Dystrophin splice variants are distinctly localized in the hippocampus

It has previously been demonstrated that Dp71, the most abundant dystrophin protein in the brain, is mainly localized in the postsynaptic densities. Here we show the localization of Dp71f, one of the splice variants of this protein, within the CA3 region of the hippocampus. Immunopositivity occurs in the postsynaptic density of small asymmetrical axospinous and axodendritic synapses, while it is absent in the postsynaptic densities of the axospinous synapses of the large mossy fiber terminals. Dp71f immunoreactivity was found to be attached to the membranes of the mossy fibers in the stratum lucidum of the CA3 area. In a certain population of thin myelinated axons the protein seems to be present within the axon proper. These data support the notion of a physiological role of Dp71f distinct from other dystrophin isoforms present in the central nervous system.

Seasonal fluctuations of glial fibrillary acidic protein (GFAP) immunoreactivity in the rat suprachiasmatic nucleus

The pacemaker of the "biological clock", the suprachiasmatic nucleus (SCN) of the hypothalamus was studied in intact male rats for glial fibrillary acidic protein (GFAP) a specific marker for astrocytes. Immunohistochemical reactions were carried out in winter (January-February) and in summer (June-July). In winter the GFAP-immunoreactivity of the SCN was found low whereas in summer it was high. Gonadectomy reduced differences. Since photic stimuli that apparently trigger the observed differences reach the SCN through identified neuronal pathways we conluded that the reaction of astrocytes is an indicator of seasonally altered neuronal function in the SCN.

Comparison of VHS video recording system with apple Macintosh-based image analysis and modified CODA-3 systems in equine motion analysis

A VHS video--computer-based image analysis combination is described as a low sampling rate motion analysis system. Video recordings were taken indoor without any artificial illumination at 25 fps sampling rate. The horse studied was running on a high-speed treadmill and observed at 1.6, 4 and 7 m/s velocities at walk, trot and canter, respectively. Left forelimb and hindlimb were recorded separately from lateral view. For comparison, parallel CODA-3 recordings were taken at the same time from the same position. Joint angles were expressed and compared in angle-time diagrams. Sampling of both systems has been synchronised by a timer device at +/- 1/300 s error level. Results obtained with the two different recording systems were comparable in all joints measured with the exception of the fetlock. Inaccuracies in fetlock recordings are thought to be eliminated by measuring at controlled illumination. As a conclusion, the VHS-Macintosh setup appears to be promising as a simplified system for gait analysis.

Sexual dimorphism of glial fibrillary acidic protein (GFAP) immunoreactivity in the rat interpeduncular nucleus

The intensity of immunostaining for the glial fibrillary acidic protein (GFAP) is outstandingly high in the interpeduncular nucleus. This nucleus was compared in males and females for its GFAP immunoreaction. Immunohistochemistry was carried out on free floating vibratome slices and evaluated by surface densitometry. While in males the reactions were similar, females showed individual variations. Since the interpeduncular nucleus is a hormonally inactive brain area where gonadal hormones do not induce plastic synaptic changes, it is concluded that concerning this astroglial marker a sexual dimorphism exists also outside the "endocrine brain".

Vasoactive intestinal polypeptide in neuroglia? Immunoelectron microscopic localization in astrocytes of the rat mesencephalon

The dorsal region of the rat interpeduncular nucleus (IPN) was found highly immunoreactive for vasoactive intestinal polypeptide (VIP). This area appeared as a cap-like structure at the midcaudal level of the nucleus. Unlike other brain areas, however, VIP immunoreactivity within the "cap" appeared vaguely punctuate with no light microscopically identifiable cell structures. Ultrastructurally, a dense meshwork of VIP-immunopositive bouton-laden axons was revealed. Labeled neuronal perikarya were not encountered. Some lightly immunoreactive dendrites were observed. In addition, immunopositive glial profiles were frequently seen. Perikarya and numerous fine processes, occasionally perivascular, identified as astroglia by established ultrastructural criteria, exhibited VIP immunoreactivity. Constant feature of the peptide immunolocalization was the predilection for the intermediate filament bundles of astrocytic perikarya and processes. This was usually accompanied by a thick coating of the inner aspect of glial plasmalemma and, in perikarya, by highly reactive vesicular profiles. Glial immunopositive elements were never seen beyond the boundaries of the diffuse "cap." In view of the repertoire of metabolic, neurotrophic, and neuroprotective mechanisms in which VIP neurons are involved in conjunction with astroglia, the presence of VIP-immunoreactive astrocytes in a circumscribed area, confirms the heterogeneity of astrocyte populations.

Retarded myelination in the lumbar spinal cord of piglets born with spread-leg syndrome

Piglets born with spread-leg syndrome, a congenital weakness of the hindlimb adductors, were investigated to determine the site of lesion leading to limb impairment. Histological and immunohistochemical studies of the motor neuron unit showed no alterations but quantitative analysis revealed a reduction of axonal diameter and myelin sheath-thickness of the fibres innervating the adductors of the affected limbs. In the lumbar spinal cord a lack of myelination was observed in the tracts descending to the lower motor neurons. Recovery from the syndrome was accompanied by a catching-up of myelination with that of the controls. The spread-leg syndrome is due to a nutritional deficiency in the sow; thus it is assumed that the deficient maternal substances, mainly choline and methionine, are essential for the normal myelin production by spinal white matter oligodendrocytes of the fetus.

Distribution and synaptology of vasoactive intestinal polypeptide (VIP) immunoreactive structures in the rat periaqueductal grey

Light microscopic analysis of the rat midbrain periaqueductal grey (PAG) showed vasoactive intestinal polypeptide immunoreactive (VIP-ir) neurons localized at the lateral and ventral walls of the aqueduct. Some varicose VIP-ir elements were detected closely associated with the ependyma. While several VIP-ir elements were encountered immediately under the ependyma, in a few cases, VIP-ir cell bodies were seen on the luminal surface of the ependymal cells lining the aqueduct. Electron microscopy revealed that most of these cells possessed the characteristics of a local circuit neuron. All VIP-ir cells had indented nuclei. Two types were distinguished: one with rounded cell body receiving numerous axo-somatic synapses established by VIP-negative axons. The other cell type was fusiform and its surface was almost fully isolated from axonal contacts by a glial sheath. The VIP-ir processes were interconnected with other periaqueductal cells by a variety of synaptic contacts. VIP-ir axon terminals formed asymmetric synapses with immunonegative dendritic shafts often in glomerulus-like assemblies. The postsynaptic immunonegative dendrites were of the aspinous, beaded type. We suggest that VIP-ir cells and processes in the midbrain PAG establish connections between the longitudinal functional columns of this region. On the basis of their morphology, VIP-ir cells in the PAG appear to be excitatory, terminating on inhibitory interneurons. Thus, a VIP-stimulated inhibition may be instrumental in the coordination of responses evoked by the stimulation of PAG columns.

Ovarian cycle-related changes of glial fibrillary acidic protein (GFAP) immunoreactivity in the rat interpeduncular nucleus

The interpeduncular nucleus (IPN) of female rats was studied across the estrous cycle to observe whether the expression of the astroglial marker, glial fibrillary acidic protein (GFAP) reacts to hormonal changes in an area not belonging to the 'endocrine brain'. A marked reduction of immunoreactive GFAP was observed in estrus as compared to the immunoreactivities in met- and proestrus. This finding is consistent with earlier observations in the endocrine hypothalamus, but also proves that gonadal steroids influence astroglia in brain regions not involved in neuroendocrine regulation. Since cyclic fluctuations of synaptic numbers in the female have been described only for the endocrine hypothalamus, decrease of immunoreactive GFAP in the IPN during estrus may reflect a down-regulation of GFAP synthesis.

Glial fibrillary acidic protein (GFAP)-immunoreactivity is reduced by castration in the interpeduncular nucleus of male rats

The interpeduncular nucleus of adult male rats was investigated for glial fibrillary acidic protein immunoreactivity. In intact animals the nucleus had an outstandingly intense immunostaining, particularly at its periphery, including the rostral, lateral, dorsomedial and dorsolateral subnuclei where, in addition to neuropil astrocytes, a substantial amount of perivascualr glia was found. Four weeks after castration, immunostaining decreased markedly in the core region of the nucleus corresponding to the caudal and medial subnuclei, and to a much lesser extent at the periphery. The immunoreactivity in pericapillary astrocytes proved to be insensitive to castration. Testosterone, if administered after castration prevented or restituted the loss of immunoreactivity. Beyond 4 months after castration, the effect of testosterone gradually declined. It is concluded that testosterone stimulates the expression of glial fibrillary acidic protein immunoreactivity in the interpeduncular nucleus. Our findings support the argument that gonadal steroids can influence astrocytes also in non-endocrine areas of the brain.

The demonstration of immunoreactive dystrophin and its developmental expression in perivascular astrocytes

Immunoreactivity of dystrophin family proteins was observed in the astrocytes of the adult and immature rat hippocampus and cerebral cortex by using Dys2, a monoclonal antibody recognizing both 427 kDa and short dystrophin isoforms. As revealed by light and electron microscopy, immunostaining of the ribosomal apparatus and of pericapillary endfeet was particularly pronounced in the adult. In the pericapillary astrocyte processes immunostaining appeared between postnatal days 10 and 20, and reached the intensity seen in the adult by postnatal day 30. In the pericapillary astrocyte process, the membrane facing the endothelial basal lamina was the earliest structure to show the immunoreaction. At later stages, the pericapillary astrocyte process was gradually filled up with immunoprecipitate. Findings suggest that dystrophins are expressed coinciding with the development of the blood-brain barrier, and it is assumed that they contribute to the formation of this system.

Pre- or postembedding immunocytochemistry: which to choose for the localization of glial fibrillary acidic protein (GFAP)?

Immunostaining for glial fibrillary acidic protein was performed in the hippocampus and cerebellum of adult rats in order to compare the distributions of immunolabelling after pre- and postembedding procedures. The reactions of protoplasmic astrocytes and pericapillary astrocyte processes were investigated at the electron microscopic level. After the pre-embedding reaction, visualized with 3,3'-diaminobenzidine tetrahydrochloride, a granular precipitate was observed to decorate the rough endoplasmic reticulum of the astrocyte cell bodies and a precipitate filled the cytoplasm in the astrocyte processes. In studies with the postembedding procedure, immunogold particles were observed to be attached exclusively to the intermediate filaments of the astrocytic cytoskeleton both in the cell body and in the processes. It is concluded that the diaminobenzidine precipitate diffuses in the cytosol, pre-embedding immunocytochemistry is therefore, suitable for the overall labelling of astrocytes, whereas the postembedding procedure reveals the exact intracytoplasmic localization of glial fibrillary acidic protein. This explains the similar pre-embedding immunostaining patterns of astrocytes with markedly different amounts of glial filaments (e.g. protoplasmic, fibrous and reactive) and stresses the importance of the use of the postembedding method when an exact intracellular localization is required. The results also suggest that, in spite of claims of soluble cytoplasmic pools of this protein, the glial filaments are the exclusive domains of immunoreactive glial fibrillary acidic protein.

Differential distribution of dystrophin in postsynaptic densities of spine synapses

Dystrophin immunocytochemistry was carried out using monoclonal antibody against the C-terminal part of dystrophin (Dys2) in rat cerebral cortex, cerebellum and hippocampus containing a high number of spine synapses of similar morphological character. Dys2 immunoreactivity was found in the spine component of spine synapses. Particularly heavy label was observed on the postsynaptic densities. In the cerebral and cerebellar cortices all spines were immunopositive. In the hippocampus some postsynaptic densities were intensely immunostained, whereas those of adjacent synapses remained unstained. The findings suggest that dystrophin is an integral protein of the postsynaptic component of spine synapses but is lacking in a subpopulation of hippocampal spine synapses. The heterogeneity of input to the hippocampal spiny sites by contrast to the homogeneous population of fibres synapsing with cerebral and cerebellar cortical spines is suggested to account for differences.

Modular distribution of vasoactive intestinal polypeptide in the rat barrel cortex: changes induced by neonatal removal of vibrissae

The distribution of vasoactive intestinal polypeptide-immunoreactive neuronal structures in the barrel cortex (posteromedial barrel subfield) of adult rats was analysed after unilateral removal of the vibrissal follicles of row C in neonatal rats. The hypothesis was tested whether the distribution of vasoactive intestinal polypeptide-immunoreactive structures depends on the normal anatomical organization of the specific sensory input. After three months survival the distribution of the vasoactive intestinal polypeptide-immunoreactive structures was morphometrically evaluated. This approach revealed alterations in the contralateral posteromedial barrel subfield, where the disappearance of barrel row C and a substantial increase in size mainly of barrel row D, but also of other rows could be detected. Increase in row D included both barrels and the interspace (septal segments between barrels in one row). As vasoactive intestinal polypeptide immunoreactivity of the barrel field was found previously to be localized in synaptic boutons involved in symmetric synapses, our present findings suggest that (i) the interspace is enriched in inhibitory vasoactive intestinal polypeptide-immunoreactive synapses as opposed to the excitatory thalamocortical input reaching the barrel hollow, (ii) the spatial distribution of the vasoactive intestinal polypeptide system in the barrel cortex is closely associated with the neuronal organization of the sensory input and reacts with a considerable plasticity to lesion-induced changes of the input, and (iii) the compensatory barrel hypertrophy in a row neighbouring the deafferented row involves an increasing number of vasoactive intestinal polypeptide-immunoreactive synapses per barrel.

Geniculo-cortical afferents form synaptic contacts with vasoactive intestinal polypeptide (VIP) immunoreactive neurons of the rat visual cortex

The lateral geniculate nucleus of the rat was injected with the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA-L) to see if geniculo-cortical axons terminate on vasoactive intestinal polypeptide immunoreactive (VIP-IR) neurons of the primary visual cortex. PHA-L-labelled boutons attached to VIP-IR perikarya and dendrites were identified as presynaptic parts of asymmetrical synapses. This geniculo-cortical projection to VIP-IR cells in the visual cortex and comparable findings in the somatosensory cortex suggest that sensory input from specific thalamic nuclei may influence local circuit inhibition and the metabolic state within the cortical domain via VIP-IR neurons.

Remote astroglial response associated with synaptic degeneration results in a net increase of perisynaptic glial fibrillary acidic protein

Remote astroglial response was evoked in the adult rat visual cortex by unilateral destruction of the corpus geniculatum laterale. Homogenates of ipsi- and contralateral (operated and control) visual cortices were analysed by immunoblotting. A peak increase in glial fibrillary acidic protein (GFAP) was observed 2 weeks after lesion which then declined but did not return to normal showing a time course similar to that of previously observed immunohistochemical changes. Findings prove that the mechanism underlying the enhanced immunoreactivity during remote astroglial response is an up-regulation of GFAP synthesis in the astroglial processes surrounding degenerating synapses.

The remote astroglial response (RAR): a holistic approach for evaluating the effects of lesions of the central nervous system

The right dorsal lateral geniculate nucleus was stereotaxically destroyed in adult albino rats. After 3 to 150 days of survival the visual cortices from both hemispheres were processed for semithin histology, electron microscopy, GFAP immunohistochemistry and immunoblotting. In visual cortices with histologically disclosed degeneration of the geniculo-cortical tract, a hypertrophy of astrocytes without change in their total numbers was seen from postoperative day 3. From day 7, a rise in GFAP immunoreactivity was observed, reaching its peak between days 11-14, after which a decrease occurred. Observations were confirmed by computer-assisted image analysis of immunohistochemical preparations. Using the immunoblot technique, relative GFAP levels were found to change in a fashion similar to immunohistochemical findings. This showed that synaptic degeneration triggered an up-regulation of GFAP synthesis in the perisynaptic astrocyte processes as a second, cytoskeletal phase of the astrocyte reaction. The phenomenon is denoted as the remote astroglial response (RAR) and is thought to be a marker of synapse removal during plastic changes either related to function or induced by lesions. An extrapolation is made to the possible significance of whole-brain GFAP levels in assessing the effects of focal CNS lesions.

Species-specificity of glial vimentin as revealed by immunocytochemical studies with the Vim 3B4 and V9 monoclonal antibodies

Two monoclonal antibodies directed against vimentin, Vim 3B4 and V9 could distinguish between vimentins originating from certain species, when tested on cell lines (Bohn et al, 1992). Our comparative immunohistochemical studies in the rat and chicken brain with the same antibodies suggest the coexistence of two vimentin forms in the glial cells of both species. One of these forms bearing the epitope present in the respective non-glial cell lines is present in astrocytes and Bergmann glia independently of the ontogenic state of the animal. The other epitope appeared also mutually in both species, albeit its expression was more restricted. These patterns suggest that in these two species, the expression of the different vimentin forms might be differently regulated.

Maturation of the GFAP-immunopositive glial network is delayed in the olfactory bulbs of rats subjected to early, low-dose X-irradiation

Young rats were subjected to low-level, repeated doses of x-irradiation from a Co60 source and examined for the presence and arrangement of their GFAP-immunopositive system at the light and electron microscopic levels. In 2-week-old control rats, labelled cells were already distributed homogeneously throughout the bulb, while in the experimental animals, a (newborn- and early postnatal-type) radial arrangement of immunoreactive fibres continued to persist even until the end of the fourth postnatal week. This delay in the maturation of the GFAP-immunopositive glial system may contribute to the hindered development of the bulbar neurones, neuronal connections, and field potentials, as found in earlier studies.

Structural maturation, cell proliferation and bioelectric activity in long-term slice-cultures of immature rat hippocampus

Explants of transverse slices of the 6-day-old rat hippocampus were grown in a serum-free medium for 2-14 days. Histology performed after various culturing periods demonstrated that these slices maintain a high degree of 3-dimensional organotypy, while undergoing growth and differentiation of the main cellular elements similar to that seen in vivo. Histological indications of continuing cell proliferation were verified by autoradiography showing a labelling of neuroblasts in the dentate gyrus and of glioblasts at the sites of gliogenesis observed in vivo. Spontaneous bioelectric activity and evoked potentials were recorded, both indicating the development of impulse generation and neuronal connectivity within the explant. Silver impregnation and electron microscopic studies lent further support for the presence of neuronal networks intrinsic to the hippocampus. These findings suggest that within the period studied the hippocampal slice cultures mature in a fashion similar to that seen in situ.

Vasoactive intestinal polypeptide immunoreactive structures in the mouse barrel field

Immunohistochemistry for vasoactive intestinal polypeptide was carried out in tangentially cut vibratome sections of the barrel cortex in adult mice. Sections through layer IV have revealed an association between the cytoarchitectonically visible modular organization of barrels and the distribution of immunoreactive axon terminals. These terminals are preferentially localized in the side region of a barrel, whereas the hollow shows a relative scarcity of these structures as shown with image analysis. This finding is the first direct demonstration of a modular distribution of vasoactive intestinal polypeptide-containing axon terminals in the neocortex.

Matching localization of vasoactive intestinal polypeptide (VIP) and VIP-receptor at pre- and postsynaptic sites in the mouse visual cortex

Vibratome sections of the mouse occipital cortex were processed by double label immunohistochemistry to demonstrate the localization of the receptor for vasoactive intestinal polypeptide and the peptide itself. The receptor was found to be distributed in the cytoplasm and major dendrites of numerous cortical cells, mainly pyramidal neurons. Vasoactive intestinal polypeptide, on the other hand, occurred in a population of non-pyramidal neurons and axonal boutons. Image analysis revealed a close spatial association of peptide-containing presynaptic terminals with receptor-containing cells. Ultrastructurally, these connections represented symmetrical axo-somatic and axo-dendritic synapses. Our findings demonstrate a matching histological localization of vasoactive intestinal polypeptide and its receptor in the brain.

Long-term effects of anterograde degeneration on astroglial reaction in the rat geniculo-cortical system as revealed by computerized image analysis

Changes in the expression of glial fibrillary acidic protein by astrocytes in the primary visual cortex of adult albino rats were analyzed with immunohistochemistry after unilateral destruction of the dorsal lateral geniculate nucleus. An increase in number of glial fibrillary acidic protein-immunoreactive astrocytes could be detected in the visual cortex of the side ipsilateral to the lesion in the short-term survival group (7-11 days post lesion), but this increase was extremely reduced after a postlesional survival time of 150 days. The quantitation of the glial response by image analysis showed, that the initial increase was mainly localized in the cortical layers II-IV, where the geniculo-cortical input terminates. The transient nature of this process was revealed by the measurements in the long-term survival group, where differences between experimental and control sides were substantially reduced. We conclude, that the remote glial response in the visual cortex is transient and that is disappearance indicates the end of a postlesional adaptation period in the neuropil.

Slices from the rat olfactory bulb maintained in vitro. Morphological aspects

Transverse, 400-microns-thick slices of 8-day-old rat olfactory bulb were incubated in Krebs-Henseleit medium with and without oxygenation. Following incubation, slices were fixed in aldehyde-osmium and embedded in resin for light and electron microscopy. After 2 h of incubation oxygenated preparations showed a structural preservation comparable to that of the freshly fixed olfactory bulb. Under hypoxic conditions mitral cells located on the medial side of the bulb were the most sensitive to the interruption of gassing, while ventricular cells and glomeruli were remarkably resistant as judged by morphological standards. The effects of short-term (up to 30 min) interruptions of gassing proved to be reversible. Our findings suggest that the incubated olfactory bulb slice may be a useful preparation for functional morphological studies.

Developmental gradients of vasoactive intestinal polypeptide (VIP)-containing neurons in the rat visual cortex detected by image analysis

The postnatal development of vasoactive intestinal polypeptide-immunoreactive (VIP-IR) neurons was followed by computer-assisted image analysis in the rat visual cortex. The laminar distribution of all VIP-IR structures was measured. These structures were subdivided into cell somata, dendritic profiles and axonal boutons and measured separately. VIP-IR neurons were first seen on postnatal day 1, mostly in the upper half of the presumptive visual cortex. A localization of cell bodies similar to that in the adult is reached between days 12 and 16. VIP-IR dendrites have a protracted growth period as compared to perikarya, involving a developmental gradient from an even distribution to a concentration in the upper cortical layers. This is due to the formation of dendritic terminal arbors after the second postnatal week. Scattered VIP-IT axonal boutons appear on day 3 in the midportion of the presumptive visual cortex. Their typical laminar distribution in layers II, IV and lower VI was observed after day 12. Our results suggest that the biochemically detected sharp increase in VIP levels after the second postnatal week is due to the maturation of cell processes as a morphological basis of neuronal connectivity.

Mapping of glial fibrillary acidic protein-immunoreactivity in the rat forebrain and mesencephalon by computerized image analysis

Computer-assisted image analysis was used to map the regional distribution of glial fibrillary acidic protein-immunoreactive (GFAP-IR) astrocytes in the rat forebrain and mesencephalon. A complete survey of packing densities of GFAP-IR structures was performed. Computer maps revealed high values in the outer and inner layers of the cortex, some hippocampal and olfactory bulb layers, prepiriform cortex, dorsal part of the caudate-putamen, globus pallidus, lateral septum, reticular thalamic nucleus, lateral habenular nucleus, circumventricular organs, nuclei of the medial hypothalamus, substantia nigra, interpeduncular nucleus, and mamillary body. These correspond to regions of the embryonic pial and ventricular brain surfaces, which undergo developmental alterations including growth and various forms of internalization. From this we conclude that in the adult brain, astrocytes of high GFAP-IR are derivatives of surface-contact glia, whereas those located in areas having developed by the local thickening of the neural tube wall show reduced or no GFAP-IR.

Enantioselectivity at the physiologically active GABAA receptor

A subfraction of cortical tissue from rat brain, containing membrane vesicles was prepared freshly with added protease inhibitors and antioxidant. The preparation was used to measure stimulation of transmembrane 36C1- flux and inhibition of bicuculline-sensitive [3H] muscimol binding by (+)-(S) and (-)-(R) enantiomers of dihydromuscimol at 30 degrees in physiological salt solution. Displacement of bound [3H]muscimol and stimulation of 36Cl- flux appeared in the 0.1-10 microM concentration range of the enantiomers, channel gating, however, required rather high concentrations. Degrees of enantioselectivity for channel gating, desensitization of and binding to GABAA receptors were estimated by the concentration ratios of dihydromuscimol enantiomers, [(-)-(R)]/[(+)-(S)], at the same level of response or displacement. Different enantioselectives were observed for channel gating (6 +/- 3), receptor binding (3 +/- 2) and desensitization (no selectivity). The low and concentration-dependent enantioselectives found for channel gating and receptor binding can be explained by desensitization and heterogeneity of GABAA receptors.

Alterations in glial fibrillary acidic protein immunoreactivity in the upper dorsal horn of the rat spinal cord in the course of transganglionic degenerative atrophy and regenerative proliferation

Transection of a peripheral nerve induces marked increase in the glial fibrillary acidic protein (GFAP) immunoreactivity in the ipsilateral, segmentally related upper dorsal horn. Increase of GFAP immunoreaction is similar to, but not identical with, that observed after dorsal rhizotomy. If the peripheral nerve succeeds in regenerating, GFAP immunoreactivity in the upper dorsal horn returns to normal. It is concluded that the amount and distribution of GFAP is determined by transganglionic degenerative atrophy. Wallerian degeneration and regenerative proliferation of dorsal root axon terminals, respectively.

Vasoactive intestinal polypeptide (VIP) containing cells in the developing rat occipital hemisphere

Numerous cells were observed to show intense vasoactive intestinal polypeptide (VIP) immunoreactivity from birth to postnatal day 8 in the subventricular zone of the rat occipital hemisphere. This cell population was markedly reduced by postnatal day 8, but isolated clusters of VIP cells persisted into adulthood. In addition, long, L-shaped VIP fibers were seen in the hemispheric wall up to postnatal day 16, but not in the adult. Parallel to the reduction in number of the subventricular VIP cells an increasing number of VIP cells appeared in the neo- and allocortex, developing by postnatal day 12 all the features of the mature cortical bipolar fusiform neurons. As possible alternatives, the migration of subventricular VIP cells into the cortex, the transient character of the subventricular VIP population or the expression of VIP by radial glia are discussed.

Remote astrocytic response as demonstrated by glial fibrillary acidic protein immunohistochemistry in the visual cortex of dorsal lateral geniculate nucleus lesioned rats

The reaction of astroglia was investigated after unilateral destruction of the dorsal lateral geniculate nucleus in the primary visual cortex of adult albino rats. The destruction of the dorsal lateral geniculate nucleus was performed by stereotaxic injections of ibotenic acid, and the location was verified in Nissl stained sections in each animal. Electron microscopic observations demonstrated the presence of degenerating axon terminals surrounded by hypertrophic astroglial processes mainly in layers III and IV of the ipsilateral primary visual cortex. The ipsilateral (impaired) and contralateral (control) sides of the primary visual cortex showed light microscopically a clearly differing appearance and distribution of glial fibrillary acidic protein (GFAP) immunoreactivity 7 to 11 days after the unilateral injection of ibotenic acid into the dorsal lateral geniculate nucleus. Whereas the control side of the primary visual cortex showed GFAP staining only in the subpial zone of layer I and close to the white matter, all layers of the impaired cortex showed an intense GFAP immunoreactivity. The increase in immunoreactivity was confined to the primary visual cortex. The extent of and increase in immunoreactivity was corroborated by image analysis. These findings were interpreted as a localized hypertrophy of astroglia caused by the anterograde degeneration of geniculocortical terminals. This hypertrophy is accompanied by an increase in GFAP, which may represent the stabilization of the cytoskeleton of newly formed glial processes involved in the rearrangement of the impaired neuropil.

Immunohisto- and cytochemical localization of cortical nicotinic cholinoceptors in rat and man

A monoclonal antibody (WF 6) raised against purified Torpedo nicotinic acetylcholine receptor was applied to study the cellular and subcellular receptor distribution in human and rat neocortex. In both species, immunostaining was most prominent in perikarya and dendrites of the projection neurons in layers III and V. In layer VI fusiform cells displayed immunoreactivity while in layers I, II and IV some round-shaped cells were immunostained. Subcellularly, immunoprecipitate was found in neuronal perikarya, dendrites and in the postsynaptic thickenings, indicating intracellular sites of synthesis, transport and membrane incorporation of receptor protein. The results suggest that WF 6-immunocytochemistry is a useful tool to label nicotinic cholinergic receptors rendering new information about the specific cell-type and subcellular receptor distribution hardly obtainable by using conventional receptor autoradiography.

Distribution of glial fibrillary acidic protein (GFAP)-immunoreactive astrocytes in the rat brain. I. Forebrain

In the first of two papers dealing with the distribution of glial fibrillary acidic protein-(GFAP)-immunoreactive elements in the rat brain, the localization of immunostaining in the forebrain is systematically described. While the limbic cortex was found to contain intensely stained, evenly distributed astrocytes, the neocortex showed clearly stratified GFAP-staining, with substantially less immunoreactivity occurring in the middle layers than in the areas close to the brain surface or the white matter. A remarkably regular staining pattern was observed in the hippocampus and dentate gyrus. The striatum remained unstained in sharp contrast to the pallidum. In the diencephalon, the main thalamic nuclei were poor in GFAP-labelled elements in contrast to the internuclear border zones. In the hypothalamus, nuclei were conspicuous by their GFAP-staining. A consistent differential staining pattern was obtained in the epithalamic structures. The observed distributional pattern of diencephalic GFAP-immunoreactivity is thought to be due to different regional proliferation of the embryonic neuroepithelium of the diencephalon. The uneven distribution of GFAP-immunoreactivity in the forebrain is explained on a mainly developmental basis.

Distribution of glial fibrillary acidic protein (GFAP)-immunoreactive astrocytes in the rat brain. II. Mesencephalon, rhombencephalon and spinal cord

The topographical mapping of glial fibrillary acidic protein (GFAP)-immunoreactivity was performed in coronal serial sections of the rat mesencephalon, rhombencephalon and spinal cord. Relative to a background of poor or moderate overall staining of the mesencephalon, the interpeduncular nucleus, substantia nigra and the periaqueductal grey matter were prominent by their intense GFAP-immunoreactivity. The pons and particularly the medulla contained more GFAP-labelled elements compared with the mesencephalon. The spinal trigeminal nucleus and Rolando substance were distinguished by their intense staining. Large fibre tracts were usually poor in immunoreactive GFAP. In a concluding discussion, findings relevant to the GFAP-mapping of the whole rat CNS are evaluated with regard to possible reasons underlying the observed differential distribution of GFAP-immunoreactivity.

Nerve endings from rat brain tissue release copper upon depolarization. A possible role in regulating neuronal excitability

Membrane vesicles from rat cerebral cortex were prepared and the functional response of the GABAA receptor was followed by monitoring GABA-activated influx of the radiotracer 36Cl- ion. CuCl2 decreased GABA-activated 36Cl- influx into synaptosomal membrane vesicles. The effect of Cu2+ was concentration dependent (5-500 microM CuCl2) and occurred with saturating (1 mM) as well as low (30 microM) GABA concentrations. A similar inhibition of the responses to muscimol (30 microM) was also observed with 50 microM CuCl2. In addition, release of copper from cortical synaptosomes and median eminence was followed by atomic absorption technique. An increased release of copper into the extracellular space was observed upon depolarization with 50 mM K+. A minimal concentration of copper was estimated to be 100 microM in the synaptic cleft. These findings suggest that copper may play a role in regulating neuronal excitability.

[Electron microscopic-cytochemical study of the effect of vinblastine on synaptosome adenylate cyclase in the rat cerebral cortex]

Adenylate cyclase activity was demonstrated by means of electron microscopic cytochemistry in rat cortical synaptosomes incubated under various conditions. It was found that vinblastine caused remarkable changes in the reaction product localization: the limiting membrane reaction diminished, but the number of synaptosomes were seen to contain a course granular precipitate filling up almost the whole presynaptic cytoplasm. The regulatory role the microtubules play in the distribution of adenylate cyclase on cellular membrane is discussed.

Effect of triiodothyronine on the muscarinic receptors and acetylcholinesterase activity of developing rat brain

The effect of triiodothyronine was investigated on the developing muscarinic system in rat cerebral cortex. Triiodothyronine was administered from birth to day 30. In the synaptosomal membrane fraction of the cerebral cortex, acetylcholinesterase activity and the binding of the muscarinic ligand 3H-quinuclidinyl-benzylate increased significantly as compared to the control. An analysis of the binding curve based on Hill plots suggested a positive cooperativity of receptors of the membrane samples obtained from both hormone treated and control animals. The results obtained are in accordance with morphological, biochemical and clinical data on the thyroid hormone effect on central nervous system maturation.

Ramification patterns of vasoactive intestinal polypeptide (VIP)-cells in the rat primary visual cortex. An immunohistochemical study

Vasoactive intestinal polypeptide (VIP)-immunoreactive cells in the primary visual cortex of the rat were classified on the basis of ramification pattern of cell processes. The distribution of cells over cortical layers, and proportions of cell classes relative to total cell numbers were evaluated by means of quantitative methods. Two main types of VIP-positive neurons, the bipolar and the multipolar were distinguished constituting 76% and 24% of the VIP populations, respectively. The axons of vertically oriented bipolars were observed to ramify within a column around the descending dendrite. By contrast, multipolar cells have a non-oriented ramification pattern. The two overlapping axonal systems form the VIP-innervation of the rat visual cortex.

Types and spatial distribution of vasoactive intestinal polypeptide (VIP)-containing synapses in the rat visual cortex

In the rat visual cortex vasoactive intestinal polypeptide (VIP)-containing structures were studied by means of light and electron microscopy and image analysis. VIP-immunoreactive axon terminals were found to form symmetric synapses with small dendritic shafts, dendritic spines and somata of pyramidal cells and interneurons. VIP-terminals often occurred in pairs with VIP-negative, asymmetric synapses on the same postsynaptic structure. VIP-immunostained dendrites and perikarya were contacted by a purely asymmetric and a mixed population of VIP-negative terminals, respectively. Synaptic connections between two VIP-neurons are seldom as compared to the other types of VIP-synapses. Quantitative studies obtained by the image analysis of VIP-stained boutons and dendritic particles in light microscopic preparations suggest a distinct laminar distribution. Dendritic particles are most frequent in layers I-II, whereas axonal boutons have three laminar accumulations: at the border of layers I-II, in layer IV and layer VI. Together with previous results, the present findings argue for a non-random spatial distribution of VIP-boutons.

Quantitative immunohistochemical analysis of VIP-neurons in the rat visual cortex

A critical appraisal of quantitative immunohistochemistry of neuropeptides is presented defining the main criteria of selecting the type of immune-staining and preparation suitable for these investigations. As an example of meeting the established criteria, the immunohistochemical demonstration of vasoactive intestinal polypeptide (VIP)-containing neurons in the rat brain and the processing of VIP-immunostained preparations for computer-controlled image analysis are described.

Immunocytochemical demonstration of radial glia in the developing rat olfactory bulb with antibodies to glial fibrillary acidic protein

Olfactory bulbs of 8-, 12-, 16- and 30-day-old rats were studied by means of immunocytochemistry using antibodies to glial fibrillary acidic protein (GFAP) and with the Toluidine blue-staining of semithin sections. Until day 12 the GFAP-reaction revealed a radial glia system, the fibres of which extended from the axial ventricular cleft to the surface. From day 16 onwards radial fibres were gradually replaced by typical astrocytes. The lack of proliferative activity within the bulb during the early postnatal period suggests that its cells are generated at and migrating from an external site. An intensely proliferating area was detected in the frontal lobe subventricular layer from where a bundle of migratory cells extends into the bulb. Radial glia may thus be of importance in guiding the migration of cells from this axial bundle to more peripheral regions of the olfactory bulb.

Importance of endogenous substrates in synaptosomal functions

Synaptosomes were found to contain endogenous substrates in sufficient amount to support physiological ion equilibrium and to maintain the resting oxygen consumption rate. Exogenous substrates were required only in functional states which brought about an increase of oxygen consumption only in the presence of a stimulating agent. Succinate increased oxygen consumption even in the resting phase but proved to be incapable of supplying energy for synaptosomal ion transport processes.

Proliferative activity in incubated slices of immature rat cerebellum

Slices of 8-day-old rat cerebella were prepared with a tissue chopper, incubated in an oxygenated Krebs-Henseleit solution followed by processing for histology. One micrometer thick sections of resin-embedded slices were stained with Toluidine blue. The external granular layer was shown to maintain its normal proliferative activity up to 3 h of incubation as suggested by the presence of all mitotic phases within this period and by a roughly 50% increase in mitotic index upon a 90-min exposure of incubated slices to 20 microM vinblastine. On this basis the incubated slice of the immature rat cerebellum may serve as a simple tool for the rapid histological testing of short-term mitogenic or cytostatic effects and the vulnerability of a brain germinal layer.

A fraction enriched in dendrodendritic synaptosomes isolated from rat olfactory bulb: morphology and transmitter release

A fraction enriched in dendro-dendritic synaptosomes was isolated from rat olfactory bulb by a rapid method. Synaptosomes preserved their ultrastructure and showed configurational changes in relation to incubation in physiological ion medium as described earlier in the case of cortical synaptosomes. Dendro-dendritic synaptosomes were larger and contained more mitochondria than cortical synaptosomes. Doublets of terminals synapsing with each other were frequently seen and each terminal contained synaptic vesicles. Oxygen consumption of dendro-dendritic synaptosomes was decreased by ouabain and increased by 2,4-dinitrophenol. High-potassium medium evoked a considerable release of GABA and dopamine but not of noradrenaline or serotonin in accordance with histochemical published data.

Reversible and irreversible neuronal damage caused by excitatory amino acid analogues in rat cerebellar slices

Slice preparations of the developing rat cerebellum were used to investigate the light and electron microscopic correlates of reversible and irreversible neuronal injury caused by the neurotoxic excitatory amino acid receptor agonists, kainate and N-methyl-D-aspartate. The slices were examined after various periods of exposure to the agonists (up to 30 min) with or without a 90 min recovery period in agonist-free medium. N-Methyl-D-aspartate (100 microM) caused necrosis of deep nuclear neurons and differentiating granule cells, the exposure times necessary to induce non-recoverable damage (leading to necrosis), being, respectively, 10 min and 20-30 min. Exposure periods of only 2-4 min with kainate (100 microM) were needed for Golgi cells to subsequently undergo necrosis. Other cell types (Purkinje, granule and deep nuclear neurons) were altered histologically by kainate but most recovered fully from 30 min exposures. Before the recovery period, the worst affected of these cells (deep nuclear neurons) displayed increased cytoplasmic and nuclear electron density and microvacuolation due to swelling of Golgi cisterns but little or no chromatin clumping or mitochondrial expansion. The neurons which were injured irreversibly by the agonists within 30 min displayed, near the time of lethal injury, increased cytoplasmic and nuclear electron lucency, marked focal aggregation of chromatin and swelling of Golgi apparatus. Mitochondrial swelling did not appear to precede lethal injury and even after exposure times sufficient, or more than sufficient, to lead to necrosis, large numbers of mitochondria remained in a condensed configuration. The significance of the histological changes is discussed and they are compared with those occurring in other pathological conditions. The time scales required for the receptor agonists to induce irreversible cellular lesions would be consistent with this being a process which is responsible for acute neuronal necrosis in the brain.

Ionic requirements for neurotoxic effects of excitatory amino acid analogues in rat cerebellar slices

The ionic requirements for the neurotoxic effects of N-methyl-D-aspartate and kainate in incubated slices of developing rat cerebellum were studied using light and electron microscopy. Under normal conditions, 30 min exposure to 100 microM N-methyl-D-aspartate followed by a 90 min recovery period in agonist-free medium resulted in the necrosis of differentiating granule cells and deep nuclear neurons, while the corresponding effect of 100 microM kainate was the death of Golgi cells. Substitution of 96% of the Cl- in the medium with isethionate did not prevent the toxicity of either agonist. However, all the ordinarily vulnerable cells survived and exhibited normal ultrastructure if the slices were exposed to the excitants in a Ca2+-free medium and were subsequently allowed to recover in a Ca2+-containing solution. Prior to this recovery period, granule, Golgi and deep nuclear neurons exposed to N-methyl-D-aspartate were markedly swollen but their mitochondria were hypercontracted and there was no clumping of chromatin or obvious swelling of the rough endoplasmic reticulum or Golgi apparatus, in contrast to observations made on slices exposed to this agonist in normal medium. Substitution of all the Na+ in the medium with a mixture of choline (118 mM) and Tris (25 mM) itself caused necrosis of granule cells and deep nuclear neurons and an intense microvacuolation of Purkinje cells, due, in large part, to high amplitude mitochondrial swelling. A low (25 mM) Na+ medium was well tolerated under control conditions. This medium protected granule cells but not deep nuclear neurons from the toxicity of N-methyl-D-aspartate and failed to prevent kainate-induced death of Golgi cells. It is concluded that the acute neurotoxic effects of the two excitatory amino acid receptor agonists in the slices are dependent on extracellular Ca2+ and are independent of extracellular Cl-. Where apparent, the protective effect of reducing extracellular Na+ on the toxicity of N-methyl-D-aspartate is likely to reflect the involvement of this ion in the primary depolarizing mechanism.

Amino acid neurotoxicity: relationship to neuronal depolarization in rat cerebellar slices

It has long been proposed that the excitatory and toxic properties of acidic amino acid receptor agonists are linked. To test this hypothesis, the depolarizing effects of quisqualate, kainate and N-methyl-D-aspartate in adult and immature rat cerebellar slices have been studied in relation to their neurotoxic effects in the same tissues (reported separately). A "grease-gap" method was used to measure the depolarizing responses of Purkinje cells and granule cells in lobule VI to the agonists. The depolarizing potencies of kainate and quisqualate were apparently similar on both cell types and at both ages studied although maximal responses to kainate were always larger. N-Methyl-D-aspartate was a very weak agonist in the adult slices but was much more effective in the immature tissues, apparently on both Purkinje cells and granule cells. Comparison of the depolarizing effects of the agonists with their neurotoxic effects on Purkinje cells and granule cells suggested that: (a) the ability to depolarize is a required condition for an agonist to be neurotoxic, (b) the magnitude of depolarization, rather than depolarizing potency, is the more pertinent determinant of neurotoxic potency and (c) resistance to the neurotoxicity of an agonist is not necessarily associated with resistance to its depolarizing actions. Histological studies indicated that the neurotoxicity of N-methyl-D-aspartate and kainate in immature cerebellar slices could largely not be replicated by veratridine (50 microM) or high extracellular K+ (124 mM) indicating that receptor-mediated ionic fluxes may be needed in addition to those caused by depolarization. Exposure of the slices to anoxia in the absence of glucose partially reproduced the toxicity of the receptor agonists. Application of ouabain for 30 min caused necrosis of all the cells which are vulnerable to the agonists but spared the cells which are not vulnerable. Profound ionic imbalance thus appears to be a sufficient explanation for amino acid neurotoxicity.

Electron-microscopic demonstration of alpha-tubulin immunoreactivity in astroglia

Vibratome sections of the cerebral cortex, hippocampus and cerebellum were immunostained for alpha-tubulin using the TU-Ol monoclonal antibody. In all three regions, electron microscopy of the immunostained preparations revealed--in addition to the previously described reaction of pyramidal apical dendritic microtubules--consistent staining of the ribosomal apparatus of astrocytes.

Vinblastine blocks stimulation-dependent vesicle redistribution in incubated synaptosomes

Rat cortical synaptosomes were depolarized by the addition of protoveratrine to the incubating medium. The resulting synaptic vesicle aggregation near the synaptic cleft was prevented by vinblastine. Electron microscopy of both routine- and phosphotungstic acid-treated materials suggests the involvement of cytoskeletal structures in stimulation-dependent vesicle redistribution.

Immunocytochemical demonstration of tubulin microheterogeneity within rat cortical and hippocampal pyramidal neurons

Rat cortical and hippocampal pyramidal cells were immunocytochemically investigated using the TU-01 monoclonal antibody recognizing alpha-tubulin. The isotypic specificity of this antibody is distinct from that of other available alpha-tubulin antibodies; therefore, an intracellular heterogeneity among neuronal microtubules could be revealed by observing intensely immunostained apical dendritic microtubules in the complete absence of staining of the microtubules in the basal dendrites and perikarya of the same pyramidal cells.

Differential localization of GABA-dependent and GABA-independent benzodiazepine binding sites within synapses of rat cerebral cortex

Fractions containing non-junctional membranes (fraction 1) could be separated from those enriched in junctional complexes (fraction 2) by sucrose gradient centrifugation of osmotically disrupted rat cerebral cortex synaptosomes. [3H]flunitrazepam binding sites were found to be homogeneous characterized by Kd = 0.65 nM, Bmax = 13 pM for fraction 1; and Kd = 2 nM, Bmax = 45 pM for fraction 2. GABA-dependent benzodiazepine receptor sites were found to be localized to the junctional complex fraction, while non-junctional membranes showed GABA-independent receptor and acceptor binding sites.