In Patas monkey, glutamic acid decarboxylase-67 and reelin mRNA coexpression varies in a manner dependent on layers and cortical areas.

In nonhuman and human primates, reelin immunoreactivity is expressed consistently in gamma-aminobutyric acid (GABA)-ergic interneurons of the three upper cortical layers (Impagnatiello et al. [1998] Proc. Natl.

Reelin in the extracellular matrix and dendritic spines of the cortex and hippocampus: a comparison between wild type and heterozygous reeler mice by immunoelectron microscopy.

Reelin is a glycoprotein ( approximately 400 kDa) secreted by GABAergic neurons into the extracellular matrix of the neocortex and hippocampus as well as other areas of adult rodent and nonhuman primate brains. Recent findings indicate that the heterozygote reeler mouse (haploinsufficient for the reeler gene) shares several neurochemical and behavioral abnormalities with schizophrenia and bipolar disorder with mania. These include (1) a downregulation of both reelin mRNA and the translated proteins, (2) a decrease in the number of dendritic spines in cortical and hippocampal neurons, (3) a concomitant increase in the packing density of cortical pyramidal neurons, and (4) an age-dependent decrease in prepulse inhibition of startle.

The heterozygote reeler mouse as a model for the development of a new generation of antipsychotics.

Neurochemical and structural prefrontal cortex abnormalities, including decreased reelin and glutamic acid decarboxylase (GAD)(67) expression, decreased thickness, increased neuronal packing density and decreased neuropil and dendritic spine number, are characteristics of schizophrenia neuropathology. Reelin is an extracellular matrix protein secreted by GABAergic interneurons that, acting through pyramidal neuron integrin receptors, provides a signal for dendritic spine plasticity. Heterozygous reeler mice that exhibit a 50% downregulation of reelin expression (mRNA and protein) replicate the dendritic spine and GABAergic defects described in schizophrenia.

Dendritic spine hypoplasticity and downregulation of reelin and GABAergic tone in schizophrenia vulnerability.

In this review, we will first present a brief overview of the current understanding of: (a) the biology of reelin; (b) the putative reelin signaling pathways via integrin receptor stimulation; (c) the cytosolic adapter protein DAB1, which appears to be operative in the transduction of reelin's pleiotropic actions in embryonic, adolescent, and adult brain; (d) the regulation of GABAergic function, including some aspects of GABAergic system development; and (e) dendritic spine function and its role in the regulation of synaptic plasticity. We argue that a downregulation of reelin expression occurring in prefrontal cortex and in every brain structure of schizophrenia patients so far studied may be associated with a decrease in dendritic spine expression that in turn may provide an important reduction of cortical function as documented by the downregulation of glutamic acid decarboxylase67 (GAD67) expression, which might be secondary to a reduction of GABAergic axon terminals. This hypothesis is supported by a genetic mouse model of reelin haploinsufficiency that replicates the above-described dendritic and presynaptic GABAergic defects documented in schizophrenia brains.

Atypical mouse cerebellar development is caused by ectopic expression of the forkhead box transcription factor HNF-3beta.

To assess the role of hepatocyte nuclear factor-3beta (HNF-3beta) in hepatocyte-specific gene transcription, we reported the characterization of the liver phenotype with transgenic mice in which the -3-kb transthyretin (TTR) promoter functioned to increase HNF-3beta expression. During breeding of the TTR-HNF-3beta transgenic mice we noticed that they displayed severe ataxia. In this study, we describe the analysis of our transgenic cerebellar phenotype and demonstrate that ectopic expression of HNF-3beta disrupted cerebellar morphogenesis and caused reduction in cerebellar size.

Glutamic acid decarboxylase and glutamate receptor changes during tolerance and dependence to benzodiazepines.

Protracted administration of diazepam elicits tolerance, whereas discontinuation of treatment results in signs of dependence. Tolerance to the anticonvulsant action of diazepam is present in an early phase (6, 24, and 36 h) but disappears in a late phase (72-96 h) of withdrawal. In contrast, signs of dependence such as decrease in open-arm entries on an elevated plus-maze and increased susceptibility to pentylenetetrazol-induced seizures were apparent 96 h (but not 12, 24, or 48 h) after diazepam withdrawal.

Down-regulation of dendritic spine and glutamic acid decarboxylase 67 expressions in the reelin haploinsufficient heterozygous reeler mouse.

Heterozygous reeler mice (HRM) haploinsufficient for reelin express approximately 50% of the brain reelin content of wild-type mice, but are phenotypically different from both wild-type mice and homozygous reeler mice. They exhibit, (i) a down-regulation of glutamic acid decarboxylase 67 (GAD(67))-positive neurons in some but not every cortical layer of frontoparietal cortex (FPC), (ii) an increase of neuronal packing density and a decrease of cortical thickness because of neuropil hypoplasia, (iii) a decrease of dendritic spine expression density on basal and apical dendritic branches of motor FPC layer III pyramidal neurons, and (iv) a similar decrease in dendritic spines expressed on the basal dendrite branches of CA1 pyramidal neurons of the hippocampus. To establish whether the defect of GAD(67) down-regulation observed in HRM is responsible for neuropil hypoplasia and decreased dendritic spine density, we studied heterozygous GAD(67) knockout mice (HG(67)M).

Decrease in reelin and glutamic acid decarboxylase67 (GAD67) expression in schizophrenia and bipolar disorder: a postmortem brain study.

Background: Reelin (RELN) is a glycoprotein secreted preferentially by cortical gamma-aminobutyric acid-ergic (GABAergic) interneurons (layers I and II) that binds to integrin receptors located on dendritic spines of pyramidal neurons or on GABAergic interneurons of layers III through V expressing the disabled-1 gene product (DAB1), a cytosolic adaptor protein that mediates RELN action. To replicate earlier findings that RELN and glutamic acid decarboxylase (GAD)(67), but not DAB1 expression, are down-regulated in schizophrenic brains, and to verify whether other psychiatric disorders express similar deficits, we analyzed, blind, an entirely new cohort of 60 postmortem brains, including equal numbers of patients matched for schizophrenia, unipolar depression, and bipolar disorder with nonpsychiatric subjects.

Methods: Reelin, GAD(65), GAD(67), DAB1, and neuron-specific-enolase messenger RNAs (mRNAs) and respective proteins were measured with quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) or Western blot analyses.

New neurochemical markers for psychosis: a working hypothesis of their operation.

Reelin (Reln) is expressed in specific GABAergic neurons in layer I and II of neocortex, and is secreted into the extracellular matrix where it surrounds dendrites, spines and neurite arborizations, and binds to integrin receptors located on post-synaptic densities of apical dendritic spines. Experiments in rodents (including wild type or reeler heterozygous mice) and non-human primates suggest the Reln secreted in the extracellular matrix of neocortex, via integrin receptors, modulates the function of the adaptor protein DAB1(drosophila disable-gene) homologous product) thereby participating in dynamic processes associated with plasticity changes in dendrites, dendritic spines and their synapses. A local protein synthesis at dendritic spines (ie the activity regulated cytoskeleton associated protein, Arc) probably acts as a signal for plastic modulatory activities in synapses operative in neural group interactions.

Colocalization of integrin receptors and reelin in dendritic spine postsynaptic densities of adult nonhuman primate cortex.

The expression of telencephalic reelin (Reln) and glutamic acid decarboxylase mRNAs and their respective cognate proteins is down-regulated in postmortem brains of schizophrenia and bipolar disorder patients. To interpret the pathophysiological significance of this finding, immunoelectron microscopic experiments are required, but these cannot be carried out in postmortem human brains. As an alternative, we carried out such experiments in the cortex of rats and nonhuman primates.

Influence of the ventral hippocampal formation on plasma vasopressin, hypothalamic-pituitary-adrenal axis, and behavioral responses to novel acoustic stress.

The ventral hippocampal formation (vHF) seems to constrain diverse responses to psychological stimuli, and disruption of this function may underlie severe neuropsychiatric diseases. In particular, the ventral subiculum inhibits hypothalamic-pituitary-adrenal axis (HPA) activity following psychological, but not systemic, stressors. Despite the difficulty in interpreting such HPA responses, they have been relied upon to further characterize vHF function, because increased HPA axis activity is implicated in neuropsychiatric disturbances, and reliance on behavioral and cognitive data is even more problematic.

Ethanol directly excites dopaminergic ventral tegmental area reward neurons.

Background: The mesolimbic/mesocortical dopamine pathway mediates the rewarding effects of ethanol and other drugs of abuse like cocaine and opiates. Dopaminergic neurons of the ventral tegmental area (VTA) are the cells of origin of the mesolimbic/mesocortical dopamine pathway. Ethanol's rewarding properties result from its ability to excite dopaminergic cell bodies in the VTA which results in increased dopamine release in the nucleus accumbens.

The phenotypic characteristics of heterozygous reeler mouse.

Histological and behavioral traits are associated with reelin (Reln) haplo-insufficiency in heterozygous reeler mouse (rl+/-). These phenotypic traits are an approximately 50% decrease of brain Reln mRNA and Reln protein, an accumulation of nicotinamide-adenine dinucleotide phosphate-diaphorase (NADPH-d)-positive neurons in subcortical white matter, an age-dependent decrease in prepulse inhibition of startle (PPI), and neophobic behavior on the elevated plus-maze. Possible analogies between these rl+/- phenotypic traits and signs of psychosis vulnerability are discussed.

Cortical bitufted, horizontal, and Martinotti cells preferentially express and secrete reelin into perineuronal nets, nonsynaptically modulating gene expression.

Reelin (Reln) is a protein with some structural analogies with other extracellular matrix proteins that functions in the regulation of neuronal migration during the development of cortical laminated structures. In the cortex of adult animals, Reln is expressed primarily in gamma-aminobutyric acid (GABA)ergic neurons and is secreted into perineuronal nets. However, only 50-60% of GABAergic interneurons express Reln.

Low resting potential and postnatal upregulation of NMDA receptors may cause Cajal-Retzius cell death.

Using in situ patch-clamp techniques in rat telencephalic slices, we have followed resting potential (RP) properties and the functional expression of NMDA receptors in neocortical Cajal-Retzius (CR) cells from embryonic day 18 to postnatal day 13, the time around which these cells normally disappear. We find that throughout their lives CR cells have a relatively depolarized RP (approximately -50 mV), which can be made more hyperpolarized (approximately -70 mV) by stimulation of the Na/K pump with intracellular ATP. The NMDA receptors of CR cells are subjected to intense postnatal upregulation, but their similar properties (EC50, Hill number, sensitivity to antagonists, conductance, and kinetics) throughout development suggest that their subunit composition remains relatively homogeneous.

A decrease of reelin expression as a putative vulnerability factor in schizophrenia.

Postmortem prefrontal cortices (PFC) (Brodmann's areas 10 and 46), temporal cortices (Brodmann's area 22), hippocampi, caudate nuclei, and cerebella of schizophrenia patients and their matched nonpsychiatric subjects were compared for reelin (RELN) mRNA and reelin (RELN) protein content. In all of the brain areas studied, RELN and its mRNA were significantly reduced (approximately 50%) in patients with schizophrenia; this decrease was similar in patients affected by undifferentiated or paranoid schizophrenia. To exclude possible artifacts caused by postmortem mRNA degradation, we measured the mRNAs in the same PFC extracts from gamma-aminobutyric acid (GABA)A receptors alpha1 and alpha5 and nicotinic acetylcholine receptor alpha7 subunits.

Simultaneous detection of glutamic acid decarboxylase and reelin mRNA in adult rat neurons using in situ hybridization and immunofluorescence.

The combination of in situ hybridization and immunocytochemical technique is an important tool to detail the biochemical phenotype of individual neurons. In this work, we have developed a double fluorescence method to show the presence of reelin mRNA in GABAergic cells. This was achieved by demonstrating the colocalization of glutamic acid decarboxylase67, the synthesizing enzyme for GABA, with the mRNA for reelin, a novel factor involved in brain development and possibly the maintenance of the synaptic organization of layered structures in adult brain.

Reelin is preferentially expressed in neurons synthesizing gamma-aminobutyric acid in cortex and hippocampus of adult rats.

During embryonic development of brain laminated structures, the protein Reelin, secreted into the extracellular matrix of the cortex and hippocampus by Cajal-Retzius (CR) cells located in the marginal zone, contributes to the regulation of migration and positioning of cortical and hippocampal neurons that do not synthesize Reelin. Soon after birth, the CR cells decrease, and they virtually disappear during the following 3 weeks. Despite their disappearance, we can quantify Reelin mRNA (approximately 200 amol/ g of total RNA) and visualize it by in situ hybridization, and we detect the translated product of this mRNA by immunocytochemistry preferentially in gamma-aminobutyric acid (GABA)ergic neurons of adult rat cortex and hippocampus.

Aging-associated up-regulation of neuronal 5-lipoxygenase expression: putative role in neuronal vulnerability.

Aging is associated with neurodegenerative processes. 5-Lipoxygenase (5-LO), which is also expressed in neurons, is the key enzyme in the synthesis of leukotrienes, inflammatory eicosanoids that are capable of promoting neurodegeneration. We hypothesized that neuronal 5-LO expression can be up-regulated in aging and that this may increase the brain's vulnerability to neurodegeneration.

Tolerance to diazepam and changes in GABA(A) receptor subunit expression in rat neocortical areas.

Long-term treatment with diazepam, a full allosteric modulator of the GABA(A) receptor, results in tolerance to its anticonvulsant effects, whereas an equipotent treatment with the partial allosteric modulator imidazenil does not produce tolerance. Use of subunit-specific antibodies linked to gold particles allowed an immunocytochemical estimation of the expression density of the alpha1, alpha2, alpha3, alpha5, gamma(2L&S) and beta(2/3) subunits of the GABA(A) receptor in the frontoparietal motor and frontoparietal somatosensory cortices of rats that received long-term treatment with vehicle, diazepam (three times daily for 14 days, doses increasing from 17.6 to 70.

Subcellular localization of the alpha 7 nicotinic receptor in rat cerebellar granule cell layer.

The distribution of the alpha 7 nicotinic receptor subunit in the rat cerebellum was studied immunohistochemically at the electron microscope level using an alpha 7 subunit-specific antibody. The granule cell layer showed a much lower level of immunoreactivity for the alpha 7 subunit than the Purkinje cell layer. Granule cell somata were completely devoid of labeling; this appeared to be restricted to glomeruli exclusively located in the membranes of granule cell dendrites.

Modifications of gamma-aminobutyric acidA receptor subunit expression in rat neocortex during tolerance to diazepam.

We evaluated whether tolerance to the antagonism of bicuculine-induced seizures by diazepam is associated with changes (i) in the content of mRNAs encoding for gamma-aminobutyric acidA (GABAA) receptor subunits, (ii) in the expression density of these subunits, and (iii) in the 1,4-benzodiazepine binding site characteristics in discrete neocortical structures. We found that in diazepam-tolerant rats, the content of the mRNA encoding for the alpha 1 subunit of the GABAA receptor decreased in the frontoparietal motor (FrPaM) cortex and in the hippocampus (42% and 20%, respectively) but not in the frontoparietal somatosensory (FrPaSS) cortex, striatum, olfactory bulb, and cerebellum. In the FrPaM cortex, gamma 2S and gamma 2L subunit mRNA contents were also decreased (48% and 30%, respectively), whereas that of alpha 5 was increased (30%).

The neuroanatomical specificity of the anxiolytic effects of intra-septal infusions of midazolam.

Microinfusions of the benzodiazepine anxiolytic midazolam into the lateral but not the medial septum suppressed fear reactions in two test of rat 'anxiety'. Midazolam infusions into the lateral septal nuclei increased open-arm exploration in the elevated plus-maze test, and blocked burying behavior in the shock-probe test, whereas midazolam infusions into the medial septum produced neither of these anxiolytic effects. The anxiolytic effects of midazolam in the lateral septum were partially blocked by pre-infusion of the benzodiazepine receptor antagonist Ro15-1788, which had no intrinsic effects by itself.

Semiquantitative immunocytochemical analysis of GABAA receptor subunit expression in the rat neostriatum.

A semiquantitative immunogold technique was used to investigate the levels of expression of specific GABAA receptor subunits in different regions (dorsolateral, dorsomedial and ventromedial regions) of the rat striatum. The results indicate that the subunits studied can be classified into three groups on the basis of their labelling density in the striatum: alpha 1 and alpha 3 (labelling density of less than 100 gold particles per 1000 microns2), gamma 2 and delta (between 100 and 200 particles per 1000 microns2), and alpha 2 and beta 2/3 (more than 300 particles per 1000 microns2). The alpha 1 and alpha 3 subunits are about 35% more abundant in the dorsal than in the ventral striatum, while the beta 2/3 and gamma 2 subunits are about 40% more abundant in the medial than in the lateral striatum.