bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential arithmetic of shunting inhibition for voltage and spike rate in neocortical pyramidal cells
Authors: Ulrich Daniel
Published: October 2003

The 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

In 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

1‐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

Neurotransmitter 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.
Elimination of serotonergic cells induces a marked increase in generation of dopaminergic neurons from mesencephalic precursors
Authors: Rodriguez‐Pallares Jannette , Guerra Maria J. , Labandeira‐Garcia Jose L.
Published: October 2003

Production of dopaminergic (DA) neurons from stem/precursor cells for transplantation in Parkinson's disease has become a major focus of research. However, the inductive signals mediating the production of DA neurons remain poorly understood, and the influence of other cell populations simultaneously generated within the cell aggregates has not been studied. We investigated whether DA phenotype (i.e. tyrosine hydroxylase‐immunoreactive, TH‐ir), serotonergic, floor plate (FP4‐ir), and fibroblast growth factor 8 (FGF‐8)‐ir cells differentiate from proliferating cell aggregates obtained from rat mesencephalic precursors, and we also investigated the effects of serotonergic cells on differentiation of DA cells. We observed FP4‐ir, FGF‐8‐ir, TH‐ir and serotonergic cells within the aggregates. The TH‐ir cells appeared within or in close proximity to a central FP4‐ir core, and then concentrated peripherally forming a cap that surrounded the central FP4‐ir area. The serotonergic cells and fibers formed a cap surrounding that of TH‐ir neurons. Cell aggregates treated with an antibody against FGF‐4 or with the serotonergic toxin 5,7‐dyhydroxytryptamine or the serotonin synthesis inhibitor dl‐p‐chlorophenylalanine showed a marked decrease in the number of 5‐HT‐ir cells (10–20% of controls) and a marked increase in that of TH‐ir neurons (700–900% of controls). The present results show that manipulation of other cell populations in the cell aggregates, particularly the serotonergic population, may be an effective method of increasing the production of DA neurons from stem/precursor cells.
Generation and phenotypic analysis of sigma receptor type I (σ1) knockout mice
Authors: Langa Francina , Codony Xavier , Tovar Victoria , Lavado Alfonso , Giménez Estela , Cozar Patricia , Cantero Marta , Dordal Albert , Hernández Enric , Pérez Raquel , Monroy Xavier , Zamanillo Daniel , Guitart Xavier , Montoliu Lluís
Published: October 2003

Sigma (σ) sites are a type of nonopiate receptor whose role has been associated with several behaviours, including anxiety, depression, analgesia, learning processes and psychosis. Although there are several known σ receptor types, only the type I receptor (σ1) has been cloned. To uncover thein vivorelevance of σ‐receptors, we have generated knockout mice for σ1. Despite the broad expression pattern found for theσ1‐gene, homozygous mutant mice are viable, fertile and do not display any overt phenotype, compared with their wild‐type litter‐mates, in mixed genetic backgrounds. However, a significant decrease in the hypermotility response has been measured in knockout mice upon challenge with (+)SKF‐10 047, in agreement with the involvement of σ1‐receptors in the induction of psychostimulant actions. The activity of σ2‐receptors seems to be unaffected in σ1‐mutant mice. These knockout mice could contribute to better understand thein vivorole of σ‐receptors.
Cannabinoid receptor and WIN 55 212‐2‐stimulated [35S]‐GTPγS binding in the brain of mu‐, delta‐ and kappa‐opioid receptor knockout mice
Authors: Berrendero Fernando , Mendizábal Victoria , Murtra Patricia , Kieffer Brigitte L. , Maldonado Rafael
Published: October 2003

Numerous studies have shown the existence of functional links between the endogenous cannabinoid and opioid systems. However, extensive research is still needed to elucidate the biochemical mechanisms involved in this cannabinoid–opioid interaction. Mice lacking mu‐ (MOR), delta‐ (DOR) and kappa‐ (KOR) opioid receptors have been generated and some specific pharmacological effects induced by cannabinoids have been reported to be modified in these animals. In order to clarify further the possible mechanisms involved in this modification of cannabinoid responses we have now evaluated the expression and functional activity of cannabinoid receptors in different brain structures in these mutant animals. For this purpose, we have performed quantitative receptor autoradiography of CB1 cannabinoid receptors and activation of GTP‐binding proteins by CB1 agonists in the brain of wild‐type and homozygous MOR, DOR and KOR knockout mice. There were no significant differences in the levels of CB1 receptors in the brain of MOR mutant mice. In contrast, the efficacy of CB1 receptor activation by the cannabinoid agonist WIN 55 212‐2 was dramatically reduced in the caudate‐putamen of MOR knockout animals. The density of CB1 receptors as well as the stimulation of GTP‐binding proteins by WIN 55 212‐2 were significantly increased in the substantia nigra of mice deficient in DOR. Finally, there were no major changes in the levels and functional activity of CB1 cannabinoid receptors in any brain region in KOR knockout mice. Taken together, these results indicate that deletion of MOR and DOR causes alterations in cannabinoid receptor levels and functional activity in specific brain structures, which could explain some of the functional interactions observed between these two neuronal systems.
Differential contributions of the basolateral and central nuclei of the amygdala in the negative affective component of chemical somatic and visceral pains in rats
Authors: Tanimoto Sachi , Nakagawa Takayuki , Yamauchi Yosuke , Minami Masabumi , Satoh Masamichi
Published: October 2003

Pain is a multidimensional conscious experience including sensory and negative affective components. The neural systems of the sensory component of pain have been extensively studied, while those of the negative affective component are less clear. The amygdala is a forebrain structure composed of several distinct nuclei including the basolateral (BLA) and central (CeA) nuclei, and is thought to be a key neural substrate underlying emotional responses. Recently, we reported that intraplantar (i.pl.) injection of formalin as a chemical somatic noxious stimulus increasedc‐fosmRNA expression in the BLA, but not CeA, while intraperitoneal (i.p.) injection of acetic acid as a chemical visceral noxious stimulus induced it highly in the CeA, and hardly in BLA [Nakagawaet al. (2003)Neurosci. Lett., 344, 197–200]. In this study, we examined the effects of discrete bilateral excitotoxic lesions of the BLA or CeA on the sensory and negative affective components of the two types of pain in Sprague–Dawley rats. In the place‐conditioning paradigm, both i.pl. formalin and i.p. acetic acid produced conditioned place aversion. The i.pl. formalin‐induced conditioned place aversion was abolished by the lesion of the BLA or CeA, while the i.p. acetic acid‐induced conditioned place aversion was abolished by the CeA‐, but not BLA‐lesion. On the other hand, the BLA‐ or CeA‐lesion failed to reduce the i.pl. formalin‐ and i.p. acetic acid‐produced nociceptive behaviours. Taken together, these results suggest that activation of distinct amygdaloid nuclei could differentially contribute to chemical somatic and visceral noxious stimuli‐induced negative affective, but not sensory components of pains.
Haploinsufficiency in trkB and/or trkC neurotrophin receptors causes structural alterations in the aged hippocampus and amygdala
Authors: Von Bohlen und Halbach Oliver , Minichiello Liliana , Unsicker Klaus
Published: October 2003

Neurotrophins and their cognate trk receptors regulate key events, most notably survival and differentiation of specific neuron populations, during the development of the nervous system. Their functions in the adult and aged CNS are far less well understood. We have analysed mice aged 21–23 months with haploinsufficiencies of the trkB and/or trkC genes with regard to morphological alterations in the hippocampus and amygdala. Neuronal densities and total numbers of neurons in the dentate gyrus were significantly decreased in trkB+/−, trkC+/−, and trkB+/−/C+/− mutants. In the hippocampal area CA2/3, neuronal density and the total number of neurons were only reduced in double‐heterozygous mice. Within the amygdala, neuronal densities were not altered. The lateral, basolateral and basomedial nuclei of the amygdala, as well as the dentate gyrus and area CA3, revealed significant increases in the densities of degenerated axonal fragments; the most pronounced changes were found in the double‐heterozygous mice. Thus, partial impairment in trkB and/or trkC receptor expression caused region‐specific neuron losses in the hippocampus and increased axonal fragmentation in both hippocampus and amygdala, which may result from degeneration of both intrinsic and extrinsic fibre systems. Together, these data indicate that endogenous ligands to the trkB and trkC receptors are essential to maintain neuronal integrity in the aged hippocampus and amygdala.
Hippocampal N‐acetyl aspartate levels do not mirror neuronal cell densities in creatine‐supplemented epileptic rats
Authors: Vielhaber Stefan , Kudin Alexei P. , Kudina Tatiana A. , Stiller Detlef , Scheich Henning , Schoenfeld Ariel , Feistner Helmut , Heinze Hans‐Jochen , Elger Christian E. , Kunz Wolfram S.
Published: October 2003

For neuroprotective therapy of neurodegenerative diseases creatine treatment has gained special interest because creatine has been shown to cross the blood–brain barrier, accumulate in the human brain in vivo and cause delayed neuronal cell death in a large number of animal models. Here, we used the pilocarpine model of temporal lobe epilepsy to determine whether creatine administration is able to attenuate the epilepsy‐associated decrease in hippocampal N‐acetyl aspartate (NAA) concentrations, impairment of mitochondrial function and neuronal cell loss. In vivo1H‐NMR spectroscopy showed, in epileptic rats after creatine administration, higher hippocampal NAA concentrations, suggesting improved neuronal survival. However, in vitro observation of hippocampal slices from creatine‐treated epileptic rats revealed a more pronounced loss of pyramidal neurons and decrease in activity of mitochondrial enzymes in hippocampal subfields. This indicates that NAA concentrations measured by in vivo1H‐NMR spectroscopy reflect alterations of metabolism rather than neuronal cell densities. Our data indicate an adverse effect of creatine on neuronal survival under conditions of enhanced neuronal activity.
Development of Ca2+‐channel and BK‐channel expression in embryos and larvae of Xenopus laevis
Authors: Jiménez‐González Cristina , McLaren Gerald J. , Dale Nicholas
Published: October 2003

The patterns and density of channels expressed in neurons critically determine their electrical properties. We have examined developmental regulation of Ca2+‐channel expression during the maturation of the spinal motor circuits in Xenopus as it develops from an embryo to a larva. In embryonic neurons ≈ 60% of the current is carried by N‐type channels, 8% by l‐type channels and the remainder by an unidentified channel. As the embryo matures, ω‐agatoxin‐sensitive P/Q channels are gradually expressed and replace the unidentified HVA channel such that at stage 42 ≈ 25% of the current is carried by P/Q channels. We have used fluorescent labelling of selective channel toxins to directly observe the distribution of P/Q, N and BK channels. The P/Q channel distribution was most prevalent on the cell surface proximal to the areas of the soma where processes emerge. Both N and BK channels were distributed throughout the soma but still exhibited concentration around the areas adjacent to the emergence of processes from the soma. The patterns of fluorescence labelling during development mirrored the development of the respective ionic currents. Both N and P/Q channels contribute roughly equally to activation of the BK current, suggesting that overlap in the distribution of the N, P/Q and BK channels is important in their functional interdependence. The newly expressed P/Q channels play a role in spike initiation and repetitive firing in larval spinal neurons and contribute to burst generation during swimming in the larva.
Attention and working memory: a dynamical model of neuronal activity in the prefrontal cortex
Authors: Deco Gustavo , Rolls Edmund T.
Published: October 2003

Cognitive behaviour requires complex context‐dependent mapping between sensory stimuli and actions. The same stimulus can lead to different behaviours depending on the situation, or the same behaviour may be elicited by different cueing stimuli. Neurons in the primate prefrontal cortex show task‐specific firing activity during working memory delay periods. These neurons provide a neural substrate for mapping stimulus and response in a flexible, context‐ or rule‐dependent, fashion. We describe here an integrate‐and‐fire network model to explain and investigate the different types of working‐memory‐related neuronal activity observed. The model contains different populations (or pools) of neurons (as found neurophysiologically) in attractor networks which respond in the delay period to the stimulus object, the stimulus position (‘sensory pools’), to combinations of the stimulus sensory properties (e.g. the object identity or object location) and the response (‘intermediate pools’), and to the response required (left or right) (‘premotor pools’). The pools are arranged hierarchically, are linked by associative synaptic connections, and have global inhibition through inhibitory interneurons to implement competition. It is shown that a biasing attentional input to define the current rule applied to the intermediate pools enables the system to select the correct response in what is a biased competition model of attention. The integrate‐and‐fire model not only produces realistic spiking dynamicals very similar to the neuronal data but also shows how dopamine could weaken and shorten the persistent neuronal activity in the delay period; and allows us to predict more response errors when dopamine is elevated because there is less different activity in the different pools of competing neurons, resulting in more conflict.
Self‐face processing in a callosotomy patient
Authors: Keenan Julian Paul , Wheeler Mark , Platek Steven M. , Lardi Gina , Lassonde Maryse
Published: October 2003

Self‐face recognition is reserved for humans, apes and possibly dolphins and is thought to be a marker of self‐awareness. Previous data have indicated that self‐face recognition may be mediated via frontal right hemisphere circuits within the brain. Testing patient M.L., who underwent a total callosotomy, we found that when searching for the self‐face in a series of morphs (composite facial images made up of his own and a famous face in inversely varying percentages) the patient made (i) more true‐positive and (ii) fewer false‐positive responses when responding with the right hemisphere (i.e. indicating with the left hand). There was no hand difference when searching for familiar faces. These data imply a right hemisphere processing advantage for self‐faces.
Lesions of the mammillothalamic tract impair the acquisition of spatial but not nonspatial contextual conditional discriminations
Authors: Vann Seralynne D. , Honey R. C. , Aggleton John P.
Published: October 2003

This study examined the influence of selective mammillothalamic tract lesions in rats on the acquisition of two kinds of contextual conditional discrimination: one involving two contexts (A and B) that differed in their visuo‐spatial properties and another involving two contexts (C and D) that differed in temperature. In contexts A (and C) presentations of a tone were paired with food whereas presentations of a clicker were not; and in contexts B (and D) presentations of the clicker were paired with food whereas those of the tone were not. Mammillothalamic tract lesions disrupted initial acquisition of the conditional discrimination involving visual contexts (A and B), but not the formally equivalent discrimination involving thermal contexts (C and D). These results provide support for the suggestion that mammillothalamic tract lesions disrupt visuo‐spatial encoding.
Sex hormone‐dependent desensitization of 5‐HT1A autoreceptors in knockout mice deficient in the 5‐HT transporter
Authors: Bouali Saoussen , Evrard Alexis , Chastanet Michel , Lesch Klaus‐Peter , Hamon Michel , Adrien Joëlle
Published: October 2003

The serotonin transporter (5‐HTT) is the target of most antidepressant drugs, whose therapeutic action is related to their facilitatory influence on 5‐HT neurotransmission. In this study, we investigated the functional adaptive properties of 5‐HT1A autoreceptors, which regulate serotonergic neuronal firing, in knockout mice deficient in 5‐HTT. Neurons of the dorsal raphe nucleus (DRN) were recorded extracellularly under chloral hydrate anaesthesia in male and female knockout 5‐HTT mice and their wild‐type counterparts. The inhibitory response of DRN neurons to intravenous injection of the 5‐HT1A agonist 8‐OH‐DPAT was dramatically reduced in knockout 5‐HTT compared with wild‐type mice, especially in females. Changes in 8‐OH‐DPAT‐induced hypothermia and autoradiographic labelling of 5‐HT1A sites in the DRN confirmed a greater level of desensitization/down‐regulation of 5‐HT1A autoreceptors in female than in male knockout 5‐HTT mice. After gonadectomy, the functional status of 5‐HT1A autoreceptors was unchanged in wild‐type mice, whereas in knockout 5‐HTT, castrated males exhibited a down‐regulation, and ovariectomized females an up‐regulation of these receptors, as shown by electrophysiological recording and autoradiographic labelling in the DRN, as well as by changes in 8‐OH‐DPAT‐induced hypothermia. Finally, in gonadectomized knockout 5‐HTT mice, treatment with testosterone or estradiol restored the DRN neuronal firing sensitivity to 8‐OH‐DPAT back to sham control level in males or females, respectively. These data indicate that sexual hormones participate in the mechanisms responsible for the desensitization of 5‐HT1A autoreceptors in knockout 5‐HTT mice. The differential effects of testosterone and estradiol on 5‐HT1A‐mediated control of 5‐HT neurotransmission might be related to the well‐established gender differences in the vulnerability to depression.
Augmentation of induced visual gamma activity by increased task complexity
Authors: Posada Andres , Hugues Etienne , Franck Nicolas , Vianin Pascal , Kilner James
Published: October 2003

Recently the study of induced gamma band oscillations has focused on their modulation by top‐down processes, mainly attention. Numerous studies have observed an increase in induced gamma band energy with increases in covert selective attention and visual perception. The current study investigated the modulation of visually induced gamma band oscillations by top‐down processes associated with task complexity. Fourteen human subjects performed a reaction time task under two experimental conditions that differed in task complexity. In one, subjects simply had to press one of four buttons that corresponded to a colour stimulus shown to the subject. In the second, the stimulus response mapping was altered by the implementation of a rule, thus increasing task complexity. Cortical electrical activity was recorded using a 65 electrode whole scalp electroencephalographic (EEG) net. The EEG activity was analysed using Morlet wavelets to produce time–frequency maps. Although induced gamma band activity was observed in both conditions, there was significantly greater energy during the rule‐operation condition at approximately 276 ms after the appearance of the stimulus. This increase was localized to electrodes overlying the right‐central parietal scalp. The results of this study show that top‐down processes modulate the level of induced gamma band activity. We discuss these findings in terms of the role of gamma oscillations in the construction of a sensory representation useful for a correct motor response.
Rapid and long‐term alterations of hippocampal GABAB receptors in a mouse model of temporal lobe epilepsy
Authors: Straessle Andrea , Loup Fabienne , Arabadzisz Dimitrula , Ohning Gordon V. , Fritschy Jean‐Marc
Published: October 2003

Alterations of γ‐aminobutyric acid (GABA)B receptor expression have been reported in human temporal lobe epilepsy (TLE). Here, changes in regional and cellular expression of the GABAB receptor subunits R1 (GBR1) and R2 (GBR2) were investigated in a mouse model that replicates major functional and histopathological features of TLE. Adult mice received a single, unilateral injection of kainic acid (KA) into the dorsal hippocampus, and GABAB receptor immunoreactivity was analysed between 1 day and 3 months thereafter. In control mice, GBR1 and GBR2 were distributed uniformly across the dendritic layers of CA1–CA3 and dentate gyrus. In addition, some interneurons were labelled selectively for GBR1. At 1 day post‐KA, staining for both GBR1 and GBR2 was profoundly reduced in CA1, CA3c and the hilus, and no interneurons were visible anymore. At later stages, the loss of GABAB receptors persisted in CA1 and CA3, whereas staining increased gradually in dentate gyrus granule cells, which become dispersed in this model. Most strikingly, a subpopulation of strongly labelled interneurons reappeared, mainly in the hilus and CA3 starting at 1 week post‐KA. In double‐staining experiments, these cells were selectively labelled for neuropeptide Y. The number of GBR1‐positive interneurons also increased contralaterally in the hilus. The rapid KA‐induced loss of GABAB receptors might contribute to epileptogenesis because of a reduction in both presynaptic control of transmitter release and postsynaptic inhibition. In turn, the long‐term increase in GABAB receptors in granule cells and specific subtypes of interneurons may represent a compensatory response to recurrent seizures.
Distribution and pharmacology of alanine–serine–cysteine transporter 1 (asc‐1) in rodent brain
Authors: Helboe Lone , Egebjerg Jan , Møller Morten , Thomsen Christian
Published: October 2003

A polyclonal antibody against the Na+‐independent alanine–serine–cysteine transporter 1 (asc‐1) was raised and the specificity of the antibody verified by Western blots performed on membranes prepared from HEK293 cells transiently transfected with the cloned murine asc‐1. The antibody was then used to localize the transporter in the brain of two rodent species by using immunohistochemistry at the light and electron microscopical level. asc‐1‐immunoreactivity (asc‐1‐ir) was widely distributed throughout the mouse and rat brain. Areas with high levels of asc‐1‐ir included hypothalamus, the medial septal area, globus pallidus, entopeduncular nucleus, cingulate and retrosplenial cortices. Moderate asc‐1‐ir was observed in several areas including layers III and V of the neocortex, thalamus, nucleus accumbens, caudate putamen, bed nucleus of stria terminalis, all amygdaloid nuclei, hippocampus (CA1–CA3 and hilus of the dentate gyrus), as well as several brainstem nuclei. asc‐1‐ir was observed as punctuate staining consistent with varicosities matching neuronal cell bodies and dendritic fields. At the ultrastructural level, asc‐1‐ir was mainly confined to presynaptic terminals. Immunostaining in either glial cell bodies or perivascular sites was not observed and white matter was completely devoid of asc‐1‐ir. Furthermore, the pharmacology of the Na+‐independent uptake site for [3H]d‐serine in rat brain synaptosomal P2 fractions was compared with the substrate specificity of the cloned human asc‐1 transporter and a high degree of correlation was demonstrated. We conclude that asc‐1‐ir is widespread in the brain and limited to neuronal structures and that asc‐1 may contribute to synaptic clearance of d‐serine in brain.
Ascending visceral regulation of cortical affective information processing
Authors: Berntson Gary G. , Sarter Martin , Cacioppo John T.
Published: October 2003

Over a century ago, William James proposed that strong emotions represent the perceptual consequences of somato‐visceral feedback. Although the strong form of this conception is no longer viable, considerable evidence has accumulated indicating a range of visceral influences on higher neurobehavioural processes. This literature has only recently begun to consolidate, because earlier reports generally remained at the demonstration level, and pathways and mechanisms for such influences were uncertain. Recently, specific effects of visceral feedback have become apparent on cortical activity, cerebral auditory‐evoked responses, anxiety, memory and behavioural aspects of immunological sickness. Moreover, considerable progress has been made recently in determining the specific neural pathways and systems underlying these actions, especially the role of noradrenergic projections from the nucleus of the tractus solitarius and the locus coeruleus to the amygdala in memory processes, and to the basal forebrain in the processing of anxiety‐related information. The present paper highlights selected recent findings in this area, and outlines relevant structures and pathways involved in the ascending visceral influence on higher neurobehavioural processes.
Increasing local levels of neuregulin (glial growth factor‐2) by direct infusion into areas of demyelination does not alter remyelination in the rat CNS
Authors: Penderis Jacques , Woodruff Rachel H. , Lakatos Andras , Li Wen‐Wu , Dunning Mark D. , Zhao Chao , Marchionni Mark , Franklin Robin J. M.
Published: October 2003

Glial growth factor‐2 (GGF‐2) is a neuronally derived isoform of neuregulin shown in vitro to promote proliferation and survival of oligodendrocytes, the myelinating cells of the CNS. Enhanced remyelination has been demonstrated in vivo following systemic delivery of human recombinant GGF‐2 (rhGGF‐2) in experimental autoimmune encephalomyelitis (EAE). However, it is uncertain whether this is the result of direct effects of rhGGF‐2 on cells of the oligodendrocyte lineage or due to modulation of the immune or inflammatory response. If this enhanced remyelination was due to direct effects of rhGGF‐2 on cells of the oligodendrocyte lineage then one would expect rhGGF‐2 to induce a similar proremyelinating response in nonimmune, gliotoxin models of demyelination. Using a gliotoxin model of demyelination we were therefore able to ascertain the in vivo effect of rhGGF‐2 following local CNS delivery in a model that is not confounded by the concurrent presence of an immune‐mediated process. No significant alteration in the rate or character of remyelination was evident following local delivery as compared to controls, and indeed nor following systemic delivery in the gliotoxin model. The results of this study therefore indicate that both direct infusion and systemic delivery of rhGGF‐2 do not alter remyelination in a nonimmune, gliotoxin model of demyelination. This suggests that the proremyelinating effects of systemically delivered rhGGF‐2 in EAE are unlikely to be due to direct effects on the oligodendrocyte lineage, but may be mediated by rhGGF‐2 inducing an environment more favourable to remyelination, possibly through modulation of the immune response.
Mice with astrocyte‐directed inactivation of connexin43 exhibit increased exploratory behaviour, impaired motor capacities, and changes in brain acetylcholine levels
Authors: Frisch Christian , Theis Martin , De Souza Silva Maria A. , Dere Ekrem , Söhl Goran , Teubner Barbara , Namestkova Katerina , Willecke KIaus , Huston Joseph P.
Published: October 2003

Gap junctions mediate communication between many cell types in the brain. Gap junction channels are composed of membrane‐spanning connexin (Cx) proteins, allowing the cell‐to‐cell passage of small ions and metabolites. Cx43 is the main constituent of the brain‐spanning astrocytic gap junctional network, controlling activity‐related changes in ion and glutamate concentrations as well as metabolic processes. In astrocytes, deletion of Cx43‐coding DNA led to attenuated gap junctional coupling and impaired propagation of calcium waves, known to influence neuronal activity. Investigation of the role of Cx43 in behaviour has been impossible so far, due to postnatal lethality of its general deletion. Recently, we have shown that deletion of Cx30, which is also expressed by astrocytes, affects exploration, emotionality, and neurochemistry in the mouse. In the present study, we investigated the effects of the astrocyte‐directed inactivation of Cx43 on mouse behaviour and brain neurochemistry. Deletion of Cx43 in astrocytes increased exploratory activity without influencing habituation. In the open field, but not in the elevated plus‐maze, an anxiolytic‐like effect was observed. Rotarod performance was initially impaired, but reached control level after further training. In the water maze, Cx43 deficient mice showed a steeper learning course, although final performance was similar between groups. Cx43 inactivation in astrocytes increased acetylcholine content in the frontal cortex of water maze‐trained animals. Results are discussed in terms of altered communication between astrocytes and neurons, possible compensation processes, and differential effects of Cx30‐ and astrocyte‐specific Cx43 deletion.
Down‐regulation of CYP1A2 induction during the maturation of mouse cerebellar granule cells in culture: role of nitric oxide accumulation
Authors: Mulero‐Navarro Sonia , Santiago‐Josefat Belen , Pozo‐Guisado Eulalia , Merino Jaime M. , Fernandez‐Salguero Pedro M.
Published: October 2003

Nitric oxide (NO) is responsible for cytochrome P450 (CYP450) loss during isolation and cytokine treatment of primary rat hepatocytes. As P450s mediate the metabolism of toxic chemicals, their inhibition could compromise the cells competence to eliminate toxins, a condition potentially relevant in neurological diseases involving constitutive activation of nitric oxide synthase (NOS) and NO over‐production. Here, we have investigated the correlation between NO accumulation and CYP1A2 down‐regulation during maturation of mouse cerebellar granule cells (CGC). As neurons matured in culture, the inducible levels of CYP1A2 protein and catalytic activity decreased to almost undetectable values. In parallel, a significant increase in NO concentration was observed. Neuronal NOS remained constitutively active during maturation, thus contributing to NO accumulation. The NOS inhibitor l‐NAME, restored CYP1A2 catalytic activity up to 9 days in vitro, supporting a role for NO in the inhibition process. Maturation was also followed by increased NMDA receptor activity and intracellular Ca2+ concentration. We suggest that maintained NOS activity during CGC maturation could lead to NO accumulation and to decreased CYP1A2 inducibility. Increased NMDA receptor activity and Ca2+ entry could contribute to this process. Thus, neurodegeneration could diminish the induction of specific P450s and impair the metabolism of foreign and/or endogenous chemicals in the CNS.
Histaminergic facilitation of electrocorticographic activation: role of basal forebrain, thalamus, and neocortex
Authors: Dringenberg Hans C. , Kuo Min‐Ching
Published: October 2003

The neuromodulator histamine plays an important role in the regulation of behavioural state and the neocortical electrocorticogram (ECoG). With the present experiments, we characterized the anatomical targets that mediate the cortical‐activating effects of histamine. Urethane‐anaesthetized rats displayed continuous large‐amplitude, low‐frequency oscillations with a maximal spectral power in the delta (0.5–3.9 Hz) frequency band. Electrical (100 Hz) stimulation of the pontine‐tegmentum suppressed slow, large‐amplitude oscillations and induced ECoG activation. Application of histamine (1 mm) into the basal forebrain cholinergic complex by reverse microdialysis enhanced ECoG activation elicited by tegmental stimulation without changing resting ECoG activity. Ventrolateral or central thalamic application of histamine had no effect on resting ECoG activity, and ventrolateral thalamic application produced only a slight enhancement of brainstem‐induced activation. Neocortical application of histamine in close proximity (< 500 µm) to the recording electrode reduced low‐frequency delta power in the resting ECoG without affecting stimulation‐induced ECoG activation. These data suggest that, under the present experimental conditions, histamine facilitates ECoG activation primarily by potentiating the excitatory influence of brainstem fibers at the level of the basal forebrain. Histamine release in some parts of the thalamus results in a minor enhancement of ECoG activation, and cortical histamine release produces a small but consistent suppression of slow delta oscillations in the resting ECoG. These concurrent subcortical and cortical actions probably permit histamine to effectively modulate cortical activation and excitability across different behavioural states.
Pneumococcal necrotizing fasciitis in a patient with Type 2 diabetes
Authors: Prakash P. K. , Biswas M. , ElBouri K. , Braithwaite P. A. , Hanna F. W.
Published: October 2003

Necrotizing fasciitis (NF) is a rare and often fatal soft‐tissue infection involving the superficial fascial layers of the extremities, abdomen or perineum. Progression to septic shock can occur very rapidly with its associated high morbidity and mortality. NF is usually caused by beta haemolytic streptococci; less often a poly‐microbial isolate is the cause. It typically occurs in patients with some degree of immune dysfunction. We present a case of severe pneumococcal necrotizing fasciitis in an obese patient with Type 2 diabetes. There was no history of trauma or evidence of diabetes‐related complications. The initial presentation was with features of septic arthritis of the left knee, which subsequently progressed to NF. Differentiation from cellulitis is often difficult in the early stages. Invasive pneumococcal infections are extremely rare, with only a few reported in the literature. Moreover, our case highlights the need to consider other differential diagnoses (and to look out for complications) in patients with diabetes, especially if there is little clinical response to the initial treatment.
Comparison of the diagnostic criteria for diabetes mellitus, WHO‐1985, ADA‐1997 and WHO‐1999 in the adult population of Asturias (Spain)
Authors: Botas P. , Delgado E. , Castaño G. , Díaz de Greñu C. , Prieto J. , Díaz‐Cadórniga F. J.
Published: October 2003

Aims  To estimate the prevalence of diabetes mellitus with three diagnostic criteria (WHO‐1985 and 1999 and ADA‐1997), evaluate their concordance and analyse the sensitivity and specificity of the different screening strategies for diabetes.

Methods  A cross‐sectional population study with two‐step sampling. One thousand and 34 people were selected randomly. A 75‐g oral glucose tolerance test (OGTT) was performed and venous blood samples were obtained fasting and at 2 h.

Results  The prevalence of known Type 2 diabetes mellitus (DM‐2) is 4%[95% confidence interval (CI) 2.8, 5.1]. By WHO‐1985 criteria the prevalence of unknown DM‐2 is 5.9% (4.5, 7.4); by ADA‐1997 criteria 3.5% (2.5, 4.6) and by WHO‐1999 criteria 7.3% (5.8, 8.8). Diagnostic overlap and statistical concordance (coefficient K) are WHO‐1985/ADA‐1997 29.3%, K = 0.42; WHO‐1985/WHO‐1999 80%, K = 0.88; ADA‐1997/WHO‐1999 48%, K = 0.63. If only fasting glucose was used (following ADA‐1997), 36.3% of those with diabetes (2‐h glucose ≥ 11.1 mmol/l) would be diagnosed. If OGTT was performed (i) in those with a fasting glucose between 6.1 mmol/l and 6.9 mmol/l (9.8% of the population) we would diagnose 66.6%, and (ii) in all those between 5.7 mmol/l and 6.9 mmol/l (18.9% of the population) 81.8% would be diagnosed.

Conclusions  The ADA criteria decrease the prevalence of DM in the adult population of Asturias by 2.4% and concordance with the classical criteria (WHO‐1985) was only 29.3%. Using fasting glucose only (ADA‐1997) diagnoses 36.3% of those with diabetes. The recent recommendations of the WHO‐1999 increases this to 66.6%. To improve the diagnostic strategy for diabetes and detect up to 81.8% of patients, we propose the use of OGTT for all those with a fasting glucose between 5.7 mmol/l and 6.9 mmol/l.
Brachial‐ankle pulse wave velocity measured automatically by oscillometric method is elevated in diabetic patients with incipient nephropathy
Authors: Yokoyama H. , Hirasawa K. , Aoki T. , Ishiyama M. , Koyama K.
Published: October 2003

Aims  To examine whether brachial‐ankle pulse wave velocity (baPWV), a possible early marker of atherosclerotic vascular damage, is associated with albuminuria in patients with Type 2 diabetes.

Methods  BaPWV was measured by automatic oscillometric method in 346 Type 2 diabetic patients with normoalbuminuria (a mean level of three times measurements of albumin‐to‐creatinine (ACR) < 30 µg/mg creatinine; n = 200), incipient nephropathy (a mean level of ACR ≥ 30 and < 300 µg/mg creatinine; n = 119), and clinical nephropathy (a mean level of ACR ≥ 300 µg/mg creatinine; n = 27), and without peripheral vascular disease.

Results  BaPWV (cm/s) was significantly higher in patients with incipient nephropathy (1722 ± 382) and clinical nephropathy (1763 ± 322) than in patients with normoalbuminuria (1559 ± 343, P < 0.0001, respectively). By univariate analysis it correlated significantly with age (r = 0.44, P < 0.0001), systolic blood pressure (r = 0.55, P < 0.0001), diastolic blood pressure (r = 0.42, P < 0.0001), albuminuria (r = 0.24, P < 0.0001) and HbA1C (r = 0.11, P < 0.05). Albuminuria revealed an independent significant association with baPWV (P < 0.01) after adjustment for age, sex, smoking, BMI, HbA1C, hyperlipidemia, and hypertension. Multiple regression analysis showed age, diastolic blood pressure and albuminuria were independently associated with baPWV (adjusted R2 = 0.42, P < 0.0001).

Conclusions  The results might indicate a possible link between the pathogenesis of atherosclerosis and diabetic nephropathy. Future studies are needed to clarify the usefulness and its predictable value.
Socio‐economic inequalities in diabetes complications, control, attitudes and health service use: a cross‐sectional study
Authors: Bachmann M. O. , Eachus J. , Hopper C. D. , Davey Smith G. , Propper C. , Pearson N. J. , Williams S. , Tallon D. , Frankel S.
Published: October 2003

Aims  To investigate socio‐economic inequalities in diabetes complications, and to examine factors that may explain these differences.

Methods  Cross‐sectional questionnaire survey of 770 individuals with diabetes among 40 general practices in Avon and Somerset. General practice, optometrist and eye hospital records over time (median 7 years) were analysed. Slope indices of inequality, odds ratios and incidence rate ratios were calculated to estimate the magnitude of inequality between the most and least educated, and the highest and lowest earning patients, adjusted for age, sex and type of diabetes, and clustering of outcomes within practices.

Results  The least educated patients were more likely than the most educated patients to have diabetic retinopathy [adjusted odds ratio (OR) 4.3; 95% confidence interval 0.8, 23.7] and heart disease (adjusted OR 3.6; 1.1, 11.8), had higher HbA1c levels (adjusted slope index of inequality 0.9; 0.3, 1.5), felt that diabetes more adversely affected their social and personal lives (adjusted slope index of inequality 0.8; 0.5, 1.1 Diabetes Care Profile units), were more likely to be recorded as non‐compliant by their health professionals, and had lower rates of hospital attendance (adjusted rate ratio 0.43; 0.26, 0.71). However, they did not see themselves as less compliant, and had higher general practice attendance rates (adjusted rate ratio 1.5; 1.1, 2.2).

Conclusions  Less educated and lower earning individuals with diabetes bear a larger burden of morbidity but use hospital care less. Health service resource allocation should reflect the distribution of chronic illness.
Comparison of repaglinide vs. gliclazide in combination with bedtime NPH insulin in patients with Type 2 diabetes inadequately controlled with oral hypoglycaemic agents
Authors: Furlong N. J. , Hulme S. A. , O'Brien S. V. , Hardy K. J.
Published: October 2003

Aims  This open‐label randomized controlled clinical trial compared the effect on glycaemic control and weight gain of repaglinide vs. gliclazide combined with bedtime NPH insulin in patients with Type 2 diabetes inadequately controlled with oral hypoglycaemic therapy [HbA1c > 7.0% (DCCT aligned assay, normal range 4.6–6.2%)].

Methods  Eighty subjects with Type 2 diabetes were randomized to 13 weeks’ open‐label treatment with repaglinide 4 mg t.i.d. or gliclazide 160 mg b.i.d. in combination with bedtime NPH insulin (initial dose 0.5 units/kg). The fasting blood glucose (FBG) target was ≤ 6.0 mmol/l.

Results  Baseline characteristics were similar for age, sex, weight, BMI, FBG and HbA1c. Glycaemic control improved similarly in both groups—insulin/gliclazide by (mean) 1.0%, from 9.2 to 8.2% (P = 0.001) and by 0.9%, from 9.4 to 8.5% in the insulin/repaglinide group (P = 0.005) (P = 0.83 between groups). Weight gain averaged (mean ± sem) 4.1 ± 0.5 and 3.4 ± 0.4 kg in the insulin/gliclazide and insulin/repaglinide groups, respectively (P < 0.0001 for both groups from baseline) (P = 0.29 between groups). The mean number of hypoglycaemic episodes experienced per patient was 2.95 ± 0.82 (insulin/gliclazide) and 2.3 ± 0.52 (insulin/repaglinide) (P = 0.81 between groups). Both treatments were associated with significant improvements in Diabetes Treatment Satisfaction [Diabetes Treatment Satisfaction Questionnaire‐potential range 0 (min) to 36 (max)]; in the insulin/gliclazide group, by 4.9 ± 1.1 points to 33.3 ± 0.6 (P < 0.0001) and by 3.0 ± 0.9 points to 34.6 ± 0.4 (P = 0.0006) in the insulin/repaglinide group (P = 0.29 between groups).

Conclusions  Over 13 weeks, both repaglinide and gliclazide, when combined with bedtime NPH insulin produce similar significant improvements in glycaemic control (−1%) and similar weight gain.