bluuebunny/crossref_metadata_2025_split huggingface dataset:
Alterations in dystrophin and utrophin expression parallel the reorganization of GABAergic synapses in a mouse model of temporal lobe epilepsy
Authors: Knuesel Irene , Zuellig Richard A. , Schaub Marcus C. , Fritschy Jean‐Marc 
Published: March 2003

AbstractDystrophin and its autosomal homologue utrophin are coexpressed in muscle cells, and utrophin is functionally able to replace dystrophin in models of Duchenne muscular dystrophy. In brain, the two proteins are expressed differentially, suggesting distinct functional roles. Dystrophin is associated with postsynaptic GABAA receptors in hippocampus, cortex and cerebellum, whereas utrophin is present extrasynaptically, notably in large brainstem neurons. Here, the regulation of dystrophin and utrophin was investigated in a model of temporal lobe epilepsy. Adult mice were injected unilaterally with kainic acid into the dorsal hippocampus to induce loss of pyramidal cells and hypertrophy of dentate gyrus (DG) granule cells, as described (Suzuki, F., Junier, M.P., Guilhem, D., Sorensen, J.C. & Onteniente, B. (1995)Neuroscience, 64, 665–674.). These morphological changes were associated with an increase in postsynaptic GABAA‐receptors in the ipsilateral DG, as demonstrated by a parallel increase in punctate immunoreactivity to GABAA‐receptor α2 subunit, gephyrin and dystrophin in the molecular layer. Thus, both dystrophin and gephyrin were involved in postsynaptic clustering of GABAA receptors. A transient induction of utrophin was seen at the onset of degeneration in CA1 and CA3 pyramidal cells and in the hilus. Most strikingly, however, utrophin immunoreactivity appeared in the granule cell layer of the DG and became very strong in hypertrophic granule cells 1–2 months post‐kainate treatment. These results suggest that utrophin provides structural support of neuronal membranes, whereas dystrophin is a component of GABAergic synapses.
VP‐RBP, a protein enriched in brain tissue, specifically interacts with the dendritic localizer sequence of rat vasopressin mRNA
Authors: Mohr Evita , Fuhrmann Carola , Richter Dietmar 
Published: March 2003

AbstractThe concept of mRNA localization suggests that this process is mediated by sequences residing in the transcript to which proteins specifically bind and ultimately deliver the mRNA along cytoskeletal elements to specific intracellular destinations. The mRNA encoding the vasopressin (VP) precursor protein is localized to the nerve cell processes both in hypothalamic magnocellular neurons and in primary cultured neurons derived from embryonic rat superior cervical ganglia microinjected with a corresponding eukaryotic expression vector. The last 395 nucleotides of the VP mRNA encompassing part of the coding region, as well as the complete 3′‐untranslated region, are sufficient to confer dendritic targeting to a normally nonlocalized reporter transcript. Here we report that, by employing in vitro crosslinking analyses with rat brain proteins and radiolabelled VP transcripts, an RNA‐binding protein specifically interacts with the dendritic localizer sequence of the VP mRNA. This protein is enriched in nerve cell tissues. Peripheral tissues and various cell lines contain only low amounts of the binding activity. It therefore represents a candidate protein that may be involved in any aspect related to subcellular VP mRNA sorting in nerve cells, including transport and anchoring of the mRNA and possibly its translational control.
Noradrenergic modulation of calcium currents and synaptic transmission in the olfactory bulb of Xenopus laevis tadpoles
Authors: Czesnik Dirk , Nezlin Leonid , Rabba Jörg , Müller Birgitt , Schild Detlev 
Published: March 2003

AbstractNorepinephrine (NE) has various modulatory roles in both the peripheral and the central nervous systems. Here we investigate the function of the locus coeruleus efferent fibres in the olfactory bulb of Xenopus laevis tadpoles. In order to distinguish unambiguously between mitral cells and granule cells of the main olfactory bulb and the accessory olfactory bulb, we used a slice preparation. The two neuron types were distinguished on the basis of their location in the slice, their typical branching pattern and by electrophysiological criteria. At NE concentrations lower than 5 µm there was only one effect of NE upon voltage‐gated conductances; NE blocked a high‐voltage‐activated Ca2+‐current in mitral cells of both the main and the accessory olfactory bulbs. No such effect was observed in granule cells. The effect of NE upon mitral cell Ca2+‐currents was mimicked by the α2‐receptor agonists clonidine and α‐methyl‐NE. As a second effect, NE or clonidine blocked spontaneous synaptic activity in granule cells of both the main and the accessory olfactory bulbs. NE or clonidine also blocked the spontaneous synaptic activity in mitral cells of either olfactory bulb. The amplitude of glutamate‐induced currents in granule cells was modulated neither by clonidine nor by α‐methyl‐NE. Taken together, the main effect of the noradrenergic, presynaptic, α2‐receptor‐mediated block of Ca2+‐currents in mitral cells appeared to be a wide‐spread disinhibition of mitral cells in the accessory olfactory bulb as well as in the main olfactory bulb.
GABAA and GABAB receptors on neocortical neurons are differentially distributed
Authors: Eder M. , Rammes G. , Zieglgänsberger W. , Dodt H.‐U. 
Published: March 2003

AbstractThe distribution of functional neurotransmitter receptors on the surface of neurons is highly relevant for synaptic transmission and signal processing. To map functional GABAA and GABAB receptors on the somadendritic membrane of rat neocortical layer V pyramidal neurons we used patch‐clamp recording in combination with infrared‐guided laser stimulation to release γ‐aminobutyric acid (GABA) photolytically. The data strongly suggest that relatively more GABAA receptors are located at the apical dendrite and relatively more GABAB receptors near the soma. Such a specific distribution of GABAA and GABAB receptors may serve to compensate for differences in electrotonic voltage attenuation between GABAA and GABAB receptor‐mediated inhibitory postsynaptic potentials (IPSPs).
Place‐cell firing does not depend on the direction of turn in a Y‐maze alternation task
Authors: Lenck‐Santini Pierre‐Pascal , Save Etienne , Poucet Bruno 
Published: March 2003

AbstractHippocampal place cells were recorded while rats solved a continuous spatial alternation task requiring short‐term spatial memory. All cells that had a firing field on the stem of the Y‐shaped maze were found to have a very similar pattern of discharge whether the rat was about to make a right or a left turn, and whether the preceding turn was a right or a left turn. Thus, the view that place cells encode a variety of events (including the direction of turns) useful for solving memory tasks is not well supported by the present data. We suggest several possible explanations to account for the discrepancy with other recent studies showing turn‐related modulation of place‐cell activity.
Restricted‐feeding‐induced anticipatory activity rhythm is associated with a phase‐shift of the expression of mPer1 and mPer2 mRNA in the cerebral cortex and hippocampus but not in the suprachiasmatic nucleus of mice
Authors: Wakamatsu Hisanori , Yoshinobu Yuko , Aida Reiko , Moriya Takahiro , Akiyama Masashi , Shibata Shigenobu 
Published: March 2003

AbstractDaily restricted feeding (RF) can produce food‐entrainable oscillations in both intact and suprachiasmatic nucleus (SCN)‐lesioned animals. Thus, there are two circadian rhythms, one of which is SCN‐dependent and the other SCN‐independent. Recently, it has been established that several mouse clock genes, such as mPer1, mPer2 and mPer3 are expressed in the SCN and other brain tissues. Although the role of mPer genes expressed in the SCN has recently been evaluated in the SCN‐dependent rhythm, their function in the SCN‐independent rhythm is still poorly understood. In order to understand the role of these genes in SCN‐independent rhythm, we examined the expression pattern of mPer1 and mPer2 mRNA in each brain area of mice under RF. Mice were allowed access to food for 4 h during either the daytime under a light‐dark cycle or the subjective daytime under constant dark. After 6 days of scheduled RF, the night‐time or subjective night‐time peak of mPer mRNA changed to a daytime peak in the cerebral cortex and hippocampus, with moderate expression in the striatum, pyriform cortex and paraventricular nucleus, and no expression in the SCN. The daytime peak in the cerebral cortex returned to a night‐time peak after the release of RF to a free‐feeding schedule. Although the basal rhythm of mPer expression disappeared in SCN‐lesioned mice, RF produced mPer mRNA rhythm in the cerebral cortex of these mice. The present results provide evidence of an association between food‐entrainable oscillations and the expression of mPer1 and mPer2 in the cerebral cortex and hippocampus.
Differential regulation by exercise of BDNF and NT‐3 in rat spinal cord and skeletal muscle
Authors: Gómez‐Pinilla F. , Ying Z. , Opazo P. , Roy R. R. , Edgerton V. R. 
Published: March 2003

AbstractWe have investigated the impact of neuromuscular activity on the expression of neurotrophins in the lumbar spinal cord region and innervating skeletal muscle of adult rats. Rats were exercised on a treadmill for 1 day or 5 consecutive days and euthanized at 0, 2 or 6 h after the last bout of exercise. By Day 1, there was no clear evidence of an increase in brain‐derived neurotrophic factor (BDNF) mRNA in the spinal cord or the soleus muscle. By Day 5, there was a significant increase in BDNF mRNA in the spinal cord at 2 h post‐training, and the soleus muscle showed a robust increase between 0 and 6 h post‐training. Immunoassays showed significant increases in BDNF protein in the soleus muscle by training Day 5. Immunohistochemical analyses showed elevated BDNF levels in motoneuron cell bodies and axons in the ventral horn. Neurotrophin‐3 (NT‐3) mRNA was measured to determine whether selected neurotrophins respond with a selective pattern of induction to neuromuscular activity. In the spinal cord, there was a progressive post‐training decrease in NT‐3 mRNA following a single bout of training, while there was a significant increase in NT‐3 mRNA at 2 h post‐training by Day 5. The soleus muscle showed a progressive increase in NT‐3 mRNA by Days 1 and 5 following training. These results show that neuromuscular activity has specific effects on the BDNF and NT‐3 systems, and that repetitive exercise affects the magnitude and stability of these responses.
Dopaminergic control of synaptic plasticity in the dorsal striatum
Authors: Centonze Diego , Picconi Barbara , Gubellini Paolo , Bernardi Giorgio , Calabresi Paolo 
Published: March 2003

AbstractCortical glutamatergic and nigral dopaminergic afferents impinge on projection spiny neurons of the striatum, providing the most significant inputs to this structure. Isolated activation of glutamate or dopamine (DA) receptors produces short‐term effects on striatal neurons, whereas the combined stimulation of both glutamate and DA receptors is able to induce long‐lasting modifications of synaptic excitability. Repetitive stimulation of corticostriatal fibres causes a massive release of both glutamate and DA in the striatum and, depending on the glutamate receptor subtype preferentially activated, produces either long‐term depression (LTD) or long‐term potentiation (LTP) of excitatory synaptic transmission. D1‐like and D2‐like DA receptors interact synergistically to allow LTD formation, while they operate in opposition during the induction phase of LTP. Corticostriatal synaptic plasticity is severely impaired after chronic DA denervation and requires the stimulation of DARPP‐32, a small protein expressed in dopaminoceptive spiny neurons which acts as a potent inhibitor of protein phosphatase‐1. In addition, the formation of LTD and LTP requires the activation of PKG and PKA, respectively, in striatal projection neurons. These kinases appear to be stimulated by the activation of D1‐like receptors in distinct neuronal populations.
Long‐trace interval eyeblink conditioning is impaired in mutant mice lacking the NMDA receptor subunit ε1
Authors: Kishimoto Yasushi , Kawahara Shigenori , Mori Hisashi , Mishina Masayoshi , Kirino Yutaka 
Published: March 2003

AbstractTo elucidate the role of the N‐methyl‐d‐aspartate (NMDA) ‐type glutamate receptor subunit ε1 (GluRε1) in classical eyeblink conditioning, delay and trace eyeblink conditioning were investigated in GluRε1‐null mutant mice. In delay conditioning and short‐trace interval conditioning with a trace interval of 250 ms, GluRε1 mutant mice attained a normal level of the conditioned response (CR), although acquisition was a little slower than in wild‐type mice. In contrast, GluRε1 mutant mice exhibited severe impairment of the attained level of the CR and disturbed temporal pattern of CR expression in trace conditioning with a longer trace interval of 500 ms. These findings indicate that GluRε1 is essential for long‐trace interval eyeblink conditioning. The impairments of the associative learning with a long temporal separation between the conditioned and unconditioned stimuli observed in the GluRε1 mutant mice could be attributed to an impairment of hippocampal long‐term potentiation in this line of mutant mice.
Place fields of rat hippocampal pyramidal cells and spatial learning in the watermaze
Authors: Hollup Stig A. , Molden Sturla , Donnett James G. , Moser May‐Britt , Moser Edvard I. 
Published: March 2003

AbstractTo provide a background for studying place‐related activity in hippocampal neurons during spatial learning, we compared the activity of hippocampal place cells in an annular watermaze and an analogous land‐based task. Complex‐spike cells had robust place correlates in both conditions, and a significant proportion of the cells had place fields at the same locations. However, the in‐field firing rates were slightly higher in the wet condition. Elevated firing was observed also in an open water task. There was no enhancement when the platform location was varied randomly or when there was no platform at all. Second, the place fields were under stronger directional modulation during swimming. In the annular task, directional sensitivity appeared regardless of whether the animals were trained to find a platform or not. There were directionally modulated units also in the open watermaze, but the number was smaller than in the corridor. Altogether, these observations suggest that place fields in the watermaze are largely controlled by the same factors as on dry land, in spite of the differences in kinaesthetic and vestibular input. Differences in firing rate and directional control may depend on the geometric and cognitive structure of the task rather than the medium on which the rats are moving.
Classical eyeblink conditioning in glutamate receptor subunit δ2 mutant mice is impaired in the delay paradigm but not in the trace paradigm
Authors: Kishimoto Yasushi , Kawahara Shigenori , Suzuki Michiyuki , Mori Hisashi , Mishina Masayoshi , Kirino Yutaka 
Published: March 2003

AbstractIn mice lacking glutamate receptor subunit δ2 (GluRδ2–/– mice), cerebellar long‐term depression (LTD) at the parallel fibre–Purkinje cell synapses is disrupted. Unlike the cerebellar LTD‐deficient mice previously used for eyeblink conditioning, however, the abnormalities of the GluRδ2–/– mice are restricted to the cerebellar cortex. In delay eyeblink conditionings (interstimulus interval of 252 and 852 ms), in which the conditioned stimulus (CS) overlaps temporally with a coterminating unconditioned stimulus (US), GluRδ2–/– mice are severely impaired in learning, strongly supporting the hypothesis that cerebellar cortical LTD is essential for delay conditioning. In the trace paradigm, in which a stimulus‐free trace interval of 500 ms intervened between the CS and US, GluRδ2–/– mice learned as successfully as wild‐type mice, indicating that cerebellar LTD is not necessary for trace conditioning. Thus, the present study has revealed a cerebellar LTD‐independent learning in eyeblink conditioning.
Correlation between electrophysiological and morphological characteristics during maturation of rat supraoptic neurons
Authors: Chevaleyre Vivien , Moos Françoise C. , Desarménien Michel G. 
Published: March 2003

AbstractThe neurohypophysial peptides oxytocin (OT) and vasopressin (AVP) are well known for their role in reproductive functions and fluid balance regulation, respectively. During development, these peptides are thought to act as trophic factors on both peripheral and central structures. However, despite this early developmental function, the maturation of their secreting neurons remains poorly investigated. In this study, we have characterized the electrical and morphological characteristics displayed by OT and AVP supraoptic (SO) neurons between embryonic day 21 and postnatal day 20. Transient changes in passive membrane properties, correlated with a transient increase in the dendritic arborization, were observed at the beginning of the second postnatal week (PW2). The action potential matured mostly during PW1 and its threshold progressively hyperpolarized in parallel with the resting membrane potential. During PW1, SO neurons displayed unique characteristics with a low‐threshold Ca2+‐dependent depolarizing potential and a prominent hyperpolarization‐activated current (Ih). This latter is involved in a depolarizing sag during hyperpolarization and an after hyperpolarizing potential following a depolarization. During this period, maintaining ECl unchanged by the use of gramicidin‐perforated patch recordings revealed excitatory GABAergic potentials, that became inhibitory during PW2, whilst glutamatergic potential appeared. The electrical activity was very erratic in young neurons and progressively differentiated in the typical firing observed in mature neurons (tonic and phasic for OT and AVP neurons, respectively) during PW2–3. These results show that the development of electrical properties of SO neurons is correlated with the maturation of their dendritic arborization.
Impairments in visual discrimination learning and recognition memory produced by neurotoxic lesions of rhinal cortex in rhesus monkeys
Authors: Baxter Mark G. , Murray Elisabeth A. 
Published: March 2003

AbstractMuch work on the cognitive functions of the primate rhinal (i.e. entorhinal plus perirhinal) cortex has been based on aspiration lesions of this structure, which might disrupt fibres passing nearby and through the rhinal cortex in addition to removing the cell bodies of the rhinal cortex itself. To determine whether damage limited to the cell bodies of the rhinal cortex is sufficient to impair visual learning and memory, four rhesus monkeys (Macaca mulatta) were preoperatively trained on a battery of visual learning and memory tasks, including single‐pair discrimination learning for primary reinforcement, single‐pair discrimination reversals, concurrent discrimination learning and reversal, and delayed matching‐to‐sample. Following acquisition of these tasks and a preoperative performance test, ibotenic acid was injected bilaterally into the rhinal cortex, and the monkeys were retested. Consistent with the results of studies using aspiration lesions, the monkeys were impaired on single‐pair discrimination learning as well as recognition memory performance postoperatively, although reliable reversal learning impairments were not observed. The magnitude of postoperative impairment in discrimination learning was not correlated with the magnitude of postoperative impairment in recognition memory, suggesting a possible dissociation between these functions within the rhinal cortex. The correspondence of behavioural deficits following aspiration and neurotoxic lesions of the rhinal cortex validates the attribution of various cognitive functions to this structure, based on the results of studies with aspiration lesions.
Social isolation after a single defeat reduces striatal dopamine transporter binding in rats
Authors: Isovich Eleonora , Engelmann Mario , Landgraf Rainer , Fuchs Eberhard 
Published: March 2003

AbstractA single social defeat in male rats has long lasting physiological and behavioural consequences, which are similar to those seen in depressive patients. In addition, the housing conditions after social defeat appear to be crucial for the development of depression‐like symptoms. Because the dopaminergic system is thought to be altered in depressive illness, we investigated the impact of individual and group housing on the temporal development of changes of dopamine transporter (DAT) binding in male rats after a single social defeat. The number of striatal DAT binding sites was reduced in animals that remained isolated after being defeated. The isolation length after social defeat amplified this effect, indicating a temporal development of the changes on the striatal DAT. In animals which returned to the familiar group after social defeat the density of striatal DAT binding sites was not affected. We conclude that social isolation after a single defeat reduces the number of DAT binding sites. In contrast, a familiar environment after a single social defeat appears to prevent the stress‐induced alterations on the dopaminergic system. This finding suggests that housing conditions are critical when investigating the central nervous effects of social defeat in male rats.
Visual analysis and image motion in locomoting cats
Authors: Sherk Helen , Fowler Garth A. 
Published: March 2003

AbstractDuring locomotion, observers see a characteristic pattern of motion referred to as an optic flow field. To investigate how they make use of this pattern, we have developed a paradigm for testing visual function during locomotion. Foot placement was recorded while cats walked down an alley cluttered with a high density of small objects; the task was to avoid stepping on any object. In the experiments reported here, motion cues were eliminated by the use of low‐frequency strobe lighting. In bright continuous light cats performed with great accuracy, and likewise at scotopic light levels. However, in strobe lighting their error rates increased more than threefold. This deterioration could not be attributed to lower acuity, since the cats' performance remained excellent when the light level was reduced well below that afforded by the strobe light. When very dim continuous light was combined with low‐frequency strobe lighting, performance was substantially better than under strobe light alone. We conclude that motion‐sensitive neurons make a major contribution to visual guidance of foot placement during locomotion. When strobe lighting is combined with very dim continuous light, even the minimal motion information available in the intervals between bright strobe flashes improves performance significantly. Cats were also trained to discriminate between complex patterns, and this discrimination was not affected by strobe lighting, suggesting that motion‐sensitive neurons are not critical for this analysis.