bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lower rhombic lip‐derived cells undergo transmedian tangential migration followed by radial migration in the chick embryo brainstem
Authors: Ono Katsuhiko , Yasui Yukihiko , Ikenaka Kazuhiro 
Published: August 2004

AbstractMigration behaviour and fate of cells originated from the lower rhombic lip (LRL) was examined in the chick embryo hindbrain. LRL‐derived cells tangentially migrate along the pial surface of the brainstem and form a transient subpial migratory stream. In the initial stages of migration, LRL‐derived cells appose each other or axon‐like processes, which is indicative of mode of homophilic chain migration and/or axophilic migration. Some LRL‐derived cells relocate rostroventrally towards the pontine region, although the majority of them migrate circumferentially to the ventral medulla oblongata. Depending on the stage of generation, LRL‐derived cells undergo transmedian migration; late‐generated LRL‐derived cells preferentially colonize the contralateral brainstem compared with early generated cells. Thus, latecomer neuron precursors may migrate past their predecessors in the migratory stream. When LRL‐derived cells leave the subpial migratory stream, they change their migratory direction to a radial one and relocate inwardly, with a profile that resembles a tangential‐to‐radial change seen in cerebellar granule cell precursors. After they enter the parenchymal region of the brainstem, they exhibited morphological differentiation, and some differentiate into excitatory neurons. The present results suggest that LRL‐derived cells migrate across boundaries such as midline or rhombomere, which may facilitate to build up cellular and functional architectures of the hindbrain.
Cognitive tuning of corticospinal excitability during human gait: adaptation to the phase
Authors: Camus Mickael , Pailhous Jean , Bonnard Mireille 
Published: August 2004

AbstractThe aim of this study was to investigate how the cognitive tuning of corticospinal (CS) excitability adapts to the type of evoked‐movement (Flexion vs. Extension) during human gait. Transcranial magnetic stimulation (TMS) was used both as a central perturbation evoking a movement and as a tool for quantifying the CS excitability of the muscles under study (RF/BF). In the first condition (Dst), the TMS occurred at mid‐stance, inducing hip extension, whereas in the second condition (Dsw), the TMS occurred at the beginning of the swing phase, inducing hip flexion. In both conditions, the subjects were asked to cognitively prepare to either not intervene (NINT) or to compensate (COMP) for the evoked‐movements. The results showed that, regardless of the type of evoked‐movement, preparing to compensate resulted in a selective increase in the CS excitability to those muscles that would be involved in counteracting the possible central perturbation, i.e. the hip extensor muscle (BF) to compensate for an evoked flexion during the swing phase or the hip flexor muscle (RF) to compensate for an evoked extension during the stance phase. This latter result offers the first evidence of a modulation in CS excitability to the proximal muscles during the stance phase. In conclusion, the cognitive tuning of CS excitability was found to adapt to the gait phases. Moreover, the same selective preparation strategy was observed whether the central perturbation occurred during the stance or the swing phase of the step cycle.
Nerve terminals of squid photoreceptor neurons contain a heterogeneous population of mRNAs and translate a transfected reporter mRNA
Authors: Gioio Anthony E. , Lavina Zeno Scotto , Jurkovicova Dana , Zhang Hengshan , Eyman Maria , Giuditta Antonio , Kaplan Barry B. 
Published: August 2004

AbstractIt is now well established that the distal structural/functional domains of the neuron contain 2a diverse population of mRNAs that program the local synthesis of protein. However, there is still a paucity of information on the composition and function of these mRNA populations in the adult nervous system. To generate empirically, hypotheses regarding the function of the local protein synthetic system, we have compared the mRNAs present in the squid giant axon and its parental cell bodies using differential mRNA display as an unbiased screen. The results of this screen facilitated the identification of 31 mRNAs that encoded cytoskeletal proteins, translation factors, ribosomal proteins, molecular motors, metabolic enzymes, nuclear‐encoded mitochondrial mRNAs, and a molecular chaperone. Results of cell fractionation and RT‐PCR analyses established that several of these mRNAs were present in polysomes present in the presynaptic nerve terminal of photoreceptor neurons, indicating that these mRNAs were being actively translated. Findings derived from in vitro transfection studies established that these isolated nerve terminals had the ability to translate a heterologous reporter mRNA. Based upon these data, it is hypothesized that the local protein synthetic system plays an important role in the maintenance/remodelling of the cytoarchitecture of the axon and nerve terminal, maintenance of the axon transport and mRNA translation systems, as well as contributing to the viability and function of the local mitochondria.
Dissociation in the effects of neonatal maternal separations on maternal care and the offspring's HPA and fear responses in rats
Authors: Macrí Simone , Mason Georgia J. , Würbel Hanno 
Published: August 2004

AbstractThe development of the hypothalamic–pituitary–adrenal (HPA) response to stress is influenced by the early mother–infant relationship. In rats, early handling (brief daily mother–offspring separations) attenuates the adult offspring's HPA and fear responses compared to both nonhandling (no separations) and maternal separation (prolonged daily separations). It has been proposed that variation in the amount of maternal care mediates these effects of neonatal manipulations on the adult offspring's stress and fear responses. Here we tested this hypothesis by assessing maternal care and the adult offspring's HPA and fear responses in Lister hooded rats which were subjected to either early handling (EH) or maternal separation (MS) from postnatal day 1–13, or were left completely undisturbed (nonhandled, NH) throughout this period. Both EH and MS induced a more active nursing style and elevated levels of maternal care compared to NH. Total levels of maternal care were indistinguishable between EH and MS, but diurnal distribution differed. MS dams showed elevated levels of maternal care following the 4‐h separation period, thereby fully compensating for the amount of maternal care provided by EH dams during the time MS dams were separated from their pups. However, while EH resulted in reduced HPA and fear responses in the adult offspring compared to NH, MS and NH offspring did not differ. Our findings therefore demonstrate dissociation in the effects of EH and MS on maternal care and on the stress and fear responses in the offspring. This indicates that maternal care cannot be the sole mediator of these effects.
Experience‐dependent changes in the hippocampus of domestic chicks: a model for spatial memory
Authors: Freire Rafael , Cheng Heng‐Wei 
Published: August 2004

AbstractIn the domestic chicken, providing visual barriers for a brief period early in life has been found to improve spatial memory [R. Freire et al. (2004)Animal Behaviour, 67, 141–150]. In the present study we compared the structure of neurons in the hippocampus and neostriatum in chicks reared with or without visual barriers. From 8 to 16 days of age, chicks were reared in pens either with two wooden screens (Treatment E) or with no screens (Treatment C). At 16 days of age, chicks were anaesthetized, perfused intracardially and brain samples collected and stained using a Golgi–Cox technique. Morphometric analysis revealed that the multipolar projection neurons of Treatment E chicks had longer dendrites (anova, F1,14 = 7.4, P < 0.05) and had more spines per 20 µm of dendrite (SLD; anova, F1,14 = 10.6, P < 0.01) than those of Treatment C chicks. By contrast, no evidence was found that rearing treatment differentially influences dendrite length or SLD in the neostriatum, suggesting that the above environment‐induced changes may be specific to the hippocampus. Multipolar projection neuron dendrites of the right hemisphere were longer (anova, F1,14 = 36.4, P < 0.0001) and had more spines (anova, F1,14 = 8.8, P < 0.05) than dendrites of the left hemisphere, supporting previous findings that the right hemisphere of chickens is predominantly involved in spatial processing. We conclude that the chicken provides a useful model for the study of developmental plasticity in brain and behaviour, partly because the possibility of rearing chicks in isolation and imprinting them on an artificial object provides a means of accurately manipulating early experience.
Regulation of striatal tyrosine hydroxylase phosphorylation by acute and chronic haloperidol
Authors: Håkansson Kerstin , Pozzi Laura , Usiello Alessandro , Haycock John , Borrelli Emiliana , Fisone Gilberto 
Published: August 2004

AbstractThe typical neuroleptic haloperidol increases the state of phosphorylation and activity of tyrosine hydroxylase (TH), the rate‐limiting enzyme in the synthesis of catecholamines. Here we show that the increases in TH phosphorylation produced by haloperidol at Ser31 and Ser40, two sites critically involved in the regulation of enzymatic activity, are abolished in dopamine D2receptor‐null mice and mimicked by the selective dopamine D2receptor antagonist, eticlopride. Moreover, the ability of haloperidol and eticlopride to stimulate phosphorylation at both seryl residues is prevented by treatment with SL327, a compound that blocks activation of extracellular signal‐regulated protein kinases 1 and 2 (ERK1/2). We also show that chronic administration of haloperidol reduces the basal levels of phosphoSer31‐TH and decreases the ability of the drug to stimulate Ser40 phosphorylation. These results provide a model accounting for the stimulation exerted by haloperidol on dopamine synthesis. According to this model, haloperidol increases TH activity via blockade of dopamine D2receptors, disinhibition of dopaminergic projection neurons and ERK1/2‐dependent phosphorylation of TH at Ser31 and Ser40. These studies also show that lower levels of phosphorylated TH are associated with chronic neuroleptic treatment and may be related to depressed dopaminergic transmission in nigrostriatal neurons.
Central blockade of muscarinic cholinergic receptors disrupts affective and attentional set‐shifting
Authors: Chen Katy C. , Baxter Mark G. , Rodefer Joshua S. 
Published: August 2004

AbstractImpairments in multiple aspects of attentional and executive function follow damage to cholinergic neurons in the central nervous system. Affective and attentional set‐shifting represent two aspects of executive function controlled by different sectors of the prefrontal cortex. The involvement of cholinergic neural mechanisms in these aspects of executive function has not been specified. To determine whether central muscarinic cholinergic receptors were involved in affective and/or attentional set‐shifting, we tested rats on a series of discrimination learning problems, which included affective (reversal learning) and attentional set (extradimensional shift)‐shifting components, under the systemic influence of scopolamine, a muscarinic antagonist. Scopolamine impaired both reversal learning and extradimensional shifting, but was without effect on learning new discrimination problems that did not require an affective or attentional shift. Systemic administration of methylscopolamine, which does not cross the blood–brain barrier, did not impair affective or attentional set‐shifting, indicating that the scopolamine effects were centrally mediated. These data implicate muscarinic receptors in the central nervous system in the control of executive function. Taken together with other recent data, they may also suggest an important role for cholinergic receptors outside of the neocortex in regulating these aspects of attention and executive function.
Repeated sensory contact with aggressive mice rapidly leads to an anticipatory increase in core body temperature and physical activity that precedes the onset of aversive responding
Authors: Pardon Marie‐Christine , Kendall David A. , Pérez‐Diaz Fernando , Duxon Mark S. , Marsden Charles A. 
Published: August 2004

AbstractThe present study investigated whether the ‘psychological threat’ induced by sensory contact with an aggressive conspecific would be a sufficient factor in inducing behavioural and physiological disturbances. Repeated sensory contact with an aggressive mouse (social threat) in a partitioned cage was compared with repeated exposure to a novel partitioned cage in male NMRI mice. We first examined parameters of stress responsiveness (body weight, plasma corticosterone levels, frequency of self‐grooming and defecation). The temperature and physical activity responses to stress were also recorded during and after the 4 weeks of stress using radiotelemetry. Finally, cognitivo‐emotional performance was assessed after acute stress and 2 and 4 weeks of stress by measuring decision making, sequential alternation performance and behaviour in the elevated T‐maze. Social threat had a greater impact than novel cage exposure on most parameters of stress responsiveness, although mice did not habituate to either stressor. Social threat rapidly led to an anticipatory rise in core body temperature and physical activity before the scheduled stress sessions. Such anticipation developed within the first week and persisted for 9 days after ending the stress procedure. Some memory impairment in the sequential alternation test was found in stressed mice, independent of the stressor. After 4 weeks of stress, inhibitory avoidance in the elevated T‐maze was enhanced in socially stressed mice and reduced in novel cage mice. The sustained anticipation of stress in the social threat group preceded aversive responding. It remains to be established whether anticipation contributes to the development of aversive responses.
Hypoxia induces caspase‐9 and caspase‐3 activation without neuronal death in gerbil brains
Authors: Garnier Philippe , Prigent‐Tessier Anne , Van Hoecke Michaël , Bertrand Nathalie , Demougeot Céline , Sordet Olivier , Swanson Raymond A. , Marie Christine , Beley Alain 
Published: August 2004

AbstractTo investigate the in vivo apoptotic machinery in oxygen deprived brain, we examined the expression of caspase‐9 and caspase‐3 in the hippocampus of Mongolian gerbils subjected to either transient hypoxia (4% O2 for 6 min) or forebrain ischemia (10 min bilateral carotid artery occlusion) followed by 8 h to 7 days of reoxygenation or blood recirculation. Apoptotic death was characterized by isolating hippocampal genomic DNA and analysing DNA fragmentation as well as histological studies including TUNEL assay and toluidine blue staining of brain sections. The results showed that both hypoxic and ischemic gerbil brains exhibited an increase in caspase‐9 and caspase‐3 gene expression. However, no cell damage was detectable following hypoxia, while marked DNA fragmentation and extensive cell death was observed following ischemia. Moreover, although hypoxia did not lead to cell death, both hypoxia and ischemia were associated with cleavage of procaspase‐9 and procaspase‐3 and increases in their activities as well as cleavage of poly(ADP‐ribose) polymerase‐1 (PARP‐1), a major caspase‐3 substrate. These results indicate that, in vivo, even late apoptotic events such as caspase activation and PARP‐1 cleavage in hypoxic brains do not necessarily induce an irreversible commitment to apoptotic neuronal death.
Altered agonist sensitivity and desensitization of neuronal mGluR1 responses in knock‐in mice by a single amino acid substitution at the PKC phosphorylation site
Authors: Sato Masaaki , Tabata Toshihide , Hashimoto Kouichi , Nakamura Kenji , Nakao Kazuki , Katsuki Motoya , Kitano Jun , Moriyoshi Koki , Kano Masanobu , Nakanishi Shigetada 
Published: August 2004

AbstractmGluR1 and mGluR5 of the metabotropic glutamate receptor family are coupled to inositol trisphosphate–Ca2+ signal cascades and evoke distinct Ca2+ responses in neural cells and heterologously expressing cells. In heterologous cells, stimulation of recombinant mGluR1 evokes a single‐peaked Ca2+ response whereas mGluR5 elicits an oscillatory Ca2+ response. The distinct Ca2+ responses are interchangeable by single amino substitution of aspartate for threonine at the corresponding position of the carboxy‐terminal cytoplasmic regions of mGluR1 and mGluR5, respectively. In this investigation, we generated knock‐in mice, termed mGluR1 D854T mice, in which aspartate of mGluR1 was replaced with threonine. We examined the effect of this D854T substitution on Ca2+ and current responses mediated by mGluR1 in cultured cerebellar Purkinje cells. Stimulation of mGluR1 D854T by a group 1 mGluR agonist, 3,5‐dihydroxyphenylglycine (DHPG) evoked, as in wild‐type mGluR1, only single‐peaked Ca2+ responses as measured by Ca2+ fluorometric analysis. We then examined mGluR1‐induced inward currents carried by nonselective cation channels during whole‐cell recordings from cultured Purkinje cells. The mGluR1 D854T mutation abolished the responsiveness of mGluR1 to low concentrations of DHPG (0.5–500 nm) and reduced its desensitization during prolonged agonist application. mGluR1 D854T homozygous mutants showed no apparent behavioural abnormality as analysed by motor movement tests. These results indicate that, although additional modulatory mechanisms seem to be required to produce oscillatory Ca2+ responses of mGluR1, the single amino acid substitution at position 854 of mGluR1 is capable of influencing the kinetics of neuronal mGluR1 responses, most probably through PKC‐mediated phosphorylation.
Inwardly rectifying potassium channels in rat retinal ganglion cells
Authors: Chen Ling , Yu Yong‐Chun , Zhao Jing‐Wei , Yang Xiong‐Li 
Published: August 2004

AbstractInwardly rectifying potassium channels (Kir channels) are important for neuronal signalling and membrane excitability. In the present work we characterized, for the first time, Kir channels in rat retinal ganglion cells (RGCs), the output neurons in the retina, using immunocytochemical and patch‐clamp techniques. Various subunits of Kir channels (Kir1.1, 2.1, 2.3, 3.1, 3.2 and 3.3) were expressed in RGCs, but with distinct subcellular localization. Kir1.1 was mainly expressed in axons of RGCs. Kir2.1 and Kir2.3 were both present in somata of RGCs. Whereas staining for Kir3.1 was profoundly present in an endoplasmic reticulum‐like structure and Kir3.2 was strongly expressed in the cytoplasm and the cytomembrane of somata, dendrites and axons of RGCs, faint, sparse labelling for Kir3.3 was seen in the cytomembrane. Immunoreactivity for Kir4.1 and Kir4.2 was not detectable in RGCs. Whole‐cell currents mediated by Kir channels were recorded in isolated RGCs and they differed from hyperpolarization‐activated currents (Ih) by showing full activation in < 10 ms, no inactivation, and being significantly suppressed by 300 µm Ba2+. Unlike in retinal horizontal cells and bipolar cells, these currents were mainly mediated by G‐protein‐coupled Kir3 (GIRK) channels, as demonstrated by the fact that GDPβS and GTPγS included in the pipette solution markedly decreased and increased the currents, respectively. Furthermore, the GIRK channels were probably coupled to GABAB receptors, because baclofen considerably increased the Kir currents and the increased currents were suppressed by Ba2+. These characteristics of the Kir currents provide more versatility for signalling of RGCs.
Rhythmic regulation of membrane potential and potassium current persists in SCN neurons in the absence of environmental input
Authors: Kuhlman Sandra J. , McMahon Douglas G. 
Published: August 2004

AbstractNeurons of the mammalian suprachiasmatic nucleus (SCN) generate self‐sustained rhythms of action potential frequency having a period of approximately 24 h. It is generally believed that cell autonomous circadian oscillation of a network of biological clock genes drives the circadian rhythm in neuronal firing rate through as yet unspecified effects on the neuronal membrane. While it is clear that cyclic gene expression continues in constant darkness, previous studies have not examined which specific membrane properties of SCN neurons continue to oscillate in constant conditions. Here, we demonstrate that SCN neurons exhibit robust rhythms in resting membrane potential and input resistance in constant darkness. Furthermore, application of the K+ channel blocker tetraethylammonium revealed a rhythm in K+ current amplitude that persists in constant darkness and underlies the rhythm in membrane potential.
Genetic deletion and pharmacological blockade of CB1 receptors modulates anxiety in the shock‐probe burying test
Authors: Degroot Aldemar , Nomikos George G. 
Published: August 2004

AbstractCannabinoids affect various behavioral processes, including emotion, learning and memory, which may bspecifically regulated through the CB1 receptors. The exact role CB1 receptors play in anxiety remains unclear. Both genetic and pharmacological blockade of CB1 receptors have produced inconsistent effects on anxiety. However, these studies examined passive avoidance as an index of anxiety. In the present study, both active and passive avoidance were examined using the shock‐probe burying test while CB1 receptors were blocked genetically or pharmacologically. In the shock‐probe burying test, anxiety is reflected by increased burying (increased active avoidance) and increased freezing (increased passive avoidance). In addition, probe‐contacts may reflect cognitive performance and/or passive avoidance. As there have been few studies examining mouse behavior in the shock‐probe burying test, experiment 1 was designed to pharmacologically validate this model in mice. Our results indicated that administration (i.p.) of chlordiazepoxide (4 mg/kg) or FG7412 (5 mg/kg) decreased and increased burying behavior, respectively, without affecting freezing or the number of probe contacts. Experiments 2 and 3 showed that both CB1 knockout mice and mice injected (i.p.) with 3 or 10 mg/kg, but not 1 mg/kg, of the CB1 receptor antagonist SR141716A had lower burying scores, fewer contacts with the probe and similar freezing times compared with wild‐type mice and mice injected with vehicle (experiments 2 and 3). Collectively, these results suggest that CB1 receptor blockade reduces some, but not all, aspects of anxiety. The decrease in probe contacts induced by CB1 receptor blockade may be due to enhanced cognition.
Effects of sensory deprivation on columnar organization of neuronal circuits in the rat barrel cortex
Authors: Schierloh Anja , Eder Matthias , Zieglgänsberger Walter , Dodt Hans‐Ulrich 
Published: August 2004

AbstractWe examined whether sensory deprivation during formation of the cortical circuitry influences the pattern of intracortical single‐cell connections in rat barrel cortex. Excitatory postsynaptic potentials (EPSPs) from layer 2/3 (L2/3) pyramidal neurons were recorded in vitro using patch‐clamp techniques. In order to evoke EPSPs, presynaptic neurons were stimulated by photolytically applied glutamate, thus generating action potentials. Synaptic connections between the stimulated and the recorded neuron were identified by the occurrence of PSPs following photostimulation. Sensory deprivation changed the pattern of projections from L4 and L2/3 neurons to L2/3 pyramidal cells. In slices of non‐deprived rats 86% of the total presynaptic neurons were located in the first and only 10% in the second barrel column. Deprivation changed these values to 67% and 26%, respectively. Therefore, the probability of presynaptic cells projecting to L2/3 neurons was shifted from adjacent to more remote barrel columns. These results indicate that deprivation of sensory input influences the pattern of intracortical connections.