bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chronic hyperammonemia impairs the glutamate–nitric oxide–cyclic GMP pathway in cerebellar neurons in culture and in the rat in vivo
Authors: Hermenegildo Carlos , Montoliu Carmina , Llansola Marta , Muñoz María‐Dolores , Gaztelu José‐María , Miñana María‐Dolores , Felipo Vicente 
Published: March 2003

AbstractThe aim of this work was to assess whether ammonia concentrations similar to the increase found in the brain of hyperammonemic rats (100 μm), impair N‐methyl‐d‐aspartate (NMDA) receptor‐mediated signal transduction. We first measured glutamate neurotoxicity, which in these neurons is mediated by activation of NMDA receptors, as an initial parameter reflecting activation of NMDA receptor‐mediated pathways. Long‐term treatment of cultured neurons with ammonia prevents glutamate‐induced neuronal death. The EC50 was 20 μm, and at 100 μm the protection was complete. The induction of the protective effect was not immediate, but took several hours.  Treatment with 100 μm ammonia did not prevent a glutamate‐ or NMDA‐induced rise of intracellular calcium. Ammonia impaired the glutamate–nitric oxide–cGMP (3′,5′‐cyclic guanosine monophosphate) pathway in a dose‐ and time‐dependent manner. Glutamate‐induced formation of cGMP was reduced by 42%, while activation of nitric oxide synthase was not affected. Ammonia reduced by 31% cGMP formation induced by S‐nitroso‐N‐acetyl‐penicillamine (SNAP), a NO‐generating agent, confirming that the interference occurs at the level of guanylate cyclase activation by nitric oxide.  To assess whether chronic moderate hyperammonemia in vivo also impairs the glutamate–nitric oxide–cGMP pathway, we determined by in vivo brain microdialysis in freely moving rats the formation of cGMP induced by NMDA. In hyperammonemic rats, the formation of cGMP induced by NMDA and SNAP was reduced by ca. 60 and 41%, respectively, indicating that chronic hyperammonemia in the animal in vivo also impairs the glutamate–nitric oxide–cGMP pathway. Impairment of this pathway can contribute to the neurological alterations found in hyperammonemia and hepatic encephalopathy.
AMPA receptors at primary afferent synapses in substantia gelatinosa after sciatic nerve section
Authors: Popratiloff A. , Weinberg R. J. , Rustioni A. 
Published: March 2003

AbstractIncreased excitability of superficial laminae of the spinal cord may contribute to the pathological pain consequent to peripheral nerve injury. Among several mechanisms that may be responsible for this occurrence is upregulation of receptors for glutamate in the spinal cord. To explore this possibility, we investigated changes in AMPA receptors in substantia gelatinosa of rats after section of the sciatic nerve. Immunofluorescence was performed on sections from the fourth lumbar segment. Quantitative analysis of digitally captured images suggested that staining for an antibody to a sequence shared by GluR2 and GluR3 (GluR2/3) was increased on the side ipsilateral to the lesion.  To determine whether antigen accumulation was at synaptic sites and to probe whether it was selective for primary afferent terminals, we performed electron microscopy on immunogold‐labelled material. Gold particles coding for GluR2/3 subunits were counted from synaptic active zones of glomerular terminals in substantia gelatinosa that originate from small calibre afferent fibres, and from active zones of terminals of probable intrinsic origin. Counts were significantly increased on the side ipsilateral to the lesion only at synapses of primary afferent terminals. These results document selective upregulation of receptor protein at the synapse. This upregulation may contribute to the increased sensitivity of dorsal horn neurons following peripheral nerve injury.
Distribution of choline acetyltransferase immunoreactivity in the vestibular nuclei of normal and unilateral vestibular neurectomized cats
Authors: Tighilet B. , Lacour M. 
Published: March 2003

AbstractPost‐lesion recovery of vestibular functions is a suitable model for studying adult central nervous system plasticity. The vestibular nuclei complex (VN) plays a major role in the recovery process and neurochemical reorganizations have been described at this brainstem level. The cholinergic system should be involved because administration of cholinergic agonists and antagonists modify the recovery time course. This study was aimed at analysing the postlesion changes in choline acetyltransferase immunoreactivity (ChAT‐Ir) in the VN of cats killed 1 week, 3 weeks or 1 year following unilateral vestibular neurectomy. ChAT‐positive neurons and varicosities were immunohistochemically labelled and quantified (cell count and surface measurement, respectively) by means of an image analysing system. The spatial distribution of ChAT‐Ir within the VN of control cats showed darkly stained neurons and varicosities mainly located in the caudal parts of the medial (MVN) and inferior (IVN) VN, the nucleus prepositus hypoglossi (PH) and, to a lesser extent, in the medial part of the superior vestibular nucleus (SVN). Lesion‐induced changes consisted in a significant increase in both the number of ChAT‐positive neurons (IVN, SVN) and the surface of ChAT‐positive varicosities (IVN, SVN, PH). They were observed bilaterally in the acute (1 year and 3 weeks) and compensated (1 year) cats for the SVN and PH, while they persisted only in the IVN on the lesioned side in the compensated cats. These findings demonstrate vestibular lesion‐induced reorganization of the cholinergic system in the IVN, SVN and PH which could contribute to postural and oculomotor function recovery.
Heat shock proteins in retinal neurogenesis: identification of the PM1 antigen as the chick Hsc70 and its expression in comparison to that of other chaperones
Authors: Morales Aixa V. , Hadjiargyrou Michael , Díaz Begoña , Hernández‐Sánchez Catalina , De Pablo Flora , De La Rosa Enrique J. 
Published: March 2003

AbstractWhile the role of heat shock proteins under experimental stress conditions is clearly characterized, their expression in unstressed cells and tissues and their functions in normal cell physiology, besides their chaperone action, remain largely undetermined. We report here the identification in chicken of the antigen recognized by the monoclonal antibody PM1 [Hernández‐Sánchez et al. (1994) Eur. J. Neurosci.6,1801–1810) as the non‐inducible chaperone heat‐shock cognate 70 (Hsc70). Its identity was determined by partial peptide sequencing, immuno‐crossreactivity & two‐dimensional gel‐electrophoresis. In addition, we examined its expression during chick embryo retinal neurogenesis. The early widespread Hsc70 immunostaining corresponding to most, if not all, of the neuroepithelial cells becomes restricted to a subpopulation of these cells in the peripheral retina as development proceeds. On the other hand, retinal ganglion cells, differentiating in the opposite central‐to‐peripheral gradient, retained Hsc70 immunostaining. Other molecular chaperones, the heat‐shock proteins Hsp40, Hsp60 & Hsp90, did not seem to compensate the loss of Hsc70. They also showed decreasing immunostaining patterns as neurogenesis proceeds, although distinctive from that of Hsc70, whereas Hsp70 was not detected in the embryonic retina. This precise cellular & developmental regulation of Hsc70, a generally considered constitutive molecular chaperone, in unstressed embryos, together with the expression of other chaperones, provides new tools & a further insight on neural precursor heterogeneity & suggests possible specific cellular roles of chaperone function during vertebrate neurogenesis.
Systemic harmaline blocks associative and motor learning by the actions of the inferior olive
Authors: Welsh John P. 
Published: March 2003

AbstractIs there a role for the inferior olive in learning? Novel paradigms of conditioning involving tongue protrusion were developed using the rat to test whether: (a) the indole alkaloid harmaline blocks associative learning via actions within the inferior olive, and (b) the inferior olive is required for associative and motor learning. Harmaline blocked associative learning as measured by the absence of conditioned responses to a tone over six daily sessions of conditioning and the absence of retention without harmaline. Harmaline's effect on associative learning was completely blocked by prior removal of the inferior olive with 3‐acetylpyridine. Rats whose inferior olives were chronically lesioned showed normal associative learning, normal associative memory, and could learn to modify tongue protrusion via a motor learning paradigm involving response shaping. Removal of the inferior olive degraded the performance of the licking motor system by increasing the latency of conditioned tongue protrusions and by increasing the temporal variability of rhythmic licking elicited by intraoral water. The experiments raise doubt as to whether the inferior olive encodes memory in the cerebellum but demonstrate that the inferior olive is essential for the temporal precision of movement. The results indicate that harmaline's antilearning action is produced by its ability to exaggerate the normal propensity of olivary neurons to fire rhythmically, a process that must be constrained under physiological conditions for normal learning to occur. It is concluded that there may be an important role for the rhythmic activity of inferior olivary neurons in the temporal processes that underlie both motor control and learning.
The murine Y1 receptor 5′ upstream sequence directs cell‐specific and developmentally regulated LacZ expression in transgenic mice CNS
Authors: Oberto Alessandra , Tolosano Emanuela , Brusa Rossella , Altruda Fiorella , Panzica Giancarlo , Eva Carola 
Published: March 2003

AbstractThe Y1 receptor for neuropeptide Y (NPY) is highly expressed in mammalian CNS where it mediates the activation of several neurobiological functions. We have previously demonstrated that a 1.3‐kb fragment upstream of the transcription initiation sites of the murine Y1 receptor gene is able to direct specific expression of reporter genes in neuronal cell cultures. In the present study transgenic mice harbouring this putative promoter region linked to the LacZ reporter gene were generated and analysed for temporal and spatial distribution. Ten transgenic lines expressed β‐galactosidase in the CNS but not in other organs such as heart, liver and kidney. Histochemical analysis of brain from adult transgenic mice showed specific expression of the transgene in specific brain regions with little variation. Four transgenic lines showed characteristic patterns of β‐galactosidase activity in the brain that are consistent with the expression of the endogenous gene. Prominent LacZ activity was present in several telencephalic and diencephalic structures, including deeper layers of cerebral cortex, amygdaloid complex, hippocampus, preoptic area, several thalamic and hypothalamic nuclei and habenula. The ontogeny analysis indicates that the LacZ expression agrees with the temporal expression pattern of rat Y1 receptor mRNA. These data demonstrate that the 1.3‐kb upstream region of the murine Y1 receptor gene contains the cis acting elements required for establishing a CNS‐restricted and developmental stage‐specific pattern of expression in vivo. Moreover they provide further information on the distribution of this NPY subtype receptor in mammalian brain.
Endogenous activation of metabotropic glutamate receptors contributes to burst frequency regulation in the lamprey locomotor network
Authors: Krieger P. , Grillner S. , Manira A. El 
Published: March 2003

AbstractThe effect of metabotropic glutamate receptor (mGluR) agonists and antagonists on the spinal cord network underlying locomotion in the lamprey has been analysed. The specific group I mGluR agonist (R,S)‐3,5‐dihydroxyphenylglycine (DHPG) and the broad‐spectrum mGluR agonist (1S,3R)‐1‐aminocyclopentane‐1,3‐dicarboxylic acid (1S,3R‐ACPD) both increased the burst frequency of N‐methyl‐d‐aspartic acid (NMDA)‐induced fictive locomotion and depolarized grey matter neurons. The burst frequency increase induced by the mGluR agonists was counteracted by the mGluR antagonists (+)‐alpha‐methyl‐4‐carboxyphenylglycine((+)‐MCPG), cyclopropan[b]chromen‐1a‐carboxylic acid ethylester (CPCCOEt) and (RS)‐1‐aminoindan‐1,5‐dicarboxylic acid (AIDA). Application of CPCCOEt alone reduced the locomotor burst frequency, indicating that mGluRs are endogenously activated during fictive locomotion. The mGluR antagonist CPCCOEt had no effect on NMDA‐, or (S)‐α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoazolepropionic acid (AMPA)‐induced depolarizations. The mGluR agonists 1S,3R‐ACPD and DHPG increased the amplitude of NMDA‐induced depolarizations, a mechanism which could account for the increase in burst frequency. The group III mGluR agonist L‐2‐amino‐4‐phosphonobutyric acid reduced intraspinal synaptic transmission and burst frequency.
NMDA and AMPA receptors on neocortical neurons are differentially distributed
Authors: Dodt H. ‐U. , Frick A. , Kampe K. , Zieglgänsberger W. 
Published: March 2003

AbstractThe distribution of glutamate receptor subtypes on the surface of neurons is highly relevant for synaptic activation and signal processing in the neocortex. As a novel approach we have used infra‐red videomicroscopy in combination with photostimulation or microiontophoresis in brain slices of rat neocortex to map the distribution of N‐methyl‐d‐aspartate (NMDA) and α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA) receptors on pyramidal neurons of layer V. Both modes of application revealed a spatially distinct distribution of glutamate receptor subtypes: the soma and the proximal dendrite of neurons are highly sensitive to NMDA, whereas the more distal parts of the dendrite are more sensitive to AMPA. An implication is that NMDA receptors near the soma might regulate the amplification of synaptic signals resulting from AMPA receptor activation on remote dendritic sites.
Delivery of a constitutively active form of the heat shock factor using a virus vector protects neuronal cells from thermal or ischaemic stress but not from apoptosis
Authors: Wagstaff M. J. D. , Smith J. , Collaco‐Moraes Y. , De Belleroche J. S. , Voellmy R. , Coffin R. S. , Latchman D. S. 
Published: March 2003

AbstractThe heat shock proteins (HSPs) are induced by stressful stimuli and have a protective effect. Different HSPs protect with different efficiencies against different stresses indicating that optimal protection would be obtained with a non‐stressful agent which induced a range of HSPs. We have prepared a herpesvirus vector expressing a constitutively active mutant form of heat shock factor 1 (HSF1) which, unlike the wild‐type form of this transcription factor, does not require stress for its activation. Upon infection of neuronal cells, this virus induced a more restricted range of HSPs than in non‐neuronal cells. Infection with the virus protected neuronal cells against subsequent thermal or ischaemic stress in accordance with its ability to induce HSP70 expression but did not protect them against apoptotic stimuli. The mechanisms of these effects and their significance for the use of HSF to manipulate HSP gene expression is discussed.
Pharmacological stimuli decreasing nucleus accumbens dopamine can act as positive reinforcers but have a low addictive potential
Authors: Marinelli Michela , Barrot Michel , Simon Hervé , Oberlander Claude , Dekeyne Anne , Moal Michel Le , Piazza Pier Vincenzo 
Published: March 2003

AbstractOpioid peptides, through μ and δ receptors, play an important part in reward. In contrast, the role of κ receptors is more controversial. We examined the possible positive reinforcing effects of a selective κ agonist, RU 51599, by studying intravenous self‐administration in the rat. The effect of RU 51599 on dopamine release in the nucleus accumbens was also studied, as opioids and dopamine seem to interact in the mediation of reward. The behavioural and dopaminergic effects of RU 51599 were compared with those of the μ agonist heroin. Rats self‐administered both RU 51599 (6.5, 20 and 60 μg/inj) and heroin (30 μg/inj) at low ratio requirement. When the ratio requirement, i.e. the number of responses necessary to receive one drug infusion, was increased, self‐administration of RU 51599 rapidly extinguished, whereas self‐administration of heroin was maintained. Intravenous infusion of RU 51599 (100, 200 and 400 μg) dose‐dependently decreased (25, 30 and 40%, respectively) extracellular concentrations of dopamine, as measured by means of microdialysis in freely moving rats. In contrast, heroin increased accumbens dopamine (130% over baseline). These results indicate that κ receptors, similarly to μ ones, can mediate positive reinforcing effects of opioid peptides. However, the strength of the reinforcement is very low for κ receptors. This suggests that changes in accumbens dopamine do not correlate with the capacity of a stimulus to induce reward or aversion. In contrast, a parallel seems to exist between an increase in accumbens dopamine and the drive to reach or obtain a positive reinforcer.
Dual effects of botulinum neurotoxin A on the secretory stages of chromaffin cells
Authors: Gil Anabel , Viniegra Salvador , Gutiérrez Luis M. 
Published: March 2003

AbstractTruncation of the C‐terminal domain of the synaptosomal associated protein of 25 kDa (SNAP‐25) by botulinum neurotoxin A (BoNT A) has been shown to block neuroendocrine cell secretion. It is unclear, however, if toxin mechanism involved the affection of a single or more events of the exocytotic cascade. BoNT A induced changes in both the degree of inhibition and the kinetics of catecholamine secretion from populations of cultured bovine chromaffin cells. Ca2+‐dependent secretion from digitonin‐permeabilized cells showed partial inhibition associated with the alteration of a slow secretory phase at different toxin concentrations. In contrast, in intact cells stimulated by depolarization, cell treatment with low concentrations (1 nm) of the toxin affected the late phase of secretion, whereas 100 nm BoNT A‐poisoned cells showed an alteration even of fast components. The high degree of inhibition associated with fast secretory component alteration was dependent on Ca2+ entry through the Ca2+ channels, as it was absent from cells permeated with the A23187 Ca2+ ionophore. Vesicle pools implicated in the effect of BoNT A on the secretory response from single cells were identified using amperometry. These studies supported the macroscopic view by showing that secretion from BoNT A‐treated permeabilized cells presented specific inhibition of late vesicle fusions. Intact cells showed alterations in the late vesicle pool (t = 39 s) recruited during prolonged or repetitive KCl depolarizations using 1 nm BoNT A‐treated cells as well as in an intermediate kinetic pool (t = 18 s) at higher toxin concentrations (100 nm). The faster resolved component (t = 8 s) or the membrane fusion event itself were not affected. Our results demonstrate that removal of the last nine C‐terminal amino acids of SNAP‐25 by BoNT A has a specific effect on two different and distal secretory stages in chromaffin cells.
Intracellular calcium stores modulate miniature GABA‐mediated synaptic currents in neonatal rat hippocampal neurons
Authors: SaviĆ Nataša , Sciancalepore Marina 
Published: March 2003

AbstractThe whole‐cell configuration of the patch clamp technique was used to record miniature γ‐aminobutyric acidA (GABAA) receptor‐mediated currents (in tetrodotoxin, 1 μm and kynurenic acid 1 mm) from CA3 pyramidal cells in thin hippocampal slices obtained from postnatal (P) day (P6–9) old rats. Switching from a Ca2+‐containing to a nominally Ca2+‐free medium (in which Ca2+ was substituted with Mg2+, in the presence or in the absence of 100 μm EGTA) did not change significantly the frequency or amplitude of miniature events. Superfusion of thapsigargin induced a concentration‐dependent increase in frequency but not in amplitude of tetrodotoxin‐resistant currents that lasted for the entire period of drug application. Mean frequency ratio (thapsigargin 10 μm over control) was 1.8 ± 0.5, (n = 9). In nominally Ca2+‐free solutions thapsigargin was ineffective. When bath applied, caffeine (10 mm), reversibly reduced the amplitude of miniature postsynaptic currents whereas, if applied by brief pressure pulses, it produced an increase in frequency but not in amplitude of spontaneous GABAergic currents. Superfusion of caffeine (10 mm) reversibly reduced the amplitude of the current induced by GABA (100 μm) indicating a clear postsynaptic effect on GABAA receptor. Superfusion of ryanodine (30 μm), in the majority of the cells (n = 7) did not significantly modify the amplitude or frequency of miniature events. In two of nine cells it induced a transient increase in frequency of miniature postsynaptic currents. These results indicate that in neonatal hippocampal neurons, mobilization of calcium from caffeine–ryanodine‐sensitive stores facilitates GABA release.
Psychotomimetic‐induction of tissue plasminogen activator mRNA in corticostriatal neurons in rat brain
Authors: Hashimoto Takanori , Kajii Yasushi , Nishikawa Toru 
Published: March 2003

AbstractWe have studied in the rat the effects of acute subcutaneous injection of psychotomimetics including methamphetamine (MAP), cocaine and phencyclidine (PCP) on the expression of a brain plasticity‐related molecule, tissue plasminogen activator (tPA) mRNA, using non‐radioactive in situ hybridization histochemistry. In addition to the constitutive expression of tPA mRNA in cerebellar Purkinje cells, ventricular ependymal cells and meningeal blood vessel‐associated cells, MAP (1–4 mg/kg), cocaine (30 mg/kg) and PCP (1.25–5 mg/kg) caused a transient and dose‐dependent induction of the transcript with its peak at 3 h postinjection in a group of neurons of the medial and insular prefrontal cortices, and the piriform cortex. Another indirect dopamine agonist nomifensine (20–40 mg/kg) mimicked the tPA mRNA induction in the prefrontal cortical areas. Moreover, MAP induction of tPA mRNA was markedly inhibited by pretreatment with a D1 (R(+)‐SCH23390: R(+)‐7‐chloro‐8‐hydroxy‐3‐methyl‐1‐phenyl‐2,3,4,5‐tetra‐hydro‐1H‐3‐benzazepine hydrochloride) or a D2 (haloperidol) dopamine receptor‐preferring antagonist. Intramedial striatum, but not intrathalamic, application of a fluorescent tracer, fluorogold, retrogradely labelled the cortical cells expressing tPA mRNA. The present results suggest that acute injections of the above psychotomimetic drugs may induce tPA mRNA in a group of the prefrontal cortical neurons that project to the medial striatum. This tPA mRNA expression may be due to the activation of the dopamine neurotransmission. Because it is well documented that single or repeated administration of methamphetamine, cocaine and PCP produces enduring changes in responses to these drugs in humans and experimental animals (e.g. behavioural sensitization), the psychotomimetic‐induction of tPA mRNA could be implicated in an initial step in the plastic rearrangements in the neuronal circuits underlying long‐lasting changes in behavioural expression.