Biomedical subjects

K Brauer

Publications and source records attributed to K Brauer.

At least 37 records · Page 2Linked to original sources

PubMed1998

Comparison of the rat dorsal and ventral striatopallidal system. A study using the GABA(A)-receptor alpha1-subunit and parvalbumin immunolabeling.

The ventral striatum is more closely related to limbic brain regions than the dorsal striatum in spite of the remarkable similarities in the structural organization between these two brain regions. The present study is focused on the comparison of ventral striatopallidal territories and the dorsal striatopallidal system regarding the GABA(A)-receptor alpha1-subunit and parvalbumin immunoreactivity, as these markers showed specific distribution patterns and coexpression sites in the more intensely studied dorsal regions. Our investigations revealed that: (1) Parvalbumin single-labeled cells and a moderate number of neurons single-labeled with the GABA(A)-receptor alpha1-subunit exist not only in the dorsal but also in the ventral striatum, including the striatal cell bridges. In addition, morphologically similar neurons positive for the alpha1-subunit were also found in the corpus callosum and anterior commissure. (2) A small number of double-labeled neurons was seen not only in dorsal but also in ventral striatal regions. Such cells were mainly located near the border with the globus pallidus and ventral pallidum. They are likely to represent a further type of striatal neuron. (3) The vast majority of neurons in the entopeduncular nucleus, the homologue of the primate internal globus pallidus segment, coexpressed alpha1-subunit and parvalbumin immunoreactivity, as reported previously for the other pallidal compartments. (4) The islands of Calleja adjoining the ventral pallidal extensions in the olfactory tubercle exhibited a strong alpha1-subunit immunoreactivity in the neuropil as well as somata single- or double-labeled for both markers. Our findings indicate that the dorsal and ventral striatopallidal compartments are similarly organized in general with respect to the occurrence and distribution of single- and double-labeled parvalbumin-immunoreactive and GABA(A)-receptor alpha1-subunit-immunoreactive neurons.

Animals↗

PubMed1998

Acute and long-lasting changes in extracellular-matrix chondroitin-sulphate proteoglycans induced by injection of chondroitinase ABC in the adult rat brain.

Lattice-like perineuronal accumulations of extracellular-matrix proteoglycans have been shown to develop during postnatal maturation and to persist throughout life as perineuronal nets (PNs) in many brain regions. However, the dynamics of their reorganization in adults are as yet unknown. The aim of the present study was to examine the capability of PNs for reconstitution after experimental destruction and to search for possible consequences of extracellular-matrix degradation for neurons and glial cells. The changes were induced by single intracortical injections of Proteus vulgaris chondroitinase ABC and studied after postinjection periods of 1 day to 5 months. The N-acetylgalactosamine-binding Wisteria floribunda agglutinin (WFA), an antibody against chondroitin-sulphate proteoglycans, three antibodies recognizing initial chondroitin or chondroitin-sulphate moieties ('stubs') of proteoglycan core proteins, an antibody against the hyaluronan-binding protein component of versican, and biotinylated hyaluronectin, which binds to hyaluronan, were used as cytochemical markers. One day postinjection, the WFA-binding sites and hyaluronan were shown to be almost completely removed within a circumscribed digestion zone. The staining of different core-protein components revealed only fragments of PNs. These changes were found to be partly compensated 4 weeks after injection of chondroitinase ABC. After 8 and 12 weeks postinjection, the cytochemical and structural characteristics as well as the area-specific distribution patterns of PNs were progressively reconstituted. At 5 months postinjection, they could not be distinguished from those in untreated tissue. In contrast to such transient changes, a diffuse chondroitin-sulphate proteoglycan immunoreactivity persisted in the neuropil. Loss of neurons or alterations of their structure as well as reactions of glial cells were not observed. We conclude from this study that PNs, enzymatically destroyed in the adult rat brain, can be completely reconstituted, but the restoration of their extracellular-matrix components needs several months.

Age Factors↗

PubMed1998

Cortical perineuronal nets in the gray short-tailed opossum (Monodelphis domestica): a distribution pattern contrasting with that shown in placental mammals.

Extracellular matrix proteoglycans accumulated in perineuronal nets and in certain neuropil zones have been shown to influence the immediate neuronal microenvironment, and to contribute to the chemoarchitectonic characteristics of neuronal networks. Studies in different placental mammals, including the human, have suggested that the major principles of extracellular matrix distribution remained constant during phylogenesis of the different mammalian strains. However, the comparison of matrix distribution between various species also indicates that striking deviations from the basic pattern may occur, although their functional significance appears unknown as yet. This study examines the extracellular matrix in the forebrain of a basic American marsupial, which has evolved independently of placental mammals for more than 100 million years. Brain sections obtained from adult gray short-tailed opossums (Monodelphis domestica) were stained for extracellular matrix components using the N-acetylgalactosamine-binding lectin Wisteria floribunda agglutinin (WFA), a polyclonal antibody against chondroitin sulfate proteoglycans (CSPG), and biotinylated hyaluronectin for the detection of hyaluronan. In subcortical regions, the distribution patterns of WFA-stained and CSPG-immunoreactive perineuronal nets were similar to those reported previously in placental mammals. In contrast, a unique distribution was found in the neocortex. This distribution was characterized by the presence of perineuronal nets around pyramidal cells and matrix components within the adjacent neuropil that together form a continuously labeled zone in layer V. Weakly stained nets ensheathed less numerous pyramidal cells in the upper layers II/III and a few multipolar cortical neurons. Dual staining experiments showed that cortical net-associated neurons were rarely immunopositive for parvalbumin. This fact, in addition to the predominant association of extracellular matrix components with layer V pyramidal cells, differentiates the neocortex in Monodelphis from that of all placental mammals studied to date. Regarding the basic phylogenetic position of this marsupial species it remains to be shown if these distribution characteristics of extracellular matrix may represent also a basic feature of cortical organization.

Acetylgalactosamine↗

PubMed1998

Low expression of extracellular matrix components in rat brain stem regions containing modulatory aminergic neurons.

Extracellular matrix proteoglycans, particularly those accumulated in perineuronal nets (PNs), have been shown to form characteristic distribution patterns in cortical and subcortical regions of adult mammals. Their involvement in sustaining mechanisms that are especially related to fast activities of neurons has been discussed as one of the possible functions. The present study deals with the spatial organization of extracellular matrix proteoglycans in brain stem regions that contain aminergic neurons, such as substantia nigra, ventral tegmental area (VTA), raphe nuclei and locus coeruleus (LC). As these nuclei are known to influence brain activity by modulatory functions exerting patterns of slow electric activity, it could be expected that PNs would be absent around aminergic cells. The staining of PNs with Wisteria floribunda agglutinin (WFA) was combined with the detection of catecholaminergic neurons by tyrosine hydroxylase immunoreactivity and of serotonergic neurons by tryptophan hydroxylase (TH) immunoreactivity using double fluorescence microscopy. It was found that the catecholaminergic and serotonergic neurons in the nuclear accumulations, as well as those scattered in adjacent regions, were not ensheathed by PNs. In contrast, several non-aminergic neurons intermingled with aminergic neurons in the raphe nuclei, in the substantia nigra pars compacta (SNC) and in the VTA, as well as many cells in the reticular part of the substantia nigra, were found to be surrounded by PNs. It can be concluded from these results that the absence of PNs around aminergic brain stem neurons, also previously shown for cholinergic basal forebrain neurons, appears as a characteristic feature common to cells that exert slow modulatory functions.

Animals↗

PubMed1997

Electron microscopic evidence for microglial phagocytic activity and cholinergic cell death after administration of the immunotoxin 192IgG-saporin in rat.

192IgG-saporin represents a novel cholinergic immunotoxin which selectively and specifically destroys cholinergic cells in rat basal forebrain. Activated microglial cells are known to play an important role in phagocytosis in regions of neuronal loss. To study the immunotoxin-induced phagocytic events in the basal forebrain activated microglial cells were visualized by lectin cytochemistry using Griffonia simplicifolia agglutinin and analyzed by electron microscopy. Three and 7 days following an intracerebro-ventricular injection of 4 microg 192IgG-saporin, increased numbers of activated microglial cells were observed at both survival times, but the number was strikingly increased at day 7 postlesion. Three days after immunotoxin application microglial cells displayed features similar to those of resting microglia. Only translucent vacuole-like hollows were found intracellularly beneath the plasma membrane of microglial cells and in the adjoining extracellular space. Most neurons in the vicinity of microglial cells did not show any signs of degeneration. However, 7 days after injection of the immunotoxin microglial cells revealed different stages of phagocytosis. The majority of microglial cells were localized in perineuronal positions attached by processes to large areas of neuronal soma or dendrites, which in general showed signs of severe degeneration. The present study provides electron microscopic evidence for phagocytic microglial reactions in the rat basal forebrain after cholinergic lesion by 192IgG-saporin.

Animals↗

PubMed1997

Co-localization of beta-amyloid peptides, apolipoprotein E and glial markers in senile plaques in the prefrontal cortex of old rhesus monkeys.

Based on the homology of human and monkey amyloid precursor proteins and the derived beta-amyloid peptides (A beta) the investigation of brains from old monkeys might be useful for the understanding of beta-amyloidosis in the aetiology of Alzheimer's disease. In the present study, the prefrontal cortex, which is known to be highly susceptible to the deposition of A beta, was screened for the occurrence of senile plaques in perfused tissue of aged rhesus monkeys (Macaca mulatta). A beta deposits were immunocytochemically detected in five of six macaques aged about 28 years. Differently N-terminal truncated A beta species in the senile plaques were simultaneously detected by a carbocyanine double fluorescence method applying the bright red fluorescent Cy3 and the novel green fluorescent Cy2. In a few cases, immunoreactivity for the shortened fragment containing the amino acids 17-42 (A beta(17-42); p3 fragment with a molecular weight of 3 kDa) was demonstrated in deposits apparently devoid of A beta(8-17). Senile plaques were further characterized by carbocyanine double labelling of A beta and astrocytes, microglia and apolipoprotein E.

Aging↗

PubMed1997

Developmental patterns of proteoglycan-containing extracellular matrix in perineuronal nets and neuropil of the postnatal rat brain.

The extracellular matrix is involved in various morphogenetic processes which are accompanied by changes in its physicochemical properties and spatial organization. In the adult brain it contributes to cellular communication and the regulation of neuronal activity. The present study deals with the postnatal appearance and transformation into adult distribution patterns of extracellular matrix components related to chondroitin-sulphate proteoglycans (CSPGs) in the rat brain. The differential accumulation of these components in neuropil and in perineuronal nets (PNs) enriched in certain regions was examined in 0-, 7-, 14-, 21- and 35-day-old rats and adult animals using the N-acetylgalactosamine-binding Wisteria floribunda agglutinin (WFA) and immunocytochemical detection of CSPGs. The lectin stained the olfactory-bulb glomerular layer and layer Ia of piriform and entorhinal cortex already in newborn animals. On postnatal day 7 diffuse neuropil staining was additionally found in certain subcortical nuclei and in deep neocortical layers. The first sharply contoured PNs were detected at this age in the brain stem, indicating the more advanced maturation of matrix components in subcortical regions. CSPG immunoreactivity yielded staining patterns largely identical to WFA-binding patterns but appeared only between postnatal day 14 and 21. The adult-like stage was revealed with both methods between 21 and 35 days after birth. The results provide further evidence that the accumulation of certain CSPGs in the extracellular space is spatiotemporally related to distinct patterns of neuronal activity at the regional and cellular level.

Animals↗

PubMed1996

Pyramidal cells ensheathed by perineuronal nets in human motor and somatosensory cortex.

This study presents data concerning the distribution of chondroitin sulphate proteoglycan-immunoreactive perineuronal nets in sensorimotor areas (Brodmann's areas 3, 1, 2 and 4) of the human cerebral cortex. In addition to previously described subpopulations of nonpyramidal neurons in neocortical areas, many large or medium-sized pyramidal cells in layers III and V, including Betz cells in the motor cortex, were shown to be net-associated and constitute about one-third of all net-associated cells. Such widespread occurrence of perineuronal nets around subpopulations of pyramidal cells is known from macaque monkeys but not from the cortex of myomorph rodents. Thus it appears that a certain proportion of net-associated pyramidal cells distinguishes individual cortical areas in highly evolved primates. This ratio may vary also with respect to species-dependent organization principles in nonprimate mammals.

Aged↗

PubMed1996

In vivo and in vitro labelling of perineuronal nets in rat brain.

Previous lectin-histochemical and immunocytochemical investigations using fixed tissue revealed perineuronal nets as lattice-like accumulations of extracellular matrix proteoglycans at the surface of several types of neurons. In the present study, perineuronal nets in the rat brain were labelled for the first time in vivo by stereotaxic injections of biotinylated Wisteria floribunda agglutinin (Bio-WFA), as well as in vitro, by incubation of unfixed brain slices with the same lectin. Six days after Bio-WFA injections into the parietal cortex, medial septum, reticular thalamic nucleus and red nucleus, the lectin remaining bound to perineuronal nets was detected by streptavidin/biotinylated peroxidase complexes or red fluorescent Cy3-streptavidin, respectively. Double-fluorescence labelling showed that Bio-WFA applied in vivo reacted with the chondroitin sulphate proteoglycan immunoreactive perineuronal nets in the injection zone. Labelling of perineuronal nets in unfixed slices was obtained with either Cy3-tagged WFA or Bio-WFA and subsequent visualization by Cy3-streptavidin which confirmed the region-dependent distribution patterns and the structural characteristics of perineuronal nets known from histochemical studies. These results provide support for the role of extracellular matrix proteoglycans to maintain a considerable chemical and, probably, spatial heterogeneity of the extracellular space in vivo. The ability of in vivo and in vitro labelling may promote the functional characterization of the extracellular matrix in various brain structures including its species-dependent neuronal association patterns.

Animals↗

PubMed1996

Extracellular matrix organization in various regions of rat brain grey matter.

Previous studies revealed the concentration of extracellular matrix proteoglycans in the so-called perineuronal nets on the one hand and in certain zones of the neuropil on the other. This nonhomogeneous distribution suggested a non-random chemical and spatial heterogeneity of the extracellular space. In the present investigation, regions dominated by one of both distribution patterns, i.e. piriform and parietal cortex, reticular thalamic nucleus, medial septum/diagonal band complex and cerebellar nuclei, were selected for correlative light and electron microscopic analysis. The labelling was performed by the use of the N-acetylgalactosamine-binding plant lectin Wisteria floribunda agglutinin visualized by peroxidase staining and additionally by photoconversion of red carbocyanine fluorescence labelling for electron microscopy. The intense labelling of the neuropil of a superficial piriform region, presumably identical with sublayer Ia, was confined to a fine meshwork spreading over the extracellular space between non-myelinated axons, dendrites and glial profiles. In the reticular thalamic nucleus the neuronal cell bodies were embedded in zones of labelled neuropil. In contrast to these patterns, the labelled extracellular matrix in different cortical layers and in the other subcortical regions was concentrated in perineuronal nets as large accumulations at surface areas of the neuronal perikarya and dendrites and the attached presynaptic boutons. Astrocytic processes usually were separated from the neuronal surface by the interposed extracellular material. Despite a great variability, the width of the extracellular space containing the labelled matrix components in all perineuronal nets appeared to be considerably larger than that in the labelled zones of neuropil and the non-labelled microenvironment of other neurons. Our results support the view that differences expressed in topographical and spatial peculiarities of the extracellular matrix constituents are related to neuron-type and system-specific functional properties.

Acetylgalactosamine↗

PubMed1996

Triple immunofluorescence labelling of parvalbumin, calbindin-D28k and calretinin in rat and monkey brain.

This study presents novel techniques for the concomitant cytochemical detection of the calcium-binding proteins parvalbumin, calbindin-D28k and calretinin which are frequently used neuronal markers. For the triple immunofluorescence labelling of such antigens in rat and monkey brain--with emphasis on the cortex--we developed four different protocols which revealed obviously identical distribution patterns in consecutive sections. These methods included the simultaneous use of purified monoclonal antibodies directed against parvalbumin and calbindin--D28k--haptenized with biotin or digoxigenin--and subsequent visualization with fluorochromated hapten-recognizing immunoreagents. For the combined visualization of the calcium-binding proteins we applied the bright red fluorescent carbocyanine Cy3, blue fluorescent 7-amino-4-methylcoumarin-3-acetic acid (AMCA) and as green fluorophore either fluorescein or the newly introduced carbocyanine Cy2. The latter showed a higher fluorescence intensity and more resistance against photobleaching than fluorescein. In addition to clearly distinguished distribution patterns of the calcium-binding proteins, neurons co-expressing parvalbumin and calbindin-D28k in the parietal and piriform cortex of rat were demonstrated. The elaborated methods might stimulate the further detailed investigation of spatial and functional relationships between structures immunopositive for selected neuroanatomical markers.

Animals↗

PubMed1996

Respiratory mechanics in patients ventilated for critical lung disease.

Respiratory mechanics, using flow interruption, was previously studied during the complete breath in healthy ventilated man, numerical techniques relieving constraints regarding flow pattern. The classical linear model of non-Newtonian behaviour was found to be valid. The present study was extended to subjects with critical lung disease. Subjects with acute lung injury (ALI; n = 2), acute respiratory distress syndrome (ARDS; n = 4), and chronic obstructive pulmonary disease (COPD; n = 3) were studied with and without positive end-expiratory pressure (PEEP). Functional residual capacity (FRC) was measured with sulphur hexafluoride (SF6) wash-out. The static pressure-volume (P-V) curve was linear at zero end-expiratory pressure (ZEEP), but nonlinear at PEEP. Its hysteresis was nonsignificant. In ALI/ARDS, PEEP increased lung volume by distension and recruitment, but only by distension in COPD. In ALI/ARDS, resistance was increased, at ZEEP. In COPD, resistance became extremely high during expiration at ZEEP. In ALI/ARDS at ZEEP, non-Newtonian behaviour, representing tissue stress relaxation and pendel-luft, complied with the classical linear model. At PEEP, the non-Newtonian compliance became volume-dependent to an extent correlated to the nonlinearity of the static P-V curve. In COPD, non-Newtonian behaviour was adequately explained only with a model with different inspiratory and expiratory behaviour. The classical model of the respiratory system is valid in ALI/ARDS at ZEEP. More advanced models are needed at PEEP and in COPD.

Adult↗

PubMed1996

Distribution patterns of Wisteria floribunda agglutinin binding sites and parvalbumin-immunoreactive neurons in the human visual cortex: a double-labelling study.

Extracellular lattic-like coatings--known as perineuronal nets (PNs)--ensheath certain types of neurons in the mammalian neocortex. PNs and densely stippled zones in some cortical layers contain proteoglycans stainable e.g. with several plant lectins. The present study is focused on the binding sites of the plant lectin Wisteria floribunda agglutinin (WFA) and on its relationship to parvalbumin-immunoreactive (PARV-ir) neuronal constituents in the human visual cortical fields 17 and 18. Size and numbers of PNs varied not only between these two areas, but also between its layers. In area 17 the PNs appeared accumulated in two conspicuous bands which included layer IV, particularly layer IVb, and layer VI. Layer IVc of area 17 contained numerous small faintly stained PNs. In area 18 a two-tiered organization of PNs in layers IIIb-c and layer V was emphasized. The neuropil staining by WFA was much more intense in layers IIIb-c of area 18 than of area 17. In areas 17 and 18 the vast majority of PNs was associated with sub-populations of PARV-ir cells resembling several classes of GABAergic cortical interneurons. Among PARV-negative cells surrounded by PNs, only exceptionally pyramide-like neurons were detected. The patterns of lectin-labelling in the human visual primary and association cortex resembled those of macaque monkeys and differed from those in the visual cortex of rat and gerbil. These differences between mammals representing divergent modes of visual specialization may support the view that such extracellular matrix components in these occipital cortical areas are involved in visual information processing subserving fast inhibitory interneuronal actions.

Agglutinins↗

PubMed1996

Spatial relationship of lectin-labelled extracellular matrix and glutamine synthetase-immunoreactive astrocytes in rat cortical forebrain regions.

Extracellular matrix proteoglycans have previously been revealed by immunocytochemical and lectin-histochemical methods as distinct perineuronal nets in the microenvironment of different types of neurons, but also as a diffuse stain throughout the neuropil in region-dependent patterns. Ultrastructural investigations of perineuronal nets in subcortical regions have demonstrated glycan components in the close vicinity of astrocyte processes, suggesting that the extracellular matrix contributes differentially to the glianeuron interface. In the present study the spatial relationship of extracellular matrix components and astrocytes was characterised at the regional and cellular level by lectin histochemistry (soybean agglutinin, Vicia villosa agglutinin, Wisteria floribunda agglutinin) and antiglutamine synthetase immunocytochemistry in the rat neocortex and hippocampus. In most cortical areas layer-specific patterns of diffuse neuropil staining revealed by the lectins could also be recognised after glutamine synthetase (GS) immunostaining. In double-labelling experiments GS-immunoreactive astrocyte processes were found to reach lectin-stained perineuronal nets. GS-immunoreactivity was often parallelled but did not coincide with the lectin label completely, but was observed to form net-like structures similar to the perineuronal lectin staining. Using immunocytochemistry with anti-GS perineuronal, net-like structures were demonstrated on certain parvalbumin-immunopositive neurons which are known to be ensheathed by lectin-stained perineuronal nets. It was evident that a single neuron may receive net-like contacts from several astrocytes and that a single astrocyte can contribute to perineuronal nets on more than one neuron. The findings support the view that N-acetylgalactosamine-containing extracellular matrix molecules and astrocytic processes are topically associated to a high degree. Different proportions of both components may specify the individual neuronal micro-environment.

Acetylgalactosamine↗

PubMed1995

Allocation of perineuronal nets and parvalbumin-, calbindin-D28k- and glutamic acid decarboxylase-immunoreactivity in the amygdala of the rhesus monkey.

Lattice-like coatings, known as perineuronal nets, were lectin-cytochemically stained with the Wisteria floribunda agglutinin in the lateral nucleus and the intermediate division of the basal nucleus of the amygdala in rhesus monkeys. Perineuronal nets were demonstrated around neurons with parvalbumin- or calbindin-D28k-immunoreactivity, but not around calretinin-containing cells. In parallel dual-peroxidase staining experiments, it was demonstrated that lattice-like coatings exclusively surround GABAergic neurons in this brain region. The novel finding of calbindin-D28k-immunoreactivity in neurons ensheathed by perineuronal nets amplifies the panel of revealed markers in such nerve cells and indicates their cytochemical heterogeneity.

Amygdala↗

PubMed1995

Regional and cellular expression sites of the alpha 1 subunit of GABAA receptors in the rat basal forebrain: a cytochemical study with glutamic acid decarboxylase, choline acetyltransferase, calcium-binding proteins and nitric oxide synthase as second markers.

Forebrain sections of adult male Wistar rats were processed for the immunohistochemical detection of the GABAA receptor alpha 1 subunit. Alternate sections were used for double-staining with antibodies to glutamic acid decarboxylase (GAD), choline acetyltransferase (ChAT), the calcium binding proteins parvalbumin (PARV), calbindin (CALB) and calretinin (CR) as well as to nitric oxide synthase (NOS). alpha 1 receptor subunit-immunoreactive neurons were found to be inhomogeneously distributed in the rat basal forebrain. Numerous alpha 1 subunit-immunostained neurons occupied the central part of medial septum and diagonal band, the whole ventral pallidum and the globus pallidus. A moderate number was found in the lateral septum, and only very few in the striatum and nucleus accumbens. Double-immunofluorescence labelling revealed an apparently complete co-expression of GAD-immunoreactivity in alpha 1 subunit-immunoreactive cells of rat basal forebrain, but only a region-dependent proportion of GAD-immunoreactive cells showed alpha 1 subunit-immunoreactivity. Co-expression of PARV-immunoreactivity characterized the vast majority of the alpha 1 subunit-immunoreactive cells in the medial septum, diagonal band, ventral pallidum and globus pallidus. Striatal alpha 1 subunit-immunopositive neurons appeared PARV-immunonegative and did also not react with the other immunoreagents used in this study, except the GAD-antibody. CR-immunoreactivity was co-expressed in alpha 1 subunit-immunopositive cells of the ventral lateral septal nucleus and only exceptionally in the ventral pallidum, where the vast majority of CR-positive cells was monolabelled. A small minority of ChAT-immunoreactive, but in no case CALB- and NOS-immunoreactive cells were found to express the alpha 1 subunit-immunoreactivity. These findings confirm the data obtained by analyses of other brain regions suggesting a preferred co-existence of this GABAA receptor subunit with PARV and to a lesser degree with CR.

Animals↗

PubMed1995

192IgG-saporin immunotoxin-induced loss of cholinergic cells differentially activates microglia in rat basal forebrain nuclei.

To characterize the specificity of a novel cholinergic immunotoxin (conjugate of the monoclonal antibody 192IgG against the low-affinity nerve growth factor receptor with the cytotoxic protein saporin), coronal sections through the basal forebrain of adult rats, that received a single intracerebro-ventricular injection of 4 micrograms of 192IgG-saporin conjugate, were subjected to histochemical and immunocytochemical procedures to evaluate cholinergic (choline acetyltransferase (ChAT)-immunoreactive, acetylcholinesterase-positive, NADPH-diaphorase-positive) and GABAergic structures (parvalbumin-immunoreactive, labeling of perineuronal nets with Wisteria floribunda agglutinin) as well as microglia (visualized with Griffonia simplicifolia agglutinin) and astrocytes (immunostaining for glial fibrillary acidic protein). Seven days following injection of the immunotoxin, ChAT-immunoreactive cells nearly completely disappeared throughout the magnocellular basal forebrain complex, including globus pallidus, as compared to vehicle-injected controls. However, there was no significant difference in the number of ChAT-positive cells in the adjacent ventral pallidum and in the caudate-putamen of immunolesioned and control animals. NADPH-diaphorase-containing cells, including a significant subpopulation of cholinergic cells, also strikingly decreased in number by more than 90% in the magnocellular basal forebrain complex following immunolesion, and only a few noncholinergic diaphorase-positive cells survived in the medial septum, vertical and horizontal diagonal band, and nucleus basalis of Meynert. In contrast, the number of parvalbumin-containing GABAergic projection neurons in the septum-diagonal band of Broca complex and nucleus basalis of Meynert from immunolesioned rats was not different from that of vehicle-injected control animals. Immunolesioning also did not result in any change in either number or shape of cells surrounded by perineuronal nets, which are frequently associated with parvalbumin-containing GABAergic neurons. Seven days following injection of the immunotoxin, a very strong activation of microglia with an identical distribution pattern was observed in all experimental animals. Large numbers of activated microglia were found in all magnocellular basal forebrain nuclei, corresponding to the distribution of degenerating cholinergic cells. Additionally, immunolesioning also resulted in a dramatic activation of microglia in the lateral septal nuclei, which are known to be almost free of cholinergic cells, but not of penetrating cholinergic dendrites in adjacent zones, and in the ventral pallidum, where there was no observed loss of cholinergic cells. There was no significant increase in microglia activation in striatum and cortical areas, and no astrocytic response in any of the basal forebrain nuclei at this particular time point of survival. These results suggest that 192IgG-saporin specifically destroys basal forebrain cholinergic neurons and does not suppress their neuronal activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1995

Co-occurrence of perineuronal nets with GABAA receptor alpha 1 subunit-immunoreactive neurones in the rat septal region.

The immunocytochemical demonstration of the GABAA receptor alpha 1 subunit was combined with the Wisteria floribunda agglutinin staining of lattice-like extracellular matrix components--known as perineuronal nets--in the rat basal forebrain. Both were found to be co-localized in the septal-diagonal band region (e.g. in the medial septum, 96%), but only exceptionally in the ventral pallidum (3-10%) and nowhere in other basal forebrain subdivisions. This co-occurrence of perineuronal nets with septo-hippocampal projection neurones--previously characterized as GABAergic--expressing the GABAA receptor alpha 1 subunit- as well as parvalbumin-immunoreactivity, suggests the involvement of these intra- and extraneuronal components in the fast spiking neuronal activity essential for the generation and maintenance of hippocampal theta rhythm.

Animals↗