bluuebunny/crossref_metadata_2025_split huggingface dataset:
Age‐related modifications of the morphological organization of pituicytes are associated with alteration of the GABAergic and dopaminergic innervation afferent to the neurohypophysial lobe
Authors: Alonso G. , Runquist M. , Hussy N. , Duvoid A. , Moos F. 
Published: October 2003

AbstractAgeing is known to induce a marked activation of astrocytes within various regions of the central nervous system. To date, the age‐related factors responsible for these modifications are unknown.The neural lobe of the hypophysis (NL) is a particular brain region which does not contain neurons but does contain specialized astrocytes, called pituicytes, and numerous terminals of afferent axons, including (i) peptidergic neurohypophysial axons which terminate on the NL blood vessels, and (ii) axons containing both gamma amino‐butyric acid (GABA) and dopamine (DA) which form contacts with pituicytes. Because evidence has recently been provided that GABA signalling mediates the morphological organization of astrocytes, the present study was designed to determine whether modifications of pituicytes during ageing were associated with modifications of the GABAergic axons innervating the NL. We show here that, in adult rats, GABA/DA axons form preferential synaptic‐like contacts with pituicytes which express both GABAA and D2 dopamine receptors. We then show that, during ageing, pituicytes undergo dramatic modifications of their morphology, correlatively with marked modifications of the GABA/DA fibres innervating the NL. Lastly, in vitro experiments indicate that modifications of the morphology of pituicytes similar to those observed during ageing were obtained by incubating isolated NL of adult rats with a GABAA receptor agonist and/or a D2 dopamine receptor antagonist, whereas inverse modifications were observed when NL of aged rats were incubated with a GABAA receptor antagonist and a D2 dopamine receptor agonist. Taken together, these data suggest that the age‐related morphological changes of pituicytes result from the alteration of the GABA/DAergic innervation of the NL.
Age‐related changes in the dynamics of human albino visual pathways
Authors: Neveu Magella M. , Jeffery Glen , Burton Linda C. , Sloper John J. , Holder Graham E. 
Published: October 2003

AbstractA deficiency of melanin in the retinal pigment epithelium, which regulates the development of neural retina, leads to chiasmal misrouting such that the uncrossed pathway (to the ipsilateral hemisphere) is reduced relative to the crossed pathway (to the contralateral hemisphere). This study examines age‐related changes in the flash and pattern appearance visual evoked potentials (VEP) of human albinos. Scalp recorded cortical VEPs to flash (FVEP) and pattern appearance stimulation were recorded in 58 albino (8 months to 60 years) and 34 normal subjects (4–55 years). VEPs were analysed by amplitude and latency. The contralateral hemisphere FVEP amplitude decreased with age in albino subjects, as in both hemispheres in normals. However, the ipsilateral hemisphere FVEP amplitude was significantly lower in young albino subjects, initially giving a marked interhemispheric asymmetry, but this normalized with age. Significant interhemispheric FVEP latency asymmetries were not observed. The contralateral pattern appearance VEP latency in albino subjects decreased with age, as in both hemispheres in normals; the ipsilateral latency increased significantly with age. Significant interhemispheric pattern appearance VEP amplitude asymmetries were not observed. These novel and unexpected observations indicate significant age‐related changes in the retinocortical pathways of the human albino. These changes have implications for our understanding of development and plasticity of the central visual pathways.
The coding of odour‐intensity in the honeybee antennal lobe: local computation optimizes odour representation
Authors: Sachse Silke , Galizia C. Giovanni 
Published: October 2003

AbstractWe investigated strategies involved in odour intensity coding by the primary olfactory centre of insects, the antennal lobe (AL), the structural and functional analogue of the olfactory bulb. Using calcium imaging in the honeybee, we simultaneously measured the projection neuron output responses and a compound signal dominated by receptor neuron input in identified olfactory glomeruli to odours spanning seven log units of concentration. A comparison of the two processing levels indicates that the intercellular computation within the AL modulates and contrast‐enhances the primary olfactory signals. As a result the AL network optimizes the olfactory code: odour representation is improved at lower concentrations, the relative activity of olfactory glomeruli allows encoding odour quality over up to four log‐unit concentrations, and odour‐intensity is reliably represented in the overall excitation across AL.
The medial prefrontal cortex differentially regulates stress‐induced c‐fos expression in the forebrain depending on type of stressor
Authors: Figueiredo Helmer F. , Bruestle Amy , Bodie Bryan , Dolgas Charles M. , Herman James P. 
Published: October 2003

AbstractThe medial prefrontal cortex (mPFC) plays an important inhibitory role in the hypothalamic‐pituitary‐adrenal (HPA) axis response. The involvement of the mPFC appears to depend on the type of stressor, preferentially affecting ‘psychogenic’ stimuli. In this study, we mapped expression of c‐fos mRNA to assess the neural circuitry underlying stressor‐specific actions of the mPFC on HPA reactivity. Thus, groups of mPFC‐lesioned and sham‐operated rats were restrained for 20 min or exposed to ether fumes for 2 min. In both cases, the animals were killed at 40 min from the onset of stress. Interestingly, bilateral lesions of the mPFC significantly enhanced c‐fos mRNA expression in the hypothalamic paraventricular nucleus of restrained animals, an effect that was paralleled by potentiation of circulating ACTH concentrations in these animals. On the other hand, lesions of the mPFC did not affect neither PVN c‐fos mRNA expression nor plasma ACTH concentrations in animals exposed to ether. Lesions of the mPFC also enhanced c‐fos activation in the medial amygdala following restraint, but not following ether exposure. Additional regions whose activity was affected by mPFC lesions or stressor differences included the ventrolateral division of the bed nucleus of the stria terminalis, CA3 hippocampus, piriform cortex, and dorsal endopiriform nucleus. Expression of c‐fos mRNA was nearly absent in the central amygdala of all stressed animals, regardless of lesion. Furthermore, prefrontal cortex lesions did not change stress‐induction levels of c‐fos in the CA1 hippocampus, dentate gyrus, anteromedial division of the bed nucleus of the stria terminalis, lateral septum, and claustrum. Taken together, this study indicates that the medial prefrontal cortex differentially regulates cellular activation of specific stress‐related brain regions, thus exerting stressor‐dependent inhibition of the HPA axis.
Contribution of Kir3.1, Kir3.2A and Kir3.2C subunits to native G protein‐gated inwardly rectifying potassium currents in cultured hippocampal neurons
Authors: Leaney Joanne L. 
Published: October 2003

AbstractG protein‐gated inwardly rectifying potassium (GIRK) channels are found in neurons, atrial myocytes and neuroendocrine cells. A characteristic feature is their activation by stimulation of Gi/o‐coupled receptors. In central neurons, for example, they are activated by adenosine and GABA and, as such, they play an important role in neurotransmitter‐mediated regulation of membrane excitability. The channels are tetrameric assemblies of Kir3.x subunits (Kir3.1–3.4 plus splice variants). In this study I have attempted to identify the channel subunits which contribute to the native GIRK current recorded from primary cultured rat hippocampal pyramidal neurons. Reverse transcriptase–polymerase chain reaction revealed the expression of mRNA for Kir3.1, 3.2A, 3.2C and 3.3 subunits and confocal immunofluorescence microscopy was used to investigate their expression patterns. Diffuse staining was observed on both cell somata and dendrites for Kir3.1 and Kir3.2A yet that for Kir3.2C was weaker and punctate. Whole‐cell patch clamp recordings were used to record GIRK currents from hippocampal pyramidal neurons which were identified on the basis of inward rectification, dependence of reversal potential on external potassium concentration and sensitivity to tertiapin. The GIRK currents were enhanced by the stimulation of a number of Gi/o‐coupled receptors and were inhibited by pertussis toxin. In order to ascertain which Kir3.x subunits were responsible for the native GIRK current I compared the properties with those of the cloned Kir3.1 + 3.2A and Kir3.1 + 3.2C channels heterologously expressed in HEK293 cells.
Involvement of transient receptor potential‐like channels in responses to mGluR‐I activation in midbrain dopamine neurons
Authors: Tozzi Alessandro , Bengtson C. Peter , Longone Patrizia , Carignani Corrado , Fusco Francesca R. , Bernardi Giorgio , Mercuri Nicola B. 
Published: October 2003

AbstractWe investigated the involvement of store‐operated channels (SOCs) and transient receptor potential (TRP) channels in the response to activation of the group I metabotropic glutamate receptor subtype 1 (mGluR1) with the agonist (S)‐3,5‐dihydroxyphenylglycine (DHPG, puff application) in dopamine neurons in rat brain slices. The mGluR1‐induced conductance reversed polarity close to 0 mV and at more positive potentials when extracellular potassium concentrations were increased, indicating the involvement of a cationic channel. DHPG currents but not intracellular calcium responses were reduced by low extracellular sodium concentrations but were not affected by sodium channel blockers, tetrodotoxin and saxitoxin or by inhibition of the h‐current with cesium. Abolition of calcium responses with intracellular BAPTA (1,2‐bis(2‐aminophenoxy)ethane‐N,N,N′,N′‐tetraacetic acid; 10 mm) did not affect current responses, indicating they were not calcium activated. Extracellular application of non‐selective SOCs and TRP channel blockers 2‐aminoethoxydiphenylborane (2‐APB), SKF96365, ruthenium red and flufenamic acid (but not gadolinium) reduced DHPG current and calcium responses. Intracellular application of ruthenium red and 2‐APB did not affect DHPG currents, indicating that IP3 and ryanodine receptors did not mediate their actions. Single‐cell PCR revealed the presence of TRPC1 and 5 mRNA in most dopamine neurons and subtypes 3, 4 and 6 in some. Store depletion evoked calcium entry indicative of SOCs, providing the first functional observation of such channels in native central neurons. Store depletion with either cyclopiazonic acid or ryanodine abolished calcium but not current responses to DHPG. The electrophysiological and pharmacological properties of the mGluR1‐induced inward current are consistent with the involvement of TRP channels whereas calcium responses are dependent on the function of SOCs in voltage clamp recordings.
Attention capture by auditory significant stimuli: semantic analysis follows attention switching
Authors: Escera Carles , Yago Elena , Corral Maria‐José , Corbera Sílvia , Nuñez M. Isabel 
Published: October 2003

AbstractEvent‐related potentials (ERPs) were recorded from the scalp to investigate a long‐standing controversy in auditory attention research, namely when the ‘breakthrough of the unattended’ takes place in the human brain. Nine subjects classified visual stimuli appearing 300 ms after task‐irrelevant standard tones (80%, i.e. P = 0.8) or novel sounds (20%, i.e. P = 0.2) into odd/even categories. After the recording session, subjects scored the novel sounds as to whether they had any particular meaning (identifiable) or were perceived as a burst of noise (non‐identifiable), and performance and ERPs were analysed according to this classification. A control condition, in which the visual stimuli were presented with no sounds, showed that subjects covertly monitored the task‐irrelevant sounds during visual task‐performance, and a further condition, in which the auditory and visual stimuli appeared regardless of each other, made it possible to trace the processing of the distracters during allocation of attention outside the auditory environment. Results yielded identical N1‐enhancement for the two types of novel sounds, indicating similar attention switching triggered to these two types of unexpected sounds. However, there was a stronger orientating of attention towards identifiable novel sounds, as indicated both by behavioural distraction and by larger novelty‐P3. Furthermore, this stronger orientating of attention was due to the sounds being contingent on the visual stimuli, as no increase in novelty‐P3 to identifiable novel sounds was observed in the control condition, in which the sounds occurred outside the attentional set. Therefore, provided that the N1‐enhancement reflects a call for focal attention, and novelty‐P3 the effective orientating of attention towards the eliciting sounds, the present results suggest that semantic analysis of significant sounds occurs after a transitory switch of attention towards the eliciting stimuli. Moreover, as the novelty‐P3 increase in amplitude was observed only when subjects covertly monitored the sounds, the present data suggest that semantic analysis of irrelevant sounds depends on the top‐down cognitive influences of the attentional set.
Distinct roles of the different ionotropic glutamate receptors within the nucleus accumbens in passive‐avoidance learning and memory in mice
Authors: De Leonibus Elvira , Costantini Vivian J. A. , Castellano Claudio , Ferretti Valentina , Oliverio Alberto , Mele Andrea 
Published: October 2003

AbstractResearch on the role of the nucleus accumbens in behaviour has been largely focused on the functions of this structure in conditioning to appetitive stimuli. It has been suggested that a network comprising the nucleus accumbens and its convergent inputs might mediate dissociable functions in the acquisition, the consolidation and the retrieval of information. However, findings related to a role of this structure in aversive conditioning are somewhat contradictory, and its involvement in this form of learning is still under debate. Moreover, very little evidence is available on the step of information processing mediated by the accumbens. Thus the purpose of this study was to investigate the effects of the blockade of the AMPA and NMDA glutamate receptors, which have been suggested to mediate the transmission of information from the limbic system to this structure, on a classical aversive conditioning task – the one‐trial step through inhibitory avoidance paradigm (24 h interval between training and testing). Intra‐accumbens focal injections of AP‐5 and DNQX (NMDA and AMPA antagonists, respectively) were performed immediately after training, before training and before testing in mice. The NMDA antagonist (37.5, 75 and 150 ng per side) impaired animal performance only if administered immediately after but not before training or before testing. Conversely, DNQX (0.5, 1.0 and 5.0 ng per side) reduced the step through latencies when administered before training and before testing. These findings suggest that NMDA receptor activation within the accumbens is necessary in formation but not expression of memory for inhibitory avoidance. AMPA receptors, instead, are necessary for the acquisition and the expression but not consolidation of inhibitory avoidance memory.
Selective psychostimulant sensitization by food restriction: differential changes in accumbens shell and core dopamine
Authors: Cadoni Cristina , Solinas Marcello , Valentini Valentina , Di Chiara Gaetano 
Published: October 2003

AbstractWe have recently reported that behavioural sensitization to morphine, amphetamine, cocaine and nicotine is associated with an increased response of dialysate dopamine to the same drugs in the nucleus accumbens core and/or a reduced response in the shell. Prolonged exposure to stressful stimuli also induces behavioural sensitization to drugs of abuse. We therefore investigated the effect of different drugs of abuse on behaviour and on dopamine transmission in the nucleus accumbens shell and core of rats stressed by 1 week schedule of food restriction. Food‐restricted rats (80% of their initial body weight) were implanted with microdialysis probes in the nucleus accumbens shell and core and challenged with cocaine (5 and 10 mg/kg i.p.), amphetamine (0.25 and 0.5 mg/kg s.c.), morphine (1 and 2 mg/kg s.c.), nicotine (0.2 and 0.4 mg/kg s.c.) and the changes in dialysate dopamine transmission were monitored together with the behaviour. Food restricted rats showed strong behavioural sensitization to cocaine and amphetamine but not to morphine or nicotine as compared to ad libitum fed controls. Behavioural sensitization to psychostimulants was associated with an increased response of dialysate dopamine in the core and with an unchanged or even reduced response in the shell. No significant differences were observed between controls and food‐restricted animals in the ability of morphine and nicotine to stimulate dopamine transmission in the shell and core. The present results indicate that a sensitized dopamine response in the nucleus accumbens core is a general feature of the expression of behavioural sensitization.
Differential arithmetic of shunting inhibition for voltage and spike rate in neocortical pyramidal cells
Authors: Ulrich Daniel 
Published: October 2003

AbstractThe main inhibitory neurotransmitter in the mammalian forebrain is γ‐amino butyric acid (GABA), which acts through A and B type receptors. GABAA receptors mediate inhibition via an increase in membrane conductance (shunting) and/or membrane potential hyperpolarization. Shunting inhibition is thought to decrease the gain between neural input and output, and thus to act as a divisor, but may do so only below the spike threshold. To investigate the role of shunting inhibition in neocortical neurons, whole‐cell patch‐clamp recordings were obtained from layer V pyramidal cells of somatosensory cortex in juvenile rats. Sub‐ and suprathreshold voltage responses were elicited by somatic step current injections and a shunting conductance was generated via a dynamic clamp. Increasing the dynamic clamp shunting conductance led to a parallel shift of the current–discharge curves and a reduced slope of the current–voltage relationship, i.e. a decrease of neural gain. Selective activation of GABAAA receptors with the competitive agonist isoguvacine or rises of endogenous GABA with the specific reuptake blocker nipecotic acid led to a proportional decrease of subthreshold membrane voltage, but a constant offset of discharge rates, thus acting like a shunting conductance. Similarly, isoguvacine and nipecotic acid decreased the gain of excitatory postsynaptic potentials. In all three experimental conditions, shunting inhibition divisively affected subthreshold voltages, while the time‐averaged suprathreshold membrane potential was offset by a constant amount. I conclude that shunting inhibition in pyramidal cells has a dual impact on neural output: it is divisive for subthreshold voltages but subtractive for spike frequencies.
Mapping responses to frequency sweeps and tones in the inferior colliculus of house mice
Authors: Hage Steffen R. , Ehret Günter 
Published: October 2003

AbstractIn auditory maps of the primary auditory cortex, neural response properties are arranged in a systematic way over the cortical surface. As in the visual system, such maps may play a critical role in the representation of sounds for perception and cognition. By recording from single neurons in the central nucleus of the inferior colliculus (ICC) of the mouse, we present the first evidence for spatial organizations of parameters of frequency sweeps (sweep speed, upward/downward sweep direction) and of whole‐field tone response patterns together with a map of frequency tuning curve shape. The maps of sweep speed, tone response patterns and tuning curve shape are concentrically arranged on frequency band laminae of the ICC with the representation of slow speeds, build up response types and sharp tuning mainly in the centre of a lamina, and all (including high) speeds, phasic response types and broad tuning mainly in the periphery. Representation of sweep direction shows preferences for upward sweeps medially and laterally and downward sweeps mainly centrally in the ICC (either striped or concentric map). These maps are compatible with the idea of a gradient of decreasing inhibition from the centre to the periphery of the ICC and by gradients of intrinsic neuronal properties (onset or sustained responding). The maps in the inferior colliculus compare favourably with corresponding maps in the primary auditory cortex, and we show how the maps of sweep speed and direction selectivity of the primary auditory cortex could be derived from the here‐found maps of the inferior colliculus.
Quantitative analysis of dopaminergic loss in relation to functional territories in MPTP‐treated monkeys
Authors: Jan Caroline , Pessiglione Mathias , Tremblay Léon , Tandé Dominique , Hirsch Etienne C. , François Chantal 
Published: October 2003

Abstract1‐Methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP) intoxication in primates results in a heterogeneous loss of dopamine in the striatum, predominating in the dorsal and caudal parts of the structure, causing functional impairment that appears to be essentially motor and cognitive. The aim of the present study was to quantify the loss of dopamine in relation to the anatomo‐functional subdivisions of the striatum, and also of the pallidum and cortex of MPTP‐treated monkeys. A severe loss of dopaminergic innervation was observed in both the sensorimotor and associative territories of all these structures in MPTP‐treated monkeys. Comparatively, the limbic territories of all these structures were little affected. The preservation of dopaminergic innervation of the limbic part of cerebral structures may explain the preservation of motivational processes mediated by these limbic regions in MPTP‐treated monkeys.
Molecular scaffold reorganization at the transmitter release site with vesicle exocytosis or botulinum toxin C1
Authors: Stanley Elise F. , Reese Tom S. , Wang Gary Z. 
Published: October 2003

AbstractNeurotransmitter release sites at the freeze‐fractured frog neuromuscular junction are composed of inner and outer paired rows of large membrane particles, the putative calcium channels, anchored by the ribs of an underlying protein scaffold. We analysed the locations of the release site particles as a reflection of the scaffold structure, comparing particle distributions in secreting terminals with those where secretion was blocked with botulinum toxin A, which cleaves a small segment off SNAP‐25, or botulinum toxin C1, which cleaves the cytoplasmic domain of syntaxin. In the idle terminal the inner and outer paired rows were located ≈25 and ≈44 nm, respectively, from the release site midline. However, adjacent to vesicular fusion sites both particle rows were displaced towards the midline by ≈25%. The intervals between the particles along each row were examined by a nearest‐neighbour approach. In control terminals the peak interval along the inner row was ≈17 nm, consistent with previous reports and the spacing of the scaffold ribs. While the average distance between particles in the outer row was also ≈17 nm, a detailed analysis revealed short ‘linear clusters’ with a ≈14 nm interval. These clusters were enriched at vesicle fusion sites, suggesting an association with the docking sites, and were eliminated by botulinum C1, but not A. Our findings suggest, first, that the release site scaffold ribs undergo a predictable, and possibly active, shortening during exocytosis and, second, that at the vesicle docking site syntaxin plays a role in the cross‐linking of the rib tips to form the vesicle docking sites.