bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synaptic glutamate receptor clustering in mice lacking the SH3 and GK domains of SAP97
Authors: Klöcker Nikolaj , Bunn Robert C. , Schnell Eric , Caruana Georgina , Bernstein Alan , Nicoll Roger A. , Bredt David S. 
Published: March 2003

AbstractPostsynaptic targeting of the Drosophila tumour suppressor discs‐large (Dlg) critically depends on its SH3 and GK domains. Here, we asked whether these domains are also involved in subcellular targeting of the mammalian Dlg homolog SAP97 and its interacting partners in CNS cortical neurons by analysing a recently described mouse mutant lacking the SH3 and GK domains of SAP97. Both wildtype and truncated SAP97 were predominantly expressed in perinuclear regions, in a pattern suggesting association with the endoplasmic reticulum. Weaker immunoreactivity was found in neurites colocalizing with both dendritic and axonal markers. As SAP97 has been implicated in the early intracellular processing of the glutamate receptor GluR1, we studied biochemical maturation and subcellular localization of GluR1 in the mutants. Both the glycosylation pattern and synaptic clustering of GluR1 were indistinguishable from wildtype mice. Synaptic clustering of the guanylate kinase domain interacting protein GKAP was also intact. Our data demonstrate that truncation of the SH3 and GK domains of SAP97 in mice does neither change its subcellular distribution nor does it disrupt synaptic structure or protein clustering, as opposed to severe missorting of the respective mutant Dlg protein in Drosophila.
Time of genesis determines projection and Neurokinin‐3 expression patterns of diencephalic neurons containing melanin‐concentrating hormone
Authors: Brischoux F. , Cvetkovic V. , Griffond B. , Fellmann D. , Risold P. Y. 
Published: March 2003

AbstractAnatomical and functional evidence suggests that the diencephalic melanin‐concentrating hormone‐ (MCH‐) containing neurons do not form a homogeneous population. In this work, the expression of the neurokinin‐3 receptor (NK3) has been researched in MCH neurons which have been retrogradely labelled following fast blue injections into either the spinal cord or the cerebral cortex. The birth‐date of these cortically and spinally projecting cells has been determined using the bromodeoxyuridine method. The results obtained show that neurons projecting to the spinal cord are born early (E11) and most of them (78,7%) do not express NK3, but neurons that send axons to the cerebral cortex are born later (E12–E13) and most of them (84,8%) express NK3. Both neuronal types are largely intermingled in the lateral hypothalamic area proper. These results are discussed in terms of the functional organization of the MCH neuronal population.
The lemniscal–cuneate recurrent excitation is suppressed by strychnine and enhanced by GABAA antagonists in the anaesthetized cat
Authors: Aguilar Juan , Soto Cristina , Rivadulla Casto , Canedo Antonio 
Published: March 2003

AbstractIn the somatosensory system, cuneolemniscal (CL) cells fire high frequency doublets of spikes facilitating the transmission of sensory information to diencephalic target cells. We studied how lemniscal feedback affects ascending transmission of cutaneous neurons of the middle cuneate nucleus. Electrical stimulation of the contralateral medial lemniscus and of the skin at sites evoking responses with minimal threshold induced recurrent activation of CL cells at a latency of 1–3.5 ms. The lemniscal feedback activation was suppressed by increasing the stimulating intensity at the same sites, suggesting recurrent‐mediated lateral inhibition. The glycine antagonist strychnine blocked the recurrent excitatory responses while GABAA antagonists uncovered those obscured by stronger stimulation. CL cells sharing a common receptive field (RF) potentiate one another by recurrent activation and disinhibition, the disinhibition being produced by serial interactions between glycinergic and GABAergic interneurons. Conversely, CL cells with different RFs inhibit each other through recurrent GABA‐mediated inhibition. The lemniscal feedback would thus enhance the surround antagonism of a centre response by increasing the spatial resolution and the transmission of weak signals.
The putative role of vanilloid receptor‐like protein‐1 in mediating high threshold noxious heat‐sensitivity in rat cultured primary sensory neurons
Authors: Ahluwalia Jatinder , Rang Humphrey , Nagy Istvan 
Published: March 2003

AbstractHigh threshold noxious heat‐activated currents and vanilloid receptor‐like protein‐1 expression were studied in rat cultured primary sensory neurons to find out the molecule(s) responsible for high threshold noxious heat‐sensitivity. The average temperature threshold and amplitude of high threshold noxious heat‐activated currents were 51.6 ± 0.13 °C and −2.0 ± 0.1nA (at a holding potential of −60 mV), respectively. The current–voltage relationship of high threshold noxious heat‐activated currents was linear at positive membrane potentials, while it showed a weak inward rectification at negative membrane potentials. The average reversal potential measured in control intracellular and extracellular solutions was 4.5 ± 0.9 mV (n = 6). Ionic substitutions revealed that the high threshold noxious heat‐activated current is a nonselective cationic current with calculated ionic permeabilities of Cs+ : Na+ : Ca2+ (1 : 1.3 : 4.5). Consecutive stimuli reduced the heat threshold from 52.2 ± 1 to 48.4 ± 1.4 °C and then to 44 ± 0.7 °C (n = 3). High threshold noxious heat‐activated currents could dose‐dependently and reversibly be reduced by ruthenium red (100 nm−10 µm) but not by capsazepine (10 µm). The average longest diameter of high threshold noxious heat‐sensitive neurons was 31.48 ± 0.5 µm (A = ≈778 µm2; n = 77). Twenty‐three percent of the total neuronal population expressed vanilloid receptor‐like protein‐1. The average area of the vanilloid receptor‐like protein‐1‐immunopositive cells was 1696 ± 65.3 µm2 (d = ∼46 µm). Vanilloid receptor‐like protein‐1‐expressing neurons did not express the vanilloid receptor 1. Comparison of our data with results obtained in vanilloid receptor‐like protein‐1‐expressing non‐neuronal cells and previous immunohistochemical findings suggests that high threshold noxious heat‐activated currents are produced by vanilloid receptor‐like protein‐1 and that high threshold heat‐sensitive dorsal root ganglion neurons are the perikarya of type I noxious heat‐sensitive fibers.
NMDA receptor‐dependent CREB activation in survival of cerebellar granule cells duringin vivoandin vitrodevelopment
Authors: Monti Barbara , Marri Lucia , Contestabile Antonio 
Published: March 2003

AbstractDuring bothin vivoandin vitrodevelopment, cerebellar granule cells depend on the activity of the NMDA glutamate receptor subtype for survival and full differentiation. With the present results, we demonstrate that CREB activation, downstream of the NMDA receptor, is a necessary step to ensure survival of these neurons. The levels of CREB expression and activity increase progressively during the second week of postnatal cerebellar development and the phosphorylated form of CREB is localized selectively to cerebellar granule cells during the critical developmental stages examined. Chronically blocking the NMDA receptor through systemic administration of the competitive antagonist, CGP 39551, during thein vivocritical developmental period, between 7–11 postnatal days, results in increased apoptotic elimination of differentiating granule neurons in the cerebellum [Monti & Contestabile, Eur. J. Neurosci., 12, 3117–3123 (2000)]. We report here that this event is accompanied by a significant decrease of CREB phosphorylation in the cerebellum of treated rat pups. When cerebellar granule neurons are explanted and maintained in dissociated cultures, the levels of CREB phosphorylation increase with differentiation, similar to that which happens duringin vivodevelopment. When granule cells are kept in non‐trophic conditions, their viability is affected and both CREB phosphorylation and transcriptional activity are decreased significantly. The neuronal viability and the deficiency of CREB activity, are both rescued by the pharmacological activation of the NMDA receptor. These results provide good circumstantial evidence for a functional link between the NMDA receptor and CREB activity in promoting neuronal survival during development.
The respective contribution of lumbar segments to the generation of locomotion in the isolated spinal cord of newborn rat
Authors: Bertrand S. , Cazalets Jean‐René 
Published: March 2003

AbstractVarious studies on isolated neonatal rat spinal cord have pointed to the predominant role played by the rostral lumbar area in the generation of locomotor activity. In the present study, the role of the various regions of the lumbar spinal cord in locomotor genesis was further examined using compartmentalization and transections of the cord. We report that the synaptic drive received by caudal motoneurons following N‐methyl‐d‐l‐aspartate (NMA)/5‐HT superfusion on the entire lumbar cord is different from that triggered by the same compounds specifically applied on the rostral segments. These differences appear to be due to the direct action of NMA/5‐HT on motoneuron membrane potential, rather than on premotoneuronal input activation. In order to assess the possible participation of the caudal lumbar segments in locomotor rhythm generation, the segments were over‐stimulated with high concentrations of NMA or K+. We find that significant variations in motor cycle period occurred during the over‐activation of the rostral segments. Over‐activation of caudal segments only si+gnificantly increased the caudal ventral roots burst amplitude. We find that low 5‐HT concentrations were unable to induce fictive locomotion under our experimental conditions. When a hemi‐transection of the cord was performed between the L2–L3 segments, rhythmic bursting in the ipsilateral L5 disappeared while rhythmicity persisted on the contralateral side. Sectioning of the remaining L2–L3 side totally suppressed rhythmic activity in both L5 ventral roots. These results show that the thoracolumbar part of the cord constitutes the key area for locomotor pattern generation.
No evidence for calcium electrogenic exchanger in frog semicircular canal hair cells
Authors: Martini M. , Rossi M. L. , Farinelli F. , Moriondo A. , Mammano F. , Rispoli G. 
Published: March 2003

AbstractWe investigated the possibility that, in hair cells mechanically isolated from frog semicircular canals, Ca2+extrusion occursviaa Na+ : Ca2+(cardiac type) or a Na+ : Ca2+,K+(retinal type) exchanger. Cells concurrently imaged during whole‐cell patch‐clamp recordings using the Ca2+sensitive fluorescent dye Oregon Green 488 BAPTA‐1 (100 µm) showed no voltage dependence of Ca2+clearance dynamics following a Ca2+load through voltage‐gated Ca2+channels. Reverse exchange was probed in hair cells dialyzed with a Ca2+‐ and K+‐free solution, containing a Na+concentration that saturates the exchanger, after zeroing the contribution to the whole‐cell current from Ca2+and K+conductances. In these conditions, no reverse exchange current was detected upon switching from a Ca2+‐free external solution to a solution containing concentrations of Ca2+alone, or Ca2+ + K+that saturated the exchanger. By contrast, the same experimental protocol elicited peak exchange currents exceeding 100 pA in gecko rod photoreceptors, used as positive controls. In both cell types, we also probed the forward mode of the exchanger by rapidly increasing the intracellular Ca2+concentration using flash photolysis of two novel caged Ca2+complexes, calcium 2,2′‐{[1‐(2‐nitrophenyl)ethane‐1,2‐diyl]bis(oxy)}bis(acetate) and calcium 2,2′‐{[1‐(4,5‐dimethoxy‐2‐nitrophenyl)ethane‐1,2‐diyl]bis(oxy)} bis(acetate), in the presence of internal K+and external Na+. No currents were evoked by UV‐triggered Ca2+jumps in hair cells, whereas exchanger conformational currents up to 400 pA, followed by saturating forward exchange currents up to 40 pA, were recorded in rod photoreceptors subjected to the same experimental conditions. We conclude that no functional electrogenic exchanger is present in this hair cell population, which leaves the abundant plasma membrane Ca2+‐ATPases as the primary contributors to Ca2+extrusion.
Calcineurin regulates induction of late phase of cerebellar long‐term depression in rat cultured Purkinje neurons
Authors: Fujii Hiroaki , Hirano Tomoo 
Published: March 2003

AbstractCerebellar long‐term depression (LTD), a candidate cellular mechanism of motor learning, is induced by conjunctive activation of parallel fibres and a climbing fibre. Previous studies have shown that combinatorial application of high potassium and glutamate (K/glu) to cultured cerebellar neurons can mimic this conjunctive stimulation of presynaptic fibres and induces the LTD of miniature excitatory postsynaptic current (mEPSC) amplitudes lasting for more than 24 h. The late phase of this LTD (LLTD, > 3 h) depends on de novo transcription induced by prolonged conditioning. Here, the role of Calcineurin in the LLTD induction was examined. Application of a Calcineurin inhibitor FK506 mimicked the effect of K/glu‐treatment by decreasing mEPSC amplitudes for more than 24 h. FK506‐induced depression, as well as the K/glu‐induced LLTD, was blocked by inhibitors of either mRNA synthesis or Ca/Calmodulin dependent kinase. In addition, the FK506‐induced depression and K/glu‐induced LLTD occluded each other, suggesting that they share the same mechanism. On the other hand, misexpression of the constitutively active form of Calcineurin in the Purkinje neuron nucleus blocked the LLTD induction by the K/glu‐treatment. These results suggest that Calcineurin is involved in the induction of LLTD as a negative regulator. Furthermore, it was found that trapping superoxide, which is increased by neuronal activity and inactivates Calcineurin, suppressed the LLTD induction. Taken together, these results suggest that the LLTD might be induced by down‐regulation of Calcineurin activity through superoxide in cultured Purkinje neurons.
Lesion response of long‐term and recently immigrated resident endoneurial macrophages in peripheral nerve explant cultures from bone marrow chimeric mice
Authors: Leonhard Christine , Müller Marcus , Hickey William F. , Ringelstein Erich B. , Kiefer Reinhard 
Published: March 2003

AbstractResident macrophages of the peripheral nervous system have recently been shown to respond rapidly to Wallerian degeneration before the influx of blood‐derived macrophages. Because resident endoneurial macrophages are slowly but incompletely exchanged from the blood within 3 months, they could potentially comprise a heterogenous cell population consisting of long‐term resident cells and more mobile cells undergoing turnover. We used bone marrow chimeric mice created by transplanting bone marrow from green fluorescent protein‐transgenic mice into irradiated wildtype recipients to selectively analyse the response of these two resident macrophage populations to Wallerian degeneration in sciatic nerve explant cultures. In such nerves, recently immigrated macrophages exhibit green fluorescence whereas long‐term resident macrophages do not. Studies in cultures from wildtype controls revealed rapid morphological changes of resident macrophages towards a bloated phenotype, a proliferative response resulting in a 3.7‐fold increase of macrophage numbers over 2 weeks, and phagocytosis of myelin basic protein‐immunoreactive myelin debris. When chimeric mice were analysed, both populations of resident endoneurial macrophages participated in morphological transformation, proliferation and phagocytosis. Quantitative studies revealed a stronger proliferative and phagocytic response in long‐term resident endoneurial macrophages compared with recently immigrated macrophages. Our results point towards subtle, but not principal, differences between the two macrophage populations, which might indicate different stages of macrophage differentiation rather than the existence of entirely distinct endoneurial macrophage populations. The results further underline the versatility of resident endoneurial macrophages following peripheral nerve injury, which is reminiscent of the lesion response of microglial cells within the brain.
Neuroanatomical distribution of CXCR4 in adult rat brain and its localization in cholinergic and dopaminergic neurons
Authors: Banisadr Ghazal , Fontanges Philippe , Haour France , Kitabgi Patrick , Rostène William , Mélik Parsadaniantz Stéphane 
Published: March 2003

AbstractAccumulating evidence supports a role of chemokines and their receptors in brain function. Up to now scarce evidence has been given of the neuroanatomical distribution of chemokine receptors. Although it is widely accepted that chemokine receptors are present on glial cells, especially in pathological conditions, it remains unclear whether they are constitutively present in normal rat brain and whether neurons have the potential to express such chemokine receptors. CXCR4, a G protein‐coupled receptor for the chemokine stromal cell‐derived factor‐1 (SDF‐1/CXCL12) was reported to have possible implications in brain development and AIDS‐related dementia. By dual immunohistochemistry on brain sections, we clearly demonstrate that CXCR4 is constitutively expressed in adult rat brain, in glial cells (astrocytes, microglia but not oligodendrocytes) as well as in neurons. Neuronal expression of CXCR4 is mainly found in cerebral cortex, caudate putamen, globus pallidus, substantia innominata, supraoptic and paraventricular hypothalamic nuclei, ventromedial thalamic nucleus and substantia nigra. Using confocal microscopy, a differential distribution of CXCR4 in neuronal perikarya and dendrites can be observed according to the brain structure. Furthermore, this work demonstrates for the first time the coexistence of a chemokine receptor with classical neurotransmitters. A localization of CXCR4 is thus observed in neuronal cell bodies expressing choline acetyltransferase‐immunoreactivity in the caudate putamen and substantia innominata, as well as in tyrosine hydroxylase‐positive neurons in the substantia nigra pars compacta. In conclusion, the constitutive neuronal CXCR4 expression suggests that SDF‐1/CXCL12 could be involved in neuronal communication and possibly linked up with cholinergic and dopaminergic neurotransmission and related disorders.
Long‐term survival and cell death of newly generated neurons in the adult rat olfactory bulb
Authors: Winner Beate , Cooper‐Kuhn Christiana M. , Aigner Robert , Winkler Jürgen , Kuhn H. Georg 
Published: March 2003

AbstractIn the adult rat olfactory bulb, neurons are continually generated from progenitors that reside in the lateral ventricle wall. This study investigates long‐term survival and cell death of newly generated cells within the adult olfactory bulb. After injecting rats at 2 months of age with 5‐bromodeoxyuridine (BrdU), the newly generated cells were quantified over a period of 19 months. A peak of BrdU‐positive cells was reached in the olfactory bulb 1 month after BrdU injection, when all new cells have finished migrating from the ventricle wall. Thereafter, a reduction of BrdU‐positive cells to about 50% was observed and it was confirmed by dUTP‐nick end‐labelling (TUNEL) that progenitors and young neurons undergo programmed cell death. However, cells that survived the first 3 months after BrdU injection persisted for up to 19 months. The majority of the BrdU‐positive cells that reach the olfactory bulb differentiate into granule cells, but a small fraction migrate further into the glomerular layer. These newborn cells differentiate more slowly into periglomerular interneurons, with a delay of more than 1 month when compared to the granule cells. The newly generated periglomerular neurons, among them a significant fraction of dopaminergic cells, showed a similar decline in number compared to the granule cell layer and long‐term survival for the remaining new neurons of up to 19 months. Rather than replacing old neurons, this data suggests that adult olfactory bulb neurogenesis utilizes the overproduction and turnover of young neurons, which is reminiscent of the cellular dynamics observed during brain development.
Autoradiography of opioid and ORL1 ligands in opioid receptor triple knockout mice
Authors: Clarke Siân , Czyzyk Traci , Ansonoff Micheal , Nitsche Joshua F. , Hsu Ming‐Sing , Nilsson Linda , Larsson Kerstin , Borsodi Anna , Toth Geza , Hill Ray , Kitchen Ian , Pintar John E. 
Published: March 2003

AbstractThree genes for the opioid receptors (µ, δ and κ) and a gene coding for a related receptor (ORL1) have been cloned but pharmacological studies suggest that further subtypes exist that remain poorly understood. To determine if there are other classically defined opioid binding sites we have carried out homogenate binding and section autoradiography with [3H]naloxone in mice that lack all three opioid genes and are hyperalgesic in a thermal nociceptive test. We have also examined [3H]bremazocine labelling in triple knockout brain and spinal cord as this ligand has been proposed to label novel κ‐receptors. No receptor labelling for either ligand was detected in the brains or spinal cord of knockout mice demonstrating that all binding is the product of the three known receptors and that there is no cross‐labelling of the ORL1 receptor. Nociceptin (1 µm) caused marked displacement of [3H]bremazocine in wild‐type brains indicating that nociceptin at high concentrations can displace classical opioid binding. As a number of studies have proposed a close association between the classical opioid receptors and the ORL1 system we also hypothesized that loss of all of the classical opioid receptors might lead to compensatory changes in ORL1 receptors. Labelling of the ORL1 receptor with [3H]nociceptin showed region‐dependent quantitative increases in triple knockout brains indicating a close relationship between the two systems in specific brain areas.
Key role for enkephalinergic tone in cortico–striatal–thalamic function
Authors: Solbrig Marylou V. , Koob George F. , Lipkin W. Ian 
Published: March 2003

AbstractWhereas the role of dopaminergic tone in the cortico‐striatal‐thalamic system is well‐established, the role of endogenous opioids in the function of this system is less understood. We show that Borna disease virus infection of adult rats results in an increase in preproenkephalin transcripts in the striatum of Borna‐infected rats, a region important for forming coordinated sequential motor actions and in developing programmes of thought and motivation. Stereotypic behaviours and dyskinesias, the clinical hallmarks of infection in adult Lewis rats (BD rats), are accompanied by a disrupted pattern of immediate early gene c‐fos activation in the motor thalamus, with significance for the breakdown in coordinated sequential motor actions. We also find increased preproenkephalin in infected cultured neuroblastoma and rat foetal glial cells. The expression pattern of enkephalin mRNA in vivo and in vitro suggest that increased enkephalin function is one of the neuropharmacological means by which Borna disease virus causes motor disease of animals and possibly cognitive and affective disease in man, and further suggest that enkephalins play a critical role in the maintenance of a balanced tone of activity in the cortico‐basal ganglia‐thalamo‐cortical loops.