Localization of the NGFI-A protein in the rat brain.

Antibodies are used to localize the NGFI-A protein in the rat brain. The protein is found in a wide variety of neurons. However, not all neurons are stained. The protein is either absent or present at undetectable levels in glial cells. Neuronal nuclei stain intensely, cytoplasmic staining is lighter. Seizures cause a detectable increase in the intensity of staining.

Boundaries defined by adhesion molecules during development of the cerebral cortex: the J1/tenascin glycoprotein in the mouse somatosensory cortical barrel field.

The distribution of the 200/220 KDa J1 glycoprotein (J1-200/220), within the developing vibrissae-related barrel field of the mouse somatosensory cortex, was studied by immunocytochemistry using a monoclonal antibody. J1-200/220, a member of the L2/HNK-1 family of adhesion molecules, also appears to be the mouse homologue of tenascin. J1/tenascin-positive barrel-like structures are visible in the somatosensory cortex between 24 and 48 hr after birth, with the molecule present in prospective barrel boundaries. Immunoelectronmicroscopy reveals labeling that is associated with glial and neuronal plasma membranes, as well as glial end-feet on blood vessels. A possible major source of J1/tenascin expression at this time is astrocyte precursor cells and radial glia. In the putative astrocyte precursor cells, immunolabeling was observed within organelles including the Golgi apparatus. At P6-7 J1/tenascin is most prevalent within prospective interbarrel septae. J1/tenascin-positive barrel boundaries are barely visible on P9 and not observed on P16. The findings indicate that J1/tenascin represents a major component of previously described "hidden" boundaries that we have seen during development using other methodologies. The expression of adhesion molecule-rich boundaries during the critical stages of barrel field formation indicates roles for such molecules during specific cerebral cortical pattern formation events.

Distribution of GAD-immunoreactive neurons in the first (SI) and second (SII) somatosensory cortex of the monkey.

The distribution of neurons immunoreactive for glutamic acid decarboxylase (GAD), the synthesizing enzyme of gamma-aminobutyric acid (GABA), was examined in the first (SI) and second (SII) somatosensory cortex of monkeys. GAD-like immunoreactive (GAD-LI) somata and puncta were present in all layers of SI and SII. All GAD-LI somata were identified as non-pyramidal neurons and were most numerous in layer IV of SI and in layer III of SII. Layer IV of SI also contained the highest density of GAD-LI puncta. In SII, GAD-LI puncta were distributed more homogeneously and did not show a dense band of labelled puncta in layer IV. The major and minor diameters of GAD-LI somata in SII ranged from 6.9 to 26.2 micron and from 6.2 to 19.0 micron, respectively. The major diameters of GAD-LI somata in SII were significantly smaller than those in SI in layers I, III and IV. Differences between the distributions of GAD-LI puncta and somata in SI and SII may be accounted for by differences in the number and/or distribution of different types of GABAergic neurons. Functional differences of neurons in SI and SII may be related to the differences in GABAergic inhibitory mechanisms and reflected in the distribution of GABAergic neurons.

Correspondence between 5-HT2 receptors and serotonergic axons in rat neocortex.

The anatomic relationship between serotonergic (5-HT) axons and 5-HT2 receptors in the rat forebrain was determined by a combined analysis of transmitter immunocytochemistry and receptor autoradiography. High densities of 5-HT2 receptors, localized by the ligand N1-methyl-2-125I-LSD (125I-MIL), are found in neocortex and striatum; these regions also receive a dense serotonergic innervation. Regional variations in the density of 5-HT2 receptors and 5-HT axons correspond closely in most, but not all, areas of the forebrain. In somatosensory cortex (SI), the laminar distribution of 5-HT2 receptors closely matches that of 5-HT axons: in particular, a dense band of 5-HT2 receptors in layer Va of SI is in precise register with a dense plexus of fine 5-HT axons. We have also observed a close spatial relationship between 5-HT2 receptors and fine axons in other areas of the forebrain, suggesting that 5-HT2 receptors may be selectively linked to a particular type of 5-HT axon terminal. Since fine axons of this type have been reported to arise from the dorsal raphe nucleus, it appears likely that 5-HT2 receptors may mediate the effects of dorsal but not median raphe projections.

A light and electron microscopic study of serotonin-immunoreactive fibers and terminals in the monkey sensory-motor cortex.

Immunocytochemical methods were used to study the distribution and ultrastructure of serotonin (5-hydroxytryptamine; 5-HT) immunoreactive fibers innervating the monkey sensory-motor cortex. Beaded 5-HT positive fibers were found in all cortical layers of both areas but with relatively fewer in middle cortical layers. Examination of 2 micron-thick plastic sections at the light microscope level, revealed that the vast majority of the bouton-like structures on the fibers lay in the neuropil and not adjacent to neuronal somata. A few beaded immunoreactive fibers were seen around certain pyramidal and non-pyramidal cell somata, very occasionally forming modest pericellular ramifications. Serial reconstructions made from electron micrographs after resectioning the 2 micron-thick sections, revealed that the dilatations of the fibers are 5-HT positive boutons but the boutons examined rarely formed morphologically identifiable synaptic contacts. Of 191 reconstructed boutons only 5 made contacts with obvious membrane specializations, all of which were of the asymmetrical type. No immunoreactive synaptic contacts were seen on pyramidal cell somata in the cortex, nor on dendrites or somata in the white matter underlying the cortex, although 5-HT positive boutons commonly lay closely adjacent to neuronal profiles in both sites. 5-HT fibers in the cortex and white matter have a similar morphological appearance and both myelinated and unmyelinated types are seen.

Characterization of antisera to glutamate and aspartate.

Antisera were raised in rabbits against glutamate (Glu) and aspartate (Asp) conjugated to the invertebrate carrier protein hemocyanin (HC) with glutaraldehyde (GA). The antisera were characterized by testing their immunocytochemical staining properties on sections cut at the level of the ventral cochlear nucleus (VCN) from fixed brains of normal rats after absorption with conjugates of compounds structurally similar and biologically relevant to Glu and Asp. Optimal staining with Glu antiserum was obtained at a dilution of 1:10,000 and was completely blocked by 303 micrograms/ml of the Glu-HC conjugate. No crossreactivity with any of 11 compounds tested was observed. Optimal staining with the Asp antiserum was obtained at 1:8000 dilution and was completely blocked by 225 micrograms/ml of the Asp-HC conjugate. Of 10 compounds tested for crossreactivity, only L-asparagine demonstrated a measurable (about 10%) crossreactivity with the Asp antiserum. The specificity of the two antisera was also tested by immunoblot analysis against 11 compounds conjugated to HC with GA. Listed in order of staining intensity, from greatest to least, conjugates that reacted with the Glu antiserum were Glu greater than Gly-Glu greater than Asp-Glu = Asp greater than N-carbamyl (NC)-Glu greater than Asn = Gln = GABA. Conjugates that reacted with the Asp antiserum, in order of decreasing staining intensity, were Asp greater than Glu-Asp = Asn greater than Gly-Asp greater than Glu. No other compounds tested for crossreactivity reacted with the two antisera in the immunoblot analysis. Glu-like immunoreactivity in rat dorsal root ganglia and somatosensory cortex, and the comparative distribution of Glu- and Asp-like immunoreactivities in the latter tissue, are presented as examples of staining patterns obtained with the two antisera.

Distribution of catecholamines, serotonin, and their major metabolites in the rat cingulate, piriform-entorhinal, somatosensory, and visual cortex: a biochemical survey using high-performance liquid chromatography.

The catecholamines noradrenaline (NA), dopamine (DA), adrenaline (AD), the indoleamine 5-hydroxytryptamine (5-HT; serotonin), as well as some of their major metabolites were assayed by high-performance liquid chromatography (HPLC) with electrochemical detection, in four well-defined areas of the rat cerebral cortex: anterior cingulate (CIN;Cg1 and Cg3), piriform and entorhinal (PiEn), hind-limb primary somatosensory (SSC;HL) and primary visual (VIS; Oc1M and Oc1B). The concentrations of NA and that of its main metabolite 3-methoxy-4-hydroxyphenylglycol were highest in PiEn, had intermediate values in CIN and were lowest for SSC and VIS cortices. The DA levels were also highest in PiEn, intermediate in CIN, while the lowest values were in SSC and VIS cortices. The different DA/NA ratios support the hypothesis that they are indeed independent neurotransmitters. In addition, the levels of 3,4-dihydroxyphenylacetic acid, homovanillic acid and 3-methoxytyramine paralleled the distribution of DA, thus confirming the presence of release sites, even in regions in which the low levels of this catecholamine could be interpreted simply as the precursor of NA. Traces of AD were detected in all the regions examined. The 5-HT contents, as well as that of its precursor 5-hydroxy-1-tryptophan and that of its metabolite 5-hydroxyindole-3-acetic acid were also found to be non-homogenous, with the highest levels measured in the PiEn and CIN regions.

Comparison of penicillin epileptogenesis in rat somatosensory and motor cortex.

The relative sensitivities of somatosensory and motor areas of the cerebral cortex in penicillin epileptogenesis were compared in urethane-anaesthetized rats. Penicillin was applied electrophoretically from a fluid-filled micro-electrode. Spontaneous focal interictal epileptiform discharges were detected by a nearby recording electrode. In motor cortex, every cortical layer was less sensitive in penicillin epileptogenesis than the corresponding layer in somatosensory cortex; epileptic spikes occurred later, were of lower amplitude and were less frequent. In motor cortex, the sensitive depth extended from the deep part of layer III to the upper part of layer V. It seemed possible that penicillin applied to motor cortex might be producing its effects by diffusing back to the sensitive somatosensory area. This was excluded by applying penicillin to motor cortex whilst recording from both somatosensory and motor areas and demonstrating that the spikes were found in motor but not in somatosensory cortex.

Synaptic organization of GABAergic neurons in the mouse SmI cortex.

Immunocytochemical methods were used to examine GABAergic neurons in the barrel region of the mouse primary somatosensory cortex. GABAergic neurons occur in all layers of the barrel cortex but are more concentrated in the upper portion of layers II/III and in layers IV and VI. Nine cells in layer IV were examined with the electron microscope, and portions of their dendrites were reconstructed from serial thin sections. These cells are of the nonspiny, multipolar or bitufted varieties, and some of them have beaded dendrites. The labeled cell bodies and their reconstructed dendrites were postsynaptic at asymmetrical synapses with thalamocortical axon terminals labeled by lesion-induced degeneration and with unlabeled axon terminals. Each cell also received symmetrical synapses from GABAergic axon terminals and from unlabeled axon terminals. Our results indicate that GABAergic cell bodies and processes receive synapses from thalamocortical axon terminals but that different cells display marked differences in the proportion of thalamocortical and other synapses they receive. These results indicate that GABAergic cells form a heterogeneous population with respect to their morphologies and patterns of synaptic inputs. The synaptic sequences revealed here for GABAergic neurons represent an anatomical substrate for various inhibitory processes known to occur within the cerebral cortex.

The sensory process in man its analysis by means of cortical and subcortical evoked potentials

El proceso sensorial del hombre se puede analizar por medio de los potenciales somatosensoriales, auditivos y visuales evocados que se registran a partir de la superficie del cuero cabelludo en todos los pacientes, y de las profundidades del cerebro en algunos pacientes que tienen electrodos implantados con finalidades diagnósticas y terapéuticas. La sensación y la percepción son dos etapas consecutivas del proceso sensorial por medio de las cuales se perciben y analizan los estímulos ambientales. La atención selectiva es un filtro funcional que facilita la percepción de los estímulos importantes y bloquea los que carecen de importancia. La sensación se valora mediante potenciales evocados de latencia breve (tempranos) que revelan la activación del receptor, de las vías específicas y de las cortezas primarias; en tanto que la percepción se valora por los potenciales de latencia larga (tardios) que revelan un sistema reticulotalámico inespecífico que media de manera parcial las funciones de filtrado de la atención y de análisis percentual. La modulación de los impulsos sensoriales por un asa corticorreticulotalamocortical (sensorial en la primera etapa cortical y motor en la segunda) en el hombre, y no a nivel periférico como ocurre en los animales, permite al cerebro humano estar informado de manera continua sobre los acontecimientos periféricos y afrontarlos con patrones sensoriales y motores organizados en tiempo y espacio mediante vías receptores y centros corticales específicos. Esto es, permite comprender y manipular el ambiente por medio de su representación en un mosaico somatosensorial cerebral

gamma-Aminobutyric acid immunoreactivity in mouse barrel field: a light microscopical study.

The barrel field of the mouse somatosensory cortex (SmI) was investigated immunocytochemically using an antiserum against the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). GABA-immunopositive cells and processes are grouped largely in the barrel side, whereas the barrel hollow is only weakly immunostained. The GABA-immunopositive cells have an ellipsoidal appearance similar to that of non-pyramidal class II barrel neurones described previously in Golgi impregnation studies of the mouse and rat barrel field.

Substance P in the human brain.

The distribution of substance P immunoreactive sites was investigated by immunoenzymatic methods in a large series of paraffin embedded human brain sections from the collection assembled by Oscar and Cécile Vogt several decades ago, as well as from more recent post-mortem material. These studies demonstrated that substance P immunoreactivity was preserved in archival material permitting a detailed account of the localization of immunoreactive cell bodies, fibre networks and tracts in the human brain. Previous observations made on experimental animals and man were confirmed and extended. Additionally, substance P immunoreactive cell bodies were seen in most cortical areas and novel features were noted in the distribution of substance P-containing elements in the tuberal region, corpus striatum, substantia nigra (particularly in relationship to blood vessels) and in association with melanin-containing cells. Reconstruction of some substance P pathways was attempted by the analysis of semi-serial sections in more than one plane. Immunocytochemistry, in combination with image analysis, enabled some measurements of the differential concentrations of substance P immunoreactive material to be made and allowed a close correlation of this with defined anatomical landmarks or enkephalin immunoreactive sites.

alpha-Methyltyrosine blocks methylamphetamine-induced degeneration in the rat somatosensory cortex.

Neurochemical and histological studies suggest that methylamphetamine (MA) administered continuously or in high doses is toxic to dopaminergic and serotonergic nerve terminals. Degeneration of the dopaminergic or serotonergic cell bodies themselves has not been reported, however. In the present study, administration of a single 100 mg/kg dose of MA was toxic to a subpopulation of neurons in the somatosensory cortex, an area of the brain which does not contain catecholaminergic or serotonergic cell bodies. This dose of MA also produced a long-lasting depletion of serotonin (5-HT) but not norepinephrine in the somatosensory cortex. Dopamine levels in the somatosensory cortices of control animals were virtually undetectable and therefore were not studied further. Administration of alpha-methyltyrosine (alpha-MT), a catecholamine synthesis inhibitor, prior to the injection of MA blocked both the depletion of 5-HT and the degeneration of cortical perikarya produced by MA alone. Since the MA-induced depletion of 5-HT and the MA-induced degeneration of cortical perikarya are correlated, we suggest that the serotonergic system may be involved in the toxic effects of MA on the cortical neurons.

An autoradiographic study of the postnatal development of pericruciate cortical projections to the neostriatum and the claustrum of the cat.

The postnatal development of corticostriatal and corticoclaustral projections was traced by light-microscopic autoradiography following injections of tritiated proline and leucine into the pericruciate cortex of kittens, 2-56 days of age, and adult cats. A medial-lateral topography of the corticostriatal pathways was present at birth, with a smaller and more restricted projection arising from the lateral pericruciate region. During postnatal development, the volume of the ipsilateral caudate nucleus filled by labelled corticostriatal fibers was reduced by 30% and these projections became constricted within the dorsolateral head and body of the caudate nucleus. During the first postnatal week, terminal fields were diffuse but lacked homogeneity since irregular patches of intensely labelled elements clustered near the internal capsule. By the end of the first month, a fenestrated organization became apparent within the caudate nucleus where elongated clusters of intensely labelled fibers radiated from the internal capsule and partially or completely surrounded islands of neuropil virtually devoid of label. Pericruciate inputs were confined to the dorsal parts of the rostral putamen and claustrum and the patchy nature of these terminal fields was limited to small labelled clusters close to the capsular margins. Contralateral terminal fields were labelled less intensely and occupied areas symmetrical to those within the ipsilateral neostriatum and claustrum.

Changes in [Ca2+]o and [K+]o during repetitive electrical stimulation and during pentetrazol induced seizure activity in the sensorimotor cortex of cats.

Changes in [Ca2+]o and [K+]o were measured in the sensorimotor cortex of cats during repetitive electrical stimulation and during pentetrazol induced epileptiform activity. Repetitive stimulation of the thalamic ventrobasal complex (VB) or of the cortical surface (CS) caused decreases in [Ca2+]o by up to 0.45 mM and increases in [K+]o by up to 7 mM. Maximum reductions of [Ca2+]o delta [Ca2+]o were found in depths of 100 to 300 micrometers below cortical surface, while rises in [K+]o were largest in depths of 600 to 1000 micrometers dependent on stimulation site. At depths below 700-900 micrometers increases in [K+]o were often accompanied by rises in [Ca2+]o of about 0.2 mM. Pentetrazol (PTZ) when injected at doses of 25 to 40 mg/kg body weight induced spontaneous seizure activity, which was in about 40% preceded by a slight fall of baseline [Ca2+]o. Repetitive stimulation and spontaneous seizures resulted in delta [Ca2+]o of up to 0.6 mM, whereas rises in [K+]o remained limited to a 'ceiling level' of about 10 mM. After PTZ application, peak delta [Ca2+]o were found at the same recording sites, but, in contrast to normal cortex, decreases in [Ca2+]o were observed in all cortical layers. The enhanced Ca2+-signals after PTZ application and the observed reduction of [Ca2+]o before seizure onset suggest that PTZ utilizes Ca2+-dependent mechanisms to initiate seizure activity.

Opiate receptor localization in rat cerebral cortex.

The differential distributions of [3H]naloxone-labeled and [3H]D-Ala-D-Leu-enkephalin-labeled opiate receptors in rat cerebral cortex were localized autoradiographically and quantified by grain counting and computerized densitometry. In addition, receptor distributions were compared to terminal patterns of thalamocortical projections labeled by axoplasmic transport of [3H]amino acids. Opiate receptors labeled with [3H]naloxone in a mu ligand selectivity pattern show striking laminar heterogeneity and are densest in limbic cortical areas, intermediate in the motor cortex, and fewest in the primary sensory areas. By contrast, opiate receptors labeled with [3H]D-Ala2-D-Leu5-enkephalin in a delta ligand selectivity pattern are much more homogeneously distributed across both regions and laminae within regions. Mu receptors in most cortical areas have density peaks in layers I and VI and each peak shows a density gradient that is sloped within the layer so that the highest densities are at the most superficial and the deepest portions of cortex. In addition, there is an intermediate peak whose laminar position varies depending on the area in which it is found. In rostral agranular cortex, including limbic and motor areas, the [3H]naloxone binding peaks are in layers I, III, and VI. In primary somatosensory cortex, the intermediate peak is in layer Va and in most of remaining homotypical cortex it is in layer IV. Some areas have only bilaminar labeling, in superficial and deep layers; these include portions of the sulcal and retrosplenial cortices. Piriform and entorhinal cortices have dense [3H]naloxone binding only in the deepest layer and show a descending gradient of density toward the superficial layer. The positions of the mu receptor peaks were compared with termination patterns of projections originating in the thalamus. Close correspondence was found between receptor binding in the prelimbic, primary somatosensory, and entorhinal areas and projection terminations arising from the thalamic mediodorsal, posterior, and central medial nuclei, respectively. Although regional variations in [3H]D-Ala2-D-Leu5-enkephalin-labeled receptor density are uncommon, a gradual decrease in the number of sites along the dorsomedial wall of the cortex from anterior cingulate to caudal retrosplenial limbic cortex can be observed. Laminar variations in binding density are small as well; higher concentrations of the peptide binding sites are usually found in the deep cortical layers. These findings emphasize aspects of opiate receptor architecture which may be relevant to identifying cortical "opiatergic" neurocircuitry and raise the possibility of opiate modulation of thalamocortical transmission.

[Changes in the concentration of extracellular potassium and the slow negative potential in the somatosensory area of the cortex in response to stimulation of the ventroposterolateral nucleus of the thalamus in the cat]. / Izmeneniia kontsentratsii vnekletochnogo kaliia i medlennyi otritsatel'nyi potentsial v somatosensornoi oblasti kory pri razdrazhenii ventroposterolateral'nogo iadra talamusa koshki.

A single electrical stimulus applied to the VPL nucleus with intensity, strong enough to elicit in gyrus sigmoideus posterior slow negativity following the primary response, caused a local increase in [K+]0 reaching 0.2 mM. On the basis of this finding it is supposed that the slow negativity reflects mainly depolarization.

An intermittent somatostatin-immunoreactivity in the cortex and basal ganglia of the rat.

Using light microscopic immunohistochemistry, somatostatin-positive structures were observed in the cortex of the rat. These structures, including cells and fibers, are widely distributed in all cortical laminae and are also found in the basal ganglia. The positive results were obtained exclusively in two groups of animals sacrificed during two different months of two subsequent years. The reason for this variability in the immunocytochemical stainability of cortical structures remains enigmatic.