bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effects of Monocular Enucleation on Ganglion Cell Number and Terminal Distribution in the Ferret's Retinal Pathway
Authors: Thompson I. D. , Morgan J. E. , Henderson Z. 
Published: April 2006

AbstractAnterograde and retrograde tracing techniques were used to examine the effects of removing one eye at birth on the remaining uncrossed retinal pathway in adult ferrets. After enucleation, the adult number of labelled ganglion cells projecting ipsilaterally changed from an average of 6068 in normal pigmented ferrets to an average of 7813 (29% increase) in pigmented enucleates. The change in albino ferrets was from 1455 in normals to 2319 in enucleates (59% increase). Labelled cells scattered across nasal retina accounted for over half the increase in the uncrossed population. After neonatal enucleation, the volume of lateral geniculate nucleus occupied by the uncrossed projection increased substantially, five‐fold in pigmented animals and 20‐fold in albinos. These results suggest that neonatal removal of one eye has a greater effect on the distribution of uncrossed terminals than on the survival of uncrossed ganglion cells. There was also an increase in the total number of axons in the surviving optic nerve of both pigmented and albino ferrets (93 000 in enucleates compared with 79 000 in normal animals), which cannot be simply explained as a disruption of binocular competition.Summary
A High Degree of Spatial Selectivity in the Axonal and Dendritic Domains of Physiologically Identified Local‐circuit Neurons in the Dentate Gyms of the Rat Hippocampus
Authors: Han Zhong‐Sheng , Buhl Eberhard H. , Lörinczi Zoltan , Somogyi Peter 
Published: April 2006

AbstractThe axonal and dendritic domains of neurons with extensive, locally arborizing axons were delineated in the dentate gyrus of the rat hippocampus. In horizontally cut slice preparations neurons were briefly recorded and subsequently filled with biocytin when one or several of the following physiological properties were observed: (i) high‐amplitude short‐latency spike afterhyperpolarization; (ii) lack of spike frequency adaptation; (iii) high firing rate in response to depolarizing current. In a sample of 14 neurons, sufficient dendritic and/or axonal detail was recovered to identify them as non‐principal cells, i.e. non‐granule, non‐mossy cells. Five distinct types of cells were recognized, based on the spatial distribution of dendrites, presumably reflecting the availability of afferents, and on the basis of the highly selective distribution of their axon terminals, indicating synaptic target selectivity. They are: (1) the hilar cell forming a dense axonal plexus in the commissural and association pathway terminal field (HICAP cell; horizontal axon extent 1.6 mm) in the inner one‐third of the molecular layer, and having dendrites extending from the hilus to the top of the molecular layer; (2) the hilar cell with its axon ramifying in the perforant path terminal field (HIPP cell, horizontal axon extent 2.0 mm) in the outer two‐thirds of the molecular layer, whereas its spiny dendrites were restricted to the hilus; (3) the molecular layer cell with its dendritic and axonal domains confined to the perforant path terminal zone (MOPP cell, horizontal extent of axon 2.0 mm); (4) the dentate basket cell (horizontal axon extent 0.9 mm) had most of its axon concentrated in the granule cell layer, the remainder being localized in the inner molecular layer and hilus; (5) the hilar chandelier cell, or axo‐axonic cell (horizontal axon extent 1.1 mm), densely innervating the granule cell layer with fascicles of radially orientated terminal rows, and also forming an extensive plexus in the hilus. The three cell types having their somata in the hilus projected to granule cells at the same septo‐temporal level where their cell bodies were located. The results demonstrate that there is a spatially selective innervation of the granule cells by at least five distinct types of dentate neurons, which terminate in several instances in mutually exclusive domains. Their dendrites may have access to all (HICAP cell) or only a few (e.g. HIPP and MOPP cell) of the hippocampal afferents. This arrangement provides a framework for independent interaction between the output of local circuit neurons and subsets of excitatory afferents providing input to principal cells.
Current Source Density Profiles of Optical Recording Maps: a New Approach to the Analysis of Spatio‐temporal Neural Activity Patterns
Authors: Plenz Dietmar , Aertsen Ad 
Published: April 2006

AbstractSpatio‐temporal spreading of activity in the CA1 region of the rat hippocampal slice was studied by two experimental approaches. At identical locations in the tissue we measured both the extracellular field potential distribution with microelectrode recordings and the intracellular potential distribution by optical recording, using voltage‐sensitive fluorescent dyes. Current source density analysis (CSD) was applied to the extracellular field potential distributions (eCSD) to enhance the spatial resolution. In order to obtain an analogous improvement for the optical recordings, we developed a new CSD transformation, which calculates the locations of the transmembrane current generators from the intracellular potential distributions (iCSD). Compared to the underlying fluorescence maps, the new iCSD profiles exhibit a considerable improvement in spatial resolution. Results can be directly interpreted in terms of physiological membrane processes, such as postsynaptic potentials and action potentials. The iCSD profiles show a surprisingly good correspondence with the classical eCSD profiles both qualitatively and quantitatively, the only difference being that cell body activity is reduced in amplitude. Thus, this new optical CSD analysis paves the way for a quantitative interpretation, rather than the hitherto predominantly qualitative interpretation of spatio‐temporal activity profiles from optical recording measurements.
Characterization of a Neurite Outgrowth Inhibitor Expressed After CNS Injury
Authors: Bovolenta Paola , Wandosell Francisco , Nieto‐Sampedro Manuel 
Published: April 2006

AbstractReactive gliosis, a general response to injury in the central nervous system grey and white matter, represents a serious obstacle to axonal regeneration in mammals. In culture, myelin‐free plasma membranes from normal rat brain tissue promoted neurite outgrowth, whereas myelin‐free membranes purified from injured tissue were inhibitory. The inhibitory activity could be solubilized by detergent, was sensible to glycosaminoglycan lyase digestion and eluted with an apparent molecular weight of 160 – 220 kDa in gel filtration chromatography. When presented as a surface‐bound molecule, the inhibitor prevented neurite initiation; when added in a soluble form to growing neurites, it induced their retraction. These results provide cellular and molecular evidence supporting the classical view that, in the mammalian central nervous system, damage‐evoked gliosis correlates with the expression of molecules capable of preventing neurite outgrowth.
The Neurotrophins BDNF, NT‐3 and NT‐4/5, But Not NGF, Up‐regulate the Cholinergic Phenotype of Developing Motor Neurons
Authors: Wong Vivien , Arriaga Ruth , Ip Nancy Y. , Lindsay Ronald M. 
Published: April 2006

AbstractAlthough developing motor neurons express low‐affinity nerve growth factor (NGF) receptors, there is no known biological effect of NGF on developing or adult motor neurons. In this study, we found that, unlike NGF, brain‐derived neurotrophic factor (BDNF), neurotrophin‐3 (NT‐3) and neurotrophin‐4/5 (NT‐4/5) stimulated cholinergic phenotype by increasing choline acetyltransferase (CAT) activity in cultures enriched with embryonic rat motor neurons. Ciliary neurotrophic factor (CNTF) also stimulated CAT activity. The effects of BDNF and NT‐4/5 on CAT activity appeared to be synergistic with that of CNTF. Cotreatment with BDNF and NT‐3 resulted in an additive effect, suggesting that signal transduction was mediated through different high‐affinity receptors tyrosine kinases B and C (Trk B and Trk C). However, cotreatment with BDNF and NT‐4/5 did not result in an increase in CAT activity greater than that of either BDNF or NT‐4/5 alone, suggesting that their effects were mediated via the same receptor Trk B. Supporting our findings that spinal cholinergic neurons are responsive to trophic actions of members of the neurotrophin family, motor neuron‐enriched cultures were found to express mRNA for Trk B and Trk C, which have been identified as high‐affinity receptors for BDNF and NT‐4/5, and NT‐3, respectively.
Effects of Intracortical Infusion of Anticholinergic Drugs on Neuronal Plasticity in Kitten Striate Cortex
Authors: Gu Qiang , Singer Wolf 
Published: April 2006

AbstractDuring a critical period of postnatal development the mammalian visual cortex is highly susceptible to experience‐dependent alterations of neuronal response properties. These modifications are facilitated by the neuromodulators noradrenalin and acetylcholine. To identify the cholinergic mechanisms responsible for this facilitation, muscarinic and nicotinic antagonists were infused into the visual cortex of kittens while the animals were subject to monocular deprivation. Subsequently the ocular dominance of cortical cells was assessed by single‐unit recording. Ocular dominance changes were suppressed by scopolamine and pirenzepine but not by gallamine, hexamethonium and mecamylamine. This blocking effect was concentration‐dependent, and control experiments revealed that it was not due to suppression of neuronal responses to light. It is concluded from these results that acetylcholine facilitates neuronal plasticity in the visual cortex through mechanisms activated by muscarinic M1receptors.
Retinal Projections to the Pretectum, Accessory Optic System and Superior Colliculus in Pigmented and Albino Ferrets
Authors: Zhang H. Y. , Hoffmann K.‐P. 
Published: April 2006

AbstractRetinal projections to the pretectal nuclei, accessory optic system and superior colliculus in pigmented and albino ferrets were studied using anterograde tracing techniques. Both Nissl‐ and myelin‐stained material was used to identify the pretectal nuclei, nuclei of the accessory optic system and the layers of the superior colliculus. Following monocular injection of either horseradish peroxidase or rhodamine‐B‐isothiocyanate, four pretectal nuclei, including the nucleus of the optic tract, posterior pretectal nucleus, anterior pretectal nucleus and the olivary pretectal nucleus, could be identified to receive direct retinal input in both pigmented and albino strains. In the accessory optic system, retinal terminals were observed in the dorsal, lateral and medial terminal nuclei as well as in the interstitial nucleus of the superior fasciculus, posterior fibres. The retinal projection to the superior colliculus was found to innervate the three superficial layers. The retinal projections to the pretectal nuclei and nuclei of the accessory optic system in the pigmented animals were bilateral, although the label was most dense contralateral to the injected eye. Ipsilateral retinal projections to the pretectal nuclei and nuclei of the accessory optic system appeared to be absent in albino ferrets, i.e. they were invisible with our methods. In both pigmented and albino ferrets retinal terminals in the contralateral superior colliculus densely innervated the three superficial layers. In both strains the ipsilateral projection appeared as clusters which were absent in rostral and caudal poles. In pigmented animals the ipsilateral projection was much denser and more extensive than in albinos. Following injection of retrograde tracers into the brainstem at the level of the dorsal cap of the inferior olive, retrogradely labelled neurons in the pretectum were found in the ipsilateral nucleus of the optic tract. Their somata overlapped mainly with scattered retinal terminals close to the pretectal surface and rarely or not all with the deeper prominent terminal clusters. In the accessory optic system, inferior olive projecting neurons were observed in all four ipsilateral nuclei and fully coincided with the retino‐recipient zones. In the superior colliculus, retrogradely labelled neurons were found contralateral to the injection site in the deep layers.
Squint Affects Synchronization of Oscillatory Responses in Cat Visual Cortex
Authors: König Peter , Engel Andreas K. , Löwel Siegrid , Singer Wolf 
Published: April 2006

AbstractAs shown previously, neurons in various areas of the cat's visual cortex respond to appropriate visual stimuli with oscillatory activity in the frequency range of 30 – 70 Hz. It has been suggested that synchronization of such responses serves to define assemblies of coherently active cells which represent individual visual objects. In this study, we have investigated this putative binding mechanism in the visual cortex of strabismic cats. We used six adult cats in which divergent squint had been induced surgically at the age of 3 weeks. Multiunit activity was recorded from area 17 with arrays of four or five closely spaced microelectrodes. Subsequently, auto‐ and cross‐correlation functions were computed for all spike trains. To quantify the oscillatory nature of the responses and the strength of synchronization between spatially remote sites, damped sine wave functions were fitted to the correlograms. Analysis of responses obtained from 202 recording sites showed that the vast majority of cells had become monocular. Auto‐correlation analysis revealed that the proportion of oscillatory firing patterns was similar to that observed in normal cats. However, cross‐correlation analysis of 153 response pairs demonstrated that synchronization was reduced significantly between cells dominated by different eyes while it was as frequent and strong as in normal cats between cells dominated by the same eye. These findings indicate that strabismus not only causes a reorganization of afferent inputs but also affects intracortical interactions. Since strabismic cats lack tangential intracortical connections between territories connected to different eyes and are unable to combine signals conveyed by the two eyes these results support the notion that response synchronization is achieved by cortico‐cortical connections and serves as a mechanism for feature binding.
Memory Impairments Following Lesions to the Mammillary Region of the Rat
Authors: Sziklas Viviane , Petrides Michael 
Published: April 2006

AbstractThe contribution of the mammillary region to learning and memory was investigated. It was demonstrated that lesions of this region impair performance on tasks that require memory for spatial information but that the deficit depends both on the amount of damage within the region and the difficulty of the task. A dissociation in the effect of such lesions on performance of comparable spatial and non‐spatial memory tasks was shown. In contrast to the deficits observed on spatial memory tasks, the acquisition and retention of a complex non‐spatial memory task was not impaired after extensive damage to the mammillary region. Such lesions also did not impair performance in a conditioned taste aversion task. These experiments suggest that the mammillary region may be selectively involved in spatial learning and memory.
Pharmacological and Immunohistochemical Evidence for Serotonergic Modulation of Cholinergic Nucleus Basalis Neurons
Authors: Khateb A. , Fort P. , Alonso A. , Jones B. E. , Mülethaler M. 
Published: April 2006

AbstractIdentified electrophysiologically by low threshold bursts and transient outward rectification, cholinergic nucleus basalis neurons were recorded and labelled intracellularly in guinea‐pig basal forebrain slices. By means of a triple labelling immunofluorescent technique, serotonin‐immunoreactive fibres were visualized in close proximity to the soma and dendrites of the biocytin‐labelled, choline acetyl transferase (ChAT)‐immunoreactive cells. By bath application, 5‐hydroxytryptamine (5‐HT) produced a direct hyperpolarization of the identified cells which was mimicked by 5‐HT1A receptor agonists, suggesting that it may inhibit the tonic firing but also modulate the low threshold bursting of the cholinergic nucleus basalis neurons.
Sarcoplasmic Calcium‐binding Proteins in Aplysia Nerve and Muscle Cells
Authors: Pauls T. L. , Cox J. A. , Heizmann C. W. , Hermann A. 
Published: April 2006

AbstractMuscle (body wall, buccal mass, heart) and neural tissue of the marine mollusc Aplysia californica was analysed for calcium‐binding proteins using transblot45Ca overlay, Western blotting and two‐dimensional polyacrylamide gel electrophoresis, and several low molecular weight calcium‐binding proteins were identified. Our results show that Aplysia muscle contains an abundant protein with a Mr of ∼20 000 with strong 45Ca2+‐binding ability and cross‐reactivity to antibodies against the sarcoplasmic calcium‐binding protein isoform II (SCP II) from Amphioxus. Immunocytochemical studies revealed that isoforms of SCP are distributed in a tissue‐specific manner, SCP II‐like protein is exclusively present in muscle fibres closely associated with the contractile machinery, whereas the isoform I (SCP I‐like protein) is exclusively present in a subset of neurons, suggesting a function in their calcium regulation. In addition, a novel 45Ca2+‐binding protein of Mr 43 000, pl 4.7, was found in muscle and in neurons. A third protein of Mr 40 000, pl 4.8, cross‐reacts with anti‐parvalbumin and anti‐calbindin D‐28K antibodies.
Characterization of a Calcium‐dependent Current Generating a Slow Afterdepolarization of CA3 Pyramidal Cells in Rat Hippocampal Slice Cultures
Authors: Caeser Manfred , Brown David A. , Gähwiler Beat H. , Knöpfel Thomas 
Published: April 2006

AbstractA depolarization‐induced, slowly decaying inward current was examined in slice‐cultured CA3 pyramidal cells by voltage‐clamp techniques and microfluorometric measurements of cytosolic free Ca2+ concentration ([Ca2+]i). Action potentials elicited by intracellular injection of short‐lasting (50 – 100 ms) depolarizing current pulses were followed by a slowly decaying afterhyperpolarization (AHP). After switching to voltage‐clamp mode, short‐lasting (50 – 100 ms) depolarizing voltage jumps from –60 mV to between –30 and 0 mV induced a slowly decaying outward aftercurrent (IAHP) which was depressed by bath application of muscarine (0.5 μM). In the presence of muscarine, the same depolarizations induced a slowly decaying afterdepolarization (ADP) or inward aftercurrent (IADP)in voltage‐clamp mode. This current was also induced in the presence of trans(±)‐1‐aminc‐1,3‐cyclopenta‐nedicarboxylic acid (t‐ACPD, 5 μM), an agonist of metabotropic glutamate receptors, but not in the presence of noradrenalin (5 μM), while both of these agonists depressed IAHP. IADP was depressed by reducing the external Ca2+ concentration from 3.8 to 0.5 mM, by external Co2+ (1 mM) and by external Cd2+ (10 – 100 μM). Combined voltage‐clamp recordings and microfluorometric measurements of [Ca2+]i using the Ca2+ indicator fura‐2 revealed that the amplitude of IADP was correlated with the amplitude of depolarization‐induced Ca2+ influx, IADP was absent at membrane potentials < –90 mV, and reached maximal amplitudes at ∼–55 mV. Raising the extracellular K+ concentration from 2.7 to 13.5 mM increased the amplitude of IADP and resulted in a positively directed shift of the apparent reversal potential of IADP. When the external Na+ concentration was reduced from 157 to 33 or 18 mM the current reversed at more negative potentials and was reduced to 40 and 21%, respectively, of control amplitude. Lowering the external Cl‐ concentration from 159 to 20 mM did not affect IADP. We conclude that IADP most likely represents a Ca2+‐activated cation current, rather than a Ca2+ tail current, or an electrogenic Ca2+ extrusion current.
Activity‐dependent Refinement of Inhibitory Connections
Authors: Sanes Dan H. , Takács Catherine 
Published: April 2006

AbstractSeveral lines of evidence suggest that excitatory synaptic transmission contributes to the maturation of precise neuronal connections. In the present study we determined whether the specific innervation pattern of single inhibitory arborizations was dependent upon neuronal activity during development. A homogeneous group of glycinergic inhibitory neurons in the central auditory system, the medial nucleus of the trapezoid body (MNTB), was functionally denervated in neonatal gerbils. The anatomical specificity of single MNTB terminal arborizations was subsequently measured along the tonotopic axis of a postsynaptic target, the lateral superior olive. Here we demonstrate that inhibitory terminal boutons spread a significantly greater distance along the frequency axis of the postsynaptic target following functional denervation. Although total arbor length remained unchanged, there was a significant increase in the number of branch points, suggesting de novo sprouting. The results indicate that normal inhibitory synaptic activity contributes to the developmental refinement of specific neuronal connections.
Phosphoproteins of Cultured Cerebellar Granule Cells and Response to the Differentiation‐promoting Stimuli NMDA, High K+ and Ionomycin
Authors: Graham Margaret E. , Burgoyne Robert D. 
Published: April 2006

AbstractIn order to investigate signalling pathways involved in the control of granule cell differentiation, survival and other functions by depolarization or activation of NMDA receptors we have characterized protein phosphorylation in cerebellar granule cells. Cultures of cerebellar granule cells were incubated with 32P orthophosphate and then challenged with NMDA, K+ or the Ca2+ ionophore ionomycin, agents which raise [Ca2+]i and stimulate differentiation and survival. Upon separation of labelled phosphoproteins by two‐dimensional gel electrophoresis three differences were found in response to all of these agents. These were an increase in acidity of two phosphoproteins of 87 and 48 kDa (p87 and p48) and increased 32P‐incorporation into a phosphoprotein of 120 kDa (p120). Treatment with PMA which stimulates neurite outgrowth but not survival affected p87 (increased its acidity) but not p48. The acidic shift of p87, therefore, is not sufficient to stimulate granule cell survival. The identification of p87 as the actin‐binding MARCKS protein and the demonstration of its presence in neurites and growth cones of granule cells suggests that it may be involved in NMDA‐stimulated neurite outgrowth. The phosphoproteins p120 and p48 may potentially be involved in events linking the rise in [Ca2+]i to increased granule cell survival or other aspects of granule cell differentiation.
Negative Regulation of Schwann Cell Myelin Protein Gene Expression by the Dorsal Root Ganglionic Microenvironment
Authors: Cameron‐Curry Patrizia , Dulac Catherine , Le Douarin Nicole M. 
Published: April 2006

Abstract In vivo, the surface glycoprotein Schwann cell myelin protein (SMP) is expressed in the quail peripheral nervous system exclusively by Schwann cells. It is not detectable at any developmental stage either in enteric glia or in ganglionic satellite cells. We demonstrate here that the satellite glial cells of the dorsal root ganglia start to express SMP on their surface when they are dissociated into single cells and cultivated in vitro. Activation of SMP synthesis is a rapid event observed in mass cultures of dorsal root ganglia dissociated cells as soon as 4 h after the onset of the culture. Confocal microscope analysis revealed that satellite cells may acquire the Schwann cell marker when still in close contact with the neuronal soma. Clonal cultures of satellite cells from E8 dorsal root ganglia demonstrated that the progeny of these SMP‐negative cells steadily express SMP. This, together with similar results previously obtained with enteric glia, suggests that the SMP‐positive phenotype is a constitutive trait of the peripheral glial cell lineage which is inhibited in satellite cells in vivo by the microenvironment prevailing in the peripheral nervous system ganglia.