bluuebunny/crossref_metadata_2025_split huggingface dataset:
GABAC receptor ρ subunits are heterogeneously expressed in the human CNS and form homo‐ and heterooligomers with distinct physical properties
Authors: Enz Ralf , Cutting Garry R. 
Published: March 2003

AbstractIn the central nervous system, receptors for γ‐aminobutyric acid (GABA) are responsible for inhibitory neurotransmission. Anatomical and electrophysiological studies indicate that GABAC receptors are composed of ρ subunits. While the ρ1 subunit of various species forms homooligomeric receptors with GABAC‐like properties, molecular cloning has identified additional ρ subunits whose functional role is unclear. By RT‐PCR, we demonstrated that ρ1 expression is primarily restricted to the retina, whereas the ρ2 subunit was present in all brain regions tested. Transfection of HEK‐293 cells with ρ2 cDNA resulted in GABA‐gated whole‐cell currents that differed from those mediated by the ρ1 subunit in two respects: maximal amplitude (ρ1:ρ2 ≈ 4:1) and inactivation time course (ρ1:ρ2 ≈ 2:1). Cotransfection of ρ1 and ρ2 cDNA in a 1:1 ratio generated whole‐cell currents with large amplitudes characteristic of ρ1 but more rapid inactivation typical for ρ2. This observation suggested formation of heterooligomeric GABAC receptors with distinct features. Therefore, we tested the assembly of ρ1 and ρ2 subunits by cotransfecting ρ2 cDNA together with a chimeric ρ1β1 subunit, known to interfere with ρ1 assembly in a dominant‐negative fashion. Reduction of ρ2 generated currents correlated with the ratio of chimeric to ρ2 cDNA. Secondly, we determined that the picrotoxinin sensitivity of cells transfected with various ratios of ρ1 and ρ2 cDNA differed from that expected of a pure mixture of homooligomeric receptors. The latter two observations support the idea that ρ1 and ρ2 subunits form heterooligomeric GABAC receptors in mammalian cells. Together, our results indicate that the presence of both ρ subunits enables the formation of heterooligomeric receptors with physical properties distinct from homooligomers, thus increasing the diversity of GABAC receptors in the CNS.
Characteristics of slow and fast phases of the optocollic reflex (OCR) in head free pigeons (Columba livia): influence of flight behaviour
Authors: Gioanni H. , Sansonetti A. 
Published: March 2003

AbstractThe effect of behavioural context on the properties of slow and fast phases of the horizontal optocollic reflex (OCR) were investigated in head free pigeons for two situations, i.e.: (i) animals were hung in a harness (‘resting condition’); (ii) animals were additionally submitted to a frontal airflow that provoked a flight posture (‘flying condition’) [Bilo & Bilo (1983) J. Comp. Physiol., 153, 111]. A ‘transient flight’ was also provoked in the ‘resting condition’ by tapping the breastbone region. Stimuli consisted either of velocity steps (30–300 °/s) or of an increasing velocity stimulus (0–300 °/s). The amplitude of nystagmic beats and the OCR gain increased in the ‘flying condition’ and during ‘transient flight’ as compared to the ‘resting condition’. The OCR working range was considerably extended toward high velocities by the flying behaviour. In the ‘resting condition’, spontaneous head oscillations generally triggered a high‐gain OCR, close to that obtained in the ‘flying condition’. One‐third of the animals showed a higher gain in response to an increasing velocity stimulus than with step stimuli, in the high velocity range. The linear relation between amplitude and peak velocity of OCR fast phases was independent of the stimulation velocity in the ‘resting condition’, whereas the amplitude and peak velocity increased with the stimulation velocity in the ‘flying condition’. In this condition, the fast phase velocity was correlated with the slow phase velocity, but not with the retinal slip velocity. Thus, both the slow and fast phases of the OCR are dependent on the behavioural context.
Impaired glucocorticoid receptor function evolves in aberrant physiological responses to bacterial endotoxin
Authors: Linthorst Astrid C. E. , Karanth Sharada , Barden Nicholas , Holsboer Florian , Reul Johannes M. H. M. 
Published: March 2003

AbstractThe consequences of glucocorticoid receptor (GR) dysfunction for neuroimmunoendocrine responses to an inflammatory challenge were studied in transgenic mice expressing antisense RNA directed against the GR [GR‐impaired (GR‐i) mice]. Mice were implanted intraperitoneally with a biotelemetry transmitter to monitor body temperature and locomotion. GR‐i mice showed decreased locomotion and body temperature during the dark phase of the diurnal cycle. Intraperitoneal administration of saline caused a rapid increase in body temperature in control mice, which was terminated within 90 min. In GR‐i mice, however, body temperature remained elevated for about 6 h. Intraperitoneal injection of endotoxin (10 μg/mouse) produced a biphasic fever in control mice. However, in endotoxin‐injected GR‐i mice, body temperature was not significantly different from their saline‐injected controls during the first 6 h. Body temperature then increased and remained elevated during the night period. Both strains showed hypolocomotion after endotoxin. In a second experiment, mice were injected intraperitoneally with saline or endotoxin and killed after 1, 3, 6 or 24 h. In GR‐i mice, endotoxin caused an augmented rise in plasma ACTH, but not in corticosterone levels. The endotoxin‐induced increase in serum levels of interleukin‐1β and interleukin‐6 was not different between the strains. However, whereas in control mice tumour necrosis factor‐α levels were below detection at the time points studied, substantial levels of this cytokine were found in the serum of GR‐i mice 1 h after endotoxin administration. It may be concluded that life‐long impairment of GR evolves in aberrant physiological and humoral responses to an acute inflammatory challenge. These findings expand our understanding about the neuroendocrine and physiological disturbances associated with stress‐related disorders.
Characterization of cultured dorsal root ganglion neuron P2X receptors
Authors: Grubb B. D. , Evans R. J. 
Published: March 2003

AbstractP2X receptors for adenosine 5′‐triphosphate (ATP) comprise a family of ligand‐gated cation channels with distinct characteristics which are dependent on the receptor subunits (P2X1–7) expressed, and the homomeric or heteromeric assembly of protein subunits in individual cells. We describe the properties of P2X receptors expressed by cultured adult rat dorsal root ganglion cells on the basis of the time course of responses to ATP, α,β‐methylene adenosine 5′‐triphosphate (α,β‐meATP) and 2‐methyl‐thioadenosine 5′‐triphosphate (2‐meSATP), and using the antagonists 2′,3′‐O‐(2,4,6‐trinitrophenyl) ATP (TNP‐ATP), a novel and highly selective purinoceptor antagonist, suramin and iso‐pyridocalphosphate‐6‐azophenyl‐2′,5′ disulphonic acid (PPADS). ATP (10 μm) evoked inward currents in ≈ 95% of neurons tested and > 80% responded with a fast transient inward current that rapidly inactivated during the continued presence of ATP. Of the remaining neurons, ≈ 4% showed a sustained response and ≈ 10% showed a combination of transient and sustained components. Rapid application of ATP, α,β‐meATP and 2meSATP demonstrated these to be full agonists of the rapidly inactivating P2X receptor (pA50 values = 5.83, 5.86 and 5.55, respectively), whilst uridine triphosphate (UTP) and 1‐β,γ‐methyleneadenosine 5′‐triphosphate (1‐β,γ‐meATP) were ineffective as agonists. These rapidly inactivating responses could be inhibited by TNP‐ATP, suramin and PPADS (pIC50 = 9.5, 6.5, 6.4, respectively). Using inactivation protocols, we demonstrate the presence of homomeric P2X3‐like receptors and non‐inactivating P2X receptors, which indicates that individual subsets of adult dorsal root ganglion neurons have distinct P2X receptor phenotypes, and that individual DRG neurons may express multiple P2X receptor subtypes.
Modulation of neurotransmitter release by dihydropyridine‐sensitive calcium channels involves tyrosine phosphorylation
Authors: Evans Gareth J. O. , Pocock Jennifer M. 
Published: March 2003

AbstractCultured rat cerebellar granule cells depolarized by high KCl, display a large component of Ca2+ influx through L‐type voltage‐dependent Ca2+ channels as defined by a sensitivity to 1 μm nifedipine. This Ca2+ influx is not coupled to neurotransmitter exocytosis but has implications for neuronal development. KCl stimulation in the absence of external Ca2+ followed by the re‐addition of Ca2+ allows the coupling of a class of L‐type Ca2+ channels to neurotransmitter exocytosis as assessed by loading of glutamatergic pools with [3H]‐d‐aspartate. KCl stimulation in the absence of external Ca2+ (‘predepolarization’) enhances tyrosine phosphorylation of several cellular proteins, and inhibitors of tyrosine kinases block both phosphorylation and the neurotransmitter release coupled to the L‐type Ca2+ channel. More specifically, an inhibitor of src family tyrosine kinases, PP1, blocks the effects of predepolarization suggesting a role for a src family kinase in the process. Furthermore, L‐type Ca2+ channel recruitment and modulation of release could be activated with the tyrosine phosphatase inhibitor sodium orthovanadate. The phosphoproteins enhanced by predepolarization, which include the cytoskeletal proteins focal adhesion kinase (FAK) and vinculin, are also highly phosphorylated early on in culture when neurite outgrowth occurs. As the neurons develop a network of neurites, both tyrosine phosphorylation and L‐type Ca2+ channel activity decrease. These results show a novel mechanism for the recruitment of L‐type Ca2+ channels and their coupling to neurotransmitter release which involves tyrosine phosphorylation. This phenomenon has a role in cerebellar granule cell development.
Subcellular distribution of survival motor neuron (SMN) protein: possible involvement in nucleocytoplasmic and dendritic transport
Authors: Béchade Catherine , Rostaing Philippe , Cisterni Claire , Kalisch Raffaël , Bella Vincenzo La , Pettmann Brigitte , Triller Antoine 
Published: March 2003

AbstractSpinal muscular atrophy (SMA) is among the most common recessive autosomal diseases and is characterized by the loss of spinal motor neurons. A gene termed ‘Survival of Motor Neurons' (SMN) has been identified as the SMA‐determining gene. Recent work indicates the involvement of the SMN protein and its associated protein SIP1 in spliceosomal snRNP biogenesis. However, the function of SMN remains unknown. Here, we have studied the subcellular localization of SMN in the rat spinal cord and more generally in the central nervous system (CNS), by light fluorescence and electron microscopy. SMN immunoreactivity (IR) was found in the different regions of the spinal cord but also in various regions of the CNS such as the brainstem, cerebellum, thalamus, cortex and hippocampus. In most neurons, we observed a speckled labelling of the cytoplasm and a discontinuous staining of the nuclear envelope. For some neurons (e.g. brainstem nuclei, dentate gyrus, cortex: layer V) and, in particular in motoneurons, SMN‐IR was also present as prominent nuclear dot‐like‐structures. In these nuclear dots, SMN colocalized with SIP1 and with fibrillarin, a marker of coiled bodies. Ultrastructural studies in the anterior horn of the spinal cord confirmed the presence of SMN in the coiled bodies and also revealed the protein at the external side of nuclear pores complexes, in association with polyribosomes, and in dendrites, associated with microtubules. These localizations suggest that, in addition to its involvement in the spliceosome biogenesis, the SMN protein could also play a part in nucleocytoplasmic and dendritic transport.
Different cortical organization of visceral and somatic sensation in humans
Authors: Schnitzler Alfons , Volkmann Jens , Enck Paul , Frieling Thomas , Witte Otto W. , Freund Hans‐Joachim 
Published: March 2003

AbstractSensory stimuli from the visceral domain exhibit perceptual characteristics different from stimuli applied to the body surface. Compared with somatosensation there is not much known about the cortical projection and functional organization of visceral sensation in humans. In this study, we determined the cortical areas activated by non‐painful electrical stimulation of visceral afferents in the distal oesophagus, and somatosensory afferents in the median nerve and the lip in seven healthy volunteers using whole‐head magnetoencephalography. Stimulation of somatosensory afferents elicited short‐latency responses (≈ 20–60 ms) in the primary somatosensory cortex (SI) contralateral (median nerve) or bilateral (lip) to the stimulated side, and long‐latency responses (≈ 60–160 ms) bilaterally in the second somatosensory cortex (SII). In contrast, stimulation of visceral oesophageal afferents did not evoke discernible responses in SI but well reproducible bilateral SII responses (≈ 70–190 ms) in close vicinity to long‐latency SII responses following median nerve and lip stimuli. Psychophysically, temporal discrimination of successive stimuli became worse with increasing stimulus repetition rates (0.25 Hz, 0.5 Hz, 1 Hz, 2 Hz) only for visceral oesophageal, but not for somatosensory median nerve stimuli. Correspondingly, amplitudes of the first cortical response to oesophageal stimulation emerging in the SII cortex declined with increasing stimulus repetition rates whereas the earliest cortical response elicited by median nerve stimuli (20 ms SI response) remained unaffected by the stimulus frequency. Our results indicate that visceral afferents from the oesophagus primarily project to the SII cortex and, unlike somatosensory afferents, lack a significant SI representation. We propose that this cortical projection pattern forms the neurophysiological basis of the low temporal and spatial resolution of conscious visceral sensation.
Myelin does not influence the choice behaviour of entorhinal axons but strongly inhibits their outgrowth length in vitro
Authors: Savaskan Nicolai E. , Plaschke Martina , Ninnemann Olaf , Spillmann Adrian A. , Schwab Martin E. , Nitsch Robert , Skutella Thomas 
Published: March 2003

AbstractMyelin is crucial for the stabilization of the entorhinohippocampal projection during late development and is a non‐permissive substrate for regrowing axons after lesion in the adult brain. We used two in vitro assays to analyse the impact of myelin on rat entorhinohippocampal projection neurons. A stripe assay was used to study the impact of myelin on the choice behaviour of axons from the entorhinal cortex (EC). Given a choice between alternating hippocampal membrane lanes from developmental stages ranging from early postnatal to adult, EC axons preferred to extend on early postnatal hippocampal membranes. Neither the neutralization of myelin‐associated factors by a specific antibody (IN‐1) nor the separation of myelin from membranes interfered with the axons' choice behaviour. The entorhinal axons showed no preference in the membrane combination of adult and myelin‐free adult hippocampal membranes. These stripe assay experiments demonstrate that support for EC axon choice in the developing hippocampus is maturation‐dependent and is not influenced by myelin. The application of IN‐1 in the outgrowth assay and the separation of myelin from membranes, enhanced elongation of outgrowing entorhinal axons on adult hippocampal membranes, whereas a control antibody did not. This shows that myelin‐associated factors have a strong inhibitory effect on the outgrowth length of entorhinal axons. In conclusion, we suggest that axonal elongation in the entorhinohippocampal system during development is strongly influenced by myelin‐associated growth inhibition factors and that specific target finding of entorhinal axons is regulated by a different mechanism.
Local inhibition of hippocampal nitric oxide synthase does not impair place learning in the Morris water escape task in rats
Authors: Blokland Arjan , De Vente Jan , Prickaerts Jos , Honig Wiel , Van Ittersum Marjanne Markerink‐ , Steinbusch Harry 
Published: March 2003

AbstractRecent studies have provided evidence that nitric oxide (NO) has a role in certain forms of memory formation. Spatial learning is one of the cognitive abilities that has been found to be impaired after systemic administration of an NO‐synthase inhibitor. As the hippocampus has a pivotal role in spatial orientation, the present study examined the role of hippocampal NO in spatial learning and reversal learning in a Morris task in adult rats. It was found that Nω‐nitro‐l‐arginine infusions into the dorsal hippocampus affected the manner in which the rats were searching the submerged platform during training, but did not affect the efficiency to find the spatial location of the escape platform. Hippocampal NO‐synthase inhibition did not affect the learning of a new platform position in the same water tank (i.e. reversal learning). Moreover, no treatment effects were observed in the probe trials (i.e. after acquisition and after reversal learning), indicating that the rats treated with Nω‐nitro‐l‐arginine had learned the spatial location of the platform. These findings were obtained under conditions where the NO synthesis in the dorsal hippocampus was completely inhibited. On the basis of the present data it was concluded that hippocampal NO is not critically involved in place learning in rats.
A new pyrrolyl‐quinoxalinedione series of non‐NMDA glutamate receptor antagonists: pharmacological characterization and comparison with NBQX and valproate in the kindling model of epilepsy
Authors: Löscher W. , Lehmann H. , Behl B. , Seemann D. , Teschendorf H. J. , Hofmann H. P. , Lubisch W. , Höger T. , Lemaire H. ‐G. , Groß G. 
Published: March 2003

AbstractAntagonists at the ionotropic non‐NMDA [AMPA (amino‐methyl proprionic acid)/kainate] type of glutamate receptors have been suggested to possess several advantages compared to NMDA (N‐methyl‐d‐aspartate) receptor antagonists, particularly in terms of risk/benefit ratio, but the non‐NMDA receptor antagonists available so far have not fulfilled this promise. From a large series of pyrrolyl‐quinoxalinedione derivatives, we selected six new competitive non‐NMDA receptor antagonists. The basis of selection was high potency and selectivity for AMPA and/or kainate receptors, high in vivo potency after systemic administration, and an acceptable ratio between neuroprotective or anticonvulsant effects and adverse effects. Pharmacological characteristics of these novel compounds are described in this study with special emphasis on their effects in the kindling model of temporal lobe epilepsy, the most common type of epilepsy in humans. In most experiments, NBQX and the major antiepileptic drug valproate were used for comparison with the novel compounds. The novel non‐NMDA receptor antagonists markedly differed in their AMPA and kainate receptor affinities from NBQX. Thus, while NBQX essentially did not bind to kainate receptors at relevant concentrations, several of the novel compounds exhibited affinity to rat brain kainate receptors or recombinant kainate receptor subtypes in addition to AMPA receptors. One compound, LU 97175, bound to native high affinity kainate receptors and rat GluR5–GluR7 subunits, i.e. low affinity kainate binding sites, with much higher affinities than to AMPA receptors. All compounds potently blocked AMPA‐induced cell death in vitro and, except LU 97175, AMPA‐induced convulsions in vivo. In the kindling model, compounds with a high affinity for GluR7 (LU 97175) or compounds (LU 115455, LU 136541) which potently bind to AMPA receptors and low affinity kainate receptor subunits were potent anticonvulsants in the kindling model, whereas the AMPA receptor‐selective LU 112313 was the least selective compound in this model, indicating that non‐NMDA antagonists acting at both AMPA and kainate receptors are more effective in this model than AMPA receptor‐selective drugs. Three of the novel compounds, i.e. LU 97175, LU 115455 and LU 136541, exerted potent anticonvulsant effects without inducing motor impairment in the rotarod test. This combination of actions is thought to be a prerequisite for selective anticonvulsant drug action.
Intrastriatal grafting of a GDNF‐producing cell line protects striatonigral neurons from quinolinic acid excitotoxicity in vivo
Authors: Pérez‐Navarro E. , Arenas E. , Marco S. , Alberch J. 
Published: March 2003

AbstractGlial cell line‐derived neurotrophic factor (GDNF) is a neurotrophic factor with a therapeutic potential in neurodegenerative disorders. GDNF is expressed in the adult striatum, but its signalling tyrosine kinase receptor, c‐ret, has not been detected in this structure by in situ hybridization. In the present work, we first examined c‐ret and GDNF receptor α1 (GFR‐α1) expression using an RNAse protection assay, and found that both receptors are expressed in the adult rat striatum. We then examined whether GDNF was able to regulate the phenotype and/or prevent the degeneration of striatal projection neurons in a well‐characterized model of excitotoxic damage. A fibroblast cell line, engineered to overexpress GDNF, was grafted in adult rats striatum 24 h before quinolinic acid (QUIN) injection. QUIN injection alone or in combination with the control cell line induced a loss of glutamic acid decarboxylase 67 (GAD)‐, preprotachykinin A (PPTA)‐, prodynorphin (DYN)‐ and preproenkephalin (PPE)‐positive neurons. GDNF selectively prevented: (i) the loss of a subpopulation of striatonigral neurons expressing GAD and PPTA; (ii) the atrophy of PPTA‐positive neurons; and (iii) the decrease in GAD, PPTA and DYN mRNA expression, after QUIN injection. Moreover, in unlesioned animals, GDNF increased the size of PPTA‐positive neurons and up‐regulated their mRNA levels. In contrast, GDNF showed no effect in intact or lesioned striatopallidal PPE‐positive neurons. Thus, our findings show that GDNF selectively regulates the phenotype and protects striatonigral neurons from QUIN‐induced excitotoxicity, suggesting that GDNF may be used for the treatment of striatonigral degenerative disorders, e.g. Huntington's disease and multiple system atrophy.
Increased cyclin D1 in vulnerable neurons in the hippocampus after ischaemia and epilepsy: a modulator of in vivo programmed cell death?
Authors: Timsit Serge , Rivera Santiago , Ouaghi Philippe , Guischard Frédérique , Tremblay Évelyne , Ben‐Ari Yezekiel , Khrestchatisky Michel 
Published: March 2003

AbstractSeveral observations suggest that delayed neuronal death in ischaemia, epilepsy and other brain disorders includes an apoptotic component, involving programmed cell death (PCD). PCD is hypothesized to result, in part, from aberrant control of the cell cycle. Because they are instrumental in mitosis, cyclins D are key markers to evaluate whether neurons indeed progress into the cell cycle in situations of pathology. Therefore, we investigated in rat brains, the expression of cyclins D in the delayed neuronal death that occurs following transient global ischaemia and kainate‐induced seizures. Following a four‐vessel occlusion insult, quantitative in situ hybridization revealed a highly significant and persistent 100% increase of cyclin D1 mRNA in the vulnerable pyramidal neurons of the CA1 hippocampal region. Ischaemia also induced a smaller and transient cyclin D1 mRNA increase in the resistant CA3 area and dentate gyrus. In contrast, the cyclin D2 and D3 mRNAs, expressed constitutively in the adult rat hippocampus, were not upregulated. Following kainate‐induced seizures, cyclin D1 mRNA was induced in the vulnerable CA3 region, and to a lesser extent, in non‐vulnerable regions. Cyclin D1 immunohistochemistry revealed increased protein levels in the cytoplasm and nucleus of neurons commited to die after ischaemia. Double labelling experiments indicate that cyclin D1 is also expressed in reactive astrocytes but not in microglial cells. Finally, we report that in neurons, cyclin D1 expression peaks before nuclear condensation and the appearance of DNA fragmentation. We propose that cyclin D1, when expressed at high levels in lesioned neurons, may act as a modulator of apoptosis.