Search PubMed⌕ Search

Biomedical subjects

A Ribeiro-da-Silva

Publications and source records attributed to A Ribeiro-da-Silva.

At least 37 records · Page 2Linked to original sources
PubMed1999

NK-1 receptor immunoreactivity in distinct morphological types of lamina I neurons of the primate spinal cord.

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.

Animals↗
PubMed1999

GM1 and piracetam do not revert the alcohol-induced depletion of cholinergic fibers in the hippocampal formation of the rat.

Chronic alcohol consumption causes a depletion of the cholinergic fiber network in the rat hippocampal formation, which is not ameliorated by alcohol withdrawal. Following withdrawal from alcohol, there is a further loss of intrinsic hippocampal cholinergic neurons. In this study, we investigated whether treatment with putative neuroprotective agents during the entire withdrawal period would have beneficial effects upon the hippocampal cholinergic innervation. Adult male rats were alcohol-fed for 6 months and subsequently withdrawn from alcohol for 6 months. Some animals were treated with either ganglioside GM1 (35 mg/kg body weight s.c.), vehicle (saline s.c.), or piracetam (800 mg/kg body weight p.o.) for the entire withdrawal period. Choline acetyltransferase (ChAT) immunoreactive (IR) fibers and neurons were analyzed quantitatively in all four animal groups. There were no significant differences in the density of the ChAT-IR hippocampal fiber network when the pure withdrawal and withdrawal + vehicle groups were compared to the withdrawal + GM1 or withdrawal + piracetam groups. In contrast, the number of ChAT-IR interneurons in the hippocampal formation was higher in the withdrawal + GM1 or withdrawal + piracetam groups than in the pure withdrawal and withdrawal + vehicle groups. These results indicate that, in the doses used, neither neuroprotective agent had an effect upon the extrinsic cholinergic innervation, but they had a beneficial effect upon the hippocampal intrinsic cholinergic system.

Animals↗
PubMed1998

Preferential synaptic relationships between substance P-immunoreactive boutons and neurokinin 1 receptor sites in the rat spinal cord.

Substance P plays an important role in the transmission of pain-related information in the dorsal horn of the spinal cord. Recent immunocytochemical studies have shown a mismatch between the distribution of substance P and its receptor in the superficial laminae of the dorsal horn. Because such a mismatch was not observed by using classical radioligand binding studies, we decided to investigate further the issue of the relationship between substance P and its receptor by using an antibody raised against a portion of the carboxyl terminal of the neurokinin 1 receptor and a bispecific monoclonal antibodies against substance P and horseradish peroxidase. Light microscopy revealed a good correlation between the distributions of substance P and the neurokinin 1 receptor, both being localized with highest densities in lamina I and outer lamina II of the spinal dorsal horn. An ultrastructural double-labeling study, combining preembedding immunogold with enzyme-based immunocytochemistry, showed that most neurokinin 1 receptor immunoreactive dendrites were apposed by substance P containing boutons. A detailed quantitative analysis revealed that neurokinin 1 receptor immunoreactive dendrites received more appositions and synapses from substance P immunoreactive terminals than those not expressing the neurokinin 1 receptor. Such preferential innervation by substance P occurred in all superficial dorsal horn laminae even though neurokinin 1 receptor immunoreactive dendrites were a minority of the total number of dendritic profiles in the above laminae. These results suggest that, contrary to the belief that neuropeptides act in a diffuse manner at a considerable distance from their sites of release, substance P should act on profiles expressing the neurokinin 1 receptor at a short distance from its site of release.

Afferent Pathways↗
PubMed1998

Nuclear localization of prostaglandin E2 receptors.

Prostaglandin E2 receptors (EP) were detected by radioligand binding in nuclear fractions isolated from porcine brain and myometrium. Intracellular localization by immunocytofluorescence revealed perinuclear localization of EPs in porcine cerebral microvascular endothelial cells. Nuclear association of EP1 was also found in fibroblast Swiss 3T3 cells stably overexpressing EP1 and in human embryonic kidney 293 (Epstein-Barr virus-encoded nuclear antigen) cells expressing EP1 fused to green fluorescent protein. High-resolution immunostaining of EP1 revealed their presence in the nuclear envelope of isolated (cultured) endothelial cells and in situ in brain (cortex) endothelial cells and neurons. Stimulation of these nuclear receptors modulate nuclear calcium and gene transcription.

3T3 Cells↗
PubMed1998

Synaptic numbers across cortical laminae and cognitive performance of the rat during ageing.

In this study, we have investigated the changes in the number of individual presynaptic boutons in the neocortex of rats and correlated them with cognitive performance. Brown Norway x Fischer 344 F1 hybrid rats, aged from one to 24 months, were used. Using synaptophysin as a marker for presynaptic boutons, we found that in the parietal II region of the neocortex an age-related decrease in the density of immunostained punctae representing presynaptic boutons occurred. Regression analysis showed that this decline in the number of presynaptic boutons correlates with ageing (r=0.495, P<0.05). Interestingly, we found that this age-related depletion of presynaptic boutons was more intense in the deeper cortical lamina, such as laminae V and VI (mean decrease of 18%), than in the superficial laminae (mean decrease of 8% in laminae I-IV). Using the Morris water maze test, we observed that young rats acquired the task at twice the speed of aged animals (48.9 +/- 9.0 s and 91.0 +/- 4.9 s for young and aged animals, respectively). Furthermore, at the end of the training period, the aged cohort still showed significantly higher escape latencies in the Morris water maze. The present findings support the concept that the decline in cognitive performances in ageing is related to the loss of synapses in the cerebral cortex.

Aging↗
PubMed1997

Responses of cortical noradrenergic and somatostinergic fibres and terminals to adjacent strokes and subsequent treatment with NGF and/or the ganglioside GM1.

The occurrence of sprouting by fibre systems in the neocortex following lesion is still a controversial issue. In previous studies, we showed a nerve growth factor (NGF)-induced sprouting and hypertrophy of presynaptic terminals in the cholinergic fibres of the rat neocortex following stroke-type lesions, effects that were potentiated by the monosialoganglioside GM1. The present study investigated whether exogenous NGF and/or GM1 treatment could also affect the noradrenergic and somatostinergic systems in the neocortex. Immediately following unilateral vascular decortication, adult rats received, via minipump, a 7-day infusion of vehicle, NGF (12 microg/day) and/or GM1 (1.5 mg/day) into the cerebroventricular space. Thirty days postlesion, the animals were perfused with histological fixatives, the brains were removed, and relevant sections were processed for dopamine beta-hydroxylase and somatostatin immunocytochemistry at the light and electron microscopic levels. A Quantimet 920 image analysis system was used for the quantification of fibre length and size of presynaptic boutons. The lesion caused a reduction in the dopamine beta-hydroxylase-immunoreactive fibre length, which was not attenuated by either NGF or GM1 treatment or both. The somatostatin-immunoreactive network, in contrast, was unaffected by the lesion, and there was no sprouting of somatostatin fibres following trophic factor therapy. We also found no significant differences in the size and number of synapses of both the dopamine beta-hydroxylase-immunoreactive and somatostatin-immunoreactive boutons following lesion and drug treatments. These results indicate that NGF and/or GM1 therapies do not cause regrowth in the noradrenergic and somatostatinergic cortical fibre networks or their presynaptic elements following a cortical devascularizing lesion.

Analysis of Variance↗
PubMed1997

Nerve growth factor stimulates growth of cortical pyramidal neurons in young adult rats.

The cytoarchitectonics of pyramidal neurons in the cerebral cortex of non-lesioned rats can be re-modeled by i.c.v. infusions of nerve growth factor (NGF). 4 months after the application of NGF, the pyramidal neurons in layers III and V of the motor cortex and layer V of the anterior cingulate cortex were analyzed and compared with pyramidal neurons from vehicle-treated rats. NGF-treated brains showed: (1) significant increase in dendritic branching in the basilar fields of the layer V, but not layer III, neurons; and (2) a significant increase in spine density in the terminal, but not proximal, dendritic branches. These findings indicated that, besides its known effects on forebrain cholinergic neurons, NGF produces a very generalized synaptic re-modeling involving the cells responsible for the major output of the cerebral cortex in the intact adult brain.

Animals↗
PubMed1997

Nerve growth factor treatment prevents dendritic atrophy and promotes recovery of function after cortical injury.

This study examined the behavioural and anatomical effects of intraventricular injections of nerve growth factor in rats with unilateral damage that included Zilles' areas Frl, FL, HL, ParI and the anterior portion of Oc2. Nerve growth factor-treated lesion rats showed attenuation of behavioural symptoms in measures of forelimb function (Whishaw reaching task) and hindlimb function (beam traversing task) as well as a measure of spatial navigation (Morris water task). Analysis of dendritic arborization using a modified Golgi. Cox procedure also showed a complete reversal of lesion-induced atrophy of dendritic fields in pyramidal neurons in motor (Zilles' Fr2) and cingulate (Zilles' Cgl) cortex. In addition, there was a reversal of a lesion-induced reduction in spine density. These results demonstrate that nerve growth factor treatment can facilitate functional recovery from cortical injury. This recovery may be mediated by a reorganization of intrinsic cortical circuitry that is reflected in changes in dendritic arborization and spine density of pyramidal neurons.

Animals↗
PubMed1997

Substance P and enkephalin immunoreactivities in axonal boutons presynaptic to physiologically identified dorsal horn neurons. An ultrastructural multiple-labelling study in the cat.

A combination of intracellular electrophysiological recording and injection of horseradish peroxidase with ultrastructural immunocytochemistry was used to investigate the synaptic interplay between substance P- and enkephalin-immunoreactive axonal boutons and three types of functionally characterized dorsal horn neurons in the cat spinal cord. The dorsal horn neurons were classified as nociceptive specific, wide dynamic range and non-nociceptive based on their responses to innocuous and noxious stimuli. Most of the nociceptive neurons (either nociceptive specific or wide dynamic range) contained enkephalin immunoreactivity, but none of the non-nociceptive neurons were positive for enkephalin. Three types of immunoreactive boutons were found in contact with the functionally characterized dorsal horn neurons. These boutons were positive for either substance P, enkephalin, or substance P+enkephalin. Quantitative analysis revealed that the percentages of substance P-immunoreactive boutons apposed to the cell bodies, proximal dendrites and distal dendrites of nociceptive neurons were significantly higher than those of non-nociceptive neurons. Furthermore, the percentages of substance P+enkephalin-immunoreactive axonal boutons apposed to the distal dendrites of nociceptive neurons were significantly higher than those of non-nociceptive neurons and the percentages of enkephalin-immunoreactive boutons apposed to the cell bodies and proximal dendrites of nociceptive neurons were significantly higher than in non-nociceptive neurons. Finally, neither enkephalin-immunoreactive nor substance P+enkephalin-immunoreactive boutons were ever seen presynaptic to substance P-immunoreactive boutons. These results provide evidence of an anatomical substrate within the dorsal horn for the interaction of substance P-mediated with enkephalin-mediated mechanisms. The data support the idea that the modulation of nociceptive input in the dorsal horn by enkephalinergic neurons occurs mainly via a postsynaptic mechanism, and thus suggest that dorsal horn enkephalinergic neurons participate in a local inhibitory feedback loop in a distinct pathway from the previously postulated opioid-mediated depression of substance P release from primary afferent terminals.

Animals↗
PubMed1997

Intracerebral grafts promote recovery of the cholinergic innervation of the hippocampal formation in rats withdrawn from chronic alcohol intake. An immunocytochemical study.

We have previously found that alcohol withdrawal aggravates the neuronal cell loss induced by chronic alcohol consumption in the rat hippocampal formation. We have also shown that intracerebral grafts of immature hippocampal tissue could reverse the progressive degeneration that occurs during this withdrawal. Furthermore, we have shown that chronic alcohol consumption reduces the areal density of choline acetyltransferase-immunoreactive neurons and the density of choline acetyltransferase-immunoreactive fibres in the hippocampal formation. Thus, we thought it would be of interest to investigate the effects of alcohol withdrawal in the hippocampal cholinergic innervation and to determine whether the intracerebral grafting of immature hippocampal tissue would have beneficial effects upon the cholinergic system in this condition. Choline acetyltransferase-immunoreactive fibres and perikarya were analysed in 14-month-old control, alcohol-fed, withdrawal and withdrawal-grafted groups of rats. The areal density of choline acetyltransferase-immunoreactive neurons was reduced in all experimental groups when compared to controls. The density of choline acetyltransferase-immunoreactive fibres was lower in the alcohol-fed and withdrawal groups than in the control and withdrawal-grafted groups. We conclude that the grafted tissue probably produced neurotrophic factors which allowed a recovery of the hippocampal cholinergic fibre network. This recovery might be of importance to reverse the cognitive dysfunction described after chronic alcohol consumption and withdrawal.

Animals↗
PubMed1995

Ectopic substance P and calcitonin gene-related peptide immunoreactive fibres in the spinal cord of transgenic mice over-expressing nerve growth factor.

The aim of this study was to investigate the in vivo effects of CNS over-expression of nerve growth factor (NGF) on primary sensory neurons. To achieve this objective a transgenic mouse model was generated which bore a chick NGF gene driven by the myelin basic protein promoter. Northern blot analysis demonstrated that high levels of NGF mRNA were detected in the spinal cord of adult transgenic mice. Using immunocytochemistry NGF-immunoreactive (IR) oligodendrocytes were observed throughout the white matter. Furthermore, numerous ectopic substance P (SP)- and calcitonin gene-related peptide (CGRP)-IR fibres were detected in the white matter of the spinal cord of transgenic mice. NGF-IR oligodendrocytes and ectopic SP- and CGRP- fibres were entirely absent from control mice. In the cervical and lumbar dorsal root ganglia, the percentages of SP-IR neurons were significantly higher in transgenic mice when compared with controls. At the electron microscope level, ectopic SP- and CGRP-IR fibres were characterized as unmyelinated axons and axonal boutons. SP colocalized with CGRP in some of those axonal boutons and fibres. Capsaicin treatment of adult mice completely abolished the ectopic SP-IR fibres, confirming their primary sensory origin. Our results indicate that primary sensory neurons are responsive to NGF over-expression in the CNS. Ectopic SP- and CGRP-IR fibres in the white matter are likely to represent collateral sprouts of the central processes of the dorsal root ganglion cells which were triggered by NGF over-expressed in the myelinating oligodendrocytes in the spinal cord of transgenic mice.

Animals↗
PubMed1995

Substance P- and GABA-like immunoreactivities are co-localized in axonal varicosities in the superficial laminae of cat but not rat spinal cord.

In the present study, we applied a combination of pre-embedding peroxidase-based immunocytochemistry and post-embedding immunogold staining to examine the synaptic interactions of substance P (SP) and gamma-aminobutyric acid (GABA) in the superficial laminae of the dorsal horn of cat and rat spinal cord. We demonstrate for the first time the co-existence of SP and GABA immunoreactivities in axonal boutons in laminae I-III of cat spinal dorsal horn. In cat, most SP + GABA immunoreactive (IR) axonal boutons established synapses with SP-IR or non-IR dendrites. These synapses were exclusively symmetric. Quantitative analysis showed that the percentage of SP/GABA double labelled bouton profiles was higher (7%) in lamina I but was considerably lower in laminae IIo, IIi and III. Similarly, the density (number of bouton profiles per 100 microns2) of SP + GABA-IR bouton profiles was highest in lamina I. However, in agreement with previous studies, the co-localization of SP and GABA immunoreactivities was never detected in the rat dorsal horn. In both species, SP + GABA-IR or GABA-IR axonal bouton profiles were never seen presynaptic to SP-IR boutons. These findings provide a morphological basis for the interaction of excitatory and inhibitory agents in the nociceptive circuits in the dorsal horn of the cat and rat spinal cord.

Animals↗
PubMed1995

Effects of chronic alcohol consumption on the cholinergic innervation of the rat hippocampal formation as revealed by choline acetyltransferase immunocytochemistry.

The specific aim of this study was to evaluate whether the cholingeric innervation of the hippocampal formation is affected by chronic alcohol consumption in the rat. Choline acetyltransferase-immunoreactive fibres and neurons were analysed in both alcohol-fed and control rats using a monoclonal antibody against choline acetyltransferase and quantitative methods. We found a global reduction in the cholinergic plexus, which was more pronounced in the hippocampus proper than in the dentate gyrus. The areal density of choline acetyltransferase immunoreactive neurons was also reduced. Differences from controls in neuronal number were particularly striking in the stratum lacunosum moleculare of the regio superior, which is precisely the zone of the hippocampal formation where choline acetyltransferase immunoreactive neurons are more abundant in controls. In conclusion, our results show that prolonged ethanol consumption leads to a substantial reduction in the cholinergic innervation of the hippocampal formation, as there was a loss of cholinergic fibres and also an apparent loss of hippocampal cholingeric neurons. These findings may help to explain the cognitive dysfunctions observed after chronic alcohol consumption.

Alcoholism↗
PubMed1995

Ultrastructural features of the colocalization of calcitonin gene related peptide with substance P or somatostatin in the dorsal horn of the spinal cord.

Calcitonin gene related peptide (CGRP), substance P (SP), and somatostatin (SOM) are probably the three most important sensory neuropeptides. However, in contrast to CGRP immunoreactivity (IR), SP- and SOM-IR occur also in neurons intrinsic to the dorsal horn. Colocalization of either SP- or SOM-IR with CGRP-IR is, therefore, strongly suggestive of a primary sensory origin. In this study, high resolution double-labelling immunocytochemistry was applied to detect CGRP/SP and CGRP/SOM colocalizations in axonal boutons of the rat superficial dorsal horn. Most boutons colocalizing CGRP-IR and SP-IR were not part of synaptic glomeruli. However, 15% of such boutons represented the central varicosities of type I synaptic glomeruli. CGRP-IR was always present in the small proportion of type I glomeruli central boutons that displayed SOM-IR. In a study in the cat combining double-labelling immunocytochemistry with intracellular injection of electrophysiologically characterized neurons, we found that nociceptive neurons received numerous synapses from varicosities colocalizing SP-IR and CGRP-IR. In contrast, non-nociceptive neurons almost completely lacked synaptic input from boutons colocalizing both immunoreactivities. This study confirms that fibres colocalizing SP-IR and CGRP-IR probably play a major role in spinal nociceptive mechanisms.

Animals↗
PubMed1993

Potentiation of nerve growth factor-induced alterations in cholinergic fibre length and presynaptic terminal size in cortex of lesioned rats by the monosialoganglioside GM1.

The effect of monosialoganglioside GM1 and/or nerve growth factor treatment on the cholinergic innervation of the rat cortex was studied using both light- and electron-microscopic techniques assisted by image analysis. Adult male Wistar rats were unilaterally decorticated and received continuous infusions, via minipump, of vehicle, GM1 (1.5 mg/day) and/or nerve growth factor (12 micrograms/day) into the cerebroventricular space. Treatments were initiated immediately post-lesion and ended after seven days. Thirty days post-lesion (i.e. 23 days after the end of drug administration) brains were processed for choline acetyltransferase immunocytochemistry for either light- or electron-microscopic analysis. At this time-point choline acetyltransferase-immunoreactive neurons in the ipsilateral nucleus basalis magnocellularis were significantly reduced in size especially in the mid portion of this nucleus, in lesion vehicle-treated rats. Moreover, decreases in choline acetyltransferase immunoreactive fibre length (ranging from 31 to 50%) and varicosity number (ranging from 26 to 39%) occurred in all cortical layers within a portion of the remaining cortex of these animals. Monosialoganglioside GM1 or nerve growth factor treatment equally attenuated deficits in nucleus basalis magnocellularis cell size and cortical choline acetyltransferase immunoreactive fibre length. However, nerve growth factor, but not monosialoganglioside GM1 treatment also increased choline acetyltransferase-immunoreactive varicosity number above control levels. In lesioned rats which received both nerve growth factor and the monosialoganglioside GM1, the mean cross-sectional area of nucleus basalis magnocellularis cholinergic neurons did not differ significantly from control values. By contrast, cortical choline acetyltransferase-immunoreactive fibre length and varicosity number were significantly increased above control values and that induced by nerve growth factor treatment alone. Quantitative electron-microscopic analysis showed that cholinergic boutons in cortical layer V were considerably shrunken in lesioned vehicle-treated rats and that GM1 treatment failed to significantly attenuate this deficit. However, exogenous nerve growth factor provoked a significant increase (35% above control values) in cortical cholinergic presynaptic terminal size which was even further augmented by concurrent GM1 treatment (69% above control values). This trophic factor-induced increase in bouton size was confirmed using serial electron microscopy and computer-assisted three-dimensional reconstruction of the cholinergic varicosities. The number of synaptic contacts in cortical layer V was also found to be significantly reduced (45% of control values) in lesioned vehicle-treated rats but was maintained at control levels by exogenous GM1 treatment. In addition, a significant increase (95% above control levels) in the number of choline acetyltransferase-immunoreactive boutons with synaptic differentiations was noted in lesioned nerve growth factor-treated rats.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Spinal neurons exhibiting a specific nociceptive response receive abundant substance P-containing synaptic contacts.

Substance P has been implicated in nociceptive transmission in the spinal cord. However, evidence for a direct correlation between a specific nociceptive response in spinal dorsal horn neurons and substance P input is lacking. In this study, we combine intracellular recording from dorsal horn neurons in vivo, characterization of their nociceptive responses, intracellular labeling by injection of horseradish peroxidase, and immunocytochemical demonstration of substance P at the electron microscopic level. The results reveal that dorsal horn neurons that respond to noxious cutaneous stimulation with a slow, prolonged excitatory postsynaptic potential receive a preferentially high number of substance P fibers compared with nonnociceptive neurons, which scarcely receive any substance P input. Therefore, this study provides direct evidence of a structural-functional link for a substance P-mediated nociceptive response.

Action Potentials↗