bluuebunny/crossref_metadata_2025_split huggingface dataset:
Age‐dependent changes in projections from locus coeruleus to hippocampus dentate gyrus and frontal cortex
Authors: Ishida Y. , Shirokawa T. , Miyaishi O. , Komatsu Y. , Isobe K. 
Published: March 2003

AbstractAge‐dependent changes in noradrenergic innervations of the hippocampal dentate gyrus (DG) and the frontal cortex (FC) have been studied in male F344 rats. The projections from the nucleus locus coeruleus (LC) to DG or FC with advancing age (from 7 to 27 months) in rats have been quantified by electrophysiological and immunohistochemical methods. In the electrophysiological study, we observed that the percentage of LC neurons activated antidromically by electrical stimulation (P‐index) of DG or FC decreased with age. We found that the percentage of LC neurons showing multiple antidromic latencies (M‐index), which suggests axonal branching of individual LC neurons, increased markedly between 15 and 17 months in DG or FC. In DG, the M‐index increased steadily between 15 and 24 months. In contrast, the increased M‐index in FC was maintained until 24 months. The increased M‐index in both targets declined at 27 months. These results suggest that LC neurons give rise to axonal branching following the loss of projections to DG or FC with age. In the immunohistochemical study, the density of dopamine‐β‐hydroxylase‐positive axonal varicosities was measured in molecular, granule cell and polymorphic layers of DG. The density in the polymorphic layer significantly decreased in the earlier stage of ageing (7–19 months), whilst the density in the molecular and granule cell layers decreased in the later stage (27 months). These findings suggested that a layer‐specific decline occurred with age in the noradrenergic axon terminals in DG.
Bilateral blockade of NMDA receptors in anterior thalamus by dizocilpine (MK‐801) injures pyramidal neurons in rat retrosplenial cortex
Authors: Tomitaka Shinichiro , Tomitaka Midori , Tolliver Bryan K. , Sharp Frank R. 
Published: March 2003

AbstractNon‐competitive N‐methyl‐ d‐aspartate (NMDA) receptor antagonists, ketamine, phencyclidine (PCP) and dizocilpine (MK‐801), produce psychosis in people. In rodents they produce cytoplasmic vacuoles in injured retrosplenial cortical neurons that express HSP70 heat shock protein. This study examined possible circuits and receptors that mediate this neuronal injury. Bilateral, but not unilateral, injection of dizocilpine (5, 10, 15, 20 μg/μL per side) into the anterior thalamus induced HSP70 protein in pyramidal neurons in deep layer III of rat retrosplenial cortex 24 h later. In contrast, bilateral dizocilpine injections (5, 10, 15, 20 μg/μL per side) into the retrosplenial cortex or into the diagonal band of Broca did not induce HSP70. Bilateral injections of muscimol (0.1, 1, 10 μg/μL per side), a GABAA (γ‐aminobutyric acid) agonist, into the anterior thalamus blocked HSP70 induction in the retrosplenial cortex produced by systemic dizocilpine (1 mg/kg). Bilateral thalamic injections of baclofen (0.1, 1, 10 μg/μL per side), a GABAB agonist, were ineffective. Anterograde tracer studies confirmed that neurons in the anterior thalamus project to superficial layer III of the retrosplenial cortex where the dendrites of HSP70‐immunostained neurons in deep layer III reside. Bilateral blockade of NMDA receptors on GABA neurons in the reticular nuclei of the thalamus is proposed to decrease GABA neuronal firing, decrease GABA release and decrease activation of GABAA receptors. This activates thalamic projection neurons that damage retrosplenial cortical neurons presumably via unblocked cortical glutamate α‐amino‐3‐hydroxy‐5‐methyl‐isoxazole‐4‐propionate (AMPA) and kainate receptors. The increases of blood flow that occur in the thalamus and retrosplenial cortex of people that have psychosis produced by NMDA antagonists could be related to thalamic excitation of the retrosplenial cortex produced by these drugs.
Repeated long‐term potentiation induces mossy fibre sprouting and changes the sensibility of hippocampal granule cells to subconvulsive doses of pentylenetetrazol
Authors: Hassan Hadir , Pohle Wulf , Rüthrich Heinz , Brödemann Rudolf , Krug Manfred 
Published: March 2003

AbstractElectrical and chemical kindling induces sprouting of the mossy fibre system and potentiation of evoked field potentials in the dentate gyrus. It has been postulated that such changes may also be induced by repeated induction of long‐term potentiation (LTP) with tetanic stimulation of the perforant pathway. LTP was induced in rats chronically implanted with stimulation electrodes in the ipsilateral and contralateral angular bundles and with a recording electrode in the ipsilateral dorsal dentate gyrus. The animals were stimulated 10 times on 10 consecutive days but with different tetanization strengths. Sprouting of the mossy fibres terminating in the CA3 region was significantly induced only in the group of ‘strongly’ tetanized animals, but not in that of ‘weakly’ tetanized animals, or in low‐frequency stimulated animals. Additionally, a novel form of potentiation which was previously found in pentylenetetrazol (PTZ)‐kindled animals was also observed in the group of ‘strongly’ and ‘weakly’ tetanized rats. Differences in duration of this potentiation were found between the two groups of animals tetanized with different strengths. The results further demonstrate that morphological and functional changes in the hippocampus, similar to those seen after kindling, can also occur in an activation paradigm leading to long‐lasting synaptic plasticity but not accompanied by seizure activity.
Relationships between image structure and gamma oscillations and synchronization in visual cortex of cats
Authors: Molotchnikoff Stéphane , Shumikhina Svetlana 
Published: March 2003

AbstractThe relationships between visual object configurations and interneuronal spike synchronization and gamma oscillations are examined in the present investigation. Cells were initially stimulated with moving, optimally oriented, single 20°‐long bars of light, centred on the compound receptive field of a pool of cortical neurons. When this kind of stimulus evoked intrinsic gamma oscillations and/or synchronization, we gradually fractured the original target. In addition, colinearity was ruptured by forming L‐ and T‐shaped configurations. All fractures and discontinuities were introduced well outside the excitatory receptive field. Multiunit activity in the visual cortex (areas 17 and 18) was recorded in anaesthetized cats. Recording sites were separated by 0.4–1.2 mm. The data analysis indicates that gamma oscillations follow a rule by which unfractured bars yielded the highest S/N ratios. Synchronization strength, as revealed by the central peak in cross‐correlograms, also seemed to depend upon stimulus configuration. However, the magnitude of the central peak failed to follow a consistent trend. For instance, the greatest magnitude of the central peak occurred for both colinear and orthogonal types of target. Our results support the notion that both gamma oscillations and neuronal synchronization are stimulus‐dependent.
Serotoninergic and noradrenergic axonal contacts associated with premotor interneurons in spinal pathways from group II muscle afferents
Authors: Maxwell D. J. , Riddell J. S. , Jankowska E. 
Published: March 2003

AbstractWe investigated the possibility that monoaminergic axons make contacts with spinal interneurons which project to motor nuclei and are monosynaptically activated by group II muscle afferents. Interneurons in midlumbar spinal segments of adult cats were characterized electrophysiologically and intracellularly labelled with tetramethylrhodamine dextran. Serotoninergic and noradrenergic axons were identified with immunofluorescence in sections containing labelled cells. Contacts between monoaminergic axons and interneurons were investigated with three‐colour confocal laser scanning microscopy and analysed with a computer reconstruction program. Cell bodies and dendritic trees of five cells were reconstructed and putative contacts were plotted. The average number of contacts formed by serotoninergic axons was 140 and the average number of noradrenergic contacts was 38. The majority (95%) of contacts were formed with dendrites; these were distributed over the entire dendritic tree, even on the most distal branches. These findings provide a morphological basis for the modulatory actions of monoamines on premotor spinal interneurons in pathways from group II muscle afferents.
(+)‐MCPG induces PKCε translocation in cortical synaptosomes through a PLD‐coupled mGluR
Authors: Pastorino L. , Colciaghi F. , Gardoni F. , Albani‐Torregrossa S. , Pellegrini‐Giampietro D. E. , Moroni F. , De Graan P. N. E. , Cattabeni F. , Di Luca M. 
Published: March 2003

AbstractWe have tested whether different agonists of metabotropic glutamate receptors could induce translocation of selective protein kinase C isozymes in nerve terminals. In rat cortical synaptosomes 1S,3R‐1‐aminocyclopentane‐1,3‐dicarboxylic acid (1S,3R‐ACPD; 100 μm) induced an increase in translocation to 124.6 ± 5.7% of basal unstimulated conditions of the Ca++‐independent protein kinase Cε, but not of the Ca++‐dependent isozyme β. This effect was counteracted by 1‐aminoindan‐1,5‐dicarboxylic acid (100 μm), an antagonist of metabotropic glutamate receptor 1. On the other hand, (+)‐α‐methyl‐4‐carboxyphenylglycine [(+)‐MCPG], an antagonist of metabotropic glutamate receptors group I and II, did not antagonize the effect of 1S,3R‐ACPD, and per se induced a translocation of protein kinase Cε of 164 ± 17.7% of basal unstimulated conditions. Because the (+)‐MCPG induction of protein kinase Cε translocation was not antagonized by 1‐aminoindan‐1,5‐dicarboxylic acid, it is suggested that 1S,3R‐ACPD and (+)‐MCPG activate this signal transduction pathway through distinct membrane receptors. Indeed (2‐[2′′‐carboxy‐3′‐phenylcyclopropyl]glycine)‐13 (300 nm), a new compound known to antagonize metabotropic glutamate receptors coupled to phospholipase D, was able to antagonize protein kinase Cε translocation induced by (+)‐MCPG. Moreover (+)‐MCPG directly induced phospholipase D activity, measured as [3H]phosphoethanol production in cortical synaptosomes. These data suggest that in cortical nerve terminals (i) distinct metabotropic glutamate receptors, coupled to different signal transduction pathways, are present, (ii) (+)‐MCPG is able to induce protein kinase Cε translocation, and that (iii) a metabotropic glutamate receptor associated to phospholipase D might influence translocation of protein kinase C in a calcium‐independent manner.
Association of neuropeptide Y Y1 receptors with glutamate‐positive and NPY‐positive neurons in rat hippocampal cultures
Authors: St‐Pierre Jacques‐André , Nouel Dominique , Dumont Yvan , Beaudet Alain , Quirion Rémi 
Published: March 2003

AbstractThe hippocampus is particularly enriched with neuropeptide tyrosine (NPY) and NPY receptors including the Y1, Y2 and Y5 subtypes. We have previously reported on the enrichment of cultured rat hippocampal neurons in specific [125I][Leu31,Pro34]PYY/BIBP3226‐sensitive (Y1) binding sites and Y1 receptor mRNAs [St‐Pierre et al. (1998) Br. J. Pharmacol., 123, p183]. We have now identified which cell types express the Y1 receptor. The majority of Y1 receptors, visualized using either the radiolabeled probe [125I][Leu31,Pro34]PYY or two antibodies directed against distinct domains of the Y1 receptor, was expressed in neurons as revealed by neuron‐specific enolase (NSE) immunostaining. One antibody was directed against the second extracelllular loop of the Y1 receptor (amino acids 185–203) whereas the second was directed against the intracellular C‐terminal loop (amino acids 355–382). The labelling was evident over both perikarya and processes. Neurons labelled by the various Y1 receptor probes were mostly glutamate‐positive as revealed by double immunostaining. Most interestingly, a number of NPY‐positive cultured hippocampal neurons were also enriched with the Y1 receptor, suggesting that this subtype may act as an autoreceptor to regulate NPY release in the hippocampus. These results thus provide an anatomical basis for the modulation of glutamate and NPY release by the Y1 receptor in the hippocampus.
Fast oscillations display sharper orientation tuning than slower components of the same recordings in striate cortex of the awake monkey
Authors: Frien Axel , Eckhorn Reinhard , Bauer Roman , Woelbern Thomas , Gabriel Andreas 
Published: March 2003

AbstractWe wanted to know whether fast oscillations (≈ 30–80 Hz) in striate cortex of awake monkeys show sharper orientation selectivity than (i) slower components, including spike rate modulations, and (ii) broad‐band signals of the same recordings. As fast oscillations are probably of cortical origin this may further clarify whether cortical network mechanisms are substantially involved in generating orientation selectivity. We recorded multi unit activity (MUA) and local field potentials (LFP, 1–140 Hz) by the same microelectrodes from upper layers of macaque striate cortex during visual stimulation with grating textures of different orientations. An orientation index (OI) was derived from the cortical responses in three frequency ranges (low, 0–11.7 Hz; medium, 11.7–31.3 Hz; and fast oscillations, 31.3–62.5 Hz) and for the broad‐band LFP and MUA power. (i) Both LFP and MUA fast oscillations reveal a higher orientation index than signal components in the low and medium frequency ranges. (ii) For MUA the orientation index was significantly higher with fast oscillations than for the lower frequency ranges and the initial broad‐band transient responses. (iii) LFPs show a significantly higher orientation index only for the fast oscillations during sustained activation compared with their broad‐band power during the transient responses. Thus, our main result is the sharper orientation tuning of fast oscillations in spike activities of local populations compared with slower components of the same broad‐band recordings. As fast oscillations occur synchronized in the awake monkey's striate cortex we assume that they have enhanced probability of activating successive stages of visual processing and hence contribute to the perception of orientation.
Functional coupling shows stronger stimulus dependency for fast oscillations than for low‐frequency components in striate cortex of awake monkey
Authors: Frien Axel , Eckhorn Reinhard 
Published: March 2003

AbstractIt has been argued that coupling among the neural signals activated by a visual object supports binding of local features into a coherent object perception. During visual stimulation by a grating texture we studied functional coupling by calculating spectral coherence among pairs of signals recorded in the striate cortex of awake monkeys. Multiple unit activity (MUA) and local field potentials (LFP, 1–140 Hz) were extracted from seven parallel broad band recordings. Spectral coherence was dominated by high‐frequency oscillations in the range 35–50 Hz and often by additional low‐frequency components (0–12 Hz). Functional coupling among separate cortical sites was more stimulus specific for MUA than for LFP: MUA coherence at high and low frequencies depended highly significantly on: (i) the similarity of the preferred orientations at the two sites − the more similar the higher the coherence; (ii) the orientation of the stimulus grating − with highest coherence at half angle between the preferred orientations at the two sites; (iii) cortical distance − coherence decreases to noise levels at ∼ 3 mm (MUA) and 6 mm (LFP). Coherence of fast oscillations did not depend on the degree of coaxiality of the orientation‐sensitive receptive fields, whereas low frequencies showed significant dependency. This indicates that different frequency components can engage different coupling networks in the striate cortex which probably support different coding tasks. Changes in average oscillation frequency with stimulus orientation were highly significant for fast oscillations while there was no dependency for low frequencies. Finally, stimulus‐related spectral power and coherence of fast oscillations were considerably higher than of low frequency components. Fast oscillations may therefore contribute more to feature binding and coding of object continuity than low‐frequency components, at least for texture surfaces as analysed here.
Developmental changes in astrocyte density in the macaque perifoveal region
Authors: Distler C. , Kopatz K. , Telkes I. 
Published: March 2003

AbstractWe studied astrocyte density both in the perifoveal region and in extrafoveal regions within the same distance of the optic disc (OD) over a time period from foveal pit formation (embryonic day E112) until 2 months after birth. The study was prompted by earlier observations that the adult macaque displays an almost astrocyte‐free region around the fovea which, however, at birth is occupied by astrocytes. Thus, we wanted to determine if the perifoveal region is invaded by astrocytes during early development to the same degree as other regions in the central retina, and how the reduction in density can be explained. From the earliest age we studied (embryonic day 112), less astrocytes were found in the perifovea than in other regions equidistant from the OD. In addition, the number of astrocytes steadily declined both in the perifovea and outside until birth. During the first week after birth, there was a further dramatic decline in perifoveal astrocyte density. Double‐labelling with glial fibrillary acidic protein (GFAP) immunocytochemistry and the TUNEL method showed that during the whole observation period astrocytes undergo DNA fragmentation and presumably die. However, the rate of TUNEL‐positive astrocytes did not significantly differ between perifovea and other regions equidistant to the OD, and at no time did we find a significant peak of apoptosis rate. Thus, the reduction in perifoveal astrocyte density cannot be explained by missing invasion or by selectively elevated apoptosis rates in the foveal and perifoveal regions. Alternative hypotheses are discussed.
Ageing alters intrahypothalamic release patterns of vasopressin and oxytocin in rats
Authors: Keck Martin E. , Hatzinger Martin , Wotjak Carsten T. , Landgraf Rainer , Holsboer Florian , Neumann Inga D. 
Published: March 2003

AbstractThe ageing process has been shown to have a profound impact on the hypothalamo–neurohypophysial system (HNS) and the hypothalamo–pituitary–adrenocortical (HPA) axis in humans as well as in rodents. Therefore, in this study, the intracerebral and peripheral release patterns of both vasopressin and oxytocin have been studied in aged male Wistar rats under basal conditions and in response to ethologically relevant stressors, using intracerebral microdialysis and chronic blood sampling techniques, respectively. Approximately a twofold higher basal release of arginine vasopressin (AVP) within the hypothalamic paraventricular nucleus (PVN), but not within the supraoptic nucleus (SON), was found in aged rats, whereas basal oxytocin (OXT) release did not differ in comparison with young rats. With increasing age the rise in intra‐PVN release of both AVP and OXT was blunted in response to forced swimming. In contrast, the intra‐SON release of AVP was unrelated to age. Simultaneously recorded basal secretion of both AVP and OXT from the neurohypophysis into blood was increased in aged rats, with a blunted OXT response to swim stress. Opposed to that, plasma AVP levels remained unchanged in both groups. Basal plasma levels of corticotropin (ACTH) and corticosterone were elevated in aged rats, whereas stress‐elicited ACTH and corticosterone responses were indistinguishable. These results indicate age‐related changes in the HNS and HPA axis with an enhanced basal activity opposed to a blunted response to stressors with increasing age. The increased basal release of AVP within the PVN suggests a role of intracerebral AVP in age‐associated alterations of HPA axis regulation.
Lack of glucocorticoids attenuates the self‐stimulation‐induced increase in the in vivo synthesis rate of dopamine but not serotonin in the rat nucleus accumbens
Authors: Nakahara Daiichiro , Nakamura Masato , Oki Yutaka , Ishida Yasushi 
Published: March 2003

AbstractOur previous study demonstrated that intracranial self‐stimulation of the medial forebrain bundle can increase the in vivo synthesis turnover rate of dopamine (DA) and serotonin (5‐HT) in the nucleus accumbens of adrenal‐intact rats. The present study examined using microdialysis whether such increases in DA and 5‐HT syntheses are influenced by adrenal hormones, which are also activated following intracranial self‐stimulation. A decarboxylase inhibitor, NSD‐1015, was perfused through reversed microdialysis which enabled the simultaneous measurement of 3,4‐dihydroxyphenylalanine (DOPA) and 5‐hydroxytryptophan (5‐HTP) as an index of the in vivo turnover rate of DA and 5‐HT syntheses. Adrenalectomy (ADX) attenuated significantly the self‐stimulation‐induced increase in dialysate levels of DOPA but not 5‐HTP. Corticosterone (Cort) replacement reversed the attenuation in DOPA levels in adrenalectomized rats. The finding indicates that activation of DA synthesis in vivo in the nucleus accumbens during intracranial self‐stimulation is dependent on, whereas that of 5‐HT synthesis is independent of glucocorticoid modulation.
NFI in the development of the olfactory neuroepithelium and the regulation of olfactory marker protein gene expression.
Authors: Behrens M. , Venkatraman G. , Gronostajski R. M. , Reed R. R. , Margolis F. L. 
Published: March 2003

AbstractNuclear factor I (NFI) proteins are DNA‐binding transcription factors that participate in the tissue specific expression of various genes. They are encoded by four different genes (NFI‐A, B, C, and X) each of which generates multiple isoforms by alternative RNA splicing. NFI‐like binding sites have been identified in several genes preferentially expressed in olfactory receptor neurons. Our prior demonstration that NFI binds to these elements led to the hypothesis that NFI is involved in the regulation of these genes. To analyse the role of NFI in the regulation of olfactory neuron gene expression we have performed transient transfection experiments in HEK 293 cells using constructs that place luciferase expression under the control of an olfactory marker protein (OMP)‐promoter fragment containing the NFI binding site. In vitro mutagenesis of this site revealed a negative modulation of luciferase expression by endogenous NFI proteins in HEK 293 cells. In addition, we have used in situ hybridization to analyse the tissue and cellular distribution of the four NFI gene transcripts during pre‐ and postnatal mouse development. We have simultaneously characterized the expression of Pax‐6, and O/E‐1, transcription factors known to regulate the phenotype of olfactory receptor neurons. We demonstrate that all of these transcription factors vary in specific spatio–temporal patterns during the development of the olfactory system. These data on NFI activity, and on transcription factor expression, provide a basis to understand the role of NFI in regulating gene expression in olfactory receptor neurons.