bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neurite morphogenesis of identified visual interneurons and its relationship to photoreceptor synaptogenesis in the flies, Musca domestica and Drosophila melanogaster
Authors: Meinertzhagen I. A. , Piper S. T. , Sun X. ‐J. , Fröhlich A. 
Published: March 2003

AbstractThe first neuropile, or lamina, of the fly's optic lobe comprises a model set of identified neurons that are arrayed in cylindrical modules, called cartridges. The cartridge acquires adult form only in the second half of the fly's pupal life. All cells are by then correctly located within each of the lamina's cartridges (Drosophila, Musca), becoming invested by glial cells after 75% of pupal development (P + 75%). In adult cartridges, two lamina cells, L1 and L2, receive input from photoreceptor terminals R1–R6, at so‐called tetrad synapses that form in the pupa when these cells' dendrites contact R1–R6. Single‐section electron microscopy (EM, Drosophila) and serial‐EM reconstructions of L1 and L2 (Musca) reveal relationships between the morphogenesis of L1/L2 dendrites and the formation of tetrads. Neurite outgrowth is initially (P + 55%) random and neurites are unbranched; many neurites invaginate surrounding terminals of R1–R6 but, later, embrace the outer surfaces of these. The maximum profusion of neurites at P + 74% coincides with peak numbers of nascent tetrads; neurites then branch vertically, in the lamina's depth. Later, neurites failing to reach R1–R6's outer surfaces regress. Down the length of their axons, L1 and L2's neurites initially form a random sequence, L1 partnering L1 as often as L2, etc., but beginning at P + 74%, L1 partners L2, and L2 partners L1, with progressive strictness. L1 has more neurites overall than L2. These observations are consistent with the following hypotheses: a neurite only survives if it contacts a presynaptic site; a synapse only survives if it progressively acquires the appropriate number and combination of postsynaptic neurites, culminating in a tetrad; an interaction exists between the neurites of L1 and L2, so that the growth of one respects the pattern of growth of the other.
Neuropsin regulates an early phase of Schaffer‐collateral long‐term potentiation in the murine hippocampus
Authors: Komai Shoji , Matsuyama Tomohiro , Matsumoto Kazumasa , Kato Keiko , Kobayashi Masayuki , Imamura Kazuyuki , Yoshida Shigetaka , Ugawa Shinya , Shiosaka Sadao 
Published: March 2003

AbstractWe found that neuropsin, an extracellular matrix serine protease, has a regulatory effect on Schaffer‐collateral long‐term potentiation (LTP) in the mouse hippocampus. Bath application of 1–170 n m recombinant neuropsin modulated early phase LTP in the Schaffer‐collateral pathway with a ‘bell‐shape’ dose–response curve. The maximum enhancing activity (134% of control LTP) was found at ∼ 2.5 nm. Bath application of a neutralizing antibody against neuropsin in the hippocampal slice resulted in a marked inhibition of the tetanus‐induced early phase of LTP. The in vivo continuous intraventricular infusion of an antisense oligonucleotide against neuropsin significantly reduced the amplitude of the tetanus‐induced early phase of LTP in vitro. Neuropsin did not directly change the N‐methyl d‐aspartate (NMDA) current. Thus, neuropsin appears to act as a regulatory molecule in the early phase of LTP via its proteolytic function on extracellular matrix rather than affecting NMDA receptor‐mediated calcium increase.
Previous experience of withdrawal from chronic diazepam ameliorates the aversiveness of precipitated withdrawal and reduces withdrawal‐induced c‐fos expression in nucleus accumbens
Authors: Dunworth Sarah J. , Mead Andy N. , Stephens David N. 
Published: March 2003

AbstractFlumazenil (20 mg/kg, i.p.)‐precipitated withdrawal from chronic treatment with diazepam (DZP, 15 mg/kg, s.c. in sesame oil for 21 days) resulted in a decreased seizure threshold to the convulsant, pentylenetetrazole (PTZ), infused into the tail vein; withdrawal from 21‐day chronic diazepam treatment, interspersed with two periods of drug withdrawal, resulted in a greater decrease in convulsant threshold. A separate experiment showed that consumption of a sucrose solution immediately prior to precipitated withdrawal resulted in a decreased subsequent consumption of the sucrose solution; no such evidence of a conditioned taste aversion (CTA) was seen in mice given prior experience of withdrawal. Thus, prior experience of withdrawal enhanced the effects of a subsequent precipitated withdrawal in increasing seizure sensitivity, but weakened the ability of this withdrawal to serve as an aversive unconditioned stimulus (US). The weakening of the aversive properties of precipitated withdrawal may reflect habituation to the withdrawal stimulus, and was accompanied by a loss of the ability of withdrawal to induce c‐fos expression in the shell of the nucleus accumbens, an area sensitive to both novel, and stressful, as well as rewarding stimuli.
Involvement of the medial septum in stress‐induced relapse to heroin seeking in rats
Authors: Highfield David , Clements Alison , Shalev Uri , McDonald Robert , Featherstone Robert , Stewart Jane , Shaham Yavin 
Published: March 2003

AbstractIntermittent footshock stress has been shown to reinstate extinguished drug‐taking behaviour in rats, but the brain areas involved in this effect are to a large degree unknown. Here we studied the role of the septum in stress‐induced reinstatement of heroin seeking. Rats were trained to self‐administer heroin for 9–10 days (three 3‐h sessions per day, 0.1 mg/kg per infusion). Following training, extinction sessions were given for 8–13 days by substituting saline for heroin, and then tests for reinstatement of heroin seeking were carried out. Reversible inactivation of the medial septum with tetrodotoxin (TTX; 1–5 ng, infused 25–40 min before the test sessions) reliably reinstated heroin seeking, mimicking the effect of 15 min of intermittent footshock. This effect of TTX was not observed after infusions made 1.5 mm dorsally into the lateral septum. In other experiments, it was found that infusions of a low, subthreshold dose of TTX (0.5 ng) into the medial septum, when combined with 2 min of footshock that in itself was ineffective, reinstated heroin seeking. Furthermore, electrical stimulation (400 μA pulses, 100 μs duration, 100 Hz frequency) of the medial septum during exposure to 10 min of intermittent footshock attenuated footshock‐induced reinstatement of heroin seeking. These data suggest a role for the medial septum in stress‐induced relapse to drug seeking. The septum is thought to be involved in neuronal processes underlying behavioural inhibition, thus we speculate that stressors provoke relapse by interfering with these processes.
Response properties of PMLS and PLLS neurons to simulated optic flow patterns
Authors: Li Bing , Li Bao‐Wang , Chen Yao , Wang Lian‐Hong , Diao Yun‐Cheng 
Published: March 2003

AbstractThe processing of optic flow information has been extensively investigated in the medial superior temporal area (MST) of the macaque. In the cat, the posteromedial area and the posterolateral area in the lateral suprasylvian cortex (PMLS and PLLS, respectively) have been suggested as likely participants according to their direction preferences to moving objects. In the present study, 203 PMLS and 123 PLLS neurons were tested with simulated optic flow patterns composed of random dots (including expansion and contraction, clockwise and counter‐clockwise rotation, and translation) and moving bar stimuli. About 90% of the neurons were found to be excited by the optic flow stimuli and most of them were multiple‐responsive to different flow patterns. Only 20–25% of the cells were selective to different optic flow modes, and in general, the direction preference was fairly modest. The selective cells showed stronger directionality to both flow field and moving bar than nonselective cells. However, the optic flow response properties in the PMLS and PLLS were not well correlated with the direction preference to moving bars. In accordance with previous findings, the PMLS was analogous to the middle temporal area of the macaque in many respects. As for the PLLS cells, they were sensitive to fewer types of stimuli, but responded better and more selectively to radial motion. All these results suggest that the two lateral suprasylvian areas are unlikely to be specialized for the analysis or discrimination of different flow patterns, but may play some kind of relay role in optic flow information processing.
Disconnecting hippocampal projections to the anterior thalamus produces deficits on tests of spatial memory in rats
Authors: Warburton E. C. , Baird A. L. , Morgan A. , Muir J. L. , Aggleton J. P. 
Published: March 2003

AbstractA disconnection procedure was used to test whether projections from the hippocampus to the anterior thalamic nuclei (AT), via the fimbria‐fornix (FX), form functional components of a spatial memory system. The behavioural effects of combined unilateral lesions in the AT and FX were compared when they were either in contralateral hemispheres (AT‐FX Contra) or the same hemisphere (AT‐FX Ipsi). Other groups received bilateral FX lesions and Sham surgeries. Expt 1 demonstrated that none of these lesions affected performance of an object recognition task, while performance of an object location task, which tests the subjects' preference for an object that has changed location, was impaired in the AT‐FX Contra and FX groups. In a T‐maze alternation task, however, the FX group was severely impaired while both the AT‐FX Ipsi and AT‐FX Contra lesion groups showed only a mild impairment. In order to test whether spared crossed projections might support spatial performance in the AT‐FX Contra group we then examined the effects of a combined AT‐FX Contra lesion coupled with transection of the hippocampal commissure. This combination of lesions produced a severe disruption in spatial memory performance in the water maze, radial arm maze and T‐maze, which was significantly greater than that produced by ipsilateral and contralateral AT‐FX lesions alone. These results support the notion that disconnection of the AT from their hippocampal inputs produces impairments on a range of spatial memory tasks, but indicate that there are an array of different routes that can subserve this function.
Regulation of GluR2 promoter activity by neurotrophic factors via a neuron‐restrictive silencer element
Authors: Brené Stefan , Messer Chad , Okado Haruo , Hartley Melissa , Heinemann Stephen F. , Nestler Eric J. 
Published: March 2003

AbstractThe AMPA glutamate receptor subunit GluR2, which plays a critical role in regulation of AMPA channel function, shows altered levels of expression in vivo after several chronic perturbations. To evaluate the possibility that transcriptional mechanisms are involved, we studied a 1254‐nucleotide fragment of the 5′‐promoter region of the mouse GluR2 gene in neural‐derived cell lines. We focused on regulation of GluR2 promoter activity by two neurotrophic factors, which are known to be altered in vivo in some of the same systems that show GluR2 regulation. Glial‐cell line derived neurotrophic factor (GDNF) and brain‐derived neurotrophic factor (BDNF) both induced GluR2 promoter activity. This was associated with increased expression of endogenous GluR2 immunoreactivity in the cells as measured by Western blotting. The effect of GDNF and BDNF appeared to be mediated via a NRSE (neuron‐restrictive silencer element) present within the GluR2 promoter. The response to these neurotrophic factors was lost upon mutating or deleting this site, but not several other putative response elements present within the promoter. Moreover, overexpression of REST (restrictive element silencer transcription factor; also referred to as NRSF or neuron restrictive silencer factor), which is known to act on NRSEs in other genes to repress gene expression, blocked the ability of GDNF to induce GluR2 promoter activity. However, GDNF did not alter endogenous levels of REST in the cells. Together, these findings suggest that GluR2 expression can be regulated by neurotrophic factors via an apparently novel mechanism involving the NRSE present within the GluR2 gene promoter.
Neural selectivity for hue and saturation of colour in the primary visual cortex of the monkey
Authors: Hanazawa Akitoshi , Komatsu Hidehiko , Murakami Ikuya 
Published: March 2003

AbstractIn the inferior temporal (IT) cortex of monkeys, which has been shown to play a critical role in colour discrimination, there are neurons sensitive to a narrow range of hues and saturation. By contrast, neurons in the retina and the parvocellular layer of the lateral geniculate nucleus (pLGN) encode colours in a way that does not provide explicit representation of hue or saturation, and the process by which hue‐ and saturation‐selectivity is elaborated remains unknown. We therefore tested the colour‐selectivity of neurons in the primary visual cortex (V1) and compared it with those of pLGN and IT neurons. Quantitative analysis was performed using a standard set of colours, systematically distributed within the CIE (Commission Internationale de l'Eclairage)‐xy chromaticity diagram. Selectivity for hue and saturation was characterized by analysing response contours reflecting the overall distribution of responses across the chromaticity diagram. We found that the response contours of almost all pLGN neurons were linear and broadly tuned for hue. Many V1 neurons behaved similarly; nonetheless, a considerable number of V1 neurons had clearly curved response contours and were selective for a narrow range of hues or saturation. The relative frequencies of neurons exhibiting various selectivities for hue and saturation were remarkably similar in the V1 and IT cortex, but were clearly different in the pLGN. Thus, V1 apparently plays a very important role in the conversion of colour signals necessary for generating the elaborate colour selectivity observed in the IT cortex.
Neurofilament protein distribution in the macaque monkey dorsolateral premotor cortex
Authors: Geyer Stefan , Zilles Karl , Luppino Giuseppe , Matelli Massimo 
Published: March 2003

AbstractRegional and laminar distribution patterns of neurofilament proteins in the dorsolateral premotor cortex (PMd) were studied with monoclonal antibody SMI‐32 in five adult macaque monkeys and compared with the cytoarchitectonical features of the PMd. Our goal was to reveal whether the increasing functional diversity of the PMd which electrophysiological studies have unravelled over the last years is reflected on a structural level by differences in the neurochemical phenotype. Differences in size, shape and packing density of immunopositive layer III and V pyramidal cells define areas much more clearly than do differences in cytoarchitecture. The PMd can be subdivided into a rostral and a caudal part at a level slightly anterior to the genu of the arcuate sulcus. The extent of these two areas matches the two cytoarchitectonically defined areas F7 and F2, respectively. Within area F2, differences in layer V immunoreactive neurons define a dorsal (F2d) and a ventral (F2v) region. The border between areas F2d and F2v lies at the superior precentral dimple and cannot be detected cytoarchitectonically in Nissl‐stained sections. Neurofilament proteins are involved in the stabilization of the cytoskeleton of the axon and have been correlated with axonal size and conduction velocity of nerve fibres. This regional variability in the neurochemical phenotype of layer V within the caudal PMd may reflect a differential organization of the descending output from this part of the premotor cortex. It might also be related to differences in the motor control of voluntary arm and leg movements.
Developmental expression of amphiphysin in the retinotectal system of the chick: from mRNA to protein
Authors: Grabs Detlev , Bergmann Mathias , Rager Günter 
Published: March 2003

AbstractThe role of amphiphysin in clathrin‐mediated endocytosis of synaptic vesicles is well established. However, it is still uncertain if the protein is also involved in developmental mechanisms, e.g. axon outgrowth and synapse formation. To investigate the developmental changes in the expression of amphiphysin we used the retinotectal system of the chick, a highly ordered and easily accessible primary neuronal pathway. Reverse transcription polymerase chain reaction (RT‐PCR) of total RNA from chick retina and tectum revealed first transcripts for amphiphysin, dynamin and synaptotagmin at embryonic day 5 (E5) for both regions. Surprisingly, Western blots of the retina revealed an increase of protein expression for amphiphysin only after E11 in the retina and the tectum. Immunofluorescence for amphiphysin was not detectable before E10 in the developing chick retina, while other presynaptic proteins like synaptotagmin showed already intense signals in the inner and outer plexiform layers. Subsequently, amphiphysin immunoreactivity follows the expression of synaptotagmin and synaptic vesicle protein 2 (SV2) as seen in the retina and the tectum, and exhibits the same staining as the other proteins in the mature chick brain. Ultrastructural data revealed for the first time that amphiphysin is not only limited to conventional synapses but is also abundant in retinal ribbon terminals. Taken together our data reveal that: (i) there is a developmental delay between mRNA transcription and protein expression for key proteins involved in endocytosis; (ii) amphiphysin gets upregulated after synapse formation; and (iii) amphiphysin is present in the synaptic vesicle cycle in retinal ribbon synapses.
MPTP selectively induces haem oxygenase‐1 expression in striatal astrocytes
Authors: Fernandez‐Gonzalez Angeles , Pérez‐Otaño Isabel , Morgan James I. 
Published: March 2003

AbstractParkinson's disease (PD) is characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta with accompanying evidence of increased oxidative damage, deficits in mitochondrial function and iron deposition. Recently, haem oxygenase‐1 levels were reported to be elevated in PD brains. Because this enzyme is involved in the response to oxidative stress and is critical for cellular haem and iron homeostasis, it could play a role in the pathogenesis of PD. Therefore, we investigated the expression of haem oxygenase isoform 1 (HO‐1) in the 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP) mouse model of PD. MPTP triggered a relatively rapid and persistent increase in HO‐1 mRNA exclusively in the mouse striatum. In situ hybridization and immunohistochemistry showed HO‐1 to be localized to striatal astrocytes. The induction of HO‐1 by MPTP was blocked by selegiline and GBR‐12909, indicating the protoxin had to be metabolized by monoamine oxidase B and taken up by dopaminergic neurons to exert its action in astrocytes. MPTP did not alter the expression of other enzymes of haem synthesis or degradation nor were the levels of mRNA for haem or iron‐binding proteins changed. Thus, expression of HO‐1 was not part of a cellular program involving haem biosynthesis or homeostasis. In addition, heat shock proteins were not induced by MPTP. Thus, MPTP elicited a selective transcriptional response in striatal astrocytes. This response appears to be mediated by molecules released from affected dopaminergic nerve terminals in the striatum acting upon neighbouring astrocytes. This signalling pathway and its potential relevance to PD are discussed.
Galanin influences the mechanosensitivity of sensory endings in the rat knee joint
Authors: Heppelmann Bernd , Just Stefan , Pawlak Matthias 
Published: March 2003

AbstractThe aim of the present study was to examine the effect of galanin on group III and IV afferent nerve fibres (n = 53) innervating normal and acutely inflamed knee joints in rats. They responded to local mechanical stimulation, movements of the joint and i.a. injections of KCl close to the joint. Single i.a. bolus injections of galanin (0.1 mm, 0.2 mL) caused no direct responses of the units. In normal and acutely inflamed joints, about half of the units did not change the responses to knee joint rotation. A significant reduction of the responses to noxious movements was found in ∼ 40% of the units reaching a mean value of 57% in normal joints and 70% in inflamed joints compared with control movements. In ∼ 10% the responses increased to 143% in normal joints and 120% in inflamed joints. Injection of a galanin receptor antagonist (M35) doubled the responses to noxious movements in 36% of the units in normal joints and reduced it in 18% to 86% of the control movements, indicating a tonic release and influence on the mechanosensitivity of a proportion of primary afferents by galanin. In conclusion, these data further support the hypothesis that the mechanosensitivity of fine afferent nerve fibres is regulated by a mixture of different substances being released into the innervated tissue. Besides the action of several pro‐inflammatory peptides there seems to exist a tonic inhibitory system.
Cellular response to texture and form defined by motion in area 19 of the cat
Authors: Khayat Paul S. , Saint‐Amour Dave , Molotchnikoff Stéphane , Lepore Franco , Guillemot Jean‐Paul 
Published: March 2003

AbstractThe present study examined the neuronal sensitivity in area 19 of the cat to a motion‐defined bar and to texture. Sensitivity was tested in normal, lesioned (areas 17–18) and split‐chiasm cats using a kinematogram, as well as a textured bar drifting on a uniform light background and a light bar drifting on a stationary textured background. Texture density was varied. The results indicate that almost all cells of area 19 recorded in the three groups of cats responded to a motion‐defined bar or to its edges. Texture density influenced the responses in that the discharge rate increased as density decreased. However, the majority of cells were sensitive to the highest texture density kinematogram. Moreover, the neural responses of all cats were either independent of the density of the textured bar or background, or were modulated by it. These results show that cells in area 19 can signal the presence of a kinetic bar and that the density of either the textured bar, the background or both can influence figure–ground detection. The results are interpreted with respect to how various inputs influence the function of area 19.
Effects of scopolamine on a novel choice serial reaction time task
Authors: Higgs Suzanne , Deacon Robert M. J. , Rawlins J. Nicholas P. 
Published: March 2003

AbstractRats were trained on a novel attentional task adapted from the five‐choice serial reaction time test first developed by Carli et al. [1983; Behav. Brain. Res., 9, 361–80]. The novel task required rats to detect the occurrence of brief light flashes in one of two spatial locations following trial initiation by a lever press. Blank trials were interleaved with stimulus trials and the rat had to make a different response to indicate the absence of a light. Occasional light‐alone trials were also presented in which the visual stimulus appeared without forewarning. Pre‐exposure to food for 60 min prior to test increased response omissions for all trials and slowed correct response latency, but failed to significantly alter accuracy. A decrease in light‐stimulus duration (1–0.4 s) decreased accuracy, increased the reporting of blank trials and the number of light‐alone trial omissions. Scopolamine (0.03–0.1 mg/kg) and scopolamine methylbromide (0.1 mg/kg) failed to affect accuracy, but increased light‐alone trial omissions and lengthened correct response latency. The results confirm that the novel task is able to distinguish between motivational and attentional manipulations, and imply that scopolamine affected performance via nonattentional mechanisms.