bluuebunny/crossref_metadata_2025 huggingface dataset:
Multimeric CREB‐binding sites in the promoter regions of a family of G‐protein‐coupled receptors related to the vertebrate galanin and nociceptin/orphanin‐FQ receptor families
Authors: Saunders Susan E. , Burke Julian F. , Benjamin Paul R.
Published: March 2003

Four related genes encoding a family of G‐protein‐coupled receptors (GPCRs) have been isolated from the mollusc Lymnaea stagnalis. The coding regions of this family of receptors share 97–99% sequence similarity at both the protein and nucleotide level, and they also share high sequence identity with vertebrate galanin and orphanin‐FQ/nociceptin GPCR families. Analysis of the promoter regions reveals shared domains, some of which encode highly conserved repeating units. One 27‐bp repeating unit, which encodes a c‐AMP response element (CRE) and binds CREB protein, is repeated 14 times in one promoter. In situ hybridization showed expression of these receptors in identified neurons of several behaviourly important networks including those involved in feeding and ion and water regulation. These Lymnaea receptors are likely to represent members of a novel family of invertebrate neuropeptide receptors extensively regulated in response to intracellular signalling cascades.
A blocker‐resistant, fast‐decaying, intermediate‐threshold calcium current in palaeocortical pyramidal neurons
Authors: Magistretti Jacopo , Brevi Sara , De Curtis Marco
Published: March 2003

The whole‐cell patch‐clamp technique was used to record Ca2+ currents in acutely dissociated neurons from layer II of guinea‐pig piriform cortex (PC). Ba2+ (5 mm) was used as charge carrier. In a subpopulation of layer II cells (≈ 22%) total Ba2+ currents (IBas) displayed a high degree (> 70%) of inactivation after 300 ms of steady depolarization. The application of L‐, N‐ and P/Q‐type Ca2+‐channel blockers to these high‐decay IBas left their fast inactivating component largely unaffected. The inactivation phase of the blocker‐resistant, fast‐decaying IBa thus isolated had a bi‐exponential time course, with a fast time constant of ≈ 20 ms and a slower time constant of ≈ 100 ms at voltage levels positive to −10 mV. The voltage dependence of activation of the blocker‐resistant, fast‐decaying IBa was shifted by ≈ 7–9 mV in the negative direction in comparison with those of other pharmacologically and/or kinetically different high‐voltage‐activated Ca2+ currents. We named this blocker‐resistant, fast‐decaying, intermediate‐threshold current IRfi. The amplitude of IRfi decreased only slightly (by ≈ 9%) when extracellular Ca2+ was substituted for Ba2+, in contrast with that of slowly decaying, high‐voltage‐activated currents, which was reduced by ≈ 41% on average. Moreover, IRfi was substantially inhibited by low concentrations of Ni2+ (50 μm). We conclude that IRfi, because of its fast inactivation kinetics, intermediate threshold of activation and resistance to organic blockers, represents a definite, identifiable Ca2+ current different from classical high‐voltage‐activated currents and clearly distinguishable from classical IT. The striking similarity found between IRfi and Ca2+ currents resulting from heterologous expression of α1E‐type channel subunits is discussed.
Altered expression and functions of serotonin 5‐HT1A and 5‐HT1B receptors in knock‐out mice lacking the 5‐HT transporter
Authors: Fabre V. , Beaufour C. , Evrard A. , Rioux A. , Hanoun N. , Lesch K. P. , Murphy D. L. , Lanfumey L. , Hamon M. , Martres M. ‐P.
Published: March 2003

By taking up serotonin (5‐hydroxytryptamine, 5‐HT) released in the extracellular space, the 5‐HT transporter (5‐HTT) regulates central 5‐HT neurotransmission. Possible adaptive changes in 5‐HT neurotransmission in knock‐out mice that do not express the 5‐HT transporter were investigated with special focus on 5‐HT1A and 5‐HT1B receptors. Specific labelling with radioligands and antibodies, and competitive RT‐PCR, showed that 5‐HT1A receptor protein and mRNA levels were significantly decreased in the dorsal raphe nucleus (DRN), increased in the hippocampus and unchanged in other forebrain areas of 5‐HTT–/– vs. 5‐HTT+/+ mice. Such regional differences also concerned 5‐HT1B receptors because a decrease in their density was found in the substantia nigra (−30%) but not the globus pallidus of mutant mice. Intermediate changes were noted in 5‐HTT+/– mice compared with 5‐HTT+/+ and 5‐HTT–/– animals. Quantification of [35S]GTP‐γ‐S binding evoked by potent 5‐HT1 receptor agonists confirmed such changes as a decrease in this parameter was noted in the DRN (−66%) and the substantia nigra (−30%) but not other brain areas in 5‐HTT–/– vs. 5‐HTT+/+ mice. As expected from actions mediated by functional 5‐HT1A and 5‐HT1B autoreceptors, a decrease in brain 5‐HT turnover rate after i.p. administration of ipsapirone (a 5‐HT1A agonist), and an increased 5‐HT outflow in the substantia nigra upon local application of GR 127935 (a 5‐HT1B/1D antagonist) were observed in 5‐HTT+/+ mice. Such effects were not detected in 5‐HTT–/– mice, further confirming the occurrence of marked alterations of 5‐HT1A and 5‐HT1B autoreceptors in these animals.
Subthalamic neuron activity related to tremor and movement in Parkinson's disease
Authors: Magariños‐Ascone Carlos M. , Figueiras‐Mendez Roberto , Riva‐Meana Concepción , Córdoba‐Fernández Andrés
Published: March 2003

Single cell activity recorded in the subthalamic nucleus (STN) of Parkinson's patients and the effect of tremor, passive and voluntary movement upon the same cells are described. Three types of cells were distinguished by the pattern of discharge: tonic, phasic and rhythmic. They all demonstrated high mean firing rates (65, 59 and 69 Hz, respectively). Simultaneous recordings of muscle activity and tremor helped in defining cell activity. The implantation of the definitive stimulating electrode in the patients was based on the number of STN cells related to tremor, active and passive movements (mean = 68%) along the track chosen. Cells were related to tremor (n = 21; 11%), modified the discharge with differences in the amplitude of tremor (n = 4), and changed the rate and pattern when tremor stopped spontaneously or artificially (n = 6). Movement‐related cells (n = 97; 51%) showed a cyclic activity correlated with phases of the movement, or modified the firing rate along the performance of the movement. Tremor and movement‐related cells (n = 11; 6%) revealed an interesting sensory‐motor integrative function.
Enhanced seizures and hippocampal neurodegeneration following kainic acid‐induced seizures in metallothionein‐I + II‐deficient mice
Authors: Carrasco Javier , Penkowa Milena , Hadberg Hanne , Molinero Amalia , Hidalgo Juan
Published: March 2003

Metallothioneins (MTs) are major zinc binding proteins in the CNS that could be involved in the control of zinc metabolism as well as in protection against oxidative stress. Mice lacking MT‐I and MT‐II (MT‐I + II deficient) because of targeted gene inactivation were injected with kainic acid (KA), a potent convulsive agent, to examine the neurobiological importance of these MT isoforms. At 35 mg/kg KA, MT‐I + II deficient male mice showed a higher number of convulsions and a longer convulsion time than control mice. Three days later, KA‐injected mice showed gliosis and neuronal injury in the hippocampus. MT‐I + II deficiency decreased both astrogliosis and microgliosis and potentiated neuronal injury and apoptosis as shown by terminal deoxynucleotidyl transferase‐mediated in situ end labelling (TUNEL), detection of single stranded DNA (ssDNA) and by increased interleukin‐1β‐converting enzyme (ICE) and caspase‐3 levels. Histochemically reactive zinc in the hippocampus was increased by KA to a greater extent in MT‐I + II‐deficient compared with control mice. KA‐induced seizures also caused increased oxidative stress, as suggested by the malondialdehyde (MDA) and protein tyrosine nitration (NITT) levels and by the expression of MT‐I + II, nuclear factor‐κB (NF‐κB), and Cu/Zn‐superoxide dismutase (Cu/Zn‐SOD). MT‐I + II deficiency potentiated the oxidative stress caused by KA. Both KA and MT‐I + II deficiency significantly affected the expression of MT‐III, granulocyte‐macrophage colony stimulating factor (GM‐CSF) and its receptor (GM‐CSFr). The present results indicate MT‐I + II as important for neuron survival during KA‐induced seizures, and suggest that both impaired zinc regulation and compromised antioxidant activity contribute to the observed neuropathology of the MT‐I + II‐deficient mice.
Transient action of the endothelial constitutive nitric oxide synthase (ecNOS) mediates the development of thermal hypersensitivity following peripheral nerve injury
Authors: Levy Dan , Tal Michael , Höke Ahmet , Zochodne Douglas W.
Published: March 2003

Neuropathic pain is a disabling feature of peripheral nerve injury. Following injury, local inflammation and the release of mediators may contribute to ectopic mechanosensitivity of the nerve‐trunk and pain hypersensitivity. In the present study we investigated whether nitric oxide (NO) action and local nitric oxide synthase (NOS) expression play a role in pain hypersensitivity and A fibre‐mediated ectopic hyperexcitability following a chronic constriction injury to a rat sciatic nerve. Using immunohistochemical methods we provide evidence for a unique endothelial constitutive nitric oxide synthase (ecNOS) immunoreactivity localized in early axonal endbulb‐like structures of injured peripheral nerve axons. Moreover, we show that following nerve injury there is increased ecNOS‐mRNA expression within the lumbar sympathetic ganglia, and that axoplasmic transport in sympathetic and other axons rather than local non‐neural synthesis accounts for its accumulation in nerve fibres. We also demonstrate here that local inhibition of NOS action with the broad‐spectrum inhibitor NG‐nitro‐l‐arginine‐methyl ester (l‐NAME), but not more specific inhibitors of other NOS isoforms, has stereospecific, dose‐ and time‐dependent analgesic effects that were reversed by local administration of l‐arginine, the natural precursor of NO. In further work, using a teased fibre preparation, we show that administration of l‐NAME, but not d‐NAME, to the injury site also blocks ectopic mechanosensitivity of injured A‐fibres. Our results indicate that an early and transient local ecNOS expression within early axonal endbulb‐like structures, some arising from sympathetic axons, plays a critical role in the development of neuropathic pain.
Upregulation of metabotropic glutamate receptor subtype mGluR3 and mGluR5 in reactive astrocytes in a rat model of mesial temporal lobe epilepsy
Authors: Aronica Eleonora , Van Vliet Erwin A. , Mayboroda Oleg A. , Troost Dirk , Da Silva Fernando H. Lopes , Gorter Jan A.
Published: March 2003

Reactive gliosis is a prominent morphological feature of mesial temporal lobe epilepsy. Because astrocytes express glutamate receptors, we examined changes in metabotropic glutamate receptor (mGluR) 2/3, mGluR5 and transforming growth factor (TGF)‐β in glial cells of the hippocampal regions in an experimental rat model of spontaneous seizures. Rats that exhibited behavioural status epilepticus (SE) directly after 1 h of electrical angular bundle stimulation, displayed chronic spontaneous seizures after a latent period of 1–2 weeks as observed using continuous electrographic monitoring. SE resulted in hypertrophy of astrocytes and microglia activation throughout the hippocampus as revealed by immunolabelling studies. A dramatic, seizure intensity‐dependent increase in vimentin immunoreactivity (a marker for reactive astrocytes) was revealed in CA3 and hilar regions where prominent neuronal loss occurs. Increased vimentin labelling was first apparent 24 h after onset of SE and persisted up to 3 months. mGluR2/3 and mGluR5 protein expression increased markedly in glial cells of CA3 and hilus by 1 week after SE, and persisted up to 3 months after SE. Double immunolabelling of brain sections with vimentin confirmed co‐localization with glial fibrillary acidic protein (GFAP), mGluR2/3 and mGluR5 in reactive astrocytes. TGF‐β, a cytokine implicated in mGluR3‐mediated neuroprotection, was also upregulated during the first 3 weeks after SE throughout the hippocampus. This study demonstrates seizure‐induced upregulation of two mGluR subtypes in reactive astrocytes, which − together with the increased production of TGF‐β − may represent a novel mechanism for modulation of glial function and for changes in glial‐neuronal communication in the course of epileptogenesis.
Evidence for glutamatergic tectotectal neurons in the cat superior colliculus: a comparison with GABAergic tectotectal neurons
Authors: Olivier E. , Corvisier J. , Pauluis Q. , Hardy O.
Published: March 2003

The tectotectal commissural pathway is commonly regarded as responsible for the reciprocal inhibition that takes place between the two superior colliculi (SC). Although this hypothesis has received strong support from electrophysiological studies, more recent investigations have suggested that some collicular cells, e.g. fixation neurons, may establish excitatory connections with cells in the contralateral SC through the collicular commissure. The goal of the present study was to seek immunohistochemical evidence for glutamatergic tectotectal cells in the cat SC by using a double‐labelling technique. Tectotectal cells were retrogradely labelled with wheat germ agglutinin (WGA) –horseradish peroxidase (HRP) coupled to colloidal gold injected in the contralateral SC, and neurons containing glutamate or γ‐aminobutyric acid (GABA) were then identified with immunohistochemical techniques. The present study provides evidence that, in the cat SC, equal numbers of tectotectal cells are immunopositive to glutamate and GABA, suggesting that the tectotectal pathway may consist of two distinct functional components. The finding that an equal number of tectotectal cells are GABAergic and glutamatergic is somewhat surprising as electrophysiological studies have invariantly indicated that the inhibitory component of the tectotectal projection predominates. Another striking feature of the GABAergic and glutamatergic tectotectal cell populations is their identical topographic distribution in the SC. These results suggest that not only cells in the rostral fixation zone establish excitatory connections with the contralateral SC. Tectotectal projections could be potentially important to shape the spatial pattern of saccade‐related activity that may occur simultaneously in the two SC during vertical and oblique orienting movements.
Retinal ganglion cells projecting to the nucleus of the optic tract and the dorsal terminal nucleus of the accessory optic system in macaque monkeys
Authors: Telkes I. , Distler C. , Hoffmann K. ‐P.
Published: March 2003

Using classical neuroanatomical retrograde tracing methods we investigated the retinal ganglion cells projecting to the nucleus of the optic tract and dorsal terminal nucleus of the accessory optic system (NOT‐DTN) in macaque monkeys. Our main aim was to quantify the strength of the projection from the ipsilateral retina to the NOT‐DTN. We therefore examined the number, distribution, and soma size of retinal ganglion cells involved in this projection. Electrophysiologically controlled small injections into the NOT‐DTN revealed a clearly bilateral retinal projection originating mainly from the central retina but also involving peripheral retinal regions. Labelled cells were found nasally in the contralateral retina and temporally in the ipsilateral retina with some overlap in the fovea. The projection from the ipsilateral retina was 36–43% of that from the contralateral retina. On average, only 1–6% of the local population of ganglion cells projected to the NOT‐DTN. Small soma size and large dendritic fields imply that in monkey rarely encountered, ‘specialized’ ganglion cells provide the direct retinal input to the accessory optic system (AOS). These results are discussed with respect to the symmetry of monocular horizontal optokinetic nystagmus (OKN) in primates.
Dedifferentiation of intrinsic response properties of motoneurons in organotypic cultures of the spinal cord of the adult turtle
Authors: Perrier Jean‐François , Noraberg Jens , Simon Magda , Hounsgaard Jørn
Published: March 2003

Explant cultures from the spinal cord of adult turtles were established and used to study the sensitivity of the intrinsic response properties of motoneurons to the changes in connectivity and milieu imposed by isolation in culture. Transverse sections 700 μm thick were explanted on cover slips and maintained in roller‐tube cultures in medium containing serum and the growth factors brain‐derived neurotrophin factor (BDNF), neurotrophin‐3 (NT3), glial cell line‐derived neurotrophic factor (GDNF) and ciliary neurotrophic factor (CNTF). The gross morphology of acute sections was maintained after 4 weeks in culture. Cell bodies of motoneurons remained stainable in fixed cultures with an antibody against choline acetyltransferase (ChAT) throughout the culture period. During culture, motoneurons maintained stable resting membrane potentials and were contacted by functional synapses. The ability to generate action potentials was also preserved as was delayed inward rectification and generation of calcium spikes in the presence of tetra‐ethyl ammonium (TEA). In response to depolarization, however, motoneurons presented strong outward rectification, and only 41% of the cells recorded from maintained the ability to fire repetitively. By the second week in culture, a fraction of motoneurons displayed fast and slow transient outward rectification and low‐threshold calcium spikes, features not seen in turtle motoneurons in acute slices. On the other hand, properties mediated by L‐type Ca2+ channels disappeared during the first few days in culture. Our observations show that the phenotypical intrinsic response properties of mature spinal motoneurons are modified in explant cultures. The properties acquired resemble the properties in juvenile motoneurons in several species of terrestrial vertebrates.
The morphological development of neurons derived from EGF‐ and FGF‐2‐driven human CNS precursors depends on their site of integration in the neonatal rat brain
Authors: Rosser Anne E. , Tyers Pamela , Dunnett Stephen B.
Published: March 2003

Neural precursor cells derived from the developing human brain were expanded in vitro under the influence of fibroblast growth factor‐2 (FGF‐2) and epidermal growth hormone (EGF), and were then transplanted into different regions of the neonatal rat brain. Four weeks later neurons were seen to have developed from human embryonic precursors, using a human‐specific antibody to tau (htau). There were morphological differences between implanted neurons developing in the hippocampus, striatum and neocortex, which were confirmed by cell volume measurements, although no specific neurochemical phenotypes were identified. Htau‐positive fibres were seen to project extensively along fibre pathways appropriate for the site of neuronal integration. This study demonstrates that, following cell division in vitro, neurons differentiating from human precursor cell populations retain the ability to respond appropriately to regional determinants present in the neonatal rat brain. This is important for the application of such cells in CNS repair strategies, in particular neural transplantation.
Enhancement of persistent Na+current by sea anemone toxin (ATX II) exerts dual action on hippocampal excitability
Authors: Brand Sabine , Seeger Thomas , Alzheimer Christian
Published: March 2003

We used anemone toxin II (ATX II) to study how a selective enhancement of persistent Na+current (INaP) would affect the excitability of CA1 pyramidal neurons in the hippocampal slice. In whole‐cell recordings from CA1 cell somata, local application of ATX II (10 μm) into the stratum pyramidale invariably depolarized the neurons and produced sustained burst discharges with depolarizing plateau potentials of variable amplitude and length. However, the strong excitatory action of ATX II, observed on the single cell level, was not mirrored in field potential recordings from the same hippocampal subfield. The amplitude of the electrically evoked population spike declined, reflecting the decreased availability of fast Na+channels, and the intracellulary recorded burst discharges were not detected by the field electrode. The lacking synchronization of cellular bursting activity was seen during both local and bath application of ATX II, suggesting that the toxin, in addition to promoting burst discharges of individual neurons, simultaneously dampens network excitability. In fact, ATX II reduced afferent fibre volleys (reflecting axonal excitability) and field excitatory postsynaptic potentials (EPSPs) in a similar fashion. As the expression of different Na+channel subtypes appears to be compartmentalized within hippocampal neurons, we propose that point mutations leading to pathologically enhanced INaPmight exert quite opposite effects, depending on the type and location of the Na+channel affected. Whereas alterations of somatodendritic Na+channels would give rise to bursting activity, alterations of axonal Na+channels would primarily decrease network excitability.
Porcine neural progenitors require commitment to the oligodendrocyte lineage prior to transplantation in order to achieve significant remyelination of demyelinated lesions in the adult CNS
Authors: Smith P. M. , Blakemore W. F.
Published: March 2003

Glial cell transplantation is a potential therapy for human demyelinating disease, though obtaining large numbers of oligodendrocyte precursors from nonrodent species is currently problematic. Culturing of multipotent neural progenitors may provide a solution to this problem, because these cells can be expanded in vitro whilst retaining the ability to differentiate into both neurons and glial cells. In order to investigate the myelinating capability of multipotent neural progenitors, we isolated cells from the porcine subventricular zone, a region rich in neural progenitors, and transplanted them into areas of persistent demyelination in the spinal cord of immunosuppressed rats, created by the injection of ethidium bromide and subsequent exposure to 40 Gy X‐irradiation. Porcine SVZ cells were transplanted either within 12 h of isolation or after 7 days in B104‐conditioned medium. Freshly isolated cells did not mature into myelinating oligodendrocytes following transplantation and instead remained as clusters of undifferentiated progenitors. However, cells exposed to B104‐conditioned medium prior to transplantation were able to effect complete remyelination of the demyelinated axons. This suggests that neural progenitors must be manipulated in vitro for commitment to the oligodendrocyte lineage prior to transplantation if significant remyelination is to be achieved.
Calcium mobilization elicited by two types of nicotinic acetylcholine receptors in mouse substantia nigra pars compacta
Authors: Tsuneki Hiroshi , Klink Ruby , Léna Clément , Korn Henri , Changeux Jean‐Pierre
Published: March 2003

Nicotinic acetylcholine receptors (nAChRs) are expressed in the midbrain ascending dopaminergic system, a target of many addictive drugs. Here we assessed the intracellular Ca2+ level by imaging fura‐2‐loaded cells in substantia nigra pars compacta in mouse brain slices, and we examined the influence on this level of prolonged exposures to nicotine using mice lacking the nAChR β2‐subunit. In control cells, superfusion with nicotine (10–100 μm) caused a long‐lasting rise of intracellular Ca2+ level which depended on extracellular Ca2+. This nicotinic response was almost completely absent in β2–/– mutant mice, leaving a small residual response to a high concentration (100 μm) of nicotine which was inhibited by the α7‐subunit‐selective antagonist, methyllycaconitine. Conversely, the α7‐subunit‐selective agonist choline (10 mm) caused a methyllycaconitine‐sensitive increase in intracellular Ca2+ level both in wild‐type and β2–/– mutant mice. Nicotine‐elicited Ca2+ mobilization was reduced by the Na+ channel blocker tetrodotoxin (TTX) and by T‐type Ca2+ channel blocking agents, whereas the choline‐elicited Ca2+ increase was insensitive to TTX. Neither nicotine nor choline produced Ca2+ increase following inhibition of the release of Ca2+ from intracellular stores by dantrolene. These results demonstrate that in nigral dopaminergic neurons, nicotine can elicit Ca2+ mobilization via activation of two distinct nAChR subtypes: that of β2‐subunit‐containing nAChR followed by activation of Na+ channel and T‐type Ca2+ channels, and/or activation of α7‐subunit‐containing nAChR. The Ca2+ influx due to nAChR activation is subsequently amplified by the recruitment of intracellular Ca2+ stores. This Ca2+ mobilization may possibly contribute to the long‐term effects of nicotine on the dopaminergic system.
SDF‐1α‐mediated modulation of synaptic transmission in rat cerebellum
Authors: Limatola Cristina , Giovannelli Aldo , Maggi Laura , Ragozzino Davide , Castellani Loriana , Ciotti Maria Teresa , Vacca Fabrizio , Mercanti Delio , Santoni Angela , Eusebi Fabrizio
Published: March 2003

The functional expression of the seven‐transmembrane domain G protein‐coupled chemokine receptor CXCR‐4/fusin in rat nerve cell was demonstrated by staining with a polyclonal anti‐CXCR‐4 Ab, and by evaluating the calcium responses to the physiological agonist stromal‐derived cell factor‐1α (SDF‐1α) in both cerebellar granule cells in culture and Purkinje neurons (PNs) in cerebellar slices. Cerebellar glial, granule and Purkinje cells showed a pronounced staining for CXCR‐4. Furthermore, cultured granule cells exhibited Ca2+ transients elicited by the application of SDF‐1α, both in cell bodies and in neuronal processes. Whole‐cell patch‐clamped PNs in cerebellar slices responded to SDF‐1α application by a slow inward current followed by an increase of both intracellular Ca2+ level and spontaneous synaptic activity. In particular, the SDF‐1α‐induced slow inward current was considerably reduced by ionotropic glutamate receptor blockers, but developed fully in a medium in which synaptic transmission was inhibited, indicating that this current might be, at least in part, mediated by extrasynaptic glutamate, possibly released from the surrounding glial and/or nerve cells. Taken together, these findings indicate a functional involvement of CXCR‐4 in the modulation of synaptic transmission, adding another member to the repertoire of the chemokine receptors exerting a neuromodulatory role in the cerebellum.
Inflammatory cytokines and related genes are induced in the rat hippocampus by limbic status epilepticus
Authors: De Simoni Maria Grazia , Perego Carlo , Ravizza Teresa , Moneta Daniela , Conti Mirko , Marchesi Francesco , De Luigi Ada , Garattini Silvio , Vezzani Annamaria
Published: March 2003

Limbic status epilepticus was induced in rats by unilateral 60‐min electrical stimulation of the CA3 region of the ventral hippocampus. As assessed by RT‐PCR followed by Southern blot analysis, transcripts of interleukin‐1β, interleukin‐6, interleukin‐1 receptor antagonist and inducible nitric oxide synthase were significantly increased 2 h after status epilepticus in the stimulated hippocampus. Induction was maximal at 6 h for interleukin‐1β (445%), interleukin‐6 (405%) and tumour necrosis factor‐α (264%) and at 24 h for interleukin‐1 receptor antagonist (494%) and inducible nitric oxide synthase (432%). In rats with spontaneous seizures (60 days after status epilepticus), interleukin‐1β mRNA was still higher than controls (241%). Immunocytochemical staining of interleukin‐1β, interleukin‐6 and tumour necrosis factor‐α was enhanced in glia with a time‐course similar to that of the respective transcripts. Sixty days after status epilepticus, interleukin‐1β immunoreactivity was increased exclusively in neurons in one third of the animals. Multiple intracerebroventricular injections of interleukin‐1 receptor antagonist (0.5 μg/3 μL) significantly decreased the severity of behavioural convulsions during electrical stimulation and selectively reduced tumour necrosis factor‐α content in the hippocampus measured 18 h after status epilepticus. Thus, the induction of spontaneously recurring seizures in rats involves the activation of inflammatory cytokines and related pro‐ and anti‐inflammatory genes in the hippocampus. These changes may play an active role in hyperexcitability of the epileptic tissue.
Intracerebral infusion of 3H‐dopamine and 3H‐mannitol in the striatum of halothane‐anaesthetized male rats.A dual‐probe microdialysis study of long‐distance diffusion
Authors: Höistad M. , Kehr J. , Andbjer B. , Jansson A. , Fuxe K.
Published: March 2003

This report characterizes an in vivo intracerebral long‐distance diffusion model using dual‐probe microdialysis. Two probes 1 mm apart were implanted into the striatum of control and 6‐hydroxydopamine (6‐OHDA)‐lesioned halothane‐anaesthetized male rats. Either tritiated dopamine (500 n m3H‐DA) or mannitol (1.5 μm3H‐mannitol) was infused continuously for 5 h, while samples were collected from the other probe. Samples (10 μl) were counted by liquid scintillation. For the DA‐infused rats, another 10 μL was separated with high‐pressure liquid chromatography (HPLC)–electrochemical detection into individual fractions containing 3,4‐dihydroxy phenylacetic acid (DOPAC) and homovanillinic acid (HVA), and counted for β‐decay. The total transfer of 3H‐labelled compounds described the overall effect of cellular uptake, metabolism and clearance into the microcirculation, and was compared with that of an extracellular marker, 3H‐mannitol. The migration reached steady‐state levels, generating an equilibrium between delivery and removal from the extracellular space. The half‐time of the steady‐state values, t50%, was in all cases lower in 6‐OHDA‐treated rats compared with control. In addition, the t50% values of 3H‐mannitol were lower than those following the 3H‐dopamine infusion in both control or 6‐OHDA‐lesioned rats. However, it was not possible to detect any unmetabolized 3H‐dopamine at the 1 mm distance. In conclusion, the dual‐probe microdialysis approach proved to be a valid method to study in vivo diffusion and migration in the brain, and the intracerebral spread of compounds highly depends on the nature of the compound infused.
Functional organization of auditory cortex in the Mongolian gerbil (Meriones unguiculatus). IV. Connections with anatomically characterized subcortical structures
Authors: Budinger Eike , Heil Peter , Scheich Henning
Published: March 2003

The subcortical connections of the four tonotopically organized fields of the auditory cortex of the Mongolian gerbil, namely the primary (AI), the anterior (AAF), the dorsoposterior (DP) and the ventroposterior field (VP), were studied predominantly by anterograde transport of biocytin injected into these fields. In order to allow the localization of connections with respect to subdivisions of subcortical auditory structures, their cyto‐, fibre‐ and chemoarchitecture was characterized using staining methods for cell bodies, myelin and the calcium‐binding protein parvalbumin. Each injected auditory cortical field has substantial and reciprocal connections with each of the three subdivision of the medial geniculate body (MGB), namely the ventral (MGv), dorsal (MGd) and medial division (MGm). However, the relative strengths of these connections vary: AI is predominantly connected with MGv, AAF with MGm and MGv, and DP and VP with MGd and MGv. The connections of at least AI and MGv are topographic: injections into caudal low‐frequency AI label laterorostral portions of MGv, whereas injections into rostral high‐frequency AI label mediocaudal portions of MGv. All investigated auditory fields send axons to the suprageniculate, posterior limitans, laterodorsal and lateral posterior thalamic nuclei, with strongest projections from DP and VP, as well as to the reticular and subgeniculate thalamic nuclei. AI, AAF, DP and VP project to all three subdivisions of the inferior colliculus, namely the dorsal cortex, external cortex and central nucleus ipsilaterally and to the dorsal and external cortex contralaterally. They also project to the deep and intermediate layers of the ipsilateral superior colliculus, with strongest projections from DP and VP to the lateral and basolateral amygdaloid nuclei, the caudate putamen, globus pallidus and the pontine nuclei. In addition, AAF and particularly DP and VP project to paralemniscal regions around the dorsal nucleus of the lateral lemniscus (DNLL), to the DNLL itself and to the rostroventral aspect of the superior olivary complex. Moreover, DP and VP send axons to the dorsal lateral geniculate nucleus. The differences with respect to the existence and/or relative strengths of subcortical connections of the examined auditory cortical fields suggest a somewhat different function of each of these fields in auditory processing.
Synaptic stimulation of nicotinic receptors in rat sympathetic ganglia is followed by slow activation of postsynaptic potassium or chloride conductances
Authors: Sacchi Oscar , Rossi Maria Lisa , Canella Rita
Published: March 2003

Two slow currents have been described in rat sympathetic neurons during and after tetanization of the whole preganglionic input. Both effects are mediated by nicotinic receptors activated by native acetylcholine (ACh). A first current, indicated as IAHPsyn, is calcium dependent and voltage independent, and is consistent with an IAHP‐type potassium current sustained by calcium ions accompanying the nicotinic synaptic current. The conductance activated by a standard synaptic train was ∼ 3.6 nS per neuron; it was detected in isolation in 14 out of a 52‐neuron sample. A novel current, IADPsyn, was described in 42/52 of the sample as a post‐tetanic inward current, which increased in amplitude with increasing membrane potential negativity and exhibited a null‐point close to the holding potential and the cell momentary chloride equilibrium potential. IADPsyn developed during synaptic stimulation and decayed thereafter according to a single exponential (mean τ = 148.5 ms) in 18 neurons or according to a two‐exponential time course (τ = 51.8 and 364.9 ms, respectively) in 19 different neurons. The mean peak conductance activated was ∼ 20 nS per neuron. IADPsyn was calcium independent, it was affected by internal and external chloride concentration, but was insensitive to specific blockers (anthracene‐9‐carboxylic acid, 9AC) of the chloride channels open in the resting neuron. It is suggested that gADPsyn represents a specific chloride conductance activatable by intense nicotinic stimulation; in some neurons it is even associated with single excitatory postsynaptic potentials (EPSCs). Both IAHP and IADPsyn are apparently devoted to reduce neuronal excitability during and after intense synaptic stimulation.
Identification of an opioid peptide secreted by rat embryonic mixed brain cells as a promoter of macrophage migration
Authors: Calvo Charles‐Félix , Cesselin François , Gelman Michèle , Glowinski Jacques
Published: March 2003

Conditioned media from embryonic mixed cells from the rat brain were used in a chemotaxis assay to look for potential chemotactic activity which could account for the infiltration of the developing central nervous system (CNS) by macrophage precursors. The most potent chemotactic activity was found in the conditioned medium from E17 mixed brain cells (E17‐CM). Based upon checkerboard analysis, this activity was shown to be chemotactic rather than chemokinetic. This chemoattraction was not restricted to brain macrophages (BM) because it was as pronounced on bone marrow‐derived macrophages. The implication of a peptide compound in this activity was suggested by its resistance to heat as well as acid treatments, and by its sensitivity to aminopeptidase M digestion. In agreement with the opioid nature of the peptide, not only naloxone, but also the delta opioid receptor antagonist ICI‐174 reduced the migration of BM in response to E17‐CM by 60%. This migratory activity was no longer effective when pertussis toxin‐treated BM were used. When the chemotactic effects of selective opioid agonists were compared to that of E17‐CM, DPDPE, the delta agonist, was the most efficient in attracting BM. Reverse transcriptase‐polymerase chain reaction (RT‐PCR) analysis indicated that delta as well as other known opioid receptors were expressed in both BM and E17 mixed brain cells. Finally, a Met‐enkephalin‐like reactivity was found by RIA in the E17‐CM. Altogether, these observations suggest that a delta‐like opioid peptide released from embryonic mixed brain cells could be responsible for the infiltration of the developing CNS by macrophages precursors.
Synaptically released 5‐HT modulates the activity of tonically discharging neuronal populations in the rostral ventral medulla (RVM)
Authors: Piguet Pascale , Stoeckel Marie‐Elisabeth , Schlichter Rémy
Published: March 2003

There is substantial evidence for an important modulating role of monoamines (catecholamines and serotonin, 5‐HT) in the rostral ventral medulla (RVM), a region which plays an important role in cardiovascular and nociceptive functions. We investigated in slices the role of endogenous monoamines in the synaptic control of the activity of rat RVM neuronal populations using intracellular recordings in the lateral RVM plus lateral aspect of nucleus paragigantocellularis lateralis. A triple‐labelling protocol allowed us to identify the location of impaled neurons and their eventual monoaminergic phenotype within the serotonergic and catecholaminergic populations of the RVM. Focal electrical stimulation revealed the existence of a functional monoaminergic input onto RVM neurons which was mediated by endogenous 5‐HT acting at inhibitory 5‐HT1A receptors but did not involve noradrenergic neurotransmission. The slow 5‐HT‐mediated inhibitory postsynaptic potential (IPSP) was only observed in the regularly discharging neurons, which were found to be neither catecholaminergic nor serotonergic. The synaptic release of 5‐HT was, itself, under an inhibitory control involving GABAA (γ‐aminobutyric acid) receptors. Moreover, we characterized the effect of the 5‐HT‐releasing agent fenfluramine on this functional 5‐HT‐mediated synaptic transmission. Our results show that the effect of fenfluramine is biphasic consisting of an initial prolongation of the serotonergic IPSP followed by a decrease in amplitude. Our data provide a basis for the previously reported inhibitory effects of exogenously applied serotonin agonists/antagonists on the autonomic functions controlled by the RVM. This 5‐HT pathway, which functionally links the serotonergic and catecholaminergic regions, might play an important role in cardiovascular and nociceptive functions.
Running and cocaine both upregulate dynorphin mRNA in medial caudate putamen
Authors: Werme Martin , Thorén Peter , Olson Lars , Brené Stefan
Published: March 2003

Physical activities such as long‐distance running can be habit forming and associated with a sense of well‐being to a degree that justifies comparison with drug‐induced addictive behaviours. To understand molecular similarities and dissimilarities controlling these behaviours in humans we compared the effects of running in running wheels to the effects of chronic cocaine or morphine administration on mRNA levels in brain reward pathways in the inbred Fischer and Lewis rat strains. These strains are both inbred from the Sprague–Dawley strain; Lewis rats display a higher preference towards addictive drugs and running than do Fischer rats. After chronic cocaine or running a similar increase of dynorphin mRNA in medial caudate putamen was found in the Lewis rat, suggesting common neuronal adaptations in this brain region to both cocaine and running. Fischer and Lewis rats both responded to cocaine with increased dynorphin mRNA levels in medial caudate putamen. However, only Lewis rats increased dynorphin mRNA after running, possibly reflecting the much higher degree of running by the Lewis strain as compared to the Fischer strain. Moreover, the running‐induced upregulation of dynorphin mRNA was blocked by the opioid receptor antagonist naloxone. We suggest that running increases dynorphin mRNA by a mechanism that involves endogenous opioids. The voluntary wheel‐running model in rats might be used to study natural reward and compulsive behaviours and possibly also to screen candidate drugs for treatment of compulsive disorders.
Stage of specification of the spinal cord and tectal projections from cortical grafts
Authors: Pinaudeau Cécile , Gaillard Afsaneh , Roger Michel
Published: March 2003

In order to determine the embryonic age at which the hodological phenotype developed by neocortical cells is specified, we have examined the spinal or tectal projections developed by embryonic (E) grafts of presumptive frontal or occipital neocortex placed into the frontal or occipital neocortex of newborn host rats. Grafts of E13, E14 and E16 cells of the frontal cortex transplanted into the occipital cortex of newborns are capable of developing and maintaining in adulthood a spinal cord axon. Grafts of E12 cells do not project to the spinal cord but send fibres to the superficial layers of the tectum. In addition, following transplantation into the frontal cortex, early embryonic (E12) cells from the presumptive occipital cortex are capable of differentiating into neurons with spinal cord projection but are practically incapable of developing a tectal projection. When grafted at E14 into the frontal cortex, occipital cells lose the capacity to project to the spinal cord but become able to send fibres to the tectum. Taken together, these findings indicate that young (E12) embryonic frontal and occipital cortical cells are competent to subsequently differentiate into neurons projecting to the spinal cord or tectum according to instructive signals available in the cortical territory where they complete their development. By E13/E14, some cortical cells are specified and their capacity to contact targets that are not appropriate to their embryonic origin is much reduced. These findings are consistent with the notion that cortical specification involves progressive restriction in cell multipotentiality and fate specification toward region‐specific phenotypes.
Regulation of NGF‐family ligands and receptors in adulthood and senescence: correlation to degenerative and regenerative changes in cutaneous innervation
Authors: Bergman Esbjörn , Ulfhake Brun , Fundin Bengt T.
Published: March 2003

During development, a highly differential neurotrophin dependency is reported for various types of nerve endings in the whisker follicle. To what extent these dependencies extend and play a role in adulthood is largely unresolved. We show here, using in situ hybridization and immunohistochemistry that the expression of neurotrophins and trk/p75 receptors persists in adulthood. As suggested by their expression profiles, many classes of cutaneous nerve endings disclose similar ligand–receptor dependencies in adult animals as during development, while other populations appear to switch their dependency. Furthermore, our data suggest that sensory endings that have a high turnover due to mechanical wear and tear, e.g. Merkel cell–neurite complexes at the level of ring sinus show a more complex ligand–receptor expression phenotype than do endings with a less vulnerable location, e.g. the Merkel cell–neurite complexes at the rete ridge collar. Thus, neurotrophin‐3 (NT3)/trkA signalling is suggested to be important for a continuous terminal plasticity of Merkel cell–neurite complexes at the level of ring sinus in adulthood. Evidence supporting a role for neurotrophin signalling in maintaining the adult cutaneous innervation also comes from the close correlation between altered ligand–receptor expression(s) and axonal/terminal aberrations in senescence. Thus, an ageing‐related decrease in target neurotrophin expression, notably NT3 and NT4, results in a site‐specific loss of sensory terminals concomitant with an aberrant growth of regenerating/sprouting axons into new target fields. Ageing of the cutaneous innervation, manifested in degenerative and regenerative events, seems strongly associated with changes in neurotrophic interactions between sensory neurons and target tissues.
Aberrant trajectory of entorhino‐dentate axons in the mutant Shaking Rat Kawasaki: a DiI‐labelling study
Authors: Woodhams Peter L. , Terashima Toshio
Published: March 2003

The Shaking Rat Kawasaki (SRK) is a neurological mutant that exhibits abnormalities of cell migration and lamination, with many similarities to the mouse reeler mutant. We recently used lamina‐specific antibody staining to show that despite severe aberrations in the laminar organization of the SRK dentate gyrus, the entorhinal terminal field in the outer dentate molecular layer appeared relatively normal (Woodhams & Terashima, 1999, J. Comp. Neurol. 409 p57). However, neurofilament immunostaining suggested that entorhino‐dentate afferents take an abnormal trajectory in reaching their appropriate targets, the granule cells dendrites. In the present study, anterograde tracing with the carbocyanine dye 1,1′‐dioctadecyl‐3,3,3′,3′‐tetramethylindocarbocyanine perchlorate (DiI) has been used to delineate directly the path that entorhinal axons take to the dentate gyrus, confirming that in SRK entorhinal axons do indeed reach their appropriate terminal fields in the molecular layer, with laminar segregation between projections from the lateral and medial entorhinal cortices. However, these fibres fail to cross the hippocampal fissure between the subiculum and the dentate gyrus, coursing instead parallel to it until they curve round the deepest point of the fissure in field CA3. Similar findings were seen in the murine reeler mutant. Insertion of DiI crystals into the entorhinal cortex of neonatal rats also retrogradely labelled the developmentally transient Cajal–Retzius cells at the hippocampal fissure; these survive for longer in SRK than in normal littermates. The presence of a marked astrogliosis at the SRK hippocampal fissure may play a part in determining the abnormal trajectory taken by entorhino‐dentate afferents in this mutant.
Single‐cell mRNA expression of HCN1 correlates with a fast gating phenotype of hyperpolarization‐activated cyclic nucleotide‐gated ion channels (Ih) in central neurons
Authors: Franz Oliver , Liss Birgit , Neu Axel , Roeper Jochen
Published: March 2003

Hyperpolarization‐activated currents (Ih) are key players in shaping rhythmic neuronal activity. Although candidate genes for Ih channels have been cloned (HCN1–HCN4), the subunit composition of different native Ih channels is unknown. We used a combined patch‐clamp and qualitative single‐cell reverse transcription multiplex polymerase chain reaction (RT‐mPCR) approach to analyse HCN1–4 coexpression profiles in four neuronal populations in mouse CNS. Coexpression of HCN2, HCN3 and HCN4 mRNA was detected in single neurons of all four neuronal cell types analysed. In contrast, HCN1 mRNA was detected in neocortical and hippocampal pyramidal neurons but not in dopaminergic midbrain and thalamocortical neurons. HCN1 expression was correlated with significantly faster activation kinetics on the level of individual neurons. Semiquantitative single‐cell RT‐mPCR analysis demonstrated that HCN1 mRNA expression is at least eightfold higher in cortical neurons than subcortical neurons. We show that single neurons possess complex coexpression patterns of Ih candidate genes. Alternative expression of HCN1 is likely to be an important molecular determinant to generate the different neuronal Ih channel species adapted to tune either subcortical or cortical network activity.