bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differential susceptibility to striatal neurodegeneration induced by quinolinic acid and kainate in inbred, outbred and hybrid mouse strains
Authors: McLin Jessica Pilar , Thompson Leslie Michels , Steward Oswald 
Published: December 2006

AbstractIn mice, the genetic background determines susceptibility to hippocampal neurodegeneration induced by the excitotoxin kainic acid (KA). If genetic background plays as significant a role in the striatum, the area most affected in Huntington's disease (HD), it is important to characterize intrinsic differences in neuronal susceptibility in mouse strains used in HD models. This study was performed to investigate whether strain differences of different HD mouse models are determinants of striatal resistance to excitotoxicity. We conducted a survey of the susceptibility of striatal neurons to neurodegeneration induced by quinolinic acid and KA in six inbred, two outbred and two F1 hybrid (resistant*vulnerable) strains. These are the same strains in which we have assessed vulnerability to KA‐induced hippocampal neurodegeneration. We found significant strain differences in response to both excitotoxins and, for the most part, the strain‐dependent patterns of susceptibility to quinolinic acid and KA were similar and comparable to those previously found with KA‐induced hippocampal neurodegeneration. There were some incongruities, suggesting that the genetic determinants may be different for the two forms of excitotoxicity or that there are important interacting factors. For example, the F1 hybrid strains exhibited neurodegeneration similar to their vulnerable parent, indicating that the vulnerable phenotype is dominant. This is in contrast to KA‐induced hippocampal neurodegeneration, where F1 hybrids exhibit the resistant phenotype. These results are also of significance with regard to the issue of region‐specific vulnerability in the context of different diseases in which genetic modifiers affect age of onset and/or disease progression.
Muscarinic control of graded persistent activity in lateral amygdala neurons
Authors: Egorov Alexei V. , Unsicker Klaus , Von Bohlen und Halbach Oliver 
Published: December 2006

AbstractThe cholinergic system is crucially involved in several cognitive processes including attention, learning and memory. Muscarinic actions have profound effects on the intrinsic firing pattern of neurons. In principal neurons of the entorhinal cortex (EC), muscarinic receptors activate an intrinsic cation current that causes multiple self‐sustained spiking activity, which represents a potential mechanism for transiently sustaining information about novel items. The amygdala appears to be important for experience‐dependent learning by emotional arousal, and cholinergic muscarinic influences are essential for the amygdala‐mediated modulation of memory. Here we show that principal neurons from the lateral nucleus of the amygdala (LA) can generate intrinsic graded persistent activity that is similar to EC layer V cells. This firing behavior is linked to muscarinic activation of a calcium‐sensitive non‐specific cation current and can be mimicked by stimulation of cholinergic afferents that originate from the nucleus basalis of Meynert (n. M). Moreover, we demonstrate that the projections from the n. M. are essential and sufficient for the control and modulation of graded firing activity in LA neurons. We found that activation of these cholinergic afferents (i) is required to maintain and to increase firing rates in a graded manner, and (ii) is sufficient for the graded increases of stable discharge rates even without an associated up‐regulation of Ca2+. The induction of persistent activity was blocked by flufenamic acid or 2‐APB and remained intact after Ca2+‐store depletion with thapsigargin. The internal ability of LA neurons to generate graded persistent activity could be essential for amygdala‐mediated memory operations.
Corrective movements in response to displacements in visual feedback are more effective during periods of 13–35 Hz oscillatory synchrony in the human corticospinal system
Authors: Androulidakis Alexandros G. , Doyle Louise M. F. , Gilbertson Thomas P. , Brown Peter 
Published: December 2006

AbstractOscillatory synchronization in the beta (∼20 Hz) band is a common feature of human motor control, manifest at cortical and muscular levels during tonic contraction. Here we test the hypothesis that the influence of visual feedback on performance in a positional hold task is increased during bursts of beta‐band synchrony in the corticospinal motor system. Healthy subjects were instructed to extend their forefinger while receiving high‐gain visual feedback of finger position on a PC screen. Small step displacements of the feedback signal were triggered either by bursts of beta oscillations in scalp electroencephalogram or randomly with respect to cortical beta activity, and the resulting positional corrections expressed as a percentage of the step displacement. Corrective responses to beta and randomly triggered step changes in visual feedback were 41.7 ± 4.9 and 31.5 ± 6.8%, respectively (P < 0.05). A marked increase in the coherence in the beta band was also found between muscle activity and cortical activity during the beta‐triggered condition. The results suggest that phasic elevations of beta activity in the corticospinal motor system are associated with an increase in the gain of the motor response to visual feedback during a tonic hold task. Beta activity may index a motor state in which processing relevant to the control of positional hold tasks is promoted, with behavioural consequences.
Induction of synchronous oscillatory activity in the rat lateral amygdala in vitro is dependent on gap junction activity
Authors: Sinfield James L. , Collins Dawn R. 
Published: December 2006

AbstractSynchronized and rhythmic activity within the amygdala is thought to play a pivotal role in the generation of fear‐ and anxiety‐related behaviour. The aim here was to determine the validity of the in vitro amygdala slice preparation to investigate the generation of rhythmic activity similar to that observed in vivo. Extracellular population activity recorded from the lateral nucleus of the amygdala in vitro showed significant enhancement of activity within the theta‐band frequency (3–9 Hz) in the presence of kainic acid (100 nm; n = 18). Alterations in the patterns of oscillatory activity within the gamma frequency band (20–40 Hz) were observed in the presence of (RS)‐3,5‐dihydroxyphenylglycine (10 µm; n = 7) or carbachol (50 µm; n = 5). Theta frequency oscillatory activity was blocked in the presence of the gap junction blocker carbenoxolone (100 mm), whereas gamma frequency oscillatory activity showed increased variability in the dominant frequency of rhythmic activity. The results suggest that the neuronal circuitry of the amygdala in vitro is capable of generating and sustaining rhythmic activity and that intercellular communication via gap junctions may play a role in the synchronization of population activity underlying this oscillatory activity.
Nicotine exposure refines visual map topography through an NMDA receptor‐mediated pathway
Authors: Yan Xiaohua , Zhao Bing , Butt Christopher M. , Debski Elizabeth A. 
Published: December 2006

AbstractThe precise mapping of one surface onto another is fundamental to visual system organization and depends upon adequate stimulation of postsynaptic targets to stabilize correctly placed synapses. As exogenous nicotine alters neuronal activity, we investigated whether it would affect the visual map created by retinal ganglion cell terminals in the frog optic tectum. Chronic exposure of the tectum to nicotine decreased the retinal area from which cells project to a given tectal site. This map refinement was also produced by exposure to either the α‐bungarotoxin sensitive nicotinic receptor agonist, anatoxin‐a or the α‐bungarotoxin‐insensitive nicotinic receptor agonist epiboxidine. Immunocytochemical studies using mAb306 and mAb22 demonstrated that α‐bungarotoxin‐sensitive and ‐insensitive nicotinic receptors, respectively, occupied different tectal sites. Choline acetyltransferase immunoreactivity overlapped with mAb306, but not mAb22, staining. The developing optic tectum was more sensitive to nicotine than the adult tectum and nicotine induced both map refinements and map disruptions in a concentration‐dependent manner. Blockade of theN‐methyl‐d‐aspartate (NMDA) receptor with D(–)‐2‐amino‐5‐phosphonopentanoic acid (D‐APV) prevented nicotine from refining the map in the adult tectum. Exposure to the use‐dependent NMDA antagonist MK801 alone had no effect on retinotectal topography but in combination with either NMDA or nicotine it disrupted the map. Exposure to NMDA alone produced refinement. We conclude that the map refinement induced by chronic nicotine treatment has as its basis an increase in the level of NMDA receptor activity. The data are consistent with a model whereby map topography can be bidirectionally affected by either increasing or decreasing NMDA receptor activity.
Regional cerebral blood flow changes associated with clitorally induced orgasm in healthy women
Authors: Georgiadis Janniko R. , Kortekaas Rudie , Kuipers Rutger , Nieuwenburg Arie , Pruim Jan , Reinders A. A. T. Simone , Holstege Gert 
Published: December 2006

AbstractThere is a severe lack of knowledge regarding the brain regions involved in human sexual performance in general, and female orgasm in particular. We used [15O]‐H2O positron emission tomography to measure regional cerebral blood flow (rCBF) in 12 healthy women during a nonsexual resting state, clitorally induced orgasm, sexual clitoral stimulation (sexual arousal control) and imitation of orgasm (motor output control). Extracerebral markers of sexual performance and orgasm were rectal pressure variability (RPstd) and perceived level of sexual arousal (PSA). Sexual stimulation of the clitoris (compared to rest) significantly increased rCBF in the left secondary and right dorsal primary somatosensory cortex, providing the first account of neocortical processing of sexual clitoral information. In contrast, orgasm was mainly associated with profound rCBF decreases in the neocortex when compared with the control conditions (clitoral stimulation and imitation of orgasm), particularly in the left lateral orbitofrontal cortex, inferior temporal gyrus and anterior temporal pole. Significant positive correlations were found between RPstd and rCBF in the left deep cerebellar nuclei, and between PSA and rCBF in the ventral midbrain and right caudate nucleus. We propose that decreased blood flow in the left lateral orbitofrontal cortex signifies behavioural disinhibition during orgasm in women, and that deactivation of the temporal lobe is directly related to high sexual arousal. In addition, the deep cerebellar nuclei may be involved in orgasm‐specific muscle contractions while the involvement of the ventral midbrain and right caudate nucleus suggests a role for dopamine in female sexual arousal and orgasm.
Mouse galectin‐1 inhibits the toxicity of glutamate by modifying NR1 NMDA receptor expression
Authors: Lekishvili Tamuna , Hesketh Shirley , Brazier Marcus W. , Brown David R. 
Published: December 2006

AbstractOne of the major causes of neuronal death in neurodegenerative disease is excitotoxicity from the neurotransmitter glutamate. This form of cell death could arise from either excess levels of glutamate due to decreased astrocyte clearance or due to increased susceptibility. We have identified galectin‐1, a galactose‐binding lectin, as a potential neuroprotective factor secreted by astrocytes. Our results show that both native and recombinant galectin‐1 protects mouse and rat cerebellar neurons from the toxic effects of glutamate. Galectin‐1 applied to neurons increased their expression of the NMDA receptor NR1 and increased the proportion of the NR1a subunit subtype while antisense knockdown of the NR1a receptor blocked the neuroprotective effect of galectin‐1. This effect of the protein was dependent upon it carbohydrate recognition domain, suggesting that the protein acts in a reduced dimerized form. In addition, galectin‐1 caused a decreased expression of PKC associated with increased resistance to glutamate toxicity. These results suggest that the astrocytic lectin galectin‐1 could protect neurons against the effects of excitotoxicity as seen in stroke and ischemic injury.
Gender‐related differences in the human subthalamic area: a local field potential study
Authors: Marceglia S. , Mrakic‐Sposta S. , Foffani G. , Cogiamanian F. , Caputo E. , Egidi M. , Barbieri S. , Priori A. 
Published: December 2006

AbstractThe objective of this study was to investigate the possible existence of gender‐related neurophysiological differences in the oscillatory activity of the human subthalamic area. To this end, we recorded local field potentials (LFPs) after neurosurgical procedures for deep brain stimulation (DBS) in 24 patients (12 males and 12 females) with Parkinson's disease. LFP recordings at rest before levodopa medication (19 nuclei from 11 female patients and 16 nuclei from ten male patients) showed significantly higher power in the alpha/low‐beta band (8–12 Hz, P < 0.01; 13–20 Hz, P = 0.03) in females than in males. After levodopa medication (ten nuclei from six female patients and 11 nuclei from seven male patients), the power in the high‐gamma band (60–90 Hz) and of the 300 Hz rhythm was significantly higher in females than in males (high‐gamma, P = 0.007; 300 Hz, P = 0.002). These findings show that functional gender‐related differences in the central nervous system involve the human subthalamic area (STN) and its response to levodopa in Parkinson's disease. Gender‐related neurophysiological differences may be important for understanding gender‐specific features of neurodegenerative disorders and should be considered when interpreting LFP data from the human basal ganglia.
Innexins in the lobster stomatogastric nervous system: cloning, phylogenetic analysis, developmental changes and expression within adult identified dye and electrically coupled neurons
Authors: Ducret E. , Alexopoulos H. , Le Feuvre Y. , Davies J. A. , Meyrand P. , Bacon J. P. , Fénelon V. S. 
Published: December 2006

AbstractGap junctions play a key role in the operation of neuronal networks by enabling direct electrical and metabolic communication between neurons. Suitable models to investigate their role in network operation and plasticity are invertebrate motor networks, which are built of comparatively few identified neurons, and can be examined throughout development; an excellent example is the lobster stomatogastric nervous system. In invertebrates, gap junctions are formed by proteins that belong to the innexin family. Here, we report the first molecular characterization of two crustacean innexins: the lobster Homarus gammarus innexin 1 (Hg‐inx1) and 2 (Hg‐inx2). Phylogenetic analysis reveals that innexin gene duplication occurred within the arthropod clade before the separation of insect and crustacean lineages. Using in situ hybridization, we find that each innexin is expressed within the adult and developing lobster stomatogastric nervous system and undergoes a marked down‐regulation throughout development within the stomatogastric ganglion (STG).The number of innexin expressing neurons is significantly higher in the embryo than in the adult. By combining in situ hybridization, dye and electrical coupling experiments on identified neurons, we demonstrate that adult neurons that express at least one innexin are dye and electrically coupled with at least one other STG neuron. Finally, two STG neurons display no detectable amount of either innexin mRNAs but may express weak electrical coupling with other STG neurons, suggesting the existence of other forms of innexins. Altogether, we provide evidence that innexins are expressed within small neuronal networks built of dye and electrically coupled neurons and may be developmentally regulated.
Impairment of microtubule‐dependent trafficking by overexpression of α‐synuclein
Authors: Lee He‐Jin , Khoshaghideh Farnaz , Lee Stephen , Lee Seung‐Jae 
Published: December 2006

AbstractAbnormal accumulation of α‐synuclein (α‐syn) has been linked to several neurological disorders, including Parkinson's disease (PD). However, the underlying mechanism by which α‐syn accumulation affects neuronal function and survival remains unknown. Here, we provide data suggesting a possible effect of aggregated α‐syn on the microtubule (MT) network. Consistent with the MT dysfunction, we also observed other degenerative changes, such as neuritic degeneration, trafficking defects, and Golgi fragmentation, which are common pathological features shared by many human neurodegenerative diseases. Neuritic degeneration and Golgi fragmentation were confirmed in primary cultures of dorsal root ganglia (DRG) neurons overexpressing α‐syn. This effect of α‐syn seems to have some selectivity to the MT system, as actin microfilaments and MT‐independent trafficking remain unaffected. Within the degenerating neurites, we found numerous spherical co‐aggregates of α‐syn and tubulins, from which actin was excluded. These studies suggest that the MT system is a potential target of α‐syn, and impairment of this system might have impacts on neuronal structure and function.
Chronic nicotine‐induced switch in Src‐family kinase signaling for long‐term potentiation induction in hippocampal CA1 pyramidal cells
Authors: Yamazaki Yoshihiko , Jia Yousheng , Wong Jamie K. , Sumikawa Katumi 
Published: December 2006

AbstractHere, we show that chronic nicotine exposure induces changes in Src signaling for the modulation of N‐methyl‐d‐aspartate receptor (NMDAR) function and LTP induction in CA1 pyramidal cells. Activation of muscarinic receptors normally potentiates NMDAR responses in pyramidal cells via a Gq/protein kinase C (PKC)/proline‐rich tyrosine kinase 2/Src signaling cascade. However, muscarinic, PKC and Src stimulation had no effect on NMDAR responses after chronic nicotine treatment. The lack of effect was apparently due to enhanced tyrosine phosphorylation, and therefore further stimulation of the signaling cascade caused no effect on NMDAR responses. Interestingly, another Src‐family kinase potentiated NMDAR responses after, but not before, chronic nicotine treatment. In control pyramidal cells, Src inhibitor peptides prevented tetanus‐induced long‐term potentiation (LTP). Conversely, in chronic nicotine‐exposed cells, the inhibitor was ineffective in blocking tetanus‐induced LTP. Furthermore, in control pyramidal cells, applying exogenous Src and administration of an endogenous Src‐family kinase activator increased α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionate receptor (AMPAR)‐mediated responses. This increase was blocked by Src inhibitor peptides and occluded tetanus‐induced LTP, as reported previously. In contrast, in chronic nicotine‐treated pyramidal cells, applying exogenous Src had no effect on AMPAR‐mediated responses and a tetanus‐induced LTP. Interestingly, however, administration of an endogenous Src‐family kinase activator enhanced AMPAR‐mediated responses, which occluded tetanus‐induced LTP. This enhancement was not prevented by co‐application of Src inhibitor peptides. Thus, it appears that chronic nicotine exposure recruits another member of the Src‐family for the regulation of NMDAR function and LTP induction. The nicotine‐induced distinct signaling cascades may be involved in long‐lasting memories of nicotine misuse.
Sex differences in the basolateral amygdala: the extracellular levels of serotonin and dopamine, and their responses to restraint stress in rats
Authors: Mitsushima Dai , Yamada Kaori , Takase Kenkichi , Funabashi Toshiya , Kimura Fukuko 
Published: December 2006

AbstractThe sex difference in the emotional response to stress suggests a sex‐specific stress response in the amygdala. To examine the sex difference in extracellular levels of serotonin (5HT) and dopamine (DA) in the basolateral amygdala (BLA) and their responses to restraint stress,in vivomicrodialysis studies were performed in male and female rats. In experiment I, dialysates were collected from the BLA at 15‐min intervals under the freely moving condition. Mean extracellular levels of 5HT or DA in the BLA were higher in male rats than in female rats. In experiment II, rats were subjected to restraint stress for 60 min to examine the stress response of 5HT or DA levels. Although restraint stress significantly increased extracellular 5HT levels in both sexes of rats, female rats showed a greater response than male rats. Moreover, restraint stress significantly increased extracellular DA levels in female rats, but not in male rats. In experiment III, rats were subjected to restraint stress for 30 min to examine behavioral responses to restraint stress. Although no sex difference was observed in the number of audible vocalizations, male rats defecated a larger number of fecal pellets than female rats. In experiment IV, rats were tested for freezing behavior to examine contextual fear responses. Conditioned male rats showed a longer freezing time than conditioned female rats. We found sex differences in the extracellular levels of 5HT and DA in the BLA and their responses to restraint stress, which may be involved in the sex‐specific emotional response to stress in rats.
Invasion in a heterogeneous world: resistance, coexistence or hostile takeover?
Authors: Melbourne Brett A. , Cornell Howard V. , Davies Kendi F. , Dugaw Christopher J. , Elmendorf Sarah , Freestone Amy L. , Hall Richard J , Harrison Susan , Hastings Alan , Holland Matt , Holyoak Marcel , Lambrinos John , Moore Kara , Yokomizo Hiroyuki 
Published: December 2006

AbstractWe review and synthesize recent developments in the study of the invasion of communities in heterogeneous environments, considering both the invasibility of the community and impacts to the community. We consider both empirical and theoretical studies. For each of three major kinds of environmental heterogeneity (temporal, spatial and invader‐driven), we find evidence that heterogeneity is critical to the invasibility of the community, the rate of spread, and the impacts on the community following invasion. We propose an environmental heterogeneity hypothesis of invasions, whereby heterogeneity both increases invasion success and reduces the impact to native species in the community, because it promotes invasion and coexistence mechanisms that are not possible in homogeneous environments. This hypothesis could help to explain recent findings that diversity is often increased as a result of biological invasions. It could also explain the scale dependence of the diversity–invasibility relationship. Despite the undoubted importance of heterogeneity to the invasion of communities, it has been studied remarkably little and new research is needed that simultaneously considers invasion, environmental heterogeneity and community characteristics. As a young field, there is an unrivalled opportunity for theoreticians and experimenters to work together to build a tractable theory informed by data.
The New Keynesian Model and the Euro Area Business Cycle*
Authors: Casares Miguel 
Published: December 2006

AbstractThis paper describes a New Keynesian model incorporating transactions‐facilitating money and a time‐to‐build constraint into endogenous capital accumulation. The calibrated New Keynesian model performs almost as well as the estimated vector autoregressive model in replicating Euro area cyclical correlations between key variables such as output and inflation, although it fares less well in predicting the procyclical dynamics of nominal interest rates. The presence of a time‐to‐build requirement in the model helps to improve its fit to Euro area data, whereas the role of transactions‐facilitating money is much less important. Impulse–response functions and a decomposition of variance complete the analysis.