RESUMEN

Nerve injury can produce hypersensitivity to noxious and normally innocuous stimulation. Injury-induced central (i.e. spinal) sensitization is thought to arise from enhanced afferent input to the spinal cord and to be critical for expression of behavioral hypersensitivity. Descending facilitatory influences from the rostral ventromedial medulla have been suggested to also be critical for the maintenance, though not the initiation, of experimental neuropathic pain. The possibility that descending facilitation from the rostral ventromedial medulla is required for the maintenance of central sensitization was examined by determining whether ablation of mu-opioid receptor-expressing cells within the rostral ventromedial medulla prevented the enhanced expression of repetitive touch-evoked FOS within the spinal cord of animals with spinal nerve ligation injury as well as nerve injury-induced behavioral hypersensitivity. Rats received a single microinjection of vehicle, saporin, dermorphin or dermorphin-saporin into the rostral ventromedial medulla and 28 days later, underwent either sham or spinal nerve ligation procedures. Animals receiving rostral ventromedial medulla pretreatment with vehicle, dermorphin or saporin that were subjected to spinal nerve ligation demonstrated both thermal and tactile hypersensitivity, and showed significantly increased expression of touch-evoked FOS in the dorsal horn ipsilateral to nerve injury compared with sham-operated controls at days 3, 5 or 10 post-spinal nerve ligation. In contrast, nerve-injured animals pretreated with dermorphin-saporin showed enhanced behaviors and touch-evoked FOS expression in the spinal dorsal horn at day 3, but not days 5 and 10, post-spinal nerve ligation when compared with sham-operated controls. These results indicate the presence of nerve injury-induced behavioral hypersensitivity associated with nerve injury-induced central sensitization. Further, the results demonstrate the novel concept that once initiated, maintenance of nerve injury-induced central sensitization in the spinal dorsal horn requires descending pain facilitation mechanisms arising from the rostral ventromedial medulla.

Asunto(s)

Bulbo Raquídeo/fisiología , Dimensión del Dolor/métodos , Traumatismos de los Nervios Periféricos , Nervios Periféricos/fisiología , Tractos Piramidales/fisiología , Animales , Masculino , Ratas , Ratas Sprague-Dawley

RESUMEN

The calbindin-immunoreactivity of spinothalamic (STT) lamina I neurons and their ascending axons was examined in two experiments. In the first experiment, lamina I STT neurons in macaque monkeys were double-labeled for calbindin and for retrogradely transported WGA*HRP following large (n=2) or small (n=1) injections that included the posterior thalamus. Most, but not all (78%) of the contralateral retrogradely labeled lamina I STT cells were positive for calbindin. Calbindin-immunoreactivity was not selectively associated with any particular anatomical type of lamina I STT cell; 82% of the fusiform cells, 78% of the pyramidal cells and 67% of the multipolar cells were double-labeled. In the second experiment, oblique transverse sections from upper cervical spinal segments of three macaque monkeys, one squirrel monkey and five humans were stained for calbindin-immunoreactivity. In each case, a distinct bundle of fibers was densely stained in the middle of the lateral funiculus. This matches the location of anterogradely labeled ascending lamina I axons observed in prior work in cats and monkeys, and it matches the location of the classically described 'lateral spinothalamic tract' in humans. This bundle had variable shape across cases, an observation that might have clinical significance. These findings support the view that lamina I STT neurons are involved in spinal cordotomies that reduce pain, temperature and itch sensations.

Asunto(s)

Axones/química , Neuronas/química , Proteína G de Unión al Calcio S100/análisis , Tractos Espinotalámicos/citología , Animales , Anticuerpos , Calbindinas , Cordotomía , Desnervación , Humanos , Macaca , Sondas Moleculares , Neuronas/ultraestructura , Nociceptores/fisiología , Proteína G de Unión al Calcio S100/inmunología , Tractos Espinotalámicos/química , Termorreceptores/fisiología , Aglutinina del Germen de Trigo-Peroxidasa de Rábano Silvestre Conjugada

RESUMEN

The nonopioid actions of spinal dynorphin may promote aspects of abnormal pain after nerve injury. Mechanistic similarities have been suggested between opioid tolerance and neuropathic pain. Here, the hypothesis that spinal dynorphin might mediate effects of sustained spinal opioids was explored. Possible abnormal pain and spinal antinociceptive tolerance were evaluated after intrathecal administration of [D-Ala(2), N-Me-Phe(4), Gly-ol(5)]enkephalin (DAMGO), an opioid mu agonist. Rats infused with DAMGO, but not saline, demonstrated tactile allodynia and thermal hyperalgesia of the hindpaws (during the DAMGO infusion) and a decrease in antinociceptive potency and efficacy of spinal opioids (tolerance), signs also characteristic of nerve injury. Spinal DAMGO elicited an increase in lumbar dynorphin content and a decrease in the mu receptor immunoreactivity in the spinal dorsal horn, signs also seen in the postnerve-injury state. Intrathecal administration of dynorphin A(1-17) antiserum blocked tactile allodynia and reversed thermal hyperalgesia to above baseline levels (i.e., antinociception). Spinal dynorphin antiserum, but not control serum, also reestablished the antinociceptive potency and efficacy of spinal morphine. Neither dynorphin antiserum nor control serum administration altered baseline non-noxious or noxious thresholds or affected the intrathecal morphine antinociceptive response in saline-infused rats. These data suggest that spinal dynorphin promotes abnormal pain and acts to reduce the antinociceptive efficacy of spinal opioids (i.e., tolerance). The data also identify a possible mechanism for previously unexplained clinical observations and offer a novel approach for the development of strategies that could improve the long-term use of opioids for pain.

Asunto(s)

Analgésicos Opioides/administración & dosificación , Tolerancia a Medicamentos , Dinorfinas/metabolismo , Hiperalgesia/metabolismo , Médula Espinal/metabolismo , Analgésicos/administración & dosificación , Animales , Dinorfinas/antagonistas & inhibidores , Dinorfinas/farmacología , Encefalina Ala(2)-MeFe(4)-Gli(5)/administración & dosificación , Miembro Posterior , Calor , Hiperalgesia/inducido químicamente , Sueros Inmunes/administración & dosificación , Inmunohistoquímica , Inyecciones Espinales , Masculino , Morfina/administración & dosificación , Dimensión del Dolor/efectos de los fármacos , Pruebas de Precipitina , Ratas , Ratas Sprague-Dawley , Tiempo de Reacción/efectos de los fármacos , Receptores Opioides mu/agonistas , Receptores Opioides mu/metabolismo , Umbral Sensorial/efectos de los fármacos , Médula Espinal/citología , Médula Espinal/efectos de los fármacos , Tacto

RESUMEN

Previous studies in the macaque monkey have identified a thalamic nucleus, the posterior portion of the ventral medial nucleus (VMpo), as a dedicated lamina I spinothalamocortical relay for pain and temperature sensation. The dense plexus of calbindin-immunoreactive fibres that characterizes VMpo in primates enables its homologue to be identified in the human thalamus by immunohistochemical labelling for calbindin. We have now analysed in detail the cytoarchitectonic characteristics of VMpo and its relationship with immunoreactivity for calbindin, substance P and calcitonin gene-related peptide (CGRP) in the human thalamus. The area in the posterolateral thalamus in which dense calbindin-immunoreactive fibre terminations are present coincides nearly completely with a distinct region that contains small to medium-sized cells with round or oval shapes that are aggregated in clusters separated by cell sparse areas. This region, which we identify as VMpo, is located posteromedial to the ventral posterior lateral (VPL) and ventral posterior medial (VPM) nuclei, ventral to the anterior pulvinar and centre médian nuclei, lateral to the limitans and parafascicular nuclei and dorsal to the medial geniculate nucleus. Calbindin-immunoreactive fibres enter VMpo from the spinal lemniscus and form large patches of dense terminal-like staining over clusters of VMpo neurons. A few of these clusters also display terminal-like substance P labelling. Small bursts of CGRP staining are intercalated between the calbindin-labelled clusters, but there is little or no overlap between these two markers. CGRP immunoreactivity is also present over small, non-clustered neurons in the calbindin-negative area that separates VMpo from the VPL and VPM nuclei, which we denote as the posterior nucleus (Po). These observations provide a concise description of VMpo in the human thalamus. Further, they suggest that the lamina I spinothalamic tract fibres (represented by calbindin and probably also substance P immunoreactivity) and vagal-solitary-parabrachial afferents (represented by CGRP immunoreactivity) form closely related, but separate, termination fields that can be considered to represent different aspects of enteroceptive information regarding the physiological status of the tissues and organs of the body. The location of VMpo and the adjacent Po fits with clinical descriptions of the thalamic area from which pain, temperature and visceral sensations can be evoked by microstimulation, and where nociceptive and thermoreceptive neurons have been recorded in humans. It also corresponds to the area in which infarcts cause analgesia and thermoanaesthesia and can lead to the paradoxical development of central pain.

Asunto(s)

Dolor/patología , Dolor/fisiopatología , Tractos Espinotalámicos/citología , Núcleos Talámicos Ventrales/química , Núcleos Talámicos Ventrales/citología , Vías Aferentes , Anciano , Anciano de 80 o más Años , Péptido Relacionado con Gen de Calcitonina/análisis , Tamaño de la Célula , Femenino , Humanos , Técnicas para Inmunoenzimas , Masculino , Persona de Mediana Edad , Neuronas/química , Neuronas/citología , Neuronas/fisiología , Tractos Espinotalámicos/fisiopatología , Sustancia P/análisis

RESUMEN

In cat and monkey, lamina I cells can be classified into three basic morphological types (fusiform, pyramidal, and multipolar), and recent intracellular labeling evidence in the cat indicates that fusiform and multipolar lamina I cells are two different types of nociceptive cells, whereas pyramidal cells are innocuous thermoreceptive-specific. Because earlier observations indicated that only nociceptive dorsal horn neurons respond to substance P (SP), we examined which morphological types of lamina I neurons express receptors for SP (NK-1r). We categorized NK-1r-immunoreactive (IR) lamina I neurons in serial horizontal sections from the cervical and lumbar enlargements of four monkeys. Consistent results were obtained by two independent teams of observers. Nearly all NK-1r-IR cells were fusiform (42%) or multipolar (43%), but only 6% were pyramidal (with 9% unclassified). We obtained similar findings in three monkeys in which we used double-labeling immunocytochemistry to identify NK-1r-IR and spinothalamic lamina I neurons retrogradely labeled with cholera toxin subunit b from the thalamus; most NK-1r-IR lamina I spinothalamic neurons were fusiform (48%) or multipolar (33%), and only 10% were pyramidal. In contrast, most (approximately 75%) pyramidal and some (approximately 25%) fusiform and multipolar lamina I spinothalamic neurons did not display NK-1r immunoreactivity. These data indicate that most fusiform and multipolar lamina I neurons in the monkey can express NK-1r, consistent with the idea that both types are nociceptive, whereas only a small proportion of lamina I pyramidal cells express this receptor, consistent with the previous finding that they are non-nociceptive. However, these findings also indicate that not all nociceptive lamina I neurons express receptors for SP.

Asunto(s)

Neuronas/clasificación , Neuronas/citología , Células Piramidales/citología , Receptores de Neuroquinina-1/análisis , Médula Espinal/citología , Animales , Transporte Axonal , Gatos , Toxina del Cólera , Inmunohistoquímica , Macaca fascicularis , Macaca mulatta , Neuronas/fisiología , Células Piramidales/fisiología , Médula Espinal/fisiología

RESUMEN

An immunohistochemically distinct zone was identified in the superficial aspect of trigeminal nucleus caudalis of the New World owl monkey that is not immunoreactive for substance P or serotonin, in stark contrast to the dense staining present in the surrounding laminae I and II. Thionin-stained sections in different planes showed that this is a subregion of lamina I containing clusters of neurons that appear to have pyramidal or polygonal somata. Extracellular microelectrode recordings in this region revealed clusters of thermoreceptive-specific (COLD) cells with nasal or labial receptive fields, whereas nociceptive neurons were found in the adjacent portions of lamina I. Anterograde tracer injections in this region produced trigeminothalamic terminal labeling in the site homologous to the lamina I spino-thalamo-cortical relay nucleus identified previously in the Old World macaque monkey and in humans. Retrograde tracer injections involving this thalamic site, where recordings of trigeminal COLD-like neurons were obtained, produced clusters of retrogradely labeled trigeminothalamic neurons in this immunohistochemically distinct subregion of lamina I, nearly all of which are pyramidal neurons. We conclude that the nocturnal owl monkey has a specialized perinasal thermoreceptive trigeminothalamic sensory pathway that is probably of behavioral significance during olfactory sniffing. In addition, these observations corroborate other findings that have indicated that lamina I COLD cells are pyramidal neurons and are not physiologically modulated by substance P or serotonin, in contrast to nociceptive neurons.

Asunto(s)

Aotidae/fisiología , Termorreceptores/fisiología , Núcleo Caudal del Trigémino/fisiología , Vías Aferentes/fisiología , Animales , Electrofisiología , Femenino , Inmunohistoquímica , Masculino , Nariz/inervación , Tálamo/fisiología

RESUMEN

Pain and temperature stimuli activate neurons of lamina I within the dorsal horn of the spinal cord, and although these neurons can be classified into three basic morphological types and three major physiological classes, earlier studies did not establish a structure/function correlation between their morphology and their physiological responses. We recorded and intracellularly labeled 38 cat lamina I neurons. All 12 fusiform cells were nociceptive-specific, responsive only to pinch and/or heat. All 11 pyramidal cells were thermoreceptive-specific, responsive only to innocuous cooling. Of ten multipolar cells, six were polymodal, responsive to heat, pinch and cold, and four were nociceptive-specific. Five unclassified cells had features consistent with this pattern. These results support the view that central pain and temperature pathways contain anatomically discrete sets of modality-selective neurons.

Asunto(s)

Neuronas/fisiología , Nociceptores/fisiología , Médula Espinal/fisiología , Termorreceptores/fisiología , Animales , Gatos , Frío , Electrofisiología , Femenino , Calor , Masculino , Neuronas/citología , Dolor/fisiopatología , Estimulación Física , Células Piramidales/fisiología , Médula Espinal/citología

RESUMEN

Lamina I spinothalamic tract (STT) neurons were identified by retrograde labeling with cholera toxin subunit b (CTb) in monkeys. On the basis of the criteria of somatal shape and dendritic orientation in horizontal sections used in prior work in the cat, three distinct morphological types were recognized: fusiform (F) cells with spindle-shaped somata and two main longitudinal dendritic arbors; pyramidal (P) cells with triangular somata and three main dendrites oriented primarily longitudinally; and multipolar (M) cells with polygonal somata and four or more dendrites directed longitudinally and mediolaterally. Some cells had transitional shapes, but cells with indeterminate shapes and a few with small round, unipolar, or eccentric somata were grouped as unclassified (U). Greater variation appeared in the monkey than had been seen in the cat, and more subtypes were noted. The overall proportions of these cell types were: 47% F, 27% P, 22% M, and 5% U. Differential longitudinal distributions were found over the length of the spinal cord (from the second cervical through the first coccygeal segments). Pyramidal and multipolar cells together predominated in the enlargements, whereas fusiform cells predominated in thoracic segments. We conclude that three distinct morphological types of lamina I STT cells are present in the monkey as in the cat. Considered with other recent findings, the present results support the possibility that these three cell types may correspond to distinct physiological classes of nociceptive and thermoreceptive lamina I STT cells.

Asunto(s)

Neuronas Aferentes/fisiología , Tractos Espinotalámicos/anatomía & histología , Animales , Macaca

RESUMEN

Despite the evidence for immunological reactions in the human CNS, in viral encephalitis and in multiple sclerosis, connections between the brain and the immune system are poorly understood. In rodents, tracers injected into the interstitial fluid of the brain drain to the cervical lymph nodes by perivascular pathways in the brain and nasal lymphatics. Similar pathways could serve as lymphatics in the human brain. In the present study, we test the hypothesis that lymphatic drainage of the brain and cervical lymph nodes play a key role in T-cell mediated immunity of the brain. Experimental allergic encephalomyelitis (EAE) was induced in Lewis rats by the injection of guinea pig spinal cord homogenate in complete Freund's adjuvant into the foot pads. This resulted in paralysis of the hind limbs and infiltration of lymphocytes and microglial activation centred mainly on the spinal cord; little inflammation was seen in the cerebrum. When a brain wound, in the form of cryolesion, was inflicted on one cerebral hemisphere, 8 days after the induction of EAE, there was a 6-fold enhancement of EAE lesions in the brain. This enhancement was reduced by 40% cervical lymphadenectomy at the time of the cryolesion. These results suggest that cervical lymph nodes play a pivotal role in cerebral EAE and may be a major source of brain-directed lymphocytes. If similar mechanisms apply in man, study of cervical lymphocytes and their manipulation could open new therapeutic avenues for the treatment of multiple sclerosis.

Asunto(s)

Encéfalo/inmunología , Derivaciones del Líquido Cefalorraquídeo , Encefalomielitis Autoinmune Experimental/terapia , Sistema Linfático/inmunología , Animales , Encefalomielitis Autoinmune Experimental/inmunología , Ratas , Ratas Endogámicas Lew

RESUMEN

There is evidence for lymphatic drainage of interstitial fluid from the brain along perivascular spaces in a number of mammalian species. Ultrastructural studies suggest that there are similar drainage pathways in the human cerebral cortex. Perivascular spaces in the basal ganglia, however, differ from those in the cortex in that they dilate to form lacunes and rarely accumulate beta-amyloid (amyloid angiopathy) in Alzheimer's disease; in the cortex, lacunes are rare but amyloid angiopathy is common. The aim of the present study is to compare the structure of perivascular spaces in the basal ganglia and at the anterior perforated substance with perivascular spaces in the cerebral cortex. Eight postmortem brains from patients aged 23-80 years (mean 68 y) were examined by light microscopy, by scanning and transmission electron microscopy and by direct visualisation of etched paraffin blocks. The results show that arteries in the basal ganglia are surrounded by 2 distinct coats of leptomeninges separated by a perivascular space which is continuous with the perivascular space around arteries in the subarachnoid space. The inner layer of leptomeninges closely invests the adventitia of the vessel wall and the outer layer is continuous with the pia mater on the surface of the brain at the anterior perforated substance. Veins in the basal ganglia have no outer layer of leptomeninges and thus the perivascular space is continuous with the subpial space. The anatomy of the periarterial spaces in the basal ganglia differs significantly from that in the cerebral cortex where there is only a single periarterial layer of leptomeninges. Differences in structure of perivascular spaces around arteries may reflect relative efficiencies in the drainage of interstitial fluid from different sites in the brain. Furthermore, the structure of the perivascular spaces may contribute to the relatively high frequency of lacunes in the basal ganglia, and the low frequency of amyloid angiopathy at this site in Alzheimer's disease.

Asunto(s)

Ganglios Basales/ultraestructura , Corteza Cerebral/ultraestructura , Adulto , Anciano , Anciano de 80 o más Años , Arterias , Ganglios Basales/irrigación sanguínea , Corteza Cerebral/irrigación sanguínea , Espacio Extracelular/fisiología , Humanos , Meninges/ultraestructura , Microscopía Electrónica , Microscopía Electrónica de Rastreo , Persona de Mediana Edad , Vías Olfatorias/ultraestructura

RESUMEN

We examined the morphology and distribution of retrogradely labeled spinothalamic tract (STT) neurons in lamina I (the marginal zone) of the spinal dorsal horn after large injections of cholera toxin subunit B (CTb) or Fast Blue (FB) into the contralateral thalamus of cats. Based on the shape and orientation of the somata and proximal dendrites in horizontal sections, three distinct cell types were identified: (1) fusiform cells with small, spindle-shaped somata and bipolar, longitudinal dendritic arbors; (2) pyramidal cells with triangular somata and three main dendritic origins with primarily longitudinal arborizations; and (3) multipolar cells with larger, multiangular somata and four or more radiating dendritic arbors directed both longitudinally and mediolaterally. These three morphological types differed significantly in the number of primary dendrites and the size of the somata. Subclasses of multipolar cells were noted. Nearly all cells could be categorized into these three classes consistently in horizontal sections. A small number of cells with transitional shapes or with small, round somata were unclassified. The proportional distributions of these cell types were found to vary over the length of the spinal cord (from the third cervical through the coccygeal segments) in three cats. The overall proportions of cell types were 34% fusiform, 36% pyramidal, 25% multipolar, and 5% unclassified. The proportions of pyramidal and multipolar cells were strikingly higher within the C7-8 and L6-7 segments and lowest in the thoracic segments. In contrast, fusiform cells formed about 20% of the labeled lamina I STT population in the C7-8 and L6-7 segments but more than 60% in thoracic segments. Across all nine cats, the proportions were similar within the cervical (C5-8) and lumbosacral (L5-S1) enlargements, although considerable interanimal variability was noted. These distinct morphological types of lamina I STT cells with differential longitudinal distributions probably have different functional roles. They may correspond to the three main physiological classes of lamina I STT cells.

Asunto(s)

Neuronas/ultraestructura , Médula Espinal/ultraestructura , Tálamo/ultraestructura , Amidinas , Animales , Gatos , Polaridad Celular/fisiología , Toxina del Cólera , Dendritas/fisiología , Dendritas/ultraestructura , Colorantes Fluorescentes , Histocitoquímica , Vías Nerviosas/citología , Vías Nerviosas/fisiología , Vías Nerviosas/ultraestructura , Células Piramidales/fisiología , Células Piramidales/ultraestructura , Médula Espinal/citología , Médula Espinal/fisiología , Tálamo/citología , Tálamo/fisiología

Asunto(s)

Encéfalo/metabolismo , Líquido Cefalorraquídeo/fisiología , Sistema Linfático/metabolismo , Animales , Tinta , Vías Olfatorias/fisiología

RESUMEN

The existence of a posterolateral thalamic relay nucleus for pain and temperature sensation was postulated in 1911, on the basis of the stroke-induced analgesia and thermanaesthesia found paradoxically in patients with thalamic pain syndrome. Pain or temperature sensations can be evoked in humans by electrical stimulation in a vaguely defined region of the posterolateral thalamus. Here we use anterograde tracing and single unit recordings to demonstrate that there is a distinct nucleus in the posterior thalamus of the macaque monkey that receives a dense, topographic input from spinothalamic lamina I neurons and in which almost all neurons are nociceptive- or thermoreceptive-specific. Immunohistochemical staining showed that this nucleus is defined by a dense calbindin-positive fibre plexus in the macaque, so we applied the same staining method to sections of human thalamus. We found a nearly identical fibre plexus localized within a distinct nucleus that is cytoarchitectonically homologous to the lamina I relay nucleus in the macaque thalamus. The stereotaxic coordinates of this nucleus and its location relative to the main somatosensory representation fit clinical descriptions of the pain-producing region in humans. We conclude that this is a specific thalamic nucleus for pain and temperature sensation in both monkey and human.

Asunto(s)

Mapeo Encefálico , Dolor , Percepción/fisiología , Núcleos Talámicos/fisiología , Sensación Térmica/fisiología , Animales , Calbindinas , Humanos , Macaca fascicularis , Neuronas/fisiología , Proteína G de Unión al Calcio S100/metabolismo , Tractos Espinotalámicos/fisiología

RESUMEN

Peptide histidine-isoleucine (PHI) is a regulatory peptide, synthesized as part of the same propeptide that includes also vasoactive intestinal peptide (VIP). The present study describes the distribution of PHI-immunoreactive nerve fibers in the sheep pineal organ and compares their location with the distribution of VIP-immunoreactive fibers in both normal and superior cervical ganglionectomized sheep in order to elucidate the origin of the PHI/VIP immunoreactive nerve fibers. Several PHI-immunoreactive nerve fibers were present in the meninges and in the pineal capsule. Numerous positive nerve fibers entered the pineal gland and travelled within connective tissue spaces. Individual PHI-positive nerve fibers were either smooth, without specialization, or varicose. Generally VIP- and PHI-immunoreactive fibers were located close to connective septa and blood vessels. However, many PHIergic and VIPergic fibers possessing varicosities of variable sizes were also dispersed between pinealocytes. The distribution, density, and morphology of PHI- and VIP-immunoreactive fibers in the sheep pineal gland were similar. In superior cervical ganglionectomized animals, intrapineal VIP- and PHI-immunoreactive nerve fibers were present with the same density as in control animals. In agreement, the concentration of immunoreactive VIP and PHI did not change after ganglionectomy. No VIP- and PHI-immunoreactive cell bodies were observed in the superior cervical ganglia. Thus this study shows that the intrapineal VIP- and PHI-immunoreactive nerve fibers do not originate from the sympathetic superior cervical ganglion.

Asunto(s)

Péptido PHI/metabolismo , Glándula Pineal/inervación , Ovinos/metabolismo , Ganglio Cervical Superior/fisiología , Péptido Intestinal Vasoactivo/metabolismo , Animales , Encéfalo/metabolismo , Ganglionectomía , Inmunohistoquímica , Masculino , Fibras Nerviosas/metabolismo

RESUMEN

Perivascular cells in the rat brain are an immunophenotypically defined group of cells which can be identified by their expression of the ED2 antigen. The present study investigates the role of perivascular cells as scavengers in the perivascular spaces of the rat brain and the relationship of these cells to microglia, macrophages, pericytes and smooth muscle cells. Particulate matter (Indian ink) was injected selectively into the perivascular spaces of the left caudoputamen of 59 rats. Animals were killed by cardiac perfusion of formalin or glutaraldehyde 2 h-2 years after ink injection. Cerebral hemispheres were examined histologically and immunocytochemically using the ED2 antibody for perivascular cells, ED1 for microglia and macrophages and OX-6 directed against Ia antigen [major histocompatibility complex (MHC) class II]. ED2+ perivascular cells ingested Indian ink in the perivascular spaces and expressed MHC class II antigen. Reactive microglia and macrophages in the perivascular parenchyma expressed ED1, but no ED2+ cells were seen outside the perivascular spaces. Transmission electron microscopy distinguished perivascular cells, which ingested carbon particles, from pericytes, which did not. The results of this study suggest that perivascular cells remain distinct from pericytes, microglia and macrophages and that they play a major role as scavengers in the perivascular spaces of the rat brain. This role reflects the importance of perivascular spaces as drainage pathways for soluble and insoluble material from the brain.

Asunto(s)

Vasos Sanguíneos/citología , Encéfalo/citología , Macrófagos/ultraestructura , Neuroglía/ultraestructura , Animales , Vasos Sanguíneos/inmunología , Vasos Sanguíneos/ultraestructura , Encéfalo/inmunología , Encéfalo/ultraestructura , Antígenos de Histocompatibilidad Clase II/análisis , Inmunohistoquímica , Macrófagos/inmunología , Masculino , Microscopía Electrónica , Neuroglía/inmunología , Ratas , Ratas Wistar , Espacio Subaracnoideo/citología

RESUMEN

There is firm physiological evidence for the lymphatic drainage of interstitial fluid and cerebrospinal fluid from the brains of rats, rabbits and cats. The object of this review, is to describe firstly the morphological aspects of lymphatic drainage pathways from the rat brain and secondly, to explore through scanning and transmission electron microscope techniques, the possibility of similar lymphatic drainage pathways in man. Interstitial and oedema fluid spreads diffusely through the white matter in the rat and appears to drain into the ventricular cerebrospinal fluid. In grey matter, however, tracers pass along perivascular spaces to the surface of the brain and into the cerebrospinal fluid. Paravascular compartments in the subarachnoid space follow the course of major arterial branches to the circle of Willis and thence along the ethmoidal arteries to the cribriform plate of the ethmoid bone. Particulate tracers, such as Indian ink, enter channels in the arachnoid beneath the olfactory bulbs and connect directly with nasal lymphatics through channels which pass through holes in the cribriform plate. Proteins and other solutes may also drain along other cranial nerves. Thus, there is a bulk flow pathway for interstitial and cerebrospinal fluid from the rat brain into cervical lymphatics. In man, it is probable that diffuse interstitial drainage of fluid from the white matter occurs in a similar way to that in the rat. Furthermore, the anatomical pathways exist by which bulk drainage of fluid could occur along perivascular spaces from the grey matter into perivascular spaces of the leptomeningeal arteries and thence into the cerebrospinal fluid (CSF).(ABSTRACT TRUNCATED AT 250 WORDS)

Asunto(s)

Encéfalo/fisiología , Líquido Cefalorraquídeo/fisiología , Animales , Encéfalo/anatomía & histología , Encéfalo/inmunología , Gatos , Humanos , Conejos , Ratas , Médula Espinal/anatomía & histología , Médula Espinal/fisiología

RESUMEN

Pathways for drainage of interstitial fluid and cerebrospinal fluid from the rat brain were investigated by the injection of 2-5 microliters Indian ink into cerebral white and grey matter and into the subarachnoid space over the vertex of the left frontal lobe. Animals were killed by formalin or glutaraldehyde perfusion 5 min-2 years after injection, and the distribution of ink over the surface of the brain, in 2-mm slices of brain cleared in cedar wood oil, in paraffin sections and by electron microscopy was documented. These investigations showed that carbon particles were distributed diffusely through the interstitial spaces of the white matter whereas they spread selectively along perivascular spaces in the grey matter outlining both arteries and veins and extending to surround capillaries within 1 h. Carbon particles were rapidly ingested by perivascular cells and, to some extent, by meningeal cells surrounding the larger vessels. Very little movement of carbon-labelled perivascular cells and perivascular macrophages was seen after 2 years. Carbon particles entering the subarachnoid space over the vertex of the cerebral hemispheres drained along selected paravascular and subfrontal pathways in the subarachnoid space to the cribriform plate and thence into nasal lymphatics and cervical lymph nodes. These studies demonstrate the diffuse spread of fluidborne tracers through cerebral white matter in the rat, the perivascular spread of tracer in grey matter and the compartmentalised directional flow or tracer through the subarachnoid space to the cribriform plate and nasal lymphatics. Furthermore, particulate matter selectively injected into perivascular spaces in rat grey matter is rapidly and efficiently ingested by perivascular cells.

Asunto(s)

Encéfalo/metabolismo , Carbono , Líquido Cefalorraquídeo/metabolismo , Espacio Extracelular/metabolismo , Animales , Colorantes , Ratas , Coloración y Etiquetado , Espacio Subaracnoideo/metabolismo

RESUMEN

This study describes the distribution of peptide sequences derived from the prepro-vasoactive intestinal polypeptide (preproVIP) molecule in perivascular nerves of rat brain arteries and arterioles. The peptides were identified by immunohistochemistry using highly specific antibodies. Five peptide sequences (preproVIP 60-76, peptide histidine isoleucine (PHI), preproVIP 111-122, VIP, and preproVIP 156-170) were identified in the perivascular nerves throughout the arterial cerebral circulation. The density of the immunoreactive fibers was highest in the nerves of the larger extracerebral arteries, declining in smaller branching arteries. All peptide sequences were identified in the nerves of small pial arterioles overlying the cortical convexity, whereas capillaries and veins contained no immunoreactive material. Dendritic processes of neocortical neurons immunoreactive for VIP and PHI could be followed towards the brain surface where the processes penetrated into the pial layer, often close to the pial vasculature. Some of the processes were also observed to enter the Virchow-Robin space, close to the arterioles. It is possible that cortical nerve cells containing VIP and PHI release the peptides in the perivascular space during periods of activity and thereby contribute to local vasodilatation associated with changes of neuronal function.

Asunto(s)

Circulación Cerebrovascular , Homeostasis/fisiología , Fragmentos de Péptidos/metabolismo , Precursores de Proteínas/metabolismo , Péptido Intestinal Vasoactivo/metabolismo , Animales , Arteriolas/metabolismo , Vasos Sanguíneos/inervación , Vasos Sanguíneos/metabolismo , Inmunohistoquímica , Masculino , Fibras Nerviosas/metabolismo , Fragmentos de Péptidos/química , Mapeo Peptídico , Péptido PHI/metabolismo , Piamadre/irrigación sanguínea , Precursores de Proteínas/química , Radioinmunoensayo , Ratas , Ratas Endogámicas , Péptido Intestinal Vasoactivo/química

RESUMEN

The distribution of tyrosine hydroxylase (TH)- and neuropeptide Y (NPY)-immunoreactive(IR) nerve fibers in the pineal complex was investigated in untreated rats and rats following bilateral removal of the superior cervical ganglia. In normal animals, a large number of TH- and NPY-IR nerve fibers were present in the pineal capsule, the perivascular spaces, and intraparenchymally between the pinealocytes throughout the superficial pineal and deep pineal gland. A small number of TH-IR and NPY-IR nerve fibers were found in the posterior and habenular commissures, a few fibers penetrating from the commissures into the deep pineal gland. To elucidate the origin of these fibers, the superior cervical ganglion was removed bilaterally in 10 animals, and the pineal complex was examined immunohistochemically. Two weeks after the ganglionectomy, the TH-IR and NPY-IR nerve fibers in the superficial pineal gland had almost completely disappeared. On the other hand, in the deep pineal and the pineal stalk, the TH-IR and NPY-IR fibers were still present after ganglionectomy. These data show that the deep pineal gland and the pineal stalk possess an extrasympathetic innervation by TH-IR and NPY-IR fibers. It is suggested that the extrasympathetic TH-IR and NPY-IR nerve fibers innervating the deep pineal and the pineal stalk originate from the brain.

Asunto(s)

Ganglios Simpáticos/cirugía , Fibras Nerviosas/inmunología , Neuropéptido Y/inmunología , Glándula Pineal/ultraestructura , Tirosina 3-Monooxigenasa/inmunología , Animales , Sueros Inmunes/inmunología , Inmunohistoquímica , Masculino , Fibras Nerviosas/ultraestructura , Glándula Pineal/inmunología , Ratas , Ratas Endogámicas

RESUMEN

Biopsies of histologically normal adult human cerebral cortex, underlying white matter and overlying leptomeninges were taken from frontal and temporal lobectomy specimens excised during the removal of cerebral tumours. Multiple blocks from 6 patients (aged 18-53 years) were examined by light and transmission electron microscopy. A thin sheath of pia mater cells was found to surround completely arterioles and arteries in the brain, in the subpial space and in the subarachnoid space. Pia mater cells, forming the perivascular sheath, were identified by the presence of desmosomes or small nexus junctions and by continuity with the pia mater itself. The presence of the pial sheath suggests that the perivascular spaces around intracerebral arteries are in direct continuity with the perivascular spaces around subarachnoid arteries. No similar pial sheath was observed around intracerebral or subpial venules. The role of the periarterial spaces, enclosed by the pial sheath, is discussed in relation to the results of physiological experiments suggesting drainage of interstitial fluid from brain tissue into the perivascular pathways along major cerebral arteries in the subarachnoid space. As arterioles in the brain become smaller and lose their smooth muscle coats, the pial sheath becomes incomplete. The anatomical relationships between the pia mater and blood vessels in the human cerebrum is summarised diagrammatically, and a possible role for pial cells as an enzymic barrier protecting the brain from exogenous catecholamines is discussed.

Asunto(s)

Encéfalo/ultraestructura , Piamadre/ultraestructura , Adolescente , Adulto , Arteriolas/ultraestructura , Corteza Cerebral/irrigación sanguínea , Femenino , Humanos , Masculino , Microscopía Electrónica , Persona de Mediana Edad , Piamadre/irrigación sanguínea , Flujo Sanguíneo Regional , Espacio Subaracnoideo/irrigación sanguínea , Vénulas/ultraestructura