Biomedical subjects

P Wahle

Publications and source records attributed to P Wahle.

At least 19 recordsLinked to original sources

PubMed1995

Oligodendrocytes differentiate in organotypic cultures of rat visual cortex and myelinate efferent axons.

We have investigated the presence and function of glia cells, especially of oligodendrocytes (OL) in organotypic cultures of rat visual cortex grown for 1-6 weeks in vitro. OL identified by strong Galactocerebroside-immunoreactivity (GalC-ir) displayed rather small somata and elaborately ramified processes. They were most concentrated in layers VIa and VIb and the remnant of the white matter. Silver staining revealed long descending or oblique processes in layers V and VI, which were often arranged in patches, and horizontal processes in the white matter. Proximal processes of OL cell bodies were connected to these long processes. DiI-labeling revealed very similar patches of processes, termed OL domains. They were identified as membraneous sheaths formed by processes of single OL around axons passing the OL domain. Confocal microscopy revealed single axons running through the membrane sheaths. We compared the molecular differentiation of glial cells in cultures to the in vivo situation with protein blots and immunohistochemistry for glial cell marker molecules. In homogenates of visual cortex in vivo, protein blots revealed the increase in expression by OL of myelin basic protein (MBP) during the fourth postnatal week. The astrocytic marker glial fibrillary acidic protein (GFAP), blotted as a control, increased over time in vivo, beginning at P14, indicating the differentiation of astrocytes. In homogenates of organotypic cortex cultures, the times course of expression of GFAP was very similar: it increased dramatically during the first 10 DIV, and remained fairly constant in older cultures.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Cellular and molecular characterization of a brain-enriched protein tyrosine phosphatase.

Regional variations in the expression of a striatal enriched protein tyrosine phosphatase called STEP were studied in the adult rat brain by a combination of immunocytochemistry, lesion studies, Western blotting, and in situ hybridization. Monoclonal antibodies generated against STEP identified multiple polypeptides of M(r) 46, 37, 33 and a doublet of M(r) 64-66 kDa on Western blots. Although the three STEP immunoreactive bands with lower molecular weights were enriched in cytosolic fractions, the 64-66 kDa doublet was enriched in membrane fractions. All of the immunoreactive forms were abundant in the caudate-putamen and were present in lower amounts or were undetectable in other brain regions. In substantia nigra, the M(r) 64-66 kDa doublet was not detected but bands with M(r) 46, 37, and 33 kDa were present. Immunocytochemical and lesion experiments demonstrated that the cytosolic STEP isoforms present in the substantia nigra are in presynaptic axons originating from the projection neurons of the caudate putamen, which innervate this structure. Additional in situ hybridization studies showed that STEP mRNA expression patterns correlate with the patterns of immunocytochemical staining. These findings indicate that there are multiple polypeptide isoforms of STEP enriched in the basal ganglia and related structures which differ in terms of their intracellular locations and functional roles.

Animals↗

PubMed1994

The SP1 antigen in subplate neurons of the developing cat cortex is an immunoglobulin-like molecule.

Monoclonal antibody subplate-1 (mAb SP1) specifically stains somata, dendrites and axons of spiny inverted pyramidal neurons in the subplate zone in the early postnatal kitten neocortex. The SP1 antigen has been previously identified as a cytosolic protein of apparent molecular weight 56 kDa. We have now employed immune-affinity chromatography to further characterize this antigen. An antigen with SP1-like immunoreactivity (ir) is present in various organs, and is particularly enriched in blood plasma. Exsanguination of the organs prior to protein extraction reduces the SP1-ir band dramatically, indicative of a blood-borne molecule. The 56 kDa SP1-ir antigen was purified from plasma by affinity chromatography and subjected to Edman degradation. The first 20 N-terminal amino acids show 80% homology to the N-terminus of immunoglobulin heavy chain of man, the mouse and the dog. If the 56 kDa SP1-ir antigen in plasma is an immunoglobulin, and if an immunoglobulin-like molecule is present in the subplate, then antisera against cat immunoglobulins should stain subplate neurons. A polyclonal antiserum against cat IgG intensely stains the somata and dendrites of subplate neurons. On protein blots, this antiserum recognizes the 56 kDa band, and an additional band of approximately 27 kDa, corresponding in size to immunoglobulin light chains. Preabsorbing mAb SP1 with cat immunoglobulin G abolishes the immunoreactivity in sections of kitten cortex. Further, it dramatically reduces the reactivity on protein blots. The results suggest that the 56 kDa SP1-ir antigen in cortical subplate neurons belongs to the immunoglobulin superfamily.

Amino Acid Sequence↗

PubMed1994

Inverted pyramidal neurons and interneurons in cat cortical subplate zone are labelled by monoclonal antibody SP1.

During development, the subplate zone of the cat neocortex contains neuronal populations with distinct morphological and neurochemical phenotypes. A subset of those are specifically recognized by a mouse monoclonal antibody termed SUBPLATE-1 (SP1), which was generated against tissue homogenates of kitten cortical white matter. SP1 stains cell bodies and proximal dendrites, but rarely distal dendrites, axonal arbors or spines. In order to characterize morphologically the SP1 immunoreactive subplate cell types, we combined SP1 immunohistochemistry with intracellular iontophoretic injections of Lucifer yellow. The majority of double-labelled neurons were inverted pyramids with a single thicker spine-covered dendrite that descended into the white matter and a tuft of thinner spinous dendrites that ascended from the upper somatic pole, but generally remained confined to the white matter. Other double-labelled neurons were multipolar to bitufted, although often equipped with one thicker descending dendrite. In inverted pyramidal cells, the axons originated from the descending dendrite or, more rarely, from the lower portion of the soma, and descended into the white matter. They formed collaterals recurring toward the grey matter. The presence of dendritic spines on double-labelled pyramidal cells and the axonal arborization patterns were two novel features not revealed previously by SP1 immunohistochemistry alone. The inverted pyramidal morphology was typical for double-labelled neurons located in the subplate zone below the apices of the gyri, whereas those located below the flanks or sulci or deep in the white matter often displayed a bitufted or multipolar spinous morphology. A minority of the double-labelled neurons were multipolar with smooth dendrites and locally branching axons. These results suggest that in the cat subplate zone, a majority of the cells expressing the SP1 antigen are spinous, and we termed the spinous subplate cells 'subplate pyramidal neurons'.

Animals↗

PubMed1994

The topography of tangential inhibitory connections in the postnatally developing and mature striate cortex of the cat.

Clustered intrinsic connections in the striate cortex of kittens originate from an unclustered, diffusely organized pattern prevailing during the first postnatal week. In order to study the participation of inhibitory neurons in this reorganization of the connections, we determined the topography of the inhibitory tangenital connections in the striate cortex of cats ranging in age between 7 and 330 days by combining retrograde transport of fluorescent microspheres with GABA immunohistochemistry. After small intracortical injections of tracer, neurons containing either microspheres only (non-GABAergic neurons) or GABA-like immunoreactivity in addition to microspheres (GABAergic neurons) are labelled at various horizontal distances from the injection. At the end of the first postnatal week, both GABAergic and non-GABAergic neurons are distributed in the horizontal plane in an unclustered fashion. During the second postnatal week, the tangential connections rearrange rapidly to form clusters. The tendency of the cells to form clusters is much weaker, however, in GABAergic than in non-GABAergic neurons. In regions > 500 microns distant from the centre of injection approximately 90% of the non-GABAergic neurons (range 87.5-92.6%) but only 63% (range 57.1-72.3%) of the GABAergic neurons reside within the clusters formed by the non-GABAergic neurons. These proportions do not change systematically with age. In the regions outside the non-GABAergic clusters, GABAergic neurons appear to be evenly distributed and not to aggregate in clusters. From postnatal day 7 forward GABAergic neurons largely retain their overall distribution and density in the horizontal plane. When considering all cortical layers (including the superficial white matter) the lateral spread of the GABAergic neurons is more restricted than that of the non-GABAergic neurons. Systematic changes in the lateral spread of inhibitory connections according to postnatal age were not observed. We conclude that, like the non-GABAergic neurons, the GABAergic neurons have attained an adult-like topography in the horizontal plane by about the end of the second postnatal week. From that time until adulthood they display much weaker clustering, a higher relative occurrence of short axon collaterals and a more restricted lateral distribution than do the excitatory neurons.

Animals↗

PubMed1994

LGN-projecting neurons of the cat's pretectum express glutamic acid decarboxylase mRNA.

There have been conflicting reports on the chemical nature of the projection of the pretectal nuclei [nucleus of the optic tract and dorsal terminal nucleus of the accessory optic tract (NOT-DTN complex) and posterior pretectal nucleus] to the lateral geniculate nucleus and inferior olive. There is evidence that the pretecto-geniculate pathway is inhibitory. However, most attempts to verify the GABAergic nature of the projection neurons have failed. In order to answer this question, we employed a combination of retrograde transport and in situ hybridization. Rhodamine-labelled latex microspheres were injected into the electrophysiologically identified lateral geniculate nucleus. In addition, fluorescein-labelled latex microspheres were injected into the inferior olive. Retrograde axonal transport labelled large pretectal neurons. We then applied riboprobes specific for glutamic acid decarboxylase mRNA. We were able to demonstrate glutamic acid decarboxylase mRNA expression in up to 70% of lateral geniculate nucleus-projecting NOT-DTN and posterior pretectal nucleus neurons but in none of the pretecto-olivary projection neurons. The results suggest that the pretecto-geniculate projection is GABAergic in nature, which would confirm previous electrophysiological and morphological observations. The pretecto-olivary projection is not GABAergic.

Animals↗

PubMed1994

Neurotransmitter profile of saccadic omnipause neurons in nucleus raphe interpositus.

Saccadic omnipause neurons (OPNs) are essential for the generation of saccadic eye movements. In primates OPNs are located near the midline within the nucleus raphe interpositus (rip). In the present study we used several different neuroanatomical methods to investigate the transmitters associated with OPNs in the monkey. Immunolabeling for the calcium-binding protein parvalbumin was employed to mark OPNs in the monkey and define the homologous cell group in cat and human. The use of antibodies against GABA, glycine (GLY), glutamate (GLU), serotonin (5-HT), and tyrosine hydroxylase revealed that the somata of OPNs are GLY immunoreactive, but they are devoid of GABA and 5-HT immunostaining. In situ hybridization with the GAD67 mRNA probe confirmed the negative GABA immunostaining of OPNs. 3H-GLY was injected into a projection field of OPNs, the rostral interstitial nucleus of the medial longitudinal fascicle (riMLF)--the vertical saccadic burst neuron area. This resulted in selective retrograde labeling of the OPNs in rip, while no labeling was found in the superior colliculus, which sends an excitatory projection to the riMLF. The somata and dendrites of putative burst neurons in the riMLF were contacted by numerous GLY-immunoreactive terminals. The quantitative analysis of immunoreactive terminal-like structures contacting OPNs revealed a strong input from GLY- and GABA-positive terminals on somata and dendrites, whereas GLU-positive puncta were mainly confined to the dendrites. Very few 5-HT and catecholaminergic terminals contacted OPN somata. Our findings suggest that OPNs use GLY as a neurotransmitter, and they receive numerous contacts from GABAergic, glycinergic, and glutaminergic afferents, and significantly fewer from monoaminergic inputs.

Animals↗

PubMed1993

Differential regulation of substance P and somatostatin in Martinotti cells of the developing cat visual cortex.

In order to determine their morphological development and ontogenetic fate, Martinotti neurons immunoreactive for substance P and somatostatin have been analysed in the cat visual cortex. Martinotti neurons are located in layers V and VI. They are multipolar to bitufted, and most dendrites remain in layers V and VI. Their typical features is the ascending axon, which emerges from an apical dendrite or from the upper pole of the soma. A number of collaterals branch off in layer V, forming a local terminal plexus. The axon then branches into 2-8 collaterals, which ascend as a bundle to layers III and II, where a second terminal plexus is formed. Some collaterals ascend to layer I where they adopt a horizontal course. Horizontal collaterals in the terminal layers V, III, II, and in layer I may reach up to 400 microns in length. Martinotti neurons begin to differentiate perinatally. The quantitative analysis reveals that the initial time course of differentiation of Martinotti cells is very similar in material stained for substance P and for somatostatin. Double immunofluorescence then confirms that the two peptides are colocalized in Martinotti cells of layers V and VI during the early postnatal period. Further, substance P is colocalized with GABA. Substance P expression in Martinotti cells can be observed only in the immature visual cortex. After postnatal day 15, the Martinotti neuron system becomes less and less detectable by substance P immunoreactivity. It declines to virtually undetectable levels after the third postnatal month. The adult visual cortex is almost devoid of substance P-immunoreactive cell bodies, processes and axon terminals. In situ hybridization confirms this finding, revealing beta-preprotachykinin mRNA-expressing cell bodies in layers V and IV at postnatal day (P)6 and P12, but not in the adult cortex. This suggests a downregulation of the substance P expression at the transcriptional level. In contrast, somatostatin-immunoreactive Martinotti cells, most of which have coexpressed substance P during early postnatal life, can still be observed in the adult cortex. Thus, the Martinotti neurons constitute a persisting cell type, although many individual neurons of this type disappear during the second postnatal month by degeneration and cell death. In summary, while somatostatin is permanently expressed in Martinotti neurons in the cat visual cortex, substance P peptide and mRNA are transiently expressed during an early postnatal period, and apparently are downregulated later in development.

Afferent Pathways↗

PubMed1993

Distribution of neurons expressing substance P receptor messenger RNA in immature and adult cat visual cortex.

We have investigated the expression of messenger RNA (mRNA) encoding substance P receptor (SPR) in the visual cortex of adult cats and 17-day-old kittens, using in situ hybridization histochemistry with two digoxigenin-labeled oligodeoxynucleotides complementary to the SPR mRNA. In the adult cortex, a subset of large pyramidal neurons of layer V and layer III is heavily labeled. Other, mainly pyramidal neurons in layers II, III and V are less intensely labeled, but most neurons in these layers appear unlabeled. Neurons in layer IV and VI, and in the white matter do not show hybridization signals above background levels. In the 17-day-old kitten, SPR mRNA-expressing cells are confined to layer V and to the upper white matter (subplate zone), whereas supragranular neurons do not yet contain SPR mRNA. A few neurons in layer VI display moderate labeling. Astrocytes, identified with anti-glial fibrillary acid protein antibodies, did not express detectable levels of SPR mRNA in both adult and kitten visual cortex. These results indicate that SPR mRNA expression is transient in neurons of the white matter, and is developmentally regulated in supragranular layers. In addition, the localization of SPR mRNA in a subset of pyramidal cells suggests that substance P modulates the excitability of certain projection neurons which are the origin of extrinsic connections.

Aging↗

PubMed1992

Morphology of neurons in the white matter of the adult human neocortex.

Neurons in the human cerebral cortical white matter below motor, visual, auditory and prefrontal orbital areas have been studied with the Golgi method, immunohistochemistry and diaphorase histochemistry. The majority of white matter neurons are pyramidal cells displaying the typical polarized, spiny dendritic system. The morphological variety includes stellate forms as well as bipolar pyramidal cells, and the expression of a certain morphological phenotype seems to depend on the position of the neuron. Spineless nonpyramidal neurons with multipolar to bitufted dendritic fields constitute less than 10% of the neurons stained for microtubule associated protein (MAP-2). Only 3% of the MAP-2 immunoreactive neurons display nicotine adenine dinucleotide-diaphorase activity. The white matter pyramidal neurons are arranged in radial rows continuous with the columns of layer VI neurons. Neuron density is highest below layer VI, and decreases with increasing distance from the gray matter. White matter neurons are especially abundant below the primary motor cortex, and are least frequent below the visual cortex area 17. In contrast to other mammalian species, the white matter neurons in man are not only present during development, but persist throughout life.

Adult↗

PubMed1992

A method of in situ hybridization combined with immunocytochemistry, histochemistry, and tract tracing to characterize the mRNA expressing cell types in heterogeneous neuronal populations.

A rapid, sensitive, non-isotopic in situ hybridization histochemistry protocol is presented to study the expression of mRNA at the single cell level in anatomically complex structures of the mammalian central nervous system. The protocol uses digoxigenin-UTP-labeled riboprobes, freefloating sections, and alkaline phosphatase and horseradish peroxidase detection. Modifications have been introduced which preserve the integrity of marker molecules, and as such enable the simultaneous identification and characterization of CNS cell types by tract tracing, histochemical, and immunocytochemical detection of intra- and extracellular markers. All pretreatments that enhance probe penetration have been omitted without substantial loss in sensitivity. The protocol has been successfully extended to vibratome sections with subsequent plastic-embedding and semithin sectioning, which considerably broadens the general applicability of this fast and easy ISHH method.

Animals↗

PubMed1991

Distribution and morphology of substance P-immunoreactive structures in the olfactory bulb and olfactory peduncle of the common marmoset (Callithrix jacchus), a primate species.

The present study describes the morphology and distribution of substance P-immunoreactive (SP-ir) elements in the olfactory bulb (OB) and olfactory peduncle (OP) of the common marmoset (Callithrix jacchus), a primate species. SP-ir neurons are very abundant in the OB and belong to two types. External tufted cells are present in the glomerular layer (GL), whereas granule cells are found in the deeper layers, especially in the granule cell layer (GRL), but also scattered in the OP. SP-ir fibers, putatively of central origin, were identified in the OP. They ascend into the bulbar layers. The SP-chemoarchitecture of the marmoset OB and OP does not differ more from rat, guinea pig and cat, than the SP-chemoarchitecture of these species varies among one another.

Animals↗

PubMed1991

The contribution of GABA-ergic neurons to horizontal intrinsic connections in upper layers of the cat's striate cortex.

The contribution of neurons containing gamma-aminobutyric acid (GABA) to horizontal intrinsic projections in layers I-III of cat's striate cortex was investigated by combining GABA-immunohistochemistry with axonal tracing. After intracortical injections of Rhodamine-labelled latex microspheres Rhodamine-labelled neurons form patch- or bandlike aggregations (clusters) separated from each other by regions containing fewer, evenly distributed or no labelled neurons. Of the Rhodamine-labelled neurons about 5% display GABA-immunoreactive material (double labelled = DL-neurons). Approximately 70% of the DL-neurons occur at distances of less than 1 mm, and the remaining 30% at distances between 1 mm and 2.5 mm from the injection. About 60% of the DL-neurons reside within clusters and 40% are located in regions between clusters; the respective percentages of the Rhodamine labelled GABA-negative neurons are about 85 and 15. Considering their small number and their spatial distribution inhibitory interneurons seem to make only minor contributions to the clustered pattern of intrinsic connections. Our results demonstrate that the topographical organization of neurons giving origin to lateral inhibitory interactions in upper layers of cat's striate cortex is different from that of neurons mediating excitatory functions.

Animals↗

PubMed1990

Substance P- and opioid-immunoreactive structures in olfactory centers of the cat: adult pattern and postnatal development.

Substance P (SP)-ir and opioid-ir structures were studied in the cat main olfactory bulb (MOB), accessory olfactory bulb (AOB), and olfactory peduncle. In the MOB, the opioid-ir and the majority of the SP-ir neurons belong to the granule cell type. SP-ir granule cells reside in the deeper granule cell layer, whereas opioid-ir granule cells reside in the superficial granule cell layer, internal plexiform, and mitral cell layer. Many granule cells are observed in the external plexiform and glomerular layer. Other granule cells were found in the bulbar/peduncular white matter, the taenia tecta, and the genu of the corpus callosum. A new substance P-ir cell type was identified in the glomerular layer. This cell type was also identified by using the technique of intracellular injection of Lucifer Yellow. The cell type corresponds neither to the external tufted type nor to the short axon cell types described so far. The AOB resembles the MOB with respect to large numbers of SP-ir and opioid-ir granule cells. In addition, a few opioid-ir neurons, probably superficial mitral cells, were found in the glomerular layer. The AOB is surrounded by islands of immunoreactive granule cells, which connect to the granule cell layer by extremely long processes. Opioid-ir and SP-ir beaded axons pass through the olfactory peduncle terminating on granule cells, and ascend as far as the glomerular layer. All subdivisions of the anterior olfactory nucleus (AON) contain immunoreactive terminal fields. Afferent fibers and terminal plexuses derive from a population of immunoreactive neurons located predominantly in the region of the septo-olfactory junction. They have large somata. Their axons form recurrent collaterals, some of which run rostrally in the peduncular white matter. Others ascend caudally towards the septal region. The fibers seem to remain ipsilaterally, since the olfactory limb of the anterior commissure and the commissure proper are devoid of SP-ir and opioid-ir fibers. During development SP and opioid immunoreactivity were found only in differentiated granule cells. The peptides were not detectable in migrating or immature granule cells, as identified in Golgi-impregnated material. The granule cell population largely develops during postnatal life. The number of opioid-ir granule cells increases slowly and continuously, reaching the adult level not before the sixth postnatal month. Strikingly, SP-ir granule cell number increases fast and reaches a transient peak during the second month. Thereafter it declines (40% decrease) to the adult density, which is similar to that of opioid-ir granule cells.

Afferent Pathways↗

PubMed1990

VIP- and PHI-immunoreactivity in olfactory centers of the adult cat.

The purpose of the study was to determine the morphology and distribution of vasoactive intestinal polypeptide- and peptide histidine isoleucine-immunoreactive (VIP- and PHI-ir) neurons and innervation patterns in the main and accessory olfactory bulb, anterior olfactory nucleus, and piriform cortex of the adult cat. In these centers, VIP- and PHI-immunoreactive material are present in the same neuronal types, respectively, therefore summarized as VIP/PHI-ir neurons. In the main olfactory bulb, the majority of VIP/PHI-ir neurons are localized in the external plexiform layer. These neurons give rise to two or more locally branching axons. They form boutons on mitral and external tufted cell bodies. According to the morphology and location, we have classified these neurons as Van Gehuchten cells. Some VIP/PHI-ir neurons are present in the glomerular layer. They have small somata and give rise to dendrites branching exclusively into glomeruli. We have classified these neurons as periglomerular cells. In the granule cell layer, neurons with long apical dendrites and one locally projecting axon are present. In the accessory olfactory bulb, VIP/PHI-ir neurons are localized in the mixed external/mitral/internal plexiform layer. They represent Van Gehuchten cells. In the anterior olfactory nucleus and piriform cortex, VIP/PHI-ir bipolar basket neurons are present. They are localized mainly in layers II/III. These neurons are characterized by a bipolar dendritic pattern and by locally projecting axons forming basket terminals on large immunonegative cell somata. Because of their common morphological features, we summarize them as the retrobulbar VIP/PHI-ir interneuron population. The PHI-ir neurons display the same morphology as the VIP-ir cells. However, they are significantly lower in number with a ratio of VIP-ir to PHI-ir cells about 2:1 in the main and accessory olfactory bulb and in the anterior olfactory nucleus. By contrast, in the piriform cortex the ratio is about 1:1.

Animals↗

PubMed1990

Morphology of neuropeptide Y-immunoreactive neurons in the cat olfactory bulb and olfactory peduncle: postnatal development and species comparison.

The distribution and morphology of Neuropeptide Y-immunoreactive (NPY-ir) neurons in the olfactory bulb and the olfactory peduncle was studied in the adult cat and rat, and the common marmoset Callithrix jacchus. Significant species differences were not observed. In all three species, the population of NPY-ir neurons is localized in the white matter extending from the main olfactory bulb to the border of the striatum. The neurons are characterized by a conspicuously looping axonal ramification pattern with some major collaterals running toward the olfactory bulb and others running toward the internal olfactory tract. The former, ipsilateral projection terminates in the granule cell layer of the main and accessory olfactory bulb and in layer II/III of the anterior olfactory nucleus. Reconstruction of the latter projection has revealed that the fibers are continuous with the olfactory limb of the anterior commissure and the anterior commissure proper suggesting a commissural contralateral projection. The analysis of the postnatal development of the cat NPY neuron system supports this assumption in a very clear-cut way. In young animals growing fibers are observed to cross the brachium of the commissure. The NPY neuron system develops postnatally. The maximum cell number is reached during the third postnatal week. The appearance of more and more NPY-ir neurons slightly precedes the formation of the terminal fields and of the fiber projection in the internal olfactory tract. The density of this early fiber projection by far exceeds the fiber density observed in the adult. Later in development the fiber density in the olfactory limb and the anterior commissure becomes considerably reduced. In contrast, the plexus density in the anterior olfactory nucleus and the granule cell layer of the main and accessory olfactory bulb undergoes only a slight reduction, and the NPY-ir cell number remains roughly constant. These observations suggest that the ipsilateral NPY-ir projection remains largely unchanged, in contrast to the contralateral projection, which exists to a large extent only for the first four postnatal months. The observation that the NPY neuron system gives rise to a contralateral projection does not support a classification of NPY neurons as short axon cells.

Animals↗

PubMed1989

Early postnatal development of vasoactive intestinal polypeptide- and peptide histidine isoleucine-immunoreactive structures in the cat visual cortex.

The early postnatal development of neurons containing vasoactive intestinal polypeptide (VIP) and peptide histidine isoleucine (PHI) has been analyzed in visual areas 17 and 18 of cats aged from postnatal day (P) 0 to adulthood. Neuronal types are established mainly by axonal criteria. Both peptides occur in the same neuronal types and display the same postnatal chronology of appearance. Several cell types are transient, which means that they are present in the cortex only for a limited period of development. According to their chronology of appearance the VIP/PHI-immunoreactive (ir) cell types are grouped into three neuronal populations. The first population comprises six cell types which appear early in postnatal life. The pseudohorsetail cells of layer I possess a vertically descending axon which initially gives rise to recurrent collaterals, then forms a bundle passing layers III to V, and finally, horizontal terminal fibers in layer VI. The neurons differentiate at P 4 and disappear by degeneration around P 30. The neurons with columnar dendritic fields of layers IV/V are characterized by a vertical arrangement of long dendrites ascending or descending parallel to each other, thus forming an up to 600 microns long dendritic column. Their axons always descend and terminate in broad fields in layer VI. The neurons appear at P 7 and are present until P 20. The multipolar neurons of layer VI occur in isolated positions and have broad axonal territories. The neurons differentiate at P 7 and persist into adulthood. Bitufted to multipolar neurons of layers II/III have axons descending as a single fiber to layer VI, where they terminate. The neurons appear at P 12 and persist into adulthood. The four cell types described above issue a vertically oriented fiber architecture in layers II-V and a horizontal terminal plexus in layer VI which is dense during the second, third and fourth week. Concurrent with the disappearance of the two transient types the number of descending axonal bundles and the density of the layer VI plexus is reduced, but the latter is maintained during adulthood by the two persisting cell types. Two further cell types belong to the first population: The transient bipolar cells of layers IV, V, and VI have long dendrites which extend through the entire cortical width. Their axons always descend, leave the gray matter, and apparently terminate in the upper white matter. The neurons differentiate concurrently with the pseudohorsetail cells at P 4, are very frequent during the following weeks, and eventually disappear at P 30.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗

PubMed1989

The anatomical substrate for telencephalic function.

The basic thesis for this study was that the telencephalon is needed to make decisions in new situations. Subsidiary hypotheses were that the telencephalon consists of: (a) a sensorimotor system which generates motor activity from sensory input and (b) a selection system which makes choices from possible motor programs. It was postulated that the selection system should fulfil the following requirements: be accessible for past and present events, have the capacity to process this information in a nondetermined way with a possibility for ordering, and have access to motor-affecting systems (the sensorimotor system). The ability of the selection system to correlate information in a nonpredetermined way was considered most important. In short: The selection system should be able to associate any information in any combination, and have the capability for internal control of neuronal activity and external selection of motor programs (see Fig. 1A.) Xenopus laevis was chosen as a subject, since it has a relatively simple telencephalon, with characteristics that it shares with "primitive" species of different vertebrate classes, and because it is easy to maintain as a laboratory animal. The main method used was the determination of connections with HRP. The pallium was in the focus of attention, since it was considered to be the core of the selection system. Immunohistochemistry was used as an additional parameter to compare Xenopus laevis forebrain with those of other vertebrates. The results showed that the pallium can be subdivided into a rostral (third) and a caudal (two-thirds) entity. The rostral third is the main recipient for thalamic and olfactory input. The caudal two-thirds are linked up to the rostral third and have a refined microcircuitry. Efferents from the pallium remain restricted to the forebrain. The entire pallium consists of a network of intrinsic reciprocal connections and can be considered to be positioned between the medial pallium (hippocampus), septum, and amygdaloid complex (amygdala). As a whole this system targets the hypothalamus. The hypothalamus in turn projects into the striatum complex (striatum with anterior entopeduncular nucleus). The rostral dorsal pallium and the amygdaloid complex also project into the striatum complex. The striatum is positioned between the sensory input from the thalamus and olfactory bulbs, and the motor output to the medulla. It is concluded, on the basis of its straightforward input-output relations and uniform appearance, that the striatum complex fulfils the requirements for a sensorimotor system. The pallium together with the septum, amygdaloid complex, and hypothalamus fulfils the requirements for a selection system.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗