bluuebunny/crossref_metadata_2025_split huggingface dataset:
Horizontal Interactions in Cat Striate Cortex: I. Anatomical Substrate and Postnatal Development
Authors: Luhmann H. J. , Singer W. , Martinez‐Millán L. 
Published: April 2006

AbstractThe system of tangential connections was studied in area 17 of normally reared (NR), binocularly deprived (BD) and dark‐reared (DR) kittens and adult cats. Connections were labelled antero‐ and retrogradely by intracortical micro‐injections of several fluorescent markers and horseradish peroxidase conjugated with wheat‐germ agglutinin (WGA‐HRP). In 5‐day‐old kittens tangential connections consist of homogeneously distributed fibres extending maximally over 2.7 mm. Around postnatal day (pnd) ten these connections start to express the patchy pattern characteristic of the adult. Retrogradely stained somata and anterogradely labelled terminals become organized in individual 300 to 350 μm wide clusters with a centre‐to‐centre spacing of about 500 μm. During the first three postnatal weeks the horizontal connections increase their span to up to 10.5 mm and the spacing between individual patches increases to about 700 μm. Over the following 4 weeks these projections become reduced in length and number. In adult NR cats, tangential connections span a distance of up to 3 mm and form a lattice of 200–500 μm wide clusters, which have an average centre‐to‐centre spacing of 1050 μm. Tangential connections originate and terminate in all cortical laminae except layer I and they are organized in register. The distances spanned are largest in supragranular, intermediate in infragranular and shortest in granular layers. In BD and DR cats older than 10 weeks, the length of intracortical tangential fibres becomes reduced to the same extent as in NR animals, but individual clusters are less numerous. The authors conclude that the lattice‐like structure of lateral connections evolves independently of visual experience, and that the selectivity of interactions results from pruning of initially exuberant connections. It is suggested that this pruning process is dependent on activity and influenced by visual experience.
Horizontal Interactions in Cat Striate Cortex: II. A Current Source‐Density Analysis
Authors: Luhmann H. J. , Greuel J. M. , Singer W. 
Published: April 2006

AbstractThe current source‐density (CSD) analysis was used to investigate the organization of tangential synaptic connections in primary visual cortex of normally reared (NR) kittens and of NR, binocularly deprived (BD) and dark‐reared (DR) adult cats. Laminar profiles of field potentials, elicited by intracortical microstimulation were measured at various distances from the stimulating electrodes. To exclude contamination by axon collaterals of antidromically stimulated thalamo‐cortical fibres, these were destroyed by injecting the cytotoxin N‐methyl‐D‐aspartate (NMDA) into the lateral geniculate nucleus 13–27 days before recording. The CSD profiles revealed distinct layer‐specific patterns of lateral spread of activity. Invariably, the most prominent, long‐lasting and far reaching responses were recorded in supragranular layers. Responses in layer IV were brief and confined to the vicinity of the stimulation site. Responses in infragranular layers spread as far as those in supragranular layers, but were of smaller amplitude. Latency considerations, the results of double shock stimulation, and the effects of translaminar cuts, suggest that these responses were monosynaptic and mediated by intracortical pathways with a conduction velocity of 0.3–5 m/s. The spatial spread of these responses changed substantially with age but was not influenced by visual deprivation. In NR adults, supra‐ and infragranular responses were recordable up to 2.5 mm from the stimulation site and layer IV responses up to 1 mm from the stimulation site. In kittens, the former responses spread up to 5 mm and the latter up to 2 mm from the site of stimulation. The amplitude of the responses decreased with distance from the stimulation site. This decrease was not always monotonic suggesting inhomogeneities in the tangential projections. The laminar distribution of current sinks and sources indicates that the pathways mediating tangential interactions form excitatory synapses on apical dendrites of pyramidal cells. It is concluded that the spatial spread of tangential excitatory interactions decreases with age, but that neither the laminar pattern nor the age‐dependent reduction in the strength of tangential interactions are influenced by visual deprivation.
Cross‐desensitization Reveals Pharmacological Specificity of Excitatory Amino Acid Receptors in Isolated Hippocampal Neurons
Authors: Kiskin N. I. , Krishtal O. A. , Tsyndrenko A. Ya. 
Published: April 2006

AbstractIonic currents elicited by excitatory amino acids were studied, using the concentration clamp method, in enzymatically isolated rat hippocampal neurons. Cross‐desensitization between the responses to various agonists was applied to separate the activity of two types of receptors, N‐methyl‐D‐aspartate (NMDA) and non‐NMDA. NMDA receptors were selectively activated by NMDA, L‐ and D‐aspartate, D‐glutamate and quinolinate. Kainate and α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionate appeared to be selective, and quisqualate relatively less selective non‐NMDA agonists, acting on the same receptor type. L‐Glutamate, L‐ and D‐homocysteate activated both receptor types. It is supposed that two receptor sites, activation site and densensitization site, control the action of agonists at the non‐NMDA receptor. When examined in the cross‐desensitization experiments, NMDA and non‐NMDA receptors appear to be represented by the two homogeneous and independent receptor populations operating different ionic channels.
Distribution of Tyrosine Hydroxylase mRNA in the Rat Central Nervous System Visualized by Alkaline Phosphatase in situ Hybridization Histochemistry
Authors: Kiyama H. , Emson P. C. , Ruth J. 
Published: April 2006

AbstractThe expression of tyrosine hydroxylase mRNA in the rat brain was examined using a novel alkaline phosphatase labelled antisense oligodeoxynucleotide probe. The alkaline phosphatase labelled probe revealed the presence of tyrosine hydroxylase mRNA in all the major cell groups and cell bodies previously described as containing catecholamine fluorescence or known to contain tyrosine hydroxylase immunoreactivity. Using standardized development protocols qualitative comparisons between the amount of mRNA signal in different adrenergic, noradrenergic or dopaminergic cell groups could be made. These studies showed that of the three known catecholaminergic cell types the level of tyrosine hydroxylase mRNA signal was high in the noradrenergic and dopaminergic cells, but much lower in the adrenergic cell groups. The sensitivity of this nonradioactive method of in situ hybridization is excellent and has considerable potential for studies of coexistence or coexpression of two mRNA signals for the localization of mRNA signals at the electron—microscope level.
Modulation of VIP‐Stimulated cAMP Formation by Excitatory Amino Acids in Mouse Cerebral Cortex
Authors: Schaad N. C. , Schorderet M. , Magistretti P. J. 
Published: April 2006

AbstractWe have investigated the modulatory action of excitatory amino acids (EAA) on vasoactive intestinal polypeptide (VIP)‐stimulated cAMP formation in mouse cerebral cortical slices. Glutamate and aspartate potentiate in a concentration‐dependent manner the effect of VIP. In order to characterize the type of receptor involved, we have used three prototypical EAA receptor agonists, that is, kainate, N‐methyl‐D‐aspartate (NMDA) and quisqualate. Kainate mimicked the effect of glutamate, NMDA was inactive and quisqualate displayed an inhibitory action. Furthermore, ibotenate also potentiated the effect of VIP on cAMP formation, while L‐homocysteate exhibited an inhibitory action. Ibotenate was 4‐fold more potent and 2.5 times more effective than glutamate. However, the effects of kainate and ibotenate were not additive, suggesting the activation of a common receptor. Thus, based on this metabotropic action, EAA can be categorized into the following classes: (i) those that potentiate the effect of VIP, such as glutamate, aspartate, kainate and ibotenate; (ii) those that inhibit the effect of VIP, such as L‐homocysteate and quisqualate; and (iii) those that are ineffective, such as NMDA and D‐homocysteate. The effects of glutamate or ibotenate on VIP‐stimulated cAMP formation were completely inhibited by L‐phosphoserine and only partially by kynurenate. In a low chloride medium, or in the presence of 8‐(N,N‐diethylamino) octyl‐3,4,5‐trimethoxybenzoate‐hydrochloride (TMB‐8), an inhibitor of calcium release from internal stores, EAA did not potentiate the effect of VIP, thus stressing the importance of these ions for the transduction of the glutamatergic signal. Our results indicate the existence of marked interactions between EAA and VIP on cAMP formation; the pharmacology of these interactions is, however, clearly distinct from the classical pharmacology of EAA which is mainly based on electrophysiological and binding studies.
Distribution of Galanin mRNA Containing Cells and Galanin Receptor Binding Sites in Human and Rat Hypothalamus
Authors: Bonnefond C. , Palacios J. M. , Probst A. , Mengod G. 
Published: April 2006

AbstractThe distribution of cells containing galanin mRNA and that of galanin receptor binding sites were investigated using in situ hybridization histochemistry and receptor autoradiography in male rat hypothalamus and in postmortem hypothalamic tissues from control human brains. Oligonucleotide probes labelled with 32P were used for hybridization experiments. The specificity of the hybridization signal was ascertained using several probes, competition assays and Northern blot analysis. High levels of hybridization were found in the paraventricular, supraoptic and arcuate nuclei of rat and human hypothalamus. Human intermediate nuclei and scattered cells of the posterior perifornical nucleus also contained galanin mRNA. Galanin mRNA was also found in the dorsomedial nucleus of the rat. The distribution of galanin receptor sites was investigated by receptor autoradiography using 125I‐labelled porcine galanin. The specificity of the binding was assessed by competition with different neuropeptides. While galanin blocked the binding at nanomolar concentrations, the other neuropeptides examined were ineffective at 10‐7 M concentrations. The highest densities of galanin binding sites were seen in the preoptic area, ventromedial and lateral nuclei, of rat and human hypothalamus. In contrast, very low densities of binding sites were observed in the paraventricular, supraoptic and arcuate nuclei. Our results show that the distribution of neurons expressing galanin is complementary to that of galanin receptors in the rat and human hypothalamus. This suggests that receptors for galanin are not located on the cell bodies of galaninergic neurons, but are probably presynaptic on or postsynaptic to the processes of these cells.
Differential Actions of Endogenous and Iontophoretic Dopamine in Rat Striatum
Authors: Williams Graham V. , Millar Julian 
Published: April 2006

AbstractWe have voltammetrically monitored dopamine release in the rat striatum evoked either by stimulation of the median forebrain bundle or by iontophoresis. Neuronal spike activity was recorded with the same microelectrode alternately with voltammetric scans. Low levels of stimulation‐evoked dopamine (< 1 μM) excited all striatal units tested. However, this effect could be converted into an inhibition at higher levels of release. In contrast to the results with neuronally released dopamine, excitation was never seen when dopamine was applied by iontophoresis. Inhibition was, however, observed at high concentrations (> 1–5 μM) of exogenous dopamine. These data show that endogenous dopamine at low levels may be predominantly an excitatory transmitter in the striatum, but exogenous (iontophoretic) dopamine does not have the same effect on striatal unit activity as the endogenous material.
Efferent Pattern of Fictive Locomotion in the Cat Forelimb: with Special Reference to Radial Motor Nuclei
Authors: Gödderz W. , Illert M. , Yamaguchi T. 
Published: April 2006

AbstractIn immobilized decerebrate cats fictive locomotion was evoked by midbrain stimulation to analyse the efferent pattern to elbow and to distal forelimb muscles innervated by the deep radial nerve. The locomotor activity was assessed by recording nerve discharges and motoneuronal membrane potential changes. The elbow flexor and extensor motoneurons showed a reciprocal activity; the membranes were correspondingly depolarized and hyperpolarized. In the motor nuclei to the wrist and digit extensors the active phases changed systematically according to the radio‐ulnar order of the muscles: the extensor carpi radialis (ECR) was flexor‐coupled, the ulnaris (ECU) extensor‐coupled, the digitorum communis (EDC), the lateralis (EDL) and the indicis proprius (EIP) displayed intermediate patterns. Intracellular recordings from these motoneurons revealed in all motor nuclei, except ECR, a double depolarization. The first occurred early and the second later in the flexor phase; a hyperpolarization was interposed. The second depolarization mainly determined the active phase. According to the radio‐ulnar order of the muscles the onset and termination of the second depolarization were delayed. This was presumably due to the interposed hyperpolarization, which progressively increased in amplitude. The ECR exhibited a single depolarization, into which the double depolarization apparently merged. The other radial motor nuclei, supinator (Sup) and Abductor pollicis longus (APL) displayed complex patterns. Sup showed tonic discharges, flexor‐type discharges or discharges extending both into the flexor and extensor phase, APL showed discharges similar to either EIP or Sup. Membrane potential changes were small in APL and Sup. Thus, the central locomotor network generates differentiated efferent activities in the distal forelimb muscles, the radio‐ulnar order of the muscles being important for the generated pattern.
The Maturation of the Superior Collicular Map of Auditory Space in the Guinea Pig is Disrupted by Developmental Auditory Deprivation
Authors: Withington‐Wray D. J. , Binns K. E. , Dhanjal S. S. , Brickley S. G. , Keating M. J. 
Published: April 2006

AbstractGuinea pigs, reared from birth in an environment of omnidirectional white noise, fail to develop a map of auditory space in the deeper layers of the superior colliculus. Collicular responses from such noise‐reared animals reveal large auditory spatial receptive fields. The representation of auditory space in the colliculus shows no topographic order. Exposing developing animals to the noise environment only for restricted time periods showed that animals reared normally up to 26 days after birth (DAB) and then placed in the noise chamber could not construct spatial maps, whereas animals reared normally to 30 DAB and then placed in the noise chamber until the terminal mapping experiment could construct topographically organized spatial maps with local receptive fields. Limiting the noise exposure to the period between 26 and 30 DAB was sufficient to prevent spatial map formation. The failure to form a map of auditory space did not reflect environmental damage to the cochlea or the functional organization of the primary auditory pathway. The response thresholds of cochlear microphonics and of auditory responses in both the inferior and superior colliculus were normal in noise‐reared animals. Similarly normal were the tonotopic organization and frequency tuning characteristics of inferior collicular neurons. The rearing environment thus appears to exert a selective effect upon the maturation of the superior collicular map of auditory space. We attribute this effect to the masking, by the omnidirectional broad‐band noise, of discrete localized auditory stimuli. Cues deriving from these latter stimuli would appear to be necessary for the elaboration of the map of auditory space. This auditory experience operates during a 4 day crucial developmental period from 26 to 30 DAB. This is the same developmental time window as that during which visual experience is required for the construction of the map.
Lateral Mobility of the Cell Adhesion Molecule L1 Within the Surface Membrane of Morphologically Undifferentiated and Differentiated Neuroblastoma Cells
Authors: Pollerberg G. Elisabeth , Davoust Jean , Schachner Melitta 
Published: April 2006

AbstractLateral mobility and localization in the surface membrane of the adhesion molecule L1 was studied in morphologically undifferentiated and differentiated neuroblastoma cells to gain insight into its possible association with the different molecular forms of N‐CAM. In undifferentiated cells, the fraction of mobile L1 molecules is high and similar to that of N‐CAM 140. Upon long‐term morphological differentiation, the fraction of mobile L1 molecules is reduced by a factor of three and is similar to that of N‐CAM 180, the predominant molecular form of N‐CAM in differentiated neuroblastoma cells. Comparable to N‐CAM 180, L1 is also preferentially accumulated at contact sites between these cells as seen by indirect immunofluorescence. These observations raise the question of whether at least part of the L1 molecules may be directly or indirectly (e.g. via N‐CAM 180) linked to the cytoskeleton, thus stabilizing cell contacts between differentiated cells.
Heterogeneity in the Dorsal Subiculum of the Rat. Distinct Neuronal Zones Project to Different Cortical and Subcortical Targets
Authors: Witter Menno P. , Ostendorf Robert H. , Groenewegen Henk J. 
Published: April 2006

AbstractThe aim of the present study was to relate the distribution of efferents of the dorsal subiculum to their origin along the proximo‐distal axis of the subiculum. The distribution of subicular projections was studied in detail by means of the sensitive anterograde tracer Phaseolus vulgaris‐leucoagglutinin (PHA‐L), and the precise origin of these projections analysed with retrogradely transported fluorescent tracers, using double‐ and triple‐labelling protocols. Injections of PHA‐L in the proximal part of the dorsal subiculum, i.e. that part which borders field CA1, result in labelling of the infralimbic, entorhinal and perirhinal cortices, the nucleus accumbens and the lateral septa) region, the interanteromedial nucleus of the thalamus, the core of the nucleus gelatinosus, and the mammillary nuclei, in particular in the rostral parts of the medial nucleus. In contrast, injections in the distal part of the dorsal subiculum, i.e. that part which borders the presubiculum, give rise to labelling in the retrosplenial and postrhinal cortices, the presubiculum, the anterior thalamic complex, the shell of the nucleus gelatinosus, and the mammillary nuclei, preferentially in the caudal part of the medial nucleus. The results of injections of different retrograde tracers, simultaneously placed in two or three targets of the subicular efferents, confirm the results of the anterograde tracing experiments. Moreover, they clearly demonstrate that the population of subicular neurons which, for example, projects to the nucleus accumbens and the interanteromedial nucleus of the thalamus is almost completely segregated from the population that projects to the retrosplenial cortex and the anterior complex of the thalamus. Thus within the dorsal subiculum, populations of neurons can be differentiated so that each population projects to a unique set of target structures. These cell populations are differentially positioned along the proximo‐distal axis. In view of additional evidence indicating that some of the major afferents to the subiculum are organized along the same axis, we suggest that the heterogeneity of the dorsal subiculum along the proximo‐distal axis reflects a general organizational characteristic of this hippocampal field.
Climbing Fibre Responses in Olivo‐cerebellar Slice Cultures. I. Microelectrode Recordings from Purkinje Cells
Authors: Knöpfel T. , Audinat E. , Gähwiler B. H. 
Published: April 2006

AbstractCerebellar slices prepared from newborn rats were co‐cultured with slices derived from the inferior olive of 4‐day‐old rats. After several weeks in vitro olivary fibres projecting into the cerebellar tissue could be assessed by anterograde labelling with the fluorescent dye 1,1‐dioctadecyl‐3,3,3,3′‐tetramethylindocarbocyanine perchlorate (Dil). Following electrical field stimulation of the olivary tissue, all‐or‐nothing complex spikes were generated in Purkinje cells, which closely resembled climbing fibre responses as seen in situ. These responses were completely and reversibly abolished by 6‐cyano‐7‐nitroquinoxaline‐2‐3‐dione (CNQX, 5 μM), an antagonist of non‐N‐methyl‐D‐aspartate excitatory amino acid receptors. Wash in of smaller concentrations of CNQX (0.5–2 μM) resulted in a graded dose‐dependent depression of the climbing fibre‐induced postsynaptic potentials and in a consecutive failure of distinct active components of the complex spikes. With climbing fibre synaptic transmission blocked by CNQX, complex spike‐like potentials could, however, still be evoked by intrasomatic injection of depolarizing current pulses. Increasing the concentration of Mg2+ in the bathing solution from 0.5 to up to 8 mM depressed regenerative complex‐spike components. Olivary stimulation elicited only monophasic postsynaptic potentials in Purkinje cells under these conditions. These observations indicate that voltage‐gated conductances which are substantially involved in the generation of the complex spike, are gated by the climbing fibre synaptic depolarization rather than directly by the climbing fibre transmitter.
Relation Between Putative Transmitter Phenotypes and Connectivity of Subplate Neurons During Cerebral Cortical Development
Authors: Antonini A. , Shatz C. J. 
Published: April 2006

AbstractDuring development, the earliest generated neurons of the mammalian telencephalon reside in a region of the white matter, the subplate, just beneath the cortical plate. Neurons in the subplate are only transiently present in the telencephalon: shortly after birth in the cat the majority have disappeared. During their brief life, however, subplate neurons mature; they extend long‐distance and local projections, and express immunoreactivity for GABA and several neuropeptides. In the present study we examined the relation between possible transmitter phenotypes of subplate neurons and their connectivity. To do so, we used a double‐label technique in which immunohistochemistry for neuropeptide Y (NPY), somatostatin (SRIF) or calbindin (CaBP) was combined with retrograde tracing. Experiments were performed in neonatal cats and in ferret kits at equivalent postconceptional ages, times when subplate neurons are numerous. Subplate neurons immunoreactive for neuropeptides and CaBP could be double‐labelled by an injection of retrograde tracer either into the cortical plate or the white matter, indicating that this particular subset of subplate neurons can make local circuit projections. In contrast, peptide or CaBP immunoreactive subplate neurons could never be retrogradely labelled from a tracer injection into the thalamus. Taken together, these observations indicate that subplate neurons immunoreactive for NPY, SRIF and CaBP are likely to be interneurons exclusively. On the other hand, subplate neurons with long‐distance projections to the thalamus or the contralateral hemisphere could be labelled by the retrograde transport of D‐[3H]aspartate, suggesting that at least some projection subplate neurons might use an excitatory amino acid as a neurotransmitter. These results indicate that there is a defined relationship between the putative transmitter phenotypes of subplate neurons and their patterns of projection. Interneurons of the subplate express peptidergic properties while projection neurons to the thalamus may use an excitatory amino acid. Thus, these basic organizational features of the transient subplate are reminiscent of those found in the adult cortical layers.