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PubMed2000

Orbitofrontal cortex pathology in Alzheimer's disease.

The orbitofrontal cortex has been examined in Alzheimer's disease (AD) from the viewpoint of neurofibrillary tangle (NFT) pathology, its laminar distribution and topography. NFT pathology in the orbitofrontal cortex is extensive in AD. In cases with extensive cortical pathology, NFTs extend from the pole of the frontal lobe to the orbitoinsular junction. In lesser affected cases, the anterior granular part of the orbital cortex is less invested by NFTs. Layers III and V contain the greatest density of NFTs and these are most dense in the dysgranular areas, posterior to the transverse orbital sulcus. Posterior and medial orbitofrontal areas, forming area 13 and the posterior tip of the paraolfactory gyrus, are the most severely damaged, as are the smaller agranular fields that surround the olfactory tract and cortex. The widespread orbitofrontal damage in AD affecting projection neurons suggests that this pathology may contribute heavily to the many non-memory-related behavior changes observed in this disorder.

Aged↗
PubMed1993

The KROX-20 transcription factor in the rat central and peripheral nervous systems: novel expression pattern of an immediate early gene-encoded protein.

The KROX-20 protein (also termed EGR-2) is encoded by an immediate early gene cloned by cross-hybridization to the Drosophila melanogaster Krüppel gene. It belongs to a class of transcription factors with zinc finger motifs and binding activity to a transcriptional regulatory DNA element termed the early growth response consensus sequence. In the present study the temporospatial expression of KROX-20 was investigated in the central and peripheral nervous systems of normal rats and after various stimuli known to induce immediate early genes, including epileptic seizures, axotomy, pharmacological treatment with glutamate and alpha-adrenergic receptor antagonists, and peripheral noxious stimulation. Immunocytochemistry was performed with a specific polyclonal antiserum generated against a fusion protein containing KROX-20 sequences. In the central nervous system, KROX-20 protein demonstrated distinct constitutive nuclear expression in specific neuronal subpopulations of the cortex, septum, amygdala, olfactory bulb and hypothalamus. In addition, distinct cytoplasmic immunoreactivity was present in spinal and medullary motoneurons, dorsal root ganglion neurons and a few neuronal cell populations of midbrain and forebrain. In the CNS, KROX-20 was only induced by bicuculline-induced epileptic seizures. Topographically, the postictal increase of KROX-20 levels was restricted to areas with constitutive expression, such as cerebral cortex, fornix and amygdala. Induction of KROX-20 peaked at 4-8 h after onset of seizure activity. No increase in immunoreactivity was observed in the hippocampus, the brain region most severely affected by bicuculline-induced seizures. Transection of central and peripheral nerve fibers did not result in KROX-20 induction in axotomized neurons. However, KROX-20 was induced in Schwann-like cells after transection of the sciatic nerve. In contrast to KROX-20, KROX-24, a related transcription factor of the zinc finger family, was markedly induced in hippocampal and spinal neurons following seizures and peripheral noxious stimulation, respectively, as well as in CNS neurons following axotomy. Our data indicate that KROX-20 represents an immediately early gene product with basal expression in selected neuronal populations of the nervous system and a restricted inducibility after intentional stimuli.

Animals↗
PubMed1999

Localization of mRNAs for synaptojanin isoforms in the brain of developing and mature rats.

The localization of mRNAs for synaptojanin 1 and 2, inositol 5-phosphatases, in the brain was examined by in situ hybridization histochemistry. Synaptojanin 1 mRNA was detected in almost all neurons of the central nervous system throughout developing and mature stages, although its splicing variant (synaptojanin 1-p145-I) mRNA was expressed dominantly in forebrain and cerebellar cortex. Synaptojanin 2 mRNA was first detected in neurons of the olfactory bulb, the cerebral cortex, the hippocampus, and the cerebellar cortex on early postnatal days. As the postnatal development proceeded, the expression signal was evident in the white matters, presumptive oligodendrocytes, with the clear expression remaining in neurons of the olfactory tubercle, hippocampal pyramidal cells and cerebellar Purkinje cells.

Animals↗
PubMed1976

[Effects of sodium n-dipropylacetate on the GABA level in various areas of the mouse brain].

Regional brain GABA distribution studies show that after administration of sodium n dipropylacetate, a competitive inhibitor of GABA transaminase, the concentration of GABA increases in some regions i.e. Olfactory Bulbs, Hypothalamus, Cortex, Cerebellum. The GABA level remains unchanged in Caudate Nucleus, Pons Medulla, Hippocampus in our experimental conditions. These variations do not correlate with the initial GABA level.

Aminobutyrates↗
PubMed1986

Nerve growth factor receptor molecules in rat brain.

We have developed a method to immunoprecipitate rat nerve growth factor (NGF) receptor proteins and have applied the method to detect NGF receptor molecules in the rat brain. Crosslinking 125I-labeled NGF to either PC12 cells or cultured rat sympathetic neurons yielded two radiolabeled molecules (90 kDa and 220 kDa) that were immunoprecipitated by monoclonal antibody 192-IgG. Further, 192-IgG precipitated two radiolabeled proteins, with the expected sizes (80 kDa and 210 kDa) of noncrosslinked NGF receptor components, from among numerous surface-iodinated PC12 cell proteins. These results demonstrate the specific immunoprecipitation of NGF receptor molecules by 192-IgG. We applied the 125I-NGF crosslinking and 192-IgG-mediated immunoprecipitation procedures to plasma membrane preparations of the following areas of rat brain: medial septum, cerebellum, brainstem, hippocampus, cerebral cortex, thalamus, and olfactory bulb. NGF receptor molecules of the same molecular masses as the peripheral receptor components were consistently detected in all of these regions and in preparations from whole brains. Removal of the peripheral sympathetic innervation of the brain did not eliminate these NGF receptor proteins, indicating that the receptor is endogenous to central nervous system tissues. We also observed retrograde transport of 125I-labeled 192-IgG from the parietal cortex to the nucleus basalis and from the hippocampus to the nucleus of the diagonal band of Broca and the medial septal nucleus. These findings demonstrate the presence in brain of NGF receptor molecules indistinguishable from those of the peripheral nervous system.

Animals↗
PubMed2001

Regional and developmental expression of Epm2a gene and its evolutionary conservation.

Lafora's disease, an autosomal recessive progressive myoclonus epilepsy, is caused by mutations in the EPM2A gene encoding a dual-specificity phosphatase (DSP) named laforin. Here, we analyzed the developmental and regional expression of murine Epm2a and discussed its evolutionary conservation. A phylogenetic analysis indicated that laforin is evolutionarily distant from other DSPs. Southern zoo blot analysis suggested that conservation of Epm2a gene is limited to mammals. Laforin orthologs (human, mouse, and rat) display more than 94% similarity. All missense mutations known in Lafora disease patients affect conserved residues, suggesting that they may be essential for laforin's function. Epm2a is expressed widely in various organs but not homogeneously in brain. The levels of Epm2a transcripts in mice brains increase postnatally, attaining its highest level in adults. The most intense signal was detected in the cerebellum, hippocampus, cerebral cortex, and the olfactory bulb. Our results suggest that Epm2a is functionally conserved in mammals and is involved in growth and maturation of neural networks.

Aging↗
PubMed1993

A splice variant of the N-methyl-D-aspartate (NMDAR1) receptor.

A splice variant of the NMDA receptor (NMDAR1) was discovered containing a deletion of 37 amino acids near the carboxyl tail and has been designated NMDAR1b. The 111 nucleotides corresponding to the deleted amino acid sequence were found in a separate exon bounded by consensus intron/exon junction sequences in rat genomic DNA. A partial restriction map of genomic DNA bounding this region placed the deleted exon approximately 600 base pairs (bp) downstream of the upstream exon. RT/PCR analysis of RNA from different brain regions showed that the deletion variant is more abundantly expressed in the brain stem and cerebellum while the full-length form is expressed more abundantly in the olfactory bulb, striatum, hippocampus, and cortex. Northern analysis of poly(A)+ RNA from different brain regions with probes specific for the deleted exon (i.e., full-length form) and for the splice junction (deletion form) indicated approximately 4.4 kb transcripts. The probe for the deleted exon hybridized to transcripts in olfactory bulb, cortex, striatum, and hippocampus while the splice junction probe hybridized most strongly to transcripts in cerebellum. The results suggest an interesting rostral to caudal shift in the expression of splice variants of the NMDAR1 which may signify important functional differences in native forms of NMDA receptors.

Alternative Splicing↗
PubMed1992

Acamprosate modulates synaptosomal GABA transmission in chronically alcoholised rats.

Male Sprague-Dawley rats were pulmonary alcoholised for 30 days. Six were treated with acamprosate (400 mg/kg/day, PO) during alcoholisation. The control nonalcoholised group also received acamprosate (400 mg/kg/day, PO) during the 30 days. At the end of the experiment, brains areas (cortex, hippocampus, thalamus, striatum, and olfactory bulbs) were dissected for the study of synaptosomal 3H-GABA uptake. In another experiment, GABA levels were determined in the same areas using HPLC with electrochemical detection. Blood ethanol levels were also measured during alcoholisation. Acamprosate treatment did not modify blood ethanol levels. In cortex and olfactory bulbs, alcoholisation increased 3H-GABA uptake (Vmax) with an increase in the affinity (Km). 3H-GABA uptake was not affected by alcoholisation in other brain areas. In hippocampus and thalamus, acamprosate treatment enhanced 3H-GABA uptake (Vmax) only in alcoholised rats. Moreover, in thalamus, alcoholisation enhanced GABA levels. The effect of alcohol and acamprosate on GABA presynaptic events is discussed and it is concluded that the action of ethanol and acamprosate on GABA transport could be, in part, responsible for the modulation by acamprosate treatment of ethanol behaviour.

Acamprosate↗
PubMed1995

D-serine, an endogenous synaptic modulator: localization to astrocytes and glutamate-stimulated release.

Using an antibody highly specific for D-serine conjugated to glutaraldehyde, we have localized endogenous D-serine in rat brain. Highest levels of D-serine immunoreactivity occur in the gray matter of the cerebral cortex, hippocampus, anterior olfactory nucleus, olfactory tubercle, and amygdala. Localizations of D-serine immunoreactivity correlate closely with those of D-serine binding to the glycine modulatory site of the N-methyl-D-aspartate (NMDA) receptor as visualized by autoradiography and are inversely correlated to the presence of D-amino acid oxidase. D-Serine is enriched in process-bearing glial cells in neuropil with the morphology of protoplasmic astrocytes. In glial cultures of rat cerebral cortex, D-serine is enriched in type 2 astrocytes. The release of D-serine from these cultures is stimulated by agonists of non-NMDA glutamate receptors, suggesting a mechanism by which astrocyte-derived D-serine could modulate neurotransmission. D-Serine appears to be the endogenous ligand for the glycine site of NMDA receptors.

Animals↗
PubMed2006

Characterization of TROY/TNFRSF19/TAJ-expressing cells in the adult mouse forebrain.

A member of the tumor necrosis factor receptor superfamily (TNFRSF), TROY/TNFRSF19/TAJ, is highly expressed in the brain of adult mice. Northern blot analysis using mRNA taken from regions of the adult CNS showed the expression of TROY in all regions examined, including the olfactory bulb, cerebral cortex, striatum, and hippocampus. In situ hybridization and immunohistochemistry revealed that TROY mRNA and protein were strongly expressed in the rostral migratory stream (RMS) and subventricular zone (SVZ) of adult mice. In the adult SVZ, some glial fibrillary acidic protein (GFAP)-positive cells (type B cells) are thought to be multipotent neural stem cells. These type B cells divide slowly and generate epidermal growth factor receptor (EGFR)-positive transit-amplifying precursor cells (type C cells) in the presence of epidermal growth factor (EGF). Type C cells give rise to neuron-specific class III beta-tubulin (TuJ1)-positive neuroblasts (type A cells) that migrate to the olfactory bulb along the RMS. TROY-expressing cells were GFAP-positive, EGFR-positive, and TuJ1-negative in the adult SVZ. From these findings, TROY appears to be expressed in type B and type C cells, but not in type A cells, which was supported by immunoelectron microscopy. In addition, TROY was expressed in GFAP-positive astrocytes of the various regions, such as the cerebral cortex, striatum, and hippocampus. Thus, TROY was expressed in uncommitted precursor cells and astroglial lineage cells, suggesting that TROY plays some roles in the regulation of gliogenesis in the adult CNS.

Animals↗
PubMed1995

Distribution of natriuretic peptide precursor mRNAs in the rat brain.

Atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP) represent members of a recently discovered neuropeptide family involved in central regulation of endocrine and autonomic functions. The present study employed an in situ hybridization approach to provide the first detailed comparative mapping of ANP, BNP, and CNP mRNAs in brain. Results indicate that ANP mRNA is highly expressed in anterior olfactory nuclei, limbic cortices, dorsal endopiriform nucleus, hippocampal subfield CA1, cortical amygdaloid nuclei, medial habenula, anteroventral periventricular and arcuate nuclei, periventricular stratum, zona incerta, mammillary nuclei, inferior olive, nucleus ambiguus, and pontine paragigantocellular nuclei. CNP mRNA is expressed at highest levels in olfactory nuclei, limbic cortices, dorsal endopiriform nucleus, hippocampal subfields CA1-3, anteroventral periventricular and arcuate nuclei, and numerous brainstem regions (including the pontine, lateral reticular, solitary tract, prepositus hypoglossal, and spinal trigeminal nuclei). Positive labeling for BNP mRNA was not observed in brain. The presence of both ANP and CNP mRNA in the same regions of distinct nuclei (e.g., the anteroventral periventricular and arcuate nuclei) suggests the potential for coexpression. Overall, the present data are consistent with a prominent role for both ANP and CNP in neuroendocrine regulation and central cardiovascular integration. The extensive localization of ANP and/or CNP mRNA in olfactory nuclei, limbic cortex, hippocampus, amygdala and diencephalic limbic relays further indicate a putative role for ANP and CNP as neuromodulators of olfactory/limbic information processing.

Animals↗
PubMed1995

NMDA and non-NMDA receptors on rat supraoptic nucleus neurons activated monosynaptically by olfactory afferents.

The recently discovered efferent projections from the main and accessory olfactory bulbs to the supraoptic nucleus (SON) were further investigated. Intracellular electrophysiological methods were used to determine (a) if these projections are monosynaptic, (b) which excitatory amino acid (EAA) receptor subtypes mediate responses to activation of these pathways and (c) whether the same receptor subtypes mediate responses of phasically firing (vasopressin) and continuously firing (putative oxytocin) neurons. Recordings were made from SON neurons in large explants and 500 microns thick horizontal slices, containing 2-6 mm of the piriform cortex and lateral olfactory tract (LOT). This allowed recording of synaptic responses to selective stimulation of the LOT. EPSPs in SON neurons faithfully followed stimulus frequencies of 50-100 Hz, indicating that these inputs were monosynaptic. Stimulus-evoked EPSPs were blocked by the non-specific EAA antagonist, kynurenate. Perifusion of the slice with Mg(2+)-free medium revealed the presence of NMDA receptors in addition to the non-NMDA receptors on both phasically and continuously firing cells, indeed, on all cells tested. Partial blockade of these EPSPs in Mg(2+)-free medium could be achieved with either the NMDA antagonist, AP5, or the non-NMDA antagonist, CNQX or NBQX. Full blockade of the stimulus-evoked EPSPs was effected by adding both types of antagonists to the medium, although spontaneous EPSPs were still observed in several cells. These results are consistent with prior studies showing both receptor subtypes in the SON. This is the first demonstration that afferent stimulation activates both subtypes in the same SON neuron regardless of its peptide content.

2-Amino-5-phosphonovalerate↗
PubMed1998

Time-dependent effects of acute ethanol administration on regional cerebral blood flow in the rat.

The present study investigated the role of the postinjection interval in determining the functional consequences of acute ethanol administration in the CNS. Regional cerebral blood flow (RCBF) was determined by the [14C]iodoantipyrine method in 33 brain structures of ethanol-naive Sprague-Dawley rats. In the first experiment, changes in RCBF were assessed 5 and 15 min after a 0.8 g/kg (i.p.) dose of ethanol or water. Five minutes after treatment, rates of RCBF were increased in the motor cortex, agranular insular cortex, and the olfactory tubercle compared to water controls. No significant differences compared to control were found at the 15-min time point, despite the continued presence of ethanol in the blood. Experiment 2 tested whether blood ethanol level was the sole determinant of this response to ethanol by comparing animals with the same blood ethanol level at the 5- and 15-min time points. Greater rates of RCBF were found at 5 min postinjection compared to 15 min, in the motor cortex, agranular insular cortex, caudate/putamen, cerebellum, and the lateral septum. These data demonstrate that the rates of cerebral blood flow are increased in regionally discrete portions of the rat brain shortly after ethanol administration. Furthermore, blood ethanol level is not the exclusive factor governing this functional response.

Animals↗
PubMed1989

The adult rat olfactory system expresses microtubule-associated proteins found in the developing brain.

We have compared the expression and localization of neuronal microtubule-associated proteins (MAPs) MAP5, MAP2, and tau in the adult rat olfactory system and cerebral cortex. Each of these MAPS is known to exist as distinct "early" and "late" forms in the developing and adult brain, respectively. Because axonal growth and dendritic reinnervation continue in the adult olfactory system, it can serve as a test of whether expression of early MAP forms is necessary for neuronal growth and plasticity. We found that for all three MAPs, the early forms continue to be expressed in the adult olfactory system, whereas the cerebral cortex switches to the late forms during neuronal maturation (between 10 and 20 days of age in the rat). For MAP2, the 6 kb mRNA and low-molecular weight MAP2c, both of which are typically found in embryonic tissue, persist in the adult olfactory bulb. For MAP5, an early highly phosphorylated form, MAP5a, is present throughout the brain and disappears during maturation simultaneously with a several-fold drop in the overall level of MAP5. However, in the olfactory bulb, MAP5 levels do not fall, and MAP5a persists in the adult. The early form of tau is also prominent in the adult olfactory bulb and, by immunohistochemistry, is mainly confined to a subset of olfactory axons, the vomeronasal nerve. Thus, in the adult olfactory bulb, both MAP protein synthesis and phosphorylation conform to a pattern associated with the developing brain. Immunohistochemistry also showed that MAP5 is concentrated in the olfactory nerve axons and the mitral cell dendrites of the olfactory bulb, i.e., exactly those elements that are involved in the olfactory nerve innervation that takes place in the adult. These results suggest that the expression of the early MAP forms is closely associated with neurite outgrowth and plasticity.

Animals↗
PubMed1991

Age-related alteration of brain gangliosides in senescence-accelerated mouse (SAM)-P/8.

The senescence-accelerated mouse (SAM)-P/8 was examined with respect to changes in the content and composition of brain gangliosides during aging from juvenile to senescence. The gangliosides were compared with those of control mice, senescence-accelerated resistant mouse (SAM)-R/1. The ganglioside contents in the whole brains of SAM-P/8 and -R/1 were at almost constant level from 0.5 to 6 months, but decreased thereafter until senescence to about 80% of the levels reached at the younger ages. Upon aging, the ganglioside compositions changed with an increase of GM1, and decreases of GD1a, GD1b and GT1b in both strains (GT1b greater than GD1a greater than GD1b). A minor component, GM3 was two to four fold higher in the molecular distributions of the whole brain gangliosides of SAM-P/8 than those of -R/1 at any age examined throughout the life span. The regional gangliosides in olfactory bulb, cerebral cortex, hippocampus, hypothalamus, cerebellum, corpora quadrigemina region, brain stem and medulla oblongata were compared between the two strains at the age of three months. The ganglioside contents in the brain stem and medulla oblongata were lower in SAM-P/8 than -R/1, but there was no significant difference between the two strains in the other regions. As a minor component, GM3 was found to occur in a higher concentration in SAM-P/8 than -R/1 in all brain regions examined, except in the olfactory bulb where GM3 was detected as a major component with no difference in the distribution level between the two strains.

Aging↗
PubMed1993

Distributions of mRNAs for alpha-2 adrenergic receptor subtypes in rat brain: an in situ hybridization study.

Selective 35S-labeled oligonucleotide probes were designed to sequences of the rat alpha-2A (RG20), alpha-2B (RNG), and alpha-2C (RG10) adrenoreceptor mRNAs for use in in situ hybridization experiments on sections of unfixed rat brain, spinal cord and kidney. After hybridized sections were exposed to film or dipped in autoradiographic emulsion, specific and selective labeling patterns characteristic for each probe and region of the central nervous system were observed. Alpha-2A mRNA labeling was most pronounced in neurons in layer six of the cerebral cortex, hypothalamic paraventricular nucleus, reticular thalamic nucleus, pontine nuclei, locus coeruleus, vestibular nuclei, trapezoid nuclei, deep cerebellar nuclei, nucleus tractus solitarii, ventrolateral medullary reticular formation, and the intermediolateral cell column of the thoracic spinal cord. In some of these locations, the receptor mRNA, in all probability, is present in noradrenaline and perhaps adrenaline neurons. The alpha-2B probe, which primarily labels the kidney, gave only a very light signal in the thalamus in the central nervous system after extended exposure times. Alpha-2C mRNA labeling was primarily observed in the olfactory bulb, cerebral cortex, islands of Calleja, striatum, hippocampal formation, cerebellar cortex, and dorsal root ganglia. Labeling patterns disappeared when excess unlabeled probes were added to their respective radiolabeled probes, or when sense probes were employed. When a hybrid antisense probe homologous to all three alpha-2 probes was used, labeling patterns also disappeared. The present study therefore justifies the pharmacological subclassification of alpha-2 receptors by providing anatomical evidence for specific and selective cell groups in the rat central nervous system containing mRNA for three alpha-2 receptor subtypes.

Amino Acid Sequence↗
PubMed1992

Regional distribution of DARPP-32 (dopamine- and adenosine 3',5'-monophosphate-regulated phosphoprotein of Mr = 32,000) mRNA in mouse brain.

DARPP-32 (dopamine- and adenosine 3',5'-monophosphate-regulated phosphoprotein of Mr = 32,000) mRNA distribution was examined in adult mouse central nervous system by in situ hybridization. In general, DARPP-32 mRNA was found in regions of brain where cells express the dopamine D1 subtype receptor. Cells of the olfactory tubercle, caudate-putamen, and nucleus accumbens had the highest levels of DARPP-32 mRNA, as did choroid plexus and Purkinje cells. Relatively high levels were found in medial habenula and lateral piriform cortex. Moderate levels were seen in cerebral cortex layer VI, medial piriform cortex, lateral entorhinal cortex, tenia tecta, anterior olfactory nucleus, and lateral bed nucleus of the stria terminalis. Low levels were observed in hippocampus, cerebral cortex layers II and III, olfactory bulb, and the nucleus of the lateral olfactory tract. DARPP-32 mRNA levels in the amygdaloid nuclei varied greatly.

Animals↗