago/ultraestrutura , Sinapses/fisiologia , Membranas Sinápticas/fisiologia , Membranas Sinápticas/ultraestrutura , Vesículas Sinápticas/fisiologia , Vesículas Sinápticas/ultraestrutura , Nervo Vago/fisiologia , Conjugado Aglutinina do Germe de Trigo-Peroxidase do Rábano SilvestreRESUMO
Blood pressure in women increases after menopause, and sympathetic tone in female rats decreases with estrogen injections in the rostral ventrolateral medulla (RVLM) region that contains bulbospinal C1 adrenergic neurons and is involved in blood pressure control. We investigated the anatomical and physiological basis for estrogen effects in the RVLM. Neurons with alpha- or beta-subtypes of estrogen receptor (ER) immunoreactivity (-ir) overlapped in distribution with tyrosine hydroxylase (TH)-containing C1 neurons. Immunoelectron microscopy revealed that ERalpha- and ERbeta-ir had distinct cellular and subcellular distributions. ERalpha-ir was most commonly in TH-lacking profiles, many of which were axons and peptide-containing afferents that contacted TH-containing dendrites. ERalpha-ir was also in some TH-containing dendrites. ERbeta-ir was most frequently in TH-containing somata and dendrites, particularly on endoplasmic reticula, mitochondria, and plasma membranes. In whole-cell patch clamp recordings from isolated bulbospinal RVLM neurons, 17beta-estradiol dose-dependently reduced voltage-gated Ca(++) currents, especially the long-lasting (L-type) component. This inhibition was reversed by washing or prevented by adding the non-subtype-selective ER antagonist ICI182780. An ERbeta-selective agonist, but not an ERalpha-selective agonist, reproduced the Ca(++) current inhibition. The data indicate that estrogens can modulate the function of RVLM C1 bulbospinal neurons either directly, through extranuclear ERbeta, or indirectly through extranuclear ERalpha in selected afferents. Moreover, Ca(++) current inhibition may underlie the decrease in sympathetic tone evoked by local 17beta-estradiol application. These findings provide a structural and functional basis for the effects of estrogens on blood pressure control and suggest a mechanism for the modulation of cardiovascular function by estrogen in women.
Assuntos
Vias Eferentes/metabolismo , Epinefrina/metabolismo , Estrogênios/metabolismo , Bulbo/metabolismo , Medula Espinal/metabolismo , Sistema Nervoso Simpático/metabolismo , Animais , Pressão Sanguínea/efeitos dos fármacos , Pressão Sanguínea/fisiologia , Dendritos/metabolismo , Dendritos/ultraestrutura , Relação Dose-Resposta a Droga , Vias Eferentes/efeitos dos fármacos , Vias Eferentes/ultraestrutura , Estradiol/metabolismo , Estradiol/farmacologia , Congêneres do Estradiol/farmacologia , Antagonistas de Estrogênios/farmacologia , Receptor alfa de Estrogênio/agonistas , Receptor alfa de Estrogênio/antagonistas & inibidores , Receptor alfa de Estrogênio/metabolismo , Receptor beta de Estrogênio/agonistas , Receptor beta de Estrogênio/antagonistas & inibidores , Receptor beta de Estrogênio/metabolismo , Estrogênios/farmacologia , Feminino , Hipertensão/etiologia , Hipertensão/fisiopatologia , Bulbo/efeitos dos fármacos , Bulbo/ultraestrutura , Potenciais da Membrana/efeitos dos fármacos , Potenciais da Membrana/fisiologia , Técnicas de Patch-Clamp , Pós-Menopausa/metabolismo , Terminações Pré-Sinápticas/metabolismo , Terminações Pré-Sinápticas/ultraestrutura , Ratos , Ratos Sprague-Dawley , Medula Espinal/efeitos dos fármacos , Medula Espinal/ultraestrutura , Sistema Nervoso Simpático/efeitos dos fármacos , Sistema Nervoso Simpático/ultraestrutura , Tirosina 3-Mono-Oxigenase/metabolismoRESUMO
Mammalian retinas are innervated by histaminergic axons that originate from perikarya in the posterior hypothalamus. To identify the targets of these retinopetal axons, we localized histamine receptors (HR) in monkey and rat retinas by light and electron microscopy. In monkeys, puncta containing HR3 were found at the tips of ON-bipolar cell dendrites in cone pedicles and rod spherules, closer to the photoreceptors than the other neurotransmitter receptors. This is the first ultrastructural localization of any histamine receptor and the first direct evidence that HR3 is present on postsynaptic membranes in the central nervous system. In rat retinas, most HR1 were localized to dopaminergic amacrine cells. The differences in histamine receptor localization may reflect the differences in the activity patterns of the two species.