bluuebunny/crossref_metadata_2025 huggingface dataset:
Substantia nigra pars reticulata neurons code initiation of a serial pattern: implications for natural action sequences and sequential disorders
Authors: Meyer‐Luehmann Melanie , Thompson Jeffrey F. , Berridge Kent C. , Aldridge J. Wayne
Published: March 2003

Sequences of movements are initiated abnormally in neurological disorders involving basal ganglia dysfunction, such as Parkinson's disease or Tourette's syndrome. The substantia nigra pars reticulata (SNpr) is one of the two primary output structures of the basal ganglia. However, little is known about how substantia nigra mediates the initiation of normal movement sequences. We studied its role in coding initiation of a sequentially stereotyped but natural movement sequence by recording neuronal activity in SNpr during behavioural performance of ‘syntactic grooming chains’. These are rule‐governed sequences of up to 25 grooming movements emitted in four predictable (syntactic) phases, which occur spontaneously during grooming behaviour by rats and other rodents. Our results show that neuronal activation in central SNpr codes the onset of this entire rule‐governed sequential pattern of grooming actions, not elemental grooming movements. We conclude that the context of sequential pattern may be more important than the elemental motor parameters in determining SNpr neuronal activation.
Changes in Fos expression in the rat brain after unilateral lesions of the anterior thalamic nuclei
Authors: Jenkins Trisha A. , Dias Rebecca , Amin Eman , Aggleton John P.
Published: March 2003

Activity of the immediate early gene c‐fos was compared across hemispheres in rats with unilateral anterior thalamic lesions. Fos protein was quantified after rats performed a spatial working memory test in the radial‐arm maze, a task that is sensitive to bilateral lesions of the anterior thalamic nuclei. Unilateral anterior thalamic lesions produced evidence of a widespread hippocampal hypoactivity, as there were significant reductions in Fos counts in a range of regions within the ipsilateral hippocampal formation (rostral CA1, rostral dentate gyrus, ‘dorsal’ hippocampus, presubiculum and postsubiculum). A decrease in Fos levels was also found in the rostral and caudal retrosplenial cortex but not in the parahippocampal cortices or anterior cingulate cortices. The Fos changes seem most closely linked to sites that are also required for successful task performance, supporting the notion that the anterior thalamus, retrosplenial cortex and hippocampus form key components of an interdependent neuronal network involved in spatial mnemonic processing.
The roles of the cerebellum and basal ganglia in timing and error prediction
Authors: Dreher Jean‐Claude , Grafman Jordan
Published: March 2003

Recent evidence that the cerebellum and the basal ganglia are activated during the performance of cognitive and attention tasks challenges the prevailing view of their primary function in motor control. The specific roles of the basal ganglia and the cerebellum in cognition, however, have been difficult to identify. At least three functional hypotheses regarding their roles have been proposed. The first hypothesis suggests that their main function is to switch attentional set. The second hypothesis states that they provide error signals regarding stimuli or rewards. The third hypothesis is that they operate as an internal timing system, providing a precise representation of temporal information. Using functional magnetic resonance imaging, we tested these three hypotheses using a task‐switching experiment with a 2 × 2 factorial design varying timing (random relative to fixed) and task order (unpredictable relative to predictable). This design allowed us to test whether switching between tasks, timing irregularity and/or task order unpredictability activate the basal ganglia and/or the cerebellum. We show that the cerebellum is primarily activated with timing irregularity while the anterior striatum is activated with task order unpredictability, supporting their distinctive roles in two forms of readjustment. Task order unpredictability alone, independent of reward delivery, is sufficient to induce striatal activation. In addition, activation of the cerebellum and basal ganglia were not specific to switching attention because these regions were both activated during switching between tasks and during the simultaneous maintenance of two tasks without switching between them.
A novel stereocilia defect in sensory hair cells of the deaf mouse mutant Tasmanian devil
Authors: Erven Alexandra , Skynner Michael J. , Okumura Katsuzumi , Takebayashi Shin‐ichiro , Brown Steve D. M. , Steel Karen P. , Allen Nicholas D.
Published: March 2003

Stereocilia are specialized actin‐filled, finger‐like processes arrayed in rows of graded heights to form a crescent or W‐shape on the apical surface of sensory hair cells. The stereocilia are deflected by the vibration of sound, which opens transduction channels and allows an influx of ions to depolarize the hair cell, in turn triggering synaptic activity. The specialized morphology and organization of the stereocilia bundle is crucial in the process of sensory transduction in the inner ear. However, we know little about the development of stereocilia in the mouse and few molecules that are involved in stereocilia maturation are known. We describe here a new mouse mutant with abnormal stereocilia development. The Tasmanian devil (tde) mouse mutation arose by insertional mutagenesis and has been mapped to the middle of chromosome 5. Homozygotes show head‐tossing and circling and have raised thresholds for cochlear nerve responses to sound. The gross morphology of the inner ear was normal, but the stereocilia of cochlear and vestibular hair cells are abnormally thin, and they become progressively disorganized with increasing age. Ultimately, the hair cells die. This is the first report of a mutant showing thin stereocilia. The association of thin stereocilia with cochlear dysfunction emphasizes the critical role of stereocilia in auditory transduction, and the discovery of the Tasmanian devil mutant provides a resource for the identification of an essential molecule in hair cell function.
Impaired acquisition in the water maze and hippocampal long‐term potentiation after chronic prenatal ethanol exposure in the guinea‐pig
Authors: Richardson D. P. , Byrnes M. L. , Brien J. F. , Reynolds J. N. , Dringenberg H. C.
Published: March 2003

In the hippocampus, the CA1 region is selectively vulnerable to the effects of chronic prenatal ethanol exposure. In the guinea‐pig, the number of CA1 pyramidal cells is decreased after chronic prenatal ethanol exposure. We tested the hypotheses that chronic prenatal ethanol exposure (through maternal ethanol ingestion) results in impairments in spatial learning and short‐ and long‐term plasticity in the CA1 region of the postnatal guinea‐pig hippocampus. Timed, pregnant guinea‐pigs were treated with ethanol (4 g/kg maternal body weight/day), isocaloric sucrose/pair‐feeding, or water throughout gestation. Offspring were studied between postnatal days 40 and 80. In the Morris water maze, animals exposed to ethanol prenatally showed slower acquisition of an escape response to a hidden platform over 5 days of training. The amplitude of the field excitatory postsynaptic potential in the CA1 region in response to contralateral CA3 stimulation was decreased in offspring exposed to ethanol prenatally. Two forms of short‐term plasticity (paired‐pulse and frequency facilitation) were unaffected by chronic prenatal ethanol exposure. Long‐term potentiation (LTP) in response to high‐frequency CA3 stimulation was induced reliably and maintained over 60 min in isocaloric‐sucrose and water control animals. However, LTP failed to be induced in the CA1 area of the hippocampus in prenatal ethanol‐exposed offspring. These data show that chronic prenatal ethanol exposure, through maternal ethanol administration, impairs spatial performance and LTP in CA1 neurons. Hippocampal dysfunction could contribute importantly to the cognitive and behavioural deficits resulting from chronic prenatal ethanol exposure.
Development of two transmitter release components during the critical period for imprinting in the chick IMHV
Authors: Kiyosue Kazuyuki , Shimabayashi Eiko , Taguchi Takahisa
Published: March 2003

Transmitter release at an excitatory synapse has two components, fast synchronous and slow asynchronous transmitter release. Using the whole cell recording technique, we investigated the developmental properties of neurotransmitter release, which is composed of the two components in the intermediate and medial part of the hyperstriatum ventral (IMHV) of chicks during the critical period for imprinting. Analysis of the paired‐pulse responses revealed that the depression of the excitatory postsynaptic currents (EPSCs), driven mainly by fast synchronous release, was frequently observed in P0–1 chicks but not in those at P5–8. The spontaneous excitatory postsynaptic currents (sEPSCs) after the paired‐pulse stimulation, which were thought to be driven by asynchronous transmitter releases, were observed more frequently in P0–1 chicks than P5–8 chicks. Furthermore, examination of Ca2+ dependency in the evoked EPSCs showed that the amplitudes in P5–8 chicks were more sensitive to reduction of the extracellular Ca2+ concentration than younger chicks. Considering that the Ca2+ dependency of EPSCs is defined by both Ca2+ sensitivity and the proportion of each type of release machineries at the release site, these results indicate that the ratio of fast synchronous to slow asynchronous transmitter release machinery changed during the critical period. These changes may play critical roles in the capacity of the avian brain to consolidate novel experience in the immediate period after hatching.
Microarray analysis suggests the involvement of proteasomes, lysosomes, and matrix metalloproteinases in the response of motor neurons to root avulsion
Authors: Hu Jian , Fink David , Mata Marina
Published: March 2003

We used microarray analysis of RNA expression from punch samples from ventral horn of spinal cord to identify alterations in gene expression in motor neurons 3 days after proximal spinal root avulsion, a traumatic injury that results in the death of 80% of the motor neurons. This analysis identified the anticipated increases in expression of genes coding for proteins involved in the apoptosis cascades and abortive cell cycle re‐entry, as well as decreases in expression of genes coding for proteins related to neuronal functional activity, including groups of genes related to energy metabolism, transporter proteins, ion channels, and receptors. It was also found that cathepsins, metalloproteinases, and proteasome‐related protein products were highly up‐regulated in motor neurons following axotomy. Each of these products represent pathways that have been implicated in other models of neuronal damage, but which have not previously been described as a response to axotomy.
Mutation in hotfoot‐4J mice results in retention of δ2 glutamate receptors in ER
Authors: Matsuda Shinji , Yuzaki Michisuke
Published: March 2003

The orphan glutamate receptor δ2 is selectively expressed in Purkinje cells and plays a critical role in cerebellar function. Recently, the ataxia of hotfoot‐4J (ho‐4J) mice was shown to be caused by a 170–amino acid deletion in the N‐terminal region of δ2 receptors. To understand δ2 receptor function, we characterized these mutant receptors (δ2ho) in Purkinje cells. Immunohistochemical staining showed that δ2ho receptors of the ho‐4J homozygotes were abundantly expressed but localized to the Purkinje cell soma; in wild‐type mice, δ2 receptors were predominantly present at distal dendrites of Purkinje cells. In addition, δ2ho receptors of the ho‐4J mice were sensitive to endoglycosidase H, a finding suggesting that δ2ho receptors were not transported beyond the endoplasmic reticulum (ER) or cis‐Golgi apparatus. To gain further insights into the mechanisms of this phenomenon, we characterized δ2ho receptors in transfected HEK293 cells. δ2ho receptors expressed in HEK293 cells were also sensitive to endoglycosidase H. Immunohistochemical staining showed that δ2ho receptors colocalized with proteins retained in the ER. Furthermore, δ2ho receptors were not labelled by membrane‐impermeable biotinylation reagents. Coimmunoprecipitation assays showed that the intermolecular interaction of δ2ho receptors was significantly weaker than those of wild‐type δ2 receptors, a finding suggesting that the ho‐4J region is involved in oligomerization of δ2 receptors. Thus, δ2ho receptors were retained in the ER, probably by the quality control mechanism that detects unstable oligomers. We conclude that the absence of δ2 receptors on the cell surface by failed transport from the ER of Purkinje cells causes ataxia.
Upregulation of [3H]methyllycaconitine binding sites following continuous infusion of nicotine, without changes of α7 or α6 subunit mRNA: an autoradiography andin situhybridization study in rat brain
Authors: Mugnaini Manolo , Tessari Michela , Tarter Giorgio , Merlo Pich Emilio , Chiamulera Cristiano , Bunnemann Bernd
Published: March 2003

It is well established that exposure of experimental animals to nicotine results in upregulation of the α4β2‐subtype of neuronal nicotinic acetylcholine receptors (nAChRs). The aim of this study was to determine the effect of nicotine on the levels of α7‐nAChRs in rat brain, for which only partial information is available. Rats were infused with nicotine (3 mg/kg/day) or saline for 2 weeks and their brains processed for receptor autoradiography with [3H]methyllycaconitine (MLA), a radioligand with nanomolar affinity for α7‐nAChRs. In control rats binding was high in hippocampus, intermediate in cerebral cortex and hypothalamus, and low in striatum, thalamus and cerebellum. There was high correlation between the distribution of [3H]MLA binding sites and α7 subunit mRNA (r = 0.816).

 With respect to saline‐treated controls, nicotine‐treated rats presented higher [3H]nicotine binding in 11 out of 15 brain regions analysed (average increase 46 ± 6%). In contrast, only four regions showed greater [3H]MLA binding, among which the ventral tegmental area (VTA) and cingulate cortex (mean increase 32 ± 3%). No changes in α7 mRNA levels were observed after nicotine treatment. Similarly, there was no variation of α6 subunit transcript in the VTA, a region which may contain MLA‐sensitive (non‐α7)‐α6*‐nAChRs (Klinket al., 2001). In conclusion, nicotine increased [3H]MLA binding, although to a smaller extent and in a more restricted regional pattern than [3H]nicotine. The enhancement of binding was not paralleled by a significant change of α7 and α6 subunit transcription. Finally, the present results provide the first anatomical description of the distribution of [3H]MLA binding sites in rat brain.
GABAA receptor heterogeneity in histaminergic neurons
Authors: Sergeeva Olga A. , Eriksson Krister S. , Sharonova Irina N. , Vorobjev Vladimir S. , Haas Helmut L.
Published: March 2003

Histaminergic neurons of the tuberomamillary nucleus display pacemaker properties; their firing rate is regulated according to behavioural state by gabaergic inhibition. Whole‐cell recordings and single‐cell RT‐PCR from acutely isolated rat tuberomamillary neurons were used to characterize GABA ‐evoked currents and to correlate them with the expression pattern of 12 GABAA receptor subunits. We report differences in sensitivity to GABA and zinc as well as in the modulation of IPSC‐decay times by zolpidem in histaminergic neurons expressing γ‐subunits at different levels. Immunocytochemistry and pharmacological analysis of whole‐cell GABA‐currents in these neurons revealed that all carry the γ2‐subunit protein and that all receptors contain at least one γ‐subunit. Neurons with different expression levels of γ‐subunits displayed a difference in cooperativity of GABA and zolpidem binding which we explain by the presence of one vs. two γ‐subunits in one receptor. Thus, we describe here native GABAA receptor function in relation to its stoichiometry.
Effect of melatonin administration on qPer2, qPer3, and qClock gene expression in the suprachiasmatic nucleus of Japanese quail
Authors: Yasuo Shinobu , Yoshimura Takashi , Bartell Paul A. , Iigo Masayuki , Makino Eri , Okabayashi Naritoshi , Ebihara Shizufumi
Published: March 2003

Temporal changes of mRNA expression of three clock genes, qPer2, qPer3 and qClock, were studied in the suprachiasmatic nucleus (SCN) of Japanese quail under different light conditions, as well as under the condition of continuous melatonin. In addition, the expression of melatonin receptor genes, Mel1a and Mel1c, in the SCN were also examined. The expression of qPer2 mRNA showed robust oscillation during both light and dark (LD) 12:12 cycles and under constant dark conditions (DD), but did not exhibit circadian rhythmicity in constant light conditions (LL), instead being expressed at a consistently high level. Expression of qPer3 also showed robust oscillation under both LD and DD conditions. Unlike qPer2 however, qPer3 mRNA expression remained rhythmic under LL conditions. Contrary to the findings on the other clock genes, no remarkable rhythmicity was detectable in either light condition. Both Mel1a and Mel1c mRNAs were detected in the SCN, however, Mel1a mRNA levels were higher than Mel1c and showed daily rhythmicity. Although implantation of melatonin tubes caused constant high levels of plasma melatonin and consequently masked the endogenous daily melatonin rhythm, no significant differences in the expression pattern of any of the three clock genes were observed between birds with and without constant melatonin. In addition, a single injection of melatonin did not affect mRNA expression of these clock genes. These results suggest that melatonin does not affect transcription of clock genes, but may act on the mechanism of synchronization among SCN oscillatory cells.
Long‐lasting enhancement of corticostriatal neurotransmission by taurine
Authors: Chepkova A. N. , Doreulee N. , Yanovsky Y. , Mukhopadhyay D. , Haas H. L. , Sergeeva O. A.
Published: March 2003

Taurine occurs at high concentrations in the forebrain and its distribution varies with (patho)physiological conditions; however, its role in neural function is poorly understood. We have now characterized its effects on corticostriatal synaptic transmission. Bath application of taurine (10 mm) to slices obtained from mice and rats exerted a biphasic action on corticostriatal field potentials. The fast and reversible inhibition by taurine was accompanied by a depolarization and conductance increase in medium spiny neurons and was sensitive to γ‐aminobutyric acid (GABA)A and glycine receptor (GlyR) antagonists. A long‐lasting enhancement (LLETAU) of field potentials was recorded after taurine withdrawal. The LLETAU was not prevented by N‐methyl‐d‐aspartate (NMDA)‐ or by GABAA receptor‐antagonists, but was sensitive to the GlyR‐antagonist strychnine and blocked by the competitive taurine uptake inhibitor guanidinoethylsulphonate (GES, 1 mm). GES at 10 mm evoked an enhancement of field potentials similar to LLETAU. LLETAU depended on protein kinase C activation as it was blocked by chelerythrine, but was unaffected by trifluoperazine, and thus independent of calmodulin. LLETAU was significantly smaller in juvenile than in mature rodents. Activation of GlyRs and the specific taurine transporter by taurine evoke a long‐lasting enhancement of corticostriatal transmission.
Differential induction and localization of mPer1 and mPer2 during advancing and delaying phase shifts
Authors: Yan Lily , Silver Rae
Published: March 2003

The mechanism whereby brief light exposure resets the mammalian circadian clock in a phase dependent manner is not known, but is thought to involve Per gene expression. At the behavioural level, a light pulse produces phase delays in early subjective night, phase advances in late subjective night, and no phase shifts in mid‐subjective night or subjective day. To understand the relationship between Per gene activity and behavioural phase shifts, we examined light‐induced mPer1 and mPer2 expression in the suprachiasmatic nucleus (SCN) of the mouse, in the subjective night, with a view to understanding SCN heterogeneity. In the VIP‐containing region of the SCN (termed ‘core’), light‐induced mPer1 expression occurs at all times of the subjective night, while mPer2 induction is seen only in early subjective night. In the remaining regions of the SCN (termed ‘shell’), a phase delaying light pulse produces no mPer1 but significant mPer2 expression, while a phase advancing light pulse produces no mPer2 but substantial mPer1 induction. Moreover, following a light pulse during mid‐subjective night, neither mPer1 nor mPer2 are induced in the shell. The results reveal that behavioural phase shifts occur only when light‐induced Per gene expression spreads from the core to the shell SCN, with mPer1 expression in shell corresponding to phase advances, and mPer2 corresponding to phase delays. The results indicate that the time course and the localization of light‐induced Per gene expression in SCN reveals important aspects of intra‐SCN communication.
Long‐term depression and long‐term potentiation in horizontal connections of the barrel cortex
Authors: Urban Joanna , Kossut Malgorzata , Hess Grzegorz
Published: March 2003

Synaptic plasticity of horizontally orientated connections between barrels, in the barrel cortex of adult mice, was studied in slice preparations cut across rows of barrels. Field potentials were evoked in the middle of one barrel column (in layer IV or V) and recorded in the neighbouring barrel (in layer IV and V). In layer IV, long‐term depression (LTD) by 26.5 ± 5% was first induced by a low‐frequency stimulation (2 Hz) applied for 10 min. After 30 min, theta‐burst stimulation was delivered to previously depressed connections, resulting in long‐term potentiation (LTP) by 28.8 ± 11.8%. When theta‐burst stimulation was delivered without an earlier low‐frequency stimulation, no LTP was induced. Similar results were obtained in layer V connections (LTD: 40.6 ± 12.5%; LTP: 26.9 ± 12.5%). In layer IV, the application of 100 µm d,l‐2‐amino‐5‐phosphonovaleric acid (APV), an antagonist of NMDA receptors, blocked the induction of both LTD and LTP. These experiments show that a potential for synaptic plasticity is retained in granular and infragranular layers of adult mice.
Differential expression of c‐fos in subtypes of GABAergic cells following sensory stimulation in the cat primary visual cortex
Authors: Van der Gucht Estel , Clerens Stefan , Cromphout Kathy , Vandesande Frans , Arckens Lutgarde
Published: March 2003

Recent immunocytochemical stainings on cat visual cortex, visually stimulated for 1 h, showed a strong induction of Fos expression in cortical neurons. We initiated immunocytochemical double staining experiments with different cytochemical markers to investigate the neurochemical and morphological character of these activated neurons showing Fos induction after sensory stimulation. Double staining with Fos and glutamic acid decarboxylase (GAD) demonstrated the presence of Fos in the nuclei of GABAergic neurons of the primary visual cortex. To further subdivide this Fos/GABAergic cell population we investigated whether Fos colocalized with parvalbumin, calbindin or calretinin. Colocalization of Fos with these calcium‐binding proteins delineated distinct neuronal subclasses of Fos‐immunoreactive neurons in supra‐ and infragranular layers of cat area 17. Quantitative analysis of the proportion of immunoreactive local circuit neurons revealed that 35% of the GABAergic neurons showed Fos induction in supragranular layers, whereas in infragranular layers a mere 10% of the GABAergic cells revealed Fos expression. Fos coexisted in about 24% of the calbindin‐immunopositive cells within supra‐ and infragranular layers, but only a minority of the parvalbumin and the calretinin neuronal subgroups were immunopositive for Fos in the corresponding layers of area 17. These findings suggest that visual stimulation induces Fos expression in distinct subsets of inhibitory neurons in cat primary visual cortex.
Visual information process in Williams syndrome: intact motion detection accompanied by typical visuospatial dysfunctions
Authors: Nakamura Miho , Kaneoke Yoshiki , Watanabe Kazuyoshi , Kakigi Ryusuke
Published: March 2003

It has been suggested that visuospatial cognitive disabilities seen in children with Williams syndrome (WMS) are related to a dysfunction of the dorsal stream in the visual information analysis system. We investigated whether visual motion detection is also impaired in WMS because it is one of the main functions of the dorsal stream. Using various psychophysical examinations and magnetoencephalography, we studied a child with WMS who had the typical features of the syndrome. We found profound impairments in the visuospatial cognitions, as previously reported in WMS. In contrast, he had normal ability for the direction discrimination of coherent motion on a background of randomly moving dots, and he perceived apparent motion as do normal children. Furthermore, the latencies of both responses to the coherent and incoherent motions as measured by magnetoencephalography were within the mean ± 2 SD among normal adults and the estimated origins were near the human homologue of V5/MT (visual area 5/middle temporal area). The results indicate that the visuospatial cognitive deficits in WMS can occur without impairment of the visual motion detection. We consider that the deficits are caused by a restricted dysfunction of the neural groups for position and three‐dimensional form perceptions in the dorsal stream of the visual system, though other possibilities are not excluded.
Synaptic glutamate receptor clustering in mice lacking the SH3 and GK domains of SAP97
Authors: Klöcker Nikolaj , Bunn Robert C. , Schnell Eric , Caruana Georgina , Bernstein Alan , Nicoll Roger A. , Bredt David S.
Published: March 2003

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

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

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

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

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

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

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

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

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

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

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

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