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PubMedDate not supplied

Microstructure of the neocortex: comparative aspects.

The appearance of the neocortex, its expansion, and its differentiation in mammals, represents one of the principal episodes in the evolution of the vertebrate brain. One of the fundamental questions in neuroscience is what is special about the neocortex of humans and how does it differ from that of other species? It is clear that distinct cortical areas show important differences within both the same and different species, and this has led to some researchers emphasizing the similarities whereas others focus on the differences. In general, despite of the large number of different elements that contribute to neocortical circuits, it is thought that neocortical neurons are organized into multiple, small repeating microcircuits, based around pyramidal cells and their input-output connections. These inputs originate from extrinsic afferent systems, excitatory glutamatergic spiny cells (which include other pyramidal cells and spiny stellate cells), and inhibitory GABAergic interneurons. The problem is that the neuronal elements that make up the basic microcircuit are differentiated into subtypes, some of which are lacking or highly modified in different cortical areas or species. Furthermore, the number of neurons contained in a discrete vertical cylinder of cortical tissue varies across species. Additionally, it has been shown that the neuropil in different cortical areas of the human, rat and mouse has a characteristic layer specific synaptology. These variations most likely reflect functional differences in the specific cortical circuits. The laminar specific similarities between cortical areas and between species, with respect to the percentage, length and density of excitatory and inhibitory synapses, and to the number of synapses per neuron, might be considered as the basic cortical building bricks. In turn, the differences probably indicate the evolutionary adaptation of excitatory and inhibitory circuits to particular functions.

Animals↗
PubMed2003

Degenerative changes and cell death in long-living homo- and heterotopic transplants from embryonic germ layers of rat neocortex.

Morphological study of allotransplants of rat embryonic neocortex 14-18 months after transplantation into the neocortex, lateral cerebral ventricle, and sciatic nerve of adult animals revealed death of nerve and glial cells in the delayed postoperation period independently on the site of transplantation. After heterotopic transplantation the count of degenerated neurons was 2 times higher that after homotopic transplantation. In heterotopic transplants a considerable number of grafted neurons underwent reversible and irreversible degenerative changes accompanied by their premature aging. Neuronal death is probably determined by insufficiency of trophic influence from afferent structures and target tissues. We hypothesized that antiapoptotic preparations can be used for prevention of transplanted cell death. It was also found that degeneration of neurons was associated with impaired vascularization of transplants and pronounced immune reaction of the recipient in late posttransplantation period. Transplantation of embryonic brain structures can serve as a model system in studies concerning involutive and pathological processes in the central nervous system and in the search for factors improving survival of neurons.

Animals↗
PubMed2001

Neurons derived from radial glial cells establish radial units in neocortex.

The neocortex of the adult brain consists of neurons and glia that are generated by precursor cells of the embryonic ventricular zone. In general, glia are generated after neurons during development, but radial glia are an exception to this rule. Radial glia are generated before neurogenesis and guide neuronal migration. Radial glia are mitotically active throughout neurogenesis, and disappear or become astrocytes when neuronal migration is complete. Although the lineage relationships of cortical neurons and glia have been explored, the clonal relationship of radial glia to other cortical cells remains unknown. It has been suggested that radial glia may be neuronal precursors, but this has not been demonstrated in vivo. We have used a retroviral vector encoding enhanced green fluorescent protein to label precursor cells in vivo and have examined clones 1-3 days later using morphological, immunohistochemical and electrophysiological techniques. Here we show that clones consist of mitotic radial glia and postmitotic neurons, and that neurons migrate along clonally related radial glia. Time-lapse images show that proliferative radial glia generate neurons. Our results support the concept that a lineage relationship between neurons and proliferative radial glia may underlie the radial organization of neocortex.

Animals↗
PubMed2003

RNAi reveals doublecortin is required for radial migration in rat neocortex.

Mutations in the doublecortin gene (DCX) in humans cause malformation of the cerebral neocortex. Paradoxically, genetic deletion of Dcx in mice does not cause neocortical malformation. We used electroporation of plasmids encoding short hairpin RNA to create interference (RNAi) of DCX protein in utero, and we show that DCX is required for radial migration in developing rat neocortex. RNAi of DCX causes both cell-autonomous and non-cell autonomous disruptions in radial migration, and creates two disruptions in neocortical development. First, many neurons prematurely stop migrating to form subcortical band heterotopias within the intermediate zone and then white matter. Second, many neurons migrate into inappropriate neocortical lamina within normotopic cortex. In utero RNAi can therefore be effectively used to study the specific cellular roles of DCX in neocortical development and to produce an animal model of double cortex syndrome.

Animals↗
PubMed2003

Pharmacological profiles of presynaptic nociceptin/orphanin FQ receptors modulating 5-hydroxytryptamine and noradrenaline release in the rat neocortex.

1 The pharmacological profiles of presynaptic nociceptin/orphanin FQ (N/OFQ) peptide receptors (NOP) modulating 5-hydroxytryptamine (5-HT) and noradrenaline (NE) release in the rat neocortex were characterized in a preparation of superfused synaptosomes challenged with 10 mM KCl. 2 N/OFQ concentration-dependently inhibited K(+)-evoked [(3)H]-5-HT and [(3)H]-NE overflow with similar potency (pEC(50) approximately 7.9 and approximately 7.7, respectively) and efficacy (maximal inhibition approximately 40%). 3 N/OFQ (0.1 micro M) inhibition of [(3)H]-5-HT and [(3)H]-NE overflow was antagonized by selective NOP receptor antagonists of peptide ([Nphe(1)]N/OFQ(1-13)NH(2) and UFP-101; 10 and 1 microM, respectively) and non-peptide (J-113397 and JTC-801; both 0.1 microM) nature. Antagonists were routinely applied 3 min before N/OFQ. However, a 21 min pre-application time was necessary for J-113397 and JTC-801 to prevent N/OFQ inhibition of [(3)H]-NE overflow. 4 The NOP receptor ligand [Phe(1)psi(CH(2)-NH)Gly(2)]N/OFQ(1-13)NH(2) ([F/G]N/OFQ(1-13)NH(2); 3 microM) did not affect K(+)-evoked [(3)H]-NE but inhibited K(+)-evoked [(3)H]-5-HT overflow in a UFP-101 sensitive manner. [F/G]N/OFQ(1-13)NH(2) antagonized N/OFQ actions on both neurotransmitters. 5 The time-dependency of JTC-801 action was studied in CHO cells expressing human NOP receptors. N/OFQ inhibited forskolin-stimulated cAMP accumulation and JTC-801, tested at different concentrations (0.1-10 microM) and pre-incubation times (0, 40 and 90 min), antagonized this effect in a time-dependent manner. The Schild-type analysis excluded a competitive type of antagonism. 6 We conclude that presynaptic NO receptors inhibiting 5-HT and NE release in the rat neocortex have similar pharmacological profiles. Nevertheless, they can be differentiated pharmacologically on the basis of responsiveness to [F/G]N/OFQ(1-13)NH(2) and time-dependent sensitivity towards non-peptide antagonists.

Animals↗
PubMed2003

A developmentally regulated and psychostimulant-inducible novel rat gene mrt1 encoding PDZ-PX proteins isolated in the neocortex.

Single or repeated exposure to psychostimulants such as amphetamines and cocaine after postnatal week 3 leads to an enduring enhancement in the psychotomimetic responses elicited by a subsequent challenge of a stimulant in rodents. This behavioral sensitization phenomenon has been considered to be the neural consequences of stimulant-induced alterations in gene expression in the brain after a critical period of postnatal development. Using a differential cloning technique, RNA arbitrarily primed PCR, we have now identified from the rat neocortex a novel and developmentally regulated methamphetamine (MAP)-inducible gene mrt1 (MAP responsive transcript 1). mrt1 encodes two major types of PDZ- and PX-domains containing proteins of approximately 62 kDa in size with different carboxy termini, Mrt1a and Mrt1b. The mrt1 mRNAs for Mrt1a, mrt1a, and for Mrt1b, mrt1b, are predominantly expressed in various brain regions and the testes, respectively. Acute MAP injection upregulated mrt1b expression in the neocortex after postnatal week 3 in a D1 receptor antagonist-sensitive manner without affecting mrt1a expression. This upregulation was mimicked by another stimulant, cocaine, whereas pentobarbital and D1 antagonist failed to change the mrt1b transcript levels. Moreover, repeated daily treatment of MAP, but not MAP plus D1 antagonist, for 5 days caused an augmentation of the basal expression of mrt1b 2 and 3 weeks after the drug discontinuation. These late-developing, cocaine-crossreactive, D1 antagonist-sensitive and long-term regulations of mrt1b by MAP are similar to the pharmacological profiles of stimulant-induced behavioral sensitization, and therefore may be associated with the initiation and/or maintenance of the long-term neuronal adaptation.

Aging↗
PubMed2003

Ultrastructure of astrocytes in the cortex of the hippocampal gyrus and in the neocortex of the temporal lobe in experimental valproate encephalopathy and after valproate withdrawal.

The aim of the study was to analyse the astrocyte ultrastructure within the hippocampal gyre cortex and neocortex of the temporal lobe in valproate encephalopathy induced by chronic administration of an anti-epileptic drug - sodium valproate (VPA) to rats for 1, 3, 6, 9 and 12 months, once daily intragastrically, in a dose of 200 mg/kg b.w. and after its withdrawal for 1 and 3 months. Prolonged application of VPA caused damage to protoplasmic astrocytes of the cortex regions examined, mainly in the pyramidal layer, which intensified in the later stages of the experiment, especially after 9 and 12 months. Ultrastructural alterations in astroglia during this experiment did not differ significantly between the hippocampal cortex and neocortex. The most pronounced astroglial abnormalities, concerning about 2/3 of protoplasmic astrocytes after 9 and 12 months, were characterized by considerable swelling of cells, with the presence of empty vacuolar structures in the cytoplasm, a substantial decrease in the number of gliofilaments or even their complete loss, which indicated fibrillopoietic failure of the cell, and the appearance of astrocytes showing phagocytic activity. The astrocytic changes coexisted with distinct damage to neurones and structural elements of the blood-brain barrier. One month after termination of chronic exposure to the drug, the abnormalities did not subside, whereas after 3 months features of distinct normalization could be observed in a considerable number, more than a half, of astrocytes. In valproate encephalopathy, apart from any direct effect of VPA and/or its metabolites on astrocytes, the main cause of the protoplasmic astroglial damage in the cortex of the CNS structures examined could be associated with changes in microcirculation in the cortex (vasogenic factor), leading to its ischaemia.

Animals↗
PubMed1999

Opioids modulate cell division in the germinal zone of the late embryonic neocortex.

Opioid effects on cell division in the embryonic cerebral cortex were examined using two experimental approaches: (i) the presence of opioid receptors in the embryonic day 16 mouse neocortex was tested using immunohistochemical techniques; (ii) the values of the indices of [3H]thymidine pulse labelled cells and mitotic indices were estimated in the ventricular zone of the embryonic day 16 mouse neocortex 2.5, 4.5 and 8.5 h after administration to pregnant females of selected opioid receptor agonists or the opioid antagonist naloxone. The immunohistochemical study demonstrated that distinct subpopulations of the ventricular zone cells express mu, delta or kappa opioid receptors. Acute exposure of mouse embryos to mu, delta and kappa opioid receptor agonists or naloxone differentially affects the indices of [3H] thymidine pulse labelled cells and mitotic indices indicating changes in the cell cycle composition. Treatment with the mu opioid receptor agonist D-Ala2-MePhe4, Gly-ol5-enkephalin (DAGO), or the partially selective kappa opioid receptor agonist bremazocine, increased the [3H]thymidine labelling and mitotic indices. In contrast, the delta receptor agonist (D-Ser8)-leucine enkephalin-Thr (DSLET) produced a decrease in the labelled cell indices and mitotic indices. Naloxone provided a biphasic effect: a decrease in the values of labelled cell indices 2.5 h after naloxone administration, followed by an increase in the values of the indices at 4.5 and 8.5 h. These results suggest that the endogenous embryonic/maternal opioid systems are involved in the regulation of cell division in the ventricular zone of the late embryonic cortex.

Animals↗
PubMed2000

Gluco- and mineralocorticoid receptor-mediated regulation of neurotrophic factor gene expression in the dorsal hippocampus and the neocortex of the rat.

Gluco- and mineralocorticoid receptors (GR and MR) act via common promoter elements but may exert different effects on gene regulation in various regions of the forebrain. In order to separately analyse the role of GR and MR in the regulation of neurotrophic factor genes and their receptors, we used adrenalectomy and subsequent hormone injections in the rat as a model system. Twenty-four hours after adrenalectomy rats were injected with a single dose of corticosterone (2 and 10 mg/kg), aldosterone (0.5 mg/kg) or the synthetic glucocorticoid agonist RU 28362 (4 mg/kg). Gene expression of basic fibroblast growth factor (bFGF) and its high-affinity receptors [fibroblast growth factor receptor subtypes 1-3 (FGF-R1, FGF-R2, FGF-R3)], as well as brain-derived growth factor (BDNF) and neurotrophin-3 (NT-3) was analysed at 4 h after the hormone injection in CA1-CA4 (cornus of Ammon areas of the hippocampus) and dentate gyrus of the dorsal hippocampus and in neocortex by means of in situ hybridization. We found that bFGF is regulated in CA2, CA3 and dentate gyrus by GR and MR together, and in CA1, CA4 and neocortex by GR alone. FGF-R2 expression in the hippocampus seems to be regulated only by MR, while BDNF expression appears to depend on both receptors. FGF-R1, FGF-R3 and NT-3 were only moderately affected by the hormone activation of GR and MR acting in concert or alone in the various regions. Thus, the present findings suggest that the adrenal cortical system through GR and MR participate in the control of neurotrophic factor signalling in a highly subregion- and cellular-dependent manner.

Adrenalectomy↗
PubMed2002

Evaluation of opioid peptide and muscarinic receptors in human epileptogenic neocortex: an autoradiography study.

PURPOSE: The main goal of the present study was to evaluate possible alterations in opioid peptide and muscarinic receptors in human neocortical epileptic focus and the surrounding area removed from patients with pharmacologically resistant epilepsy and epilepsy secondary to cerebral lesion by tumor or other causes. METHODS: In vitro quantitative autoradiography experiments were carried out to label mu, delta, and muscarinic receptors of neocortical epileptic focus and surrounding area obtained from patients with pharmacologically resistant primary epilepsy and epilepsy caused by tumors and angioma cavernosa, and compared with neocortex obtained from patients with dementia and tumors without epilepsy. RESULTS: The mu receptor levels were lower in surrounding areas (-46%). The delta receptor binding was reduced in epileptic focus obtained from patients with epilepsy secondary to cerebral lesion (-25%) and surrounding areas (-31%). In contrast, muscarinic receptor levels were higher in the focus from patients with primary epilepsy (layers I-II, 52%; layers III-IV, 44%; layers V-VI, 36%). CONCLUSIONS: It is suggested that the increased muscarinic receptors in the epileptic focus and the decreased mu and delta receptors in the surrounding area are associated with the initiation and propagation of seizure activity in human epileptogenic neocortex.

Adolescent↗
PubMed1998

Neuronal migration disorders: heterotopic neocortical neurons in CA1 provide a bridge between the hippocampus and the neocortex.

Neuronal migration disorders have been involved in various pathologies, including epilepsy, but the properties of the neural networks underlying disorders have not been determined. In the present study, patch clamp recordings were made from intrahippocampal heterotopic as well as from neocortical and hippocampal neurons from brain slices of rats with prenatally methylazoxymethanol-induced cortical malformation. We report that heterotopic neurons have morphometrical parameters and cellular properties of neocortical supragranular neurons and are integrated in both neocortical and hippocampal networks. Thus, stimulation of the white matter induces both antidromic and orthodromic response in heterotopic and neocortical neurons. Stimulation of hippocampal afferents evokes a monosynaptic response in the majority of heterotopic neurons and a polysynaptic all-or-none epileptiform burst in the presence of bicuculline to block gamma-aminobutyric acid type A inhibition. Furthermore, hippocampal paroxysmal activity generated by bath application of bicuculline can spread directly to the neocortex via the heterotopia in methylazoxymethanol-treated but not in naive rats. We conclude that heterotopias form a functional bridge between the limbic system and the neocortex, providing a substrate for pathological conditions.

Action Potentials↗
PubMed2000

Myelination defects and neuronal hyperexcitability in the neocortex of connexin 32-deficient mice.

Morphological and electrophysiological studies were performed on neocortices of adult Connexin 32 (Cx32)-deficient mice and wild-type mice to investigate the consequences of a lack of the gap junction subunit Cx32 on neocortical structure and function. Morphometrical analysis revealed a reduced volume fraction of myelin within the neuropil and a decreased thickness of the axonal myelin sheaths in the neocortex of Cx32-deficient mice. Intracellular recordings from neurons in neocortical slice preparations provided evidence for an increased membrane input resistance in neurons of Cx32-null mutant mice as compared to neurons of wild-type mice. Consequently, neurons of Cx32-deficient mice displayed an enhanced intrinsic excitability. In addition, approximately 50% of the neurons investigated in slices of Cx32-deficient mice responded to afferent stimulation with delayed and large glutamatergic excitatory postsynaptic potentials resembling paroxysmal depolarizations. GABAergic inhibition sufficient to efficiently control synaptic excitability was virtually absent in these cells. The changes in intrinsic membrane properties observed in neurons of Cx32-null mutant mice were independent of the alterations in synaptic function, since increased membrane resistances were observed also in neurons with normal synaptic response pattern. Thus, in the neocortex, lack of Cx32 correlates with myelination defects, alterations in intrinsic membrane properties and dysfunction of inhibitory synaptic transmission.

Action Potentials↗
PubMed2000

Stereotypical physiological properties emerge during early neuronal and glial lineage development in the embryonic rat neocortex.

Surface immunolabeling was used together with membrane potential and/or Ca(2+) indicator dyes to characterize physiological properties emerging among precursors, neuroglial progenitors and differentiating neurons during neurogenesis of embryonic rat neocortex. Cells were immunoidentified with tetanus toxin (TnTx), which binds to gangliosides expressed by neurons, and anti-A2B5, which reacts with gangliosides expressed by neuroglial progenitors. Microdissection of the neocortex into ventricular/subventricular zone (VZ/SVZ) and cortical plate/subplate (CP/SP) regions further resolved the TnTx/A2B5-immunoidentified cells into pre- and post-migratory subpopulations. Quantitative immunocytochemistry revealed mainly proliferative (BrdU(+)) and immature (nestin(+)) elements among TnTx(-)A2B5(-) precursors and TnTx(-)A2B5(+) progenitors in the VZ/SVZ, and the appearance of neuron-specific antigens among post-mitotic TnTx(+) subpopulations of the CP/SP. Flow cytometry of acutely prepared cells in suspension and dual-imaging of cells in culture revealed that ionotropic amino acid receptors and metabotropic acetylcholine receptors closely paralleled the emergence of voltage-dependent Na(+) and Ca(2+) channels and Na(+)-Ca(2+) exchange activity among TnTx(+) neuronal progenitors migrating from VZ/SVZ to CP/SP. During this period, TnTx(-)A2B5(-) precursors and TnTx(-)A2B5(+) neuroglial progenitors from VZ/SVZ predominantly exhibited Ca(2+) responses to ATP. Thus, stereotypical and contrasting physiologies emerge among embryonic cortical cells in vivo as they initially progress from proliferating precursors and progenitors along neuronal and glial cell lineages.

Animals↗
PubMed2000

Developmental history of the subplate and developing white matter in the murine neocortex. Neuronal organization and relationship with the main afferent systems at embryonic and perinatal stages.

The neuronal diversity of the subplate and developing white matter in the mouse was studied using a variety of neuronal markers. The subplate was first visible in lateral cortical areas at E13, coinciding with the emergence of the cortical plate. During prenatal development, this layer was formed by morphologically heterogeneous neurons, subsets of which were immunoreactive for GABA- and calcium-binding proteins. From E18 onwards, a few subplate cells also contained neuropeptides. Colocalization experiments demonstrated that the percentages of neurons immunoreactive for each antigen were similar to those described in adult neocortex. By E15, subplate cells had received synaptic contacts. Moreover, a second early-neuronal population was conspicuous from E13 in the lower intermediate zone: the intermediate-subventricular population. Unlike subplate cells, these neurons were morphologically uniform, smaller and horizontally oriented. Nevertheless, a few of these cells also appeared within the ventricular zone, with a perpendicular/ oblique orientation. Most of these cells were GABA-positive and showed calbindin immunoreactivity. At the electron microscopic level, no synaptic contacts were found in these neurons. Tracing studies using DiI showed that subplate neurons were the first to send axons outside the neocortex towards the ganglionic eminence at E13. At E14, subplate axons and ingrowing thalamic fibers met in the striate primordium. Subplate cells retained their projection to the thalamus during prenatal development. Thalamocortical axons reached the subplate at E15, and 1 day later began to invade the upper cortical layers. Early callosal axons, in contrast, did not run through the subplate to reach the contralateral hemisphere, nor did subplate cells send out callosal fibers. Callosal axons ran just above the subventricular zone, intermingled with the intermediate-subventricular neuronal population. We conclude that the subplate neuronal population has a chemical heterogeneity reminiscent of that of the adult cortex and is crucial to the establishment of thalamocortical relationships, whereas the intermediate-subventricular neurons constituted a particular GABAergic population, which includes resident cells and tangentially migrating postmitotic neurons spatially related to the development of callosal connections.

Afferent Pathways↗
PubMed2001

The early differentiation of the neocortex: a hypothesis on neocortical evolution.

During development, a cerebral cortex appears in the wall of the telencephalic vesicle in reptiles and mammals. It arises from a cell-dense cortical plate, which develops within a primordial preplate. The neurons of the preplate are essential for cortical development; they regulate the neuronal migration of the cortical plate neurons and form the first axonal connections. In the reptilian cortex and in the hippocampus of the mammalian cerebral cortex, most ingrowing afferent axons run above the cortical plate, in the zone where the receptive tufts of apical dendrites of the cortical pyramidal neurons branch extensively. In the mammalian neocortex, however, axons enter mainly from below the cortical plate where they do not encounter the apical tufts of these pyramidal neurons. In this paper, we discuss the idea that this difference in cortical development has relieved a functional constraint in the expansion of the cortex during evolution. We hypothesize that the entrance of axons below the cell-dense cortical plate, together with the inside-out migration of cortical neurons, ensures that the neocortex remains an "open" system, able to differentiate into new (sub)layers and more cortical areas.

Animals↗
PubMed1997

Expression of peripherin, NADPH-diaphorase and NOS in the adult rat neocortex.

Peripherin is mainly expressed in peripheral neurones and in CNS neurones which extend axons into peripheral nerves. However, this intermediate filament protein has also been detected in a few other neurones entirely located within the CNS. The present study focuses on the adult rat neocortex. Peripherin immunoreactive (P+) neuronal somata and their neuritic extensions were observed in cortical layers II, III, V and VI, while a few P+ nerve fibres could be seen in layer I. All the P+ neurones could be selectively stained using reduced nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) histochemistry, a typical feature of aspiny neurones. Some of the P+ neurones could also be immunostained with an antibody raised against nitric oxide synthase (NOS). These results provide evidence that peripherin is present in a discrete population of aspiny interneurones of the adult rat neocortex. The functional significance of the co-expression of peripherin and NOS needs further investigation.

Animals↗
PubMed2001

Microglia/macrophages proliferate in striatum and neocortex but not in hippocampus after brief global ischemia that produces ischemic tolerance in gerbil brain.

The current study determined whether short durations of ischemia that produce ischemia-induced tolerance stimulate glial proliferation in brain. Adult male gerbils were injected with BrdU (50 mg/kg) and dividing cells were detected using immunocytochemistry after sham operations, 2.5 or 5 minutes of global ischemia, or ischemia-induced tolerance. The 2.5-minute ischemia and the ischemia-induced tolerance did not kill hippocampal CA1 pyramidal neurons, whereas the 5-minute ischemia did kill the neurons. At 4 days after 2.5-minute global ischemia, when cell proliferation was maximal, BrdU-labeled cells increased in striatum and in neocortex, but not in hippocampus. The majority of the BrdU-labeled cells were double-labeled with isolectin B4, showing that these dividing cells were primarily microglia or macrophages, or both. Similarly, BrdU-labeled microglia/macrophages were found in striatum and neocortex but not in hippocampus of most animals 4 days after ischemia-induced tolerance (2.5 minutes of global ischemia followed 3 days later by 5 minutes of global ischemia). No detectable neuronal cell death existed in striatal and cortical regions where the microglia/macrophage proliferation occurred. Though 3 of 7 animals subjected to 2.5 minutes of ischemia showed decreased myelin-associated glycoprotein (MAG) immunostaining and increased numbers of adenomatous polyposis coli-stained oligodendrocytes in lateral striatum, this did not explain the microglia/macrophage proliferation. Data show that ischemia-induced tolerance in the gerbil is associated with proliferation of microglia/macrophages in striatum and cortex but not in hippocampus. Because there is no apparent neuronal death, it is postulated that the microglia/macrophage proliferation occurs in response to an unknown nonlethal injury to neurons or glia and may be beneficial.

Adenomatous Polyposis Coli Protein↗
PubMed2001

COUP-TFI: an intrinsic factor for early regionalization of the neocortex.

Regionalization of the cerebral cortex is thought to involve two phases: an early regionalization phase and a later refinement phase. It has been shown that early regionalization of the neocortex does not require thalamic inputs and is regulated by intrinsic factors. Recently, two such intrinsic factors, Pax6 and Emx2, have been identified. In this study, we identified COUP-TFI as a regulatory factor for early neocortical regionalization. The spatial and temporal expression pattern of COUP-TFI suggested a role in specification of the neocortex and in maintaining cortical identity. Altered region-specific expression of marker genes in the cortex as well as miswired area-specific connections between the cortex and the thalamus in COUP-TFI null mice indicate COUP-TFI plays a critical role in regulating early regionalization. Our results substantiate that COUP-TFI, an intrinsic factor, may work in concert with Pax6 and Emx2 to specify neocortical identity.

Animals↗