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PubMed1981

Two visual pathways to the telencephalon in the nurse shark (Ginglymostoma cirratum). II. Ascending thalamo-telencephalic connections.

As part of a study on retino-telencephalic pathways the ascending connections to the telencephalic central nucleus were investigated by retrograde transport of horseradish peroxidase. The central nucleus of the telencephalon, which is the main recipient for input from the brainstem, grossly can be divided into three rostrocaudal parts according to their afferent connections. The rostral third receives input mainly from the contralateral central thalamic nucleus and to a lesser degree from the lateral geniculate nucleus, periventricular gray, and a nucleus called the ventral mesencephalic tegmentum. The middle third of the central nucleus maintains an afferent connection with contralateral lateral geniculate, ventrolateral optic, and central thalamic nucleus, with the ventral mesencephalic tegmentum and periventricular gray bilaterally, and with a group of cells in the superior raphé nucleus. Caudal central nucleus injections of HRP resulted in labeling of cells in the contralateral lateral geniculate nucleus, ventral mesencephalic tegmentum, and central thalamic bilaterally, and in the superior raphé nucleus preoptic area and periventricular gray. From these results it can be concluded that visual information may reach the central telencephalic nucleus by two separate pathways: one pathway from retina via ventrolateral optic nucleus to the middle third of the central nucleus, and a second pathway from retina to optic tectum, which reportedly projects to the lateral geniculate nucleus, which in turn provides afferents to the caudal two-thirds of the central nucleus. As such the nurse shark's visual system possesses structural features that are homologous to the two visual systems of higher vertebrate groups.

Animals↗
PubMed1983

Extrinsic and intrinsic fiber connections of the telencephalon in a teleost, Sebastiscus marmoratus.

Extrinsic and intrinsic fiber connections of the telencephalic subdivisions of Nieuwenhuys ('62) in a teleost, Sebastiscus marmoratus, were studied by means of horseradish peroxidase (HRP) and Fink-Heimer methods. The olfactory bulb projects bilaterally to area dorsalis pars posterior, area ventralis pars ventralis, pars lateralis, pars posterior, pars intermedia, and the nucleus posterior tuberis of Peter et al. ('75) and receives fibers from ipsilateral area dorsalis pars centralis, pars posterior, area ventralis pars dorsalis, and pars supracommissuralis. Area dorsalis pars posterior sends numerous fibers to the ipsilateral ventral region of area dorsalis pars medialis, from which fibers of the medial forebrain bundle arise and terminate in the inferior lobe and nucleus posterior tuberis. Area dorsalis pars lateralis, pars dorsalis, and the dorsal region of pars medialis are the main targets of extratelencephalic ascending afferents. Area dorsalis pars lateralis receives fibers from the ipsilateral nucleus prethalamicus of Meader ('34), where tectal projections terminate massively. Area dorsalis pars dorsalis and the dorsal region of pars medialis receive afferents from the ipsilateral nucleus preglomerulosus of Schnitzlein ('62), nucleus posterior tuberis, area preoptica pars medialis of Crosby and Showers ('69), and nucleus entopeduncularis of Sheldon ('12). Raphe nuclei and locus ceruleus project bilaterally to area dorsalis pars centralis, pars dorsalis, pars lateralis, and the dorsal region of pars medialis. Area dorsalis pars centralis, pars dorsalis, and the dorsal region of pars medialis are important sources of extratelencephalic efferents. These subdivisions give rise to the lateral forebrain bundle and project to the ipsilateral nucleus prethalamicus, nucleus preglomerulosus, inferior lobe, nucleus paracommissuralis of Ito et al. ('82), optic tectum, torus semicircularis, and the bilateral mesencephalic tegmentum. Within the telencephalon, most of the ventral subdivisions project to ipsilateral area dorsalis pars centralis, pars dorsalis, pars lateralis, and the dorsal region of pars medialis. Area dorsalis pars centralis has reciprocal connections with ipsilateral area dorsalis pars lateralis, pars dorsalis, pars posterior, and the dorsal region of pars medialis. A dorsal part of the anterior commissure is composed of axons of the ventral region of area dorsalis pars medialis destined to the contralateral ventral region of area dorsalis pars medialis. A ventral part of the anterior commissure contains axons of area dorsalis pars centralis destined to contralateral area dorsalis pars lateralis.

Animals↗
PubMed1985

Cytoarchitecture and ultrastructure of the avian ectostriatum: afferent terminals from the dorsal telencephalon and some nuclei in the thalamus.

The cytoarchitecture, ultrastructure, and afferent terminals in the ectostriatal complex of the Japanese quail were examined. The complex consists of the central core (Ec) and peripheral belt (Ep). Terminals in the complex were categorized into three main groups according to the shape of synaptic vesicles: S (spherical), P (pleomorphic), and F (flat). S terminals are further classified into three types: Ss, small terminals which have densely packed vesicles and a long active zone and are presynaptic to large spines; Sm, medium-sized to large terminals which have a relatively short active zone and contact dendritic spines, trunks, and somata; Sl, large terminals which have many mitochondria and cored vesicles and form synapses only with somata. Some of the Sm terminals are derived from myelinated axons. The Sl terminals are frequently combined with gap junctions as so-called mixed synapses. The P terminal occasionally surrounds an axon hillock, making symmetric synaptic contacts. The F terminals often cover a wide area of the soma. A few gap junctions are also recognized between adjacent somata. Afferent sources of the ectostriatal complex were examined by means of horseradish peroxidase (HRP) retrograde transport. Many large HRP-labeled cells were recognized in the nucleus rotundus (Rt). HRP-labeled cells were seen in the nucleus triangularis (Tr), nucleus dorsolateralis posterior thalami (DLP), and a few labeled cells were scattered in the hyperstriatum ventrale (HV). Substantial numbers of Sm terminals in Ec degenerated after destruction of Rt; they made synaptic contacts with dendritic trunks (71.8%) and small spines (28.2%). Degenerating and intact Sm terminals were found to form synapses with the same dendritic trunk by the reconstruction of serial thin sections. Among the 167 Sm terminals, 20 terminals (12.0%) degenerated after lesions in Rt. The Sm terminals in Ec degenerated after destruction of Tr and the terminals formed synapses with somata as well as dendritic trunks and spines. After lesions of the dorsal telencephalon including HV, degenerating fibers sparsely entered the ectostriatal complex associated with the Ss terminal degeneration. DLP seemed to project mainly on the medial area of posterior Ep. The terminals from DLP made asymmetric synaptic contacts with dendritic spines, trunks, and somata. Some of the terminals from DLP were identified as the Sl type, but other S types could not be identified.

Animals↗
PubMed1986

Thalamic fiber connections in a teleost (Sebastiscus marmoratus): visual somatosensory, octavolateral, and cerebellar relay region to the telencephalon.

Fiber connections of the nucleus ventromedialis thalami (VM) of Schnitzlein (J. Comp. Neurol. 118:225-267, '62) in a teleost (Sebastiscus marmoratus) were examined by means of the horseradish peroxidase (HRP) tracing method. This nucleus receives fibers from the ipsilateral telencephalon (area dorsalis pars centralis), contralateral retina, contralateral VM, ipsilateral optic tectum, ipsilateral torus semicircularis, contralateral corpus cerebelli, contralateral sensory nucleus of the trigeminal nerve, bilateral bulbospinal reticular formation, contralateral obex region, and contralateral dorsal portion of upper spinal segments. In turn, axons arising from VM terminate in the dorsal telencephalic areas (pars centralis, pars dorsalis, and pars medialis) ipsilaterally, ventral telencephalic area (pars supracommissuralis) bilaterally, nucleus prethalamicus of Meader (J. Comp. Neurol. 60:361-407, '34) bilaterally, nucleus dorsomedialis thalami bilaterally, VM contralaterally, optic tectum bilaterally, torus semicircularis bilaterally, and nucleus lateralis valvulae ipsilaterally. Based on the cytoarchitecture and fiber connections, VM is subdivided into rostral and caudal components. The caudal part of VM in Sebastiscus is considered to be a multimodal thalamic complex that contains some cells that constitute the dorsal thalamus in other vertebrate groups.

Afferent Pathways↗
PubMed1991

The distribution of neurotransmitters and neurotransmitter-related enzymes in the dorsomedial telencephalon of the pigeon (Columba livia).

Immunoreactivity to four neurotransmitters/transmitter-related enzymes was found in the dorsomedial telencephalon (hippocampal region) of the pigeon. Putative afferent fibers containing choline acetyltransferase-like, serotonin-like, and tyrosine hydroxylase-like immunoreactivity were seen in a fiber tract passing through the septo-hippocampal junction and along the medial wall of the hippocampal region. The most intensive labeling of neuropil and terminals of all four substances was found in the dorsomedial area of the hippocampal region. Glutamic acid decarboxylase-like immunoreactivity was seen in sparsely scattered cells throughout the region. These results are discussed in relation to hypotheses about the boundaries and subdivisions of the hippocampal region of the pigeon.

Afferent Pathways↗
PubMed1991

The distribution of neuropeptides in the dorsomedial telencephalon of the pigeon (Columba livia): a basis for regional subdivisions.

The distribution of six neuropeptides [substance P (SP), leucine (leu5-) enkephalin (LENK), vasoactive intestinal polypeptide (VIP), cholecystokinin (CCK), neuropeptide Y (NPY), and somatostatin (SS)] in the dorsomedial telencephalon (hippocampal region) of the pigeon was studied by immunohistochemistry. All six peptides were found in fibers passing through the septo-hippocampal junction and along the medial wall of the hippocampal region. NPY-, SS-, and VIP-like staining of fibers was seen in the hippocampal commissure. NPY and SS had similar distributions within the hippocampal region, both being most conspicuous in cell bodies, terminals, and fibers of the medial hippocampal region. VIP-positive cells were found in an area dorsal to the SS/NPY cell region. CCK-like immunoreactivity was found in terminal baskets surrounding large cells of a v-shaped structure in the ventromedial hippocampal region. SP- and LENK-like immunoreactivity was found in neuropils in a lateral-dorsal region, the two substances showing similar distributions. This region is thought to lie lateral to the limit of the hippocampal region. Parallels with the distribution of immunoreactivity in the mammalian hippocampus are used to suggest possible equivalent subdivisions of the avian and mammalian hippocampal regions.

Animals↗
PubMed1993

Histoautoradiographic detection of oxytocin- and vasopressin-binding sites in the telencephalon of the rat.

Localization of oxytocin- and vasopressin-binding sites has so far been studied in the rat brain by means of film autoradiographs. The disposal of iodinated ligands with high specificity has allowed us to develop histoautoradiography on emulsion-coated sections and to reinvestigate on a microscopic scale the distribution of these sites in the telencephalon (septum, striatopallidal system, amygdala and hippocampus). This technique showed that oxytocin and vasopressin labelling presented distinct distributions and coincided with delimited zones, corresponding to anatomical subdivisions defined on cytoarchitectural and immunocytochemical bases. Vasopressin sites were seen in the dorsal and intermediate parts of the lateral septum and the juxtacapsular nucleus of the bed nucleus of the stria terminalis. Oxytocin sites were located in the ventral and intermediate parts of the lateral septum, the oval and the principal nuclei of the bed nucleus of the stria terminalis and the septofimbrial nucleus. In the striatopallidal system, vasopressin sites were found in the accumbens nucleus and the fundus striati, whereas oxytocin sites were in the accumbens nucleus, the head, and the posterolateral parts of the caudate-putamen, the striatal cell bridges, and the olfactory tubercle. In the amygdala, vasopressin sites were not found, but oxytocin sites were located in the central, medial, and basomedial nuclei. In the hippocampus, vasopressin sites were located in the dentate gyrus (polymorph and molecular layers), and oxytocin sites, in the subiculum (molecular and pyramidal layers) and in the field CA1 of Ammon's horn (lacunosum moleculare and pyramidal layers). The localization of the binding sites at the microscopic level permitted us to reinvestigate whether or not correlation existed in a same area between innervation, electrophysiological effects, and presence of binding sites.

Animals↗
PubMed1995

Evidence for muscarinic acetylcholine receptor subtypes in the pigeon telencephalon.

At least five subtypes of muscarinic acetylcholine receptors are expressed in various mammalian tissue preparations. The following experiment, through the use of direct binding assays (using tritiated quinuclidinyl benzilate), competitive binding assays (using tritiated quinuclidinyl benzilate and unlabeled pirenzepine or AF-DX 116), and autoradiographic techniques, examined whether two of these five putative muscarinic acetylcholine receptor subtypes can be found in avian brain. Accordingly, autoradiographic mapping of pirenzepine-sensitive (M1-like) and AF-DX 116-sensitive (M2-like) muscarinic acetylcholine receptor subtypes in the pigeon telencephalon was conducted. Although both ligands bound throughout the brain, most telencephalic regions, including the archistriatum, the neostriatum, and basal ganglia structures like lobus paraolfactorius, nucleus accumbens, and paleostriatum, showed a higher density of M1-like sites. The exception to this finding was the nucleus basalis which appeared as a region where M2-like sites predominated. Moreover, the telencephalic region with the largest ratio of M1-like to M2-like sites was the lateral portion of the parahippocampus; a characteristic shared with the mammalian dentate gyrus. The findings reported here are generally consistent with previous reports of mammalian M1/M2 receptor distributions.

Animals↗
PubMed2003

Early oligodendrocyte progenitor cells in the human fetal telencephalon.

Oligodendrocytes, the myelin-producing cells in the central nervous system, represent a large portion of the total number of cells in the human brain. Using cell-specific markers and antibodies to ventral homeodomain transcription factors, NKX2.1 and DLX2, we show here that a subpopulation of early oligodendrocyte progenitor cells (OPCs) in the human telencephalon may originate in the ganglionic eminence (GE). DLX2-labeled OPCs form a well-delineated stream of cells connecting the GE subventricular zone (SVZ) to the cortical intermediate zone through the anterior cortical SVZ. This population of cells is labeled by early OPCs markers, PDGFRalpha, Olig1, and NG2, and not with either neuronal, astrocyte, or late OPCs markers. Intriguingly, numerous CD68(+) microglia/macrophages, nestin(+) neural stem cells, and CD34(+) hematopoietic stem cells (HSCs) are also present in both the GE stream and the cortical SVZ. These cells could be colabeled with DLX2 as well as early OPCs markers. A separate subpopulation of early OPCs, present in the GE and cortical SVZ, did not express either DLX2 or CD68. These findings suggest that different subpopulations of early OPCs, characterized with different sets of transcription factors and cell-specific markers, are present in human forebrain. These subpopulations may have different origins; one may originate in the cortical SVZ, while others may come from the GE and/or outside the CNS as hematopoietic stem cells.

Cell Differentiation↗
PubMed2004

Specific characteristic of radial glia in the human fetal telencephalon.

Phenotypic characteristics of cells in the developing human telencephalic wall were analyzed using electron microscopy and immunocytochemistry with various glial and neuronal cell markers. The results suggest that multiple defined cell types emerge in the neocortical proliferative zones and are differentially regulated during embryonic development. At 5-6 weeks gestation, three major cell types are observed. Most proliferating ventricular zone (VZ) cells are labeled with radial glial (RG) markers such as vimentin, glial fibrillary acidic protein (GFAP), and glutamate astrocyte-specific transporter (GLAST) antibodies. A subpopulation of these RG cells also express the neuronal markers beta III-tubulin, MAP-2, and phosphorylated neurofilament SMI-31, in addition to the stem cell marker nestin, indicating their multipotential capacity. In addition, the presence of VZ cells that immunoreact only with neuronal markers indicates the emergence of restricted neuronal progenitors. The number of multipotential progenitors in the VZ gradually decreases, whereas the number of more restricted progenitors increases systematically during the 3-month course of human corticogenesis. These results suggest that multipotential progenitors coexist with restricted neuronal progenitors and RG cells during initial corticogenesis in the human telencephalon. Since the multipotential VZ cells disappear during the major wave of neocortical neurogenesis, the RG and restricted neuronal progenitors appear to serve as the main sources of cortical neurons. Thus, the diversification of cells in human VZ and overlying subventricular zone (SVZ) begins earlier and is more pronounced than in rodents.

Adult↗
PubMed2005

Sequence of oligodendrocyte development in the human fetal telencephalon.

Oligodendrocytes (OL), cells that myelinate axons in the CNS, differentiate from early to late oligodendrocyte progenitor cells (OPC) to become mature OL. Unlike the case in the rodent brain, myelin formation starts prenatally in the human brain, but the sequence of OL development and the onset of myelination are not well understood. We studied the human fetal forebrain at midgestation (17-23 gestational weeks, g.w.) using OL lineage-specific antibodies and mRNA probes. Early OPC were present in a gradient from the subventricular zone to the cortical plate. Their close apposition to radial glia fibers suggests a possible role of these fibers in OPC migration. Late OPC reached peak density in the subplate layer, whereas multipolar cells with the morphology of mature OL were restricted to the emerging white matter. At 20 g.w., myelinated axons were observed in the diencephalon, but not in the telencephalon, consistent with caudal-to-rostral progression of myelination. Interestingly, in organotypic slice cultures of the same gestational ages, the subventricular zone contained a considerably greater number of the mature OL cells, suggesting the presence of inhibitory signals in vivo. Overall, in addition to considerable similarities with rodents, important differences in temporal and spatial distribution and regulatory signals for OL differentiation exist in the human brain.

Antigens↗
PubMed1993

Platelet-activating factor antagonists reduce excitotoxic damage in cultured neurons from embryonic chick telencephalon and protect the rat hippocampus and neocortex from ischemic injury in vivo.

The neuroprotective effects of the platelet-activating factor (PAF) antagonists BN 52020 and BN 52021 were determined in a temperature-controlled model of transient forebrain ischemia in the rat (occlusion of both common carotid arteries combined with lowering of the mean arterial blood pressure to 40 mm Hg for 10 min). After 7 days of recirculation, the ischemic neuronal damage was evaluated histologically within the hippocampus and neocortex. Combined pre- and post-treatment with the PAF antagonists (2 x 25 mg/kg, s.c.) significantly reduced the resulting neuronal damage of the CA1 and CA3 hippocampal subfields and of the occipital and parietal cerebral cortex. The two PAF antagonists were also tested for their neuroprotective activity in primary neuronal cultures isolated from embryonic chick telencephalon. Since an excessive activation of excitatory amino acid receptors is discussed to be of importance for the ischemic brain damage, the cultured neurons were exposed to the excitatory amino acid L-glutamate (1 mM) for a period of 60 min. Twenty hours after the excitotoxic insult, BN 52020- and BN 52021-treated cultures (1-100 microM) showed both a better preserved morphology, as well as a dose-dependent increase in cell viability and protein content compared to the control cultures. Our results demonstrate that the PAF antagonists BN 52020 and BN 52021 have the capacity to protect brain tissue against ischemic neuronal damage independent of hypothermic effects and are also capable of reducing excitotoxic damage of telencephalic neurons from chick embryos cultured in the absence of glial or endothelial cells. We thus propose that PAF plays an important role in the pathophysiology of ischemic/excitotoxic neuronal injury via a direct action on neurons.

Animals↗
PubMed2003

CB1 cannabinoid receptor activation inhibits a neural correlate of song recognition in an auditory/perceptual region of the zebra finch telencephalon.

A notable consequence of CB1 cannabinoid receptor activation in vertebrates is an impairment of cognitive function related to learning and short-term memory. The mechanisms of this impairment remain unclear, but one possibility is that cannabinoids influence encoding of stimuli at sensory and/or perceptual levels. Here, by treating zebra finches with the cannabinoid agonist WIN55212-2 and then measuring expression of the transcription factor zenk following presentation of novel zebra finch song, we show that cannabinoid receptor activation differentially influences zenk expression in sensory versus perceptual regions of the songbird auditory telencephalon. That is, WIN55212-2 dose-dependently inhibited zenk expression in a region for auditory perception (NCM, the caudomedial neostriatum), but had no effect on zenk expression in the primary auditory area, the Field L complex. The inhibitory effects of WIN55212-2 on zenk expression in NCM were reversed by coadministration of the CB1-selective antagonist SR141716A. Moreover, we found that the habituation of the NCM zenk response to repeated presentation of the same song, a well-established neural correlate of song recognition, was blocked when birds were treated with WIN55212-2 during habituation trials. Our data suggest that activation of CB1 cannabinoid receptors can selectively influence perceptual and mnemonic aspects of auditory experience.

Animals↗
PubMed1979

An aberrant nucleus in the telencephalon following administration of ENU during neuroembryogenesis.

Administration of ENU to rats during embryonic development caused the emergence of aberrant nuclei in the dorsal telencephalon. They were located in the corpus callosum, and were composed of pyramidal and stellate neurons. This suggested that the aberrant nuclei arose out of the neurons of cerebral cortex that had failed to migrate during embryogenesis. The aberrant nuclei were found predominantly in the animals receiving ENU on day 18 or earlier of gestation.

Animals↗
PubMed1999

Immunohistochemical and ultrastructural characterization of cortical plate microvasculature in the human fetus telencephalon.

The blood-brain barrier (BBB) differentiation was investigated by immunohistochemistry and electron microscopy in the radial microvasculature of the telencephalon cortical plate (CP) of 12- and 18-week human fetuses. The BBB-specific glucose transporter isoform 1 (GLUT1) is expressed in both stages, with a main localization on the ablumenal and lateral plasma membranes of the endothelial cells. The endothelial cells are welded by short junctions with fusion points of the plasma membranes at 12 weeks and by extensive tight junctions at 18 weeks. The basal lamina is discontinuous beneath the endothelium-pericyte layer at 12 weeks and splits into two continuous layers circumscribing the pericytes in the later stage. The expression of laminin, a basal lamina glycoprotein, is continuous already at 12 weeks. The CP microvessels are tightly surrounded by processes of glial cells. Immunodetection of the cytoskeletal filament proteins, vimentin (VIM), and glial fibrillary acidic protein (GFAP), demonstrates that at 12 weeks the perivascular glial processes are mostly represented by VIM-stained fibers of the radial glia. At 18 weeks, GFAP-stained radial glia fibers, processes of VIM-stained astroblasts, and GFAP-positive astrocytes also build the perivascular envelopes. The results indicate that the vessel differentiation is already under way in the human CP at the midgestational age and entails the establishment of some barrier devices. The early relationship between perivascular glia coverage formation and endothelial barrier maturation suggests that also immature astroglial cells are involved in the setting up of the BBB.

Adult↗
PubMed1996

Death of cultured telencephalon neurons induced by glutamate is reduced by the peptide derivative Cerebrolysin.

Glutamate induced neurotoxicity has been proposed to account for the loss of neurons after ischemia as well as in the cause of neurodegenerative diseases. We have studied the effects of exogenous glutamate on survival of neurons from chick embryo telencephalon, precultured with a peptide derivative for 8 days. The peptide derivative Cerebrolysin is a drug produced by standardised enzymatic breakdown consisting of 80% peptides and 20% amino acids. Toxic effects of acute glutamate exposure were prevented by Cerebrolysin in a concentration-dependent manner. 20 and 40 microliters Cerebrolysin produce distinct neuroprotective effects. However, 80 microliters Cerebrolysin/ml nutrition medium more than doubles neuronal viability compared to untreated control cells. These concentration-dependent effects of Cerebrolysin were evident even at the light microscopic level.

Amino Acids↗
PubMed1992

Direct retinal projections of the "non-image forming" system to the hypothalamus, anterodorsal thalamus and basal telencephalon of mink (Mustela vison) brain.

The retinal projections of the "non-image forming" system to the hypothalamus, anterodorsal thalamus and basal telencephalon were visualized in adult mink using the anterograde transport of cholera toxin conjugated to horseradish peroxidase injected intraocularly. A major and nearly symmetrical bilateral input of labeled retinal fibers to the suprachiasmatic nuclei was observed. A dense innervation was also evident in both paraventricular nuclei, and in the anterior, lateral and mediobasal hypothalamus on the side contralateral to the injection. Two projections leaving the optic tract at the level of the lateral hypothalamus or after crossing the geniculate body entered the anterior thalamus and ran in a ventro-dorsal or a caudorostral direction before terminating in the stria terminalis. Fibers were also observed in the horizontal limb of the diagonal band of Broca. These observations are compared to those in other mammalian species and discussed according to their possible implication in photoperiodic signal processing.

Animals↗