bluuebunny/crossref_metadata_2025 huggingface dataset:
Properties of Single Calcium‐activated Potassium Channels of Large Conductance in Rat Hippocampal Neurons in Culture
Authors: Wann K. T. , Richards C. D.
Published: April 2006

Patch‐clamp recordings were made on rat hippocampal neurons maintained in culture. In cell‐attached and excised inside‐out and outside‐out patches a large single‐channel current was observed. This channel had a conductance of 220 and 100 pS in 140 mM [K+]i/140 mM [K+]o and 140 mM [K+]i/3 mM [K+]o respectively. From the reversal potential the channel was highly selective for K+, the PK+/Pna+ ratio being 50/1. Channel activity was voltage‐dependent, the open probability at 100 mM [Ca2+]i increasing by e‐fold for a 22 mV depolarization. It was also dependent on [Ca2+]i at both resting and depolarized membrane potentials. Channel open states were best described by the sum of two exponentials with time constants that increased as the membrane potential became more positive. Channel activity was sensitive to both external (500 μM) and internal (5 mM) tetraethylammonium chloride. These data are consistent with the properties of maxi‐K+ channels described in other preparations, and further suggest a role for maxi‐channel activity in regulating neuronal excitability at the resting membrane potential. Channel activity was not altered by 8‐chlorophenyl thio cAMP, concanavalin A, pH reduction or neuraminidase. In two of five patches lemakalim (BRL 38227) increased channel activity. Internal ruthenium red (10 μM) blocked the channel by shortening the duration of both open states. This change in channel gating was distinct from the ‘mode switching’ seen in two patches, where a channel switched spontaneously from normal activity typified by two open states to a mode where only short openings were represented.
Hypothalamo‐preoptic Histaminergic Projections in Sleep‐Wake Control in the Cat
Authors: Lin J. S. , Sakai K. , Jouvet M.
Published: April 2006

Cats were chronically implanted with electrodes for polygraphic recordings and cannulae for intracerebral microinjections in order to study the functional role of histaminergic innervation of the preoptic‐anterior hypothalamus in sleep‐wake control. α‐Fluoromethylhistidine (αFMH, 50 μg in 1 μl), a specific inhibitor of the histamine‐synthesizing enzyme, when injected bilaterally into the preoptic area, where numerous histaminergic fibres and terminal‐like structures are present, caused a significant increase in deep slow wave sleep (S2) and paradoxical sleep (PS) and a decrease in wakefulness. In contrast, microinjections of histamine (5 or 30 μg in 1 μl) in the same area dose‐relatedly increased wakefulness and decreased both slow wave sleep and paradoxical sleep. The effects of histamine were reduced by pretreatment with mepyramine (1 mg/kg i. p.), a well known histamine H1receptor antagonist, and were mimicked by a local injection of impromidine (1 μg in 1 μl), a potent histamine H2receptor agonist. Microinjections of mepyramine alone (120 μg in 1 μl) caused an increase in slow wave sleep. These results suggest that preoptic histaminergic innervation is involved in sleep‐wake control and that the action might be mediated via both H1and H2receptors.
Retrograde Axonal Transport of the α‐Subunit of the GTP‐binding Protein Gz in Mouse Sciatic Nerve: a Potential Pathway for Signal Transduction In Neurons
Authors: Crouch Michael F. , Heydon Katharina , Garnaut Sonja M. , Milburn Peter J. , Hendry Ian A.
Published: April 2006

We have utilized antibodies against the α subunit of Gz in fluorescence immunohistochemistry to determine whether this GTP‐binding protein can translocate along nerves by intra‐axonal transport. After ligation of the mouse sciatic nerve we found an increase in Gz‐like immunoreactivity on the proximal and distal side with time, suggesting that the α subunit undergoes orthograde axonal transport and also returns to the cell body by retrograde axonal transport in the sciatic nerve. Unlike the retrograde transport of Giα, shown in a previous study to be present in most sciatic axons, Gzα only accumulated in a subpopulation of axons, suggesting that different G‐proteins could convey information specific to neuronal subtypes. These results support our proposal that Gz may play a second messenger role in communicating information from the terminals back to cell bodies. Giαand Gzα may be representative of relatively stable signalling molecules by which the signal from some neurotrophic molecules can be translocated from the neuronal periphery to the cell body without the need for the retrograde transport of the neurotrophic factor itself.
A Neuromagnetic Study of the Functional Organization of the Sensorimotor Cortex
Authors: Kristeva‐Feige R. , Walter H. , Lütkenhöner B. , Hampson S. , Ross B. , Knorr U. , Steinmetz H. , Cheyne D.
Published: April 2006

Movement‐related neuromagnetic fields from eight healthy human subjects were investigated in a Bereitschaftspotential paradigm. The three conditions studied were right‐sided mouth, index finger and foot movement. The neuromagnetic field patterns corresponding to the motor field and the movement‐evoked field I were analysed using a moving dipole model. For both components a somatotopic organization was found: the estimated dipole locations for the mouth were more lateral and those for the foot more medial than the estimated dipole positions for the index finger movement. With regard to possible clinical applications, e.g. non‐invasive mapping of the sensorimotor cortex and studies of plasticity of the motor function, the present results suggest that the investigation of movement‐evoked field I for the index finger condition is most likely to yield further results.
Melanin and the Regulation of Mammalian Photoreceptor Topography
Authors: Jeffery Glen , Darling Katherine , Whitmore Alan
Published: April 2006

Melanin, or products directly associated with it, regulates the maturation of the neural retina because in hypopigmented mammals the central retina fails to develop fully. To determine whether this deficit is reflected in the distribution of photoreceptors, their topography has been studied in the retinae of normally reared pigmented and albino ferrets and animals reared under reduced light conditions. In both strains, the general distribution of rods and cones was similar to that in the cat, cone density peaking in the central retina and rod density peaking in an annulus around the area centralis. The cone population was organized in the form of an orderly mosaic whose regularity was measured at a wide range of retinal eccentricities. No differences were found in cone numbers or their mosaic distribution between pigmented and albino strains, either at the area centralis or at more peripheral regions. In both cases order within the cone mosaic was independent of cell density or retinal eccentricity. In the albinos there was a significant deficit in the number of rods at all retinal locations when compared with rod numbers in the pigmented animals. There were no differences between normally reared and dark‐reared animals in this respect either within or between the strains. Therefore, the albino gene must have a selective and specific effect on the development of this cell type in the outer retina. Ganglion cells and rods are both affected by the albino gene, while cones are not. Because cones and ganglion cells are generated during the same period and rods are generated later, the albino gene cannot be acting during a particular developmental time window. Because the cone mosaic was normal in the albinos, in spite of a large rod deficit, the factors that regulate the spacing of cones cannot depend in any significant manner upon the later generation and subsequent addition of rods to the outer retina.
Developmental Loss of GABA‐ and Glycine‐induced Depolarization and Ca2+ Transients in Embryonic Rat Dorsal Horn Neurons in Culture
Authors: Wang Jian , Reichling David B. , Kyrozis Andreas , MacDermott Amy B.
Published: April 2006

More than 90% of dorsal horn neurons from embryonic day 15–16 rats responded to the inhibitory amino acids GABA and glycine by a transient elevation of intracellular Ca2+ concentration ([Ca2+]i) when maintained in culture for <1 week. This [Ca2+]i response has previously been shown to be due to depolarization and subsequent Ca2+ entry through voltage‐gated Ca2+ channels following activation of bicuculline‐sensitive GABAA receptors and strychnine‐sensitive glycine receptors. Both the number of cells responding to GABA and glycine and the amplitude of the [Ca2+]i response diminished over time in culture. By 30 days in culture, none of the cells responded to GABA, muscimol or glycine by elevation of [Ca2+]i. The loss of the [Ca2+]i response was not due to a change in the abundance or the properties of voltage‐gated Ca2+ channels, since over the same period of time dorsal horn neurons showed a large increase in the amplitude of the [Ca2+]i transient in response to 30 mM K+. Nor was the loss of the [Ca2+]i response due to a loss of GABA and glycine receptors. Instead, the decrease in the [Ca2+]i response over time paralleled a similar change in the electrophysiological responses. More than 90% of the neurons tested were depolarized in response to inhibitory amino acids during the first week in culture. After 30 days, all neurons tested responded to GABA and glycine with a hyperpolarization. These observations add support to the suggestion that GABA and glycine may excite dorsal horn neurons earlyin development and play a role in postmitotic differentiation.
Opposing Excitatory and Inhibitory Influences from the Cerebellum and Basal Ganglia Converge on the Superior Colliculus: an Electrophysiological Investigation in the Rat
Authors: Westby G. W. Max , Collinson Christine , Redgrave Peter , Dean Paul
Published: April 2006

We recently showed (Westby et al., Eur. J. Neurosci., 5, 1378–1388, 1993) that the cerebellar interpositus nucleus is a source of excitatory drive for a population of spontaneously active neurons in the lateral intermediate layers of the contralateral superior colliculus. Anatomical and physiological studies have shown that this region of the colliculus contains cells of origin of the crossed descending tectoreticulospinal tract and receives GABAergic input from the ipsilateral basal ganglia. In the present study we tested the hypothesis that the same neurons receiving excitatory drive from the cerebellum also receive tonic inhibitory input from the substantia nigra pars reticulata. From a sample of 73 spontaneously active collicular cells we found that in 53% the firing rate was suppressed by GABA microinjection into the contralateral deep cerebellar nuclei; a further 15% showed a frequency increase. Of the collicular cells identified as receiving excitatory cerebellar input, 85% were found to be disinhibited by nigral GABA microinjection. The remainder were all inhibited by nigral GABA. These data show that the main excitatory influence from the cerebellum and the main inhibitory influence from the substantia nigra converge on at least one population of spontaneously active cells in the lateral intermediate layers of the superior colliculus. This finding is discussed in relation to the possible function of these spontaneous cells in movement control and nociception.
Regulation of Neuropeptides in Adult Rat Forebrain by the Neurotrophins BDNF and NGF
Authors: Croll Susan D. , Wiegand Stanley J. , Anderson Keith D. , Lindsay Ronald M. , Nawa Hiroyuki
Published: April 2006

The expression of neuropeptides and neurotrophic factors is altered in the hippocampus after seizure induction in rats. Because the increase in brain‐derived neurotrophic factor (BDNF) and nerve growth factor (NGF) mRNAs precede changes in neuropeptide expression after seizure, it is possible that BDNF and NGF mediate subsequent alterations in peptide expression. To test this hypothesis directly, BDNF or NGF was infused into the hippocampus and cortex of adult rats. To ascertain the regional specificity of any observed effects of neurotrophin administration on neuropeptide expression, infusions into the striatum were also studied. To control for specificity, vehicle was also infused into the same sites. Peptide and mRNA alterations were assessed by Northern analysis, immunohistochemistry and radioimmunoassay. BDNF produced elevations of peptide and mRNA for neuropeptide Y and cholecystokinin in hippocampus and cortex, and somatostatin in cortex. BDNF increased mRNAs for neuropeptide Y, cholecystokinin, substance P and dynorphin in striatum. In contrast, BDNF decreased dynorphin peptide and mRNA in hippocampus. NGF's effects were limited to small mRNA increases, without corresponding changes in peptide levels, for neuropeptide Y in hippocampus and striatum, substance P in cortex and cholecystokinin in striatum. The distinct and limited effects of NGF infusion on neuropeptide expression demonstrate that BDNF's effects are not non‐specific results of protein infusion into the brain. These findings indicate that BDNF may play a regionally specific role in modulating neuropeptide expression in the normal brain as well as in various pathophysiological states.
Low Density, but not High Density, C6 Glioma Cells Support Dorsal Root Ganglion and Sympathetic Ganglion Neurite Growth
Authors: Watanabe Eiji , Hosokawa Hiroshi , Kobayashi Hiroaki , Murakami Fujio
Published: April 2006

Accumulating evidence suggests that an inhibitory influence of the environment on growth cones plays a crucial role in development and regeneration of neuronal projections. Oligodendrocyte‐associated neurite growth inhibiting substance is one of the most extensively studied molecules. Molecular biological studies, however, remain slow in progress. Although finding clonal cells that express such factors would facilitate the analysis of inhibitory influences on neurite growth, few cell lines have been reported to express neurite growth inhibitor. We therefore investigated the possibility of a clonal glial cell line to differentiate and express inhibitory or non‐permissive features for neurite outgrowth in culture. We chose the C6 glioblastoma cell line and examined neurite extension from chick dorsal root ganglion (DRG) explants. Neurites from embryonic day 9 DRG extensively grew on C6 cells that were cultured at low cell density, while they failed to grow on C6 cells cultured at high density, even in the presence of nerve growth factor in high concentrations. Membrane extract from high density C6 cells, when used as culture substratum, was less permissive for neurite outgrowth compared to extract from low density cells. Treatment of the membrane extract derived from high density C6 cells with trypsin made it less non‐permissive for neurite growth. These results suggest that C6 cells are induced to express a non‐permissive property for neurite outgrowth by culturing them at high density.
Ultrastructure and GABA Immunoreactivity in Layers 8 and 9 of the Optic Tectum of Xenopus laevis
Authors: Rybicka Krystyna Kielan , Udin Susan B.
Published: April 2006

This study presents an ultrastructural analysis of layers 8 and 9 in the optic tectum of Xenopus laevis. Retinotectal axons were labelled with horseradish peroxidase and tectal cells were labelled with antibody to GABA. Four distinct axonal and dendritic structures were identified. GABA‐negative axon terminals formed asymmetric synapses and were categorized as type a‐1 (which included retinotectal axons), characterized by medium size synaptic vesicles and pale mitochondria, and type a‐2 (non‐retinotectal) with large vesicles and dense mitochondria. GABA‐negative dendrites (type d) contained dense mitochondria, microtubules in the dendritic shafts, and dendritic spines devoid of microtubules. GABA‐positive structures contained small synaptic vesicles and dense mitochondria. Some dendrites (type D) were not only postsynaptic but were also presynaptic elements, as defined by the presence of vesicles and distinct synaptic clefts with symmetric specializations. GABA‐positive presynaptic structures were mostly located in vesicle‐filled, bulbous extensions of dendritic shafts and usually terminated onto dendritic spines. Some type D dendrites were the middle element in serial synapses, with input from either GABA‐positive or GABA‐negative structures and output to GABA‐negative structures. Retinotectal terminals were identified as one of the synaptic inputs to GABA‐positive processes. Glia were characterized by granular cytoplasm and large mitochondria, often displaying a crystalline matrix structure. These results indicate that GABA‐positive neurons are a prominent component of circuitry in the superficial layers of the tectum of Xenopus and that, as in mammals, they participate in serial synaptic arrangements in which retinotectal axons are the first element. These arrangements are consistent with complex processing of visual input to the tectum and a central role for inhibitory processes in the shaping of tectal responses.
Cortical Magnification Theory Fails to Predict Visual Recognition
Authors: Strasburger Hans , Rentschler Ingo , Harvey Lewis O.
Published: April 2006

The sense of form is poor in indirect view. Yet the cortical magnification theory asserts that the disadvantage can be made up by scaling the image size according to the spatial variation in the mapping of the retina onto the cortex. It is thus assumed that all visual information passes through a functionally homogeneous neural circuitry, with the spatial sampling of input signals varying across the visual field. We challenge this notion by showing that character recognition in the visual field cannot be accommodated by any concept of sole size scaling but requires increasing both size and contrast of the target being viewed. This finding is formalized into a hyperbolic law which states that target size multiplied by log contrast is constant across the visual field. We conclude that the scalar cortical magnification theory fails for character recognition since the latter depends on multidimensional pattern representations in higher, i.e. striate and prestriate, cortical areas.
Development of Tonotopy in the Inferior Colliculus II: 2‐DG Measurements in the Kitten
Authors: Ehret Günter , Romand Raymond
Published: April 2006

The development of size and tonotopy in the inferior colliculus of the kitten was studied using the [14C]2‐deoxyglucose technique and tone stimulation with 2 and 15 kHz at a maximum 110 dB sound pressure level. At 2 days of age, frequency‐specific labelling cannot be detected. Two kilohertz labelling is distinctly visible in the rostral and central inferior colliculus at day 6; 15 kHz labelling occurs first at day 11. In the rostral and central inferior colliculus, 2 kHz labelling starts at a ventral and central position and shifts dorsalwards and to a more lateral location between postnatal days 6 and 21. Such a shift is not seen in the caudal inferior colliculus. There, the focus of 2 kHz labelling remains rather constant; only the extension of the labelling increases in the older animals. In all parts of the inferior colliculus, 15 kHz labelling starts at a ventromedial position and shifts to a more lateral location while extending also more dorsalwards as the age increases. These changes in 15 kHz labelling continue up to 3 months. In addition to the ventromedial‐to‐dorsolateral shift and expansion of labelling, there is also a rostral‐to‐caudal gradient of maturation, in that in older animals frequency‐specific labelling reaches farther caudalwards. The reported changes in frequency representation in the inferior colliculus can be explained on the basis of a shift in frequency input and input sensitivity to the laminae of the inferior colliculus, mainly due to maturational changes within the cochlea and/or as a consequence of the increasing size of the inferior colliculus.
Reduced Synchronization in the Visual Cortex of Cats with Strabismic Amblyopia
Authors: Roelfsema Pieter R. , König Peter , Engel Andreas K. , Sireteanu Ruxandra , Singer Wolf
Published: April 2006

Synchronous firing of spatially separate neurons was studied with multi‐electrode recordings in area 17 of the visual cortex of strabismic cats which had developed behaviourally verified amblyopia of the deviated eye. Responses of neurons were evoked with moving light bars or gratings of different spatial frequency. Neurons driven by the normal eye displayed stronger synchronization of their responses than neurons dominated by the amblyopic eye. These interocular differences were highly significant and particularly pronounced for grating stimuli of high spatial frequency. No interocular differences were noted with respect to the amplitudes of responses to the light bars and gratings. These results suggest reduced synchronization of population responses as a neurophysiological correlate of strabismic amblyopia and underline the importance of correlated firing of spatially separate cortical neurons for normal processing of visual information.
Muscarinic Receptor Profiles of Mouse Brain Astrocytes in Culture Vary With Their Tissue Of Origin but Differ From Those of Neurons
Authors: André C. , Santos G. Dos , Koulakoff A.
Published: April 2006

The two main cell populations in brain tissues are neurons and astrocytes. Cultures of both bear muscarinic acetylcholine receptors (mAChRs). Available data indicate that astrocyte mAChRs are heterogeneous, but the particular subtypes on these cells are not known, nor is there any information as to whether there is a regional variation in the mAChR profile of astrocytes. This paper describes the mAChR profiles of cultured astrocytes derived from the cerebral hemispheres, mesencephalon and medulla‐pons, and is a continuation of our study on cultures of neurons from these same tissues. Pharmacological studies showed that the astrocytes accumulated small amounts of mAChRs with distinct pharmacological profiles which, for a given area, differed from those of neurons in culture. Northern blot analyses showed transcripts for ml and m3 mAChRs only. Their concentrations differed from one cell population to another. Astrocyte cultures from the mesencephalon contained ml mRNA amounts close to those in the tissue. Thus, at least part of the mAChR profile in vitro might be a true reflection of the cell's properties in vivo. Functional studies showed that mAChRs mediate the stimulation of phosphoinositide turnover in all three astrocyte cultures, that the amplitude of this response varies greatly with the origin of the cell, and that two pharmacological subclasses, M1 and M1–2‐, are involved in these responses, but to different extents. Thus the CNS contains discrete astrocyte populations which in culture differ in their mAChR profiles at the molecular, the pharmacological and the functional levels.
Developmental Shift From Long‐term Depression to Long‐term Potentiation at the Mossy Fibre Synapses in the Rat Hippocampus
Authors: Battistin Tiziana , Cherubini Enrico
Published: April 2006

During development, in the CA1 hippocampal region, long‐term potentiation (LTP) starts appearing at postnatal (P) day 7 and reaches its maximal expression towards the end of the second postnatal week. However, LTP is often preceded by long‐term depression (LTD), an activity‐dependent and long‐lasting reduction of synaptic strength. LTD can be induced by sustained, low‐frequency stimulation of the afferent pathway and is dependent on activation of N‐methyl‐D‐aspartate (NMDA) receptors. We report here that, in the CA3 hippocampal region, during a critical period of postnatal development, between P6 and P14, a high‐frequency stimulation train (100 Hz, 1 s) to the mossy fibres in the presence of the NMDA receptor antagonist (+)‐3‐(2‐carboxy‐piperazin‐4‐yl)‐propyl‐1‐phosphonic acid (CPP; 20 μM) induced LTD. The depression of the amplitude of the field excitatory postsynaptic potential (EPSP) was 28 ± 7% (n= 21). This form of LTD was NMDA‐independent and synapse‐specific. When a tetanus was applied in the presence of CPP and 6‐cyano‐7‐nitroquinoxaline‐2, 3‐dione (CNQX; 50 μM), which blocked the field EPSP, it failed to induce LTD upon washout of CNQX. LTD was probably postsynaptic in origin since it did not affect paired‐pulse facilitation. A rise in extracellular calcium concentration (from 2 to 4 mM) produced LTP instead of LTD. At the end of the second postnatal week, the same high‐frequency stimulation train to the mossy fibres induced LTP as in adult neurons. Functional changes in synaptic connections during development may control membrane depolarization and the amount of intracellular calcium necessary to trigger either LTD or LTP.
Location and Anatomical Connections of a Paradoxical Sleep Induction Site in the Cat Ventral Pontine Tegmentum
Authors: Reinoso‐Suárez Fernando , de Andrés Isabel , Rodrigo‐Angulo Margarita L. , Rodríguez‐Veiga Elisia
Published: April 2006

The brainstem mechanisms for the generation of paradoxical sleep are under considerable debate. Previous experiments in cats have demonstrated that injections of the cholinergic agonist carbachol into the oral pontine tegmentum elicit paradoxical sleep behaviour and its polygraphic correlates. The different results on the pontine structures that mediate this effect do not agree. We report here that limited microinjections of a carbachol solution into the ventral part of the oral pontine reticular nucleus in the cat induce, with a short latency, a dramatic, long‐lasting increase in paradoxical sleep. Moreover, neuronal tracing experiments show that this pontine site is connected with brain structures responsible for the different bioelectric events of paradoxical sleep. These two facts suggest that the ventral part of the oral pontine reticular nucleus is a nodal link in the neuronal network underlying paradoxical sleep mechanisms.
Juvenile Visual Callosal Axons in Kittens Display Origin‐and Fate‐related Morphology and Distribution of Arbors
Authors: Aggoun‐Zouaoui Djamila , Innocenti Giorgio M.
Published: April 2006

In kittens, callosal axons originating either from medial area 17 (transient axons) or near the 17/18 border (mostly permanent axons) were labelled with anterogradely transported biocytin; they were reconstructed by computer from serial sections, and their morphologies compared at different ages. During the first and second postnatal weeks both sets of axons branched profusely in the white matter of the lateral gyrus and the number of branches increased with age. The most common type of axon ending was the growth cone; others may have been collapsing growth cones, branches in the process of elimination or early synaptic boutons. Axons from medial area 17 distributed over a broad territory, including the 17/18 border where callosal axons terminate in the adult cat, but without aiming specifically at any one area. The majority of axons and their branches terminated in the white matter or at the bottom of layer VI; exceptionally they extended further into the cortex. Most of the axons originating near the 17/18 border were different from those described above, and the difference increased with age. Although they also terminated profusely in the white matter of the lateral gyrus, most of the branches terminated near the contralateral 17/18 border; they frequently entered the grey matter up to the superficial layers and branched into it. During the third week, axons from medial area 17 were rarely found to extend beyond the corpus callosum, probably because they were in the process of being eliminated. In contrast, axons originating near the 17/18 border had increased their number of branches in the grey matter. In conclusion, during the first and second postnatal weeks axons grew and differentiated according to their origin, and this anticipated whether they would be maintained or eliminated. Neurotrophic signals, possibly from the white matter or the subplate, and growth‐inhibiting signals from area 17 may be involved in this process.
Involvement of Metabotropic and lonotropic Glutamate Receptors in Inositol Polyphosphate Formation in Carp Retinal Slices
Authors: Janssen‐Bienhold U. , Wenzel A. , Hannken T. , Weiler R.
Published: April 2006

The contribution of ionotropic and metabotropic glutamate receptors to inositol polyphosphate accumulation in carp retinal slices was investigated using myo‐[2‐3H]inositol prelabelling. In the presence of the glutamate agonists quisqualate, (RS)‐α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole propionic acid (AMPA) and trans‐(±)‐1‐amino‐1, 3‐cyclopentane‐dicarboxylic acid (t‐ACPD), formation of [3H]inositol phosphate was significantly increased in a dose‐dependent manner, with EC50 values of 350 nM, 1.5 μM and 10 μM respectively. The complete AMPA‐induced response and a large component of the quisqualate‐induced response were inhibited in a competitive manner when the ionotropic antagonist 6‐cyano‐7‐nitroquinoxaline‐2, 3‐dione (CNQX) was present. Furthermore, the remaining level of quisqualate‐induced [3H]inositol phosphate formation closely matched that produced by ACPD alone, and coincubation of AMPA and ACPD showed additive effects, suggesting that the quisqualate‐induced response resulted from coactivation of metabotropic and ionotropic glutamate receptors. The ionotropic component was partially reduced in the presence of cobalt, suggesting indirect effects resulting from synaptic interactions. We could exclude indirect effects through depolarization‐induced release of other neurotransmitters. Only serotonin (EC50 1 μM) and carbachol (at a concentration of 1 mM) stimulated [3H]inositol phosphate formation, but their antagonists did not affect the quisqualate response and coactivation with quisqualate and serotonin or carbachol resulted in additive effects. The ionotropic component was completely suppressed when Ca2+ was omitted from the medium and cobalt was present. This makes it likely that the ionotropic component resulted from Ca2+ entry through AMPA‐gated channels and subsequent Ca2+‐dependent activation of phospholipase C.
Galanin Receptor Binding Sites in Adult Rat Spinal Cord Respond Differentially to Neonatal Capsaicin, Dorsal Rhizotomy and Peripheral Axotomy
Authors: Kar S. , Quirion R.
Published: April 2006

The discrete distribution and possible changes in specific [125I]galanin binding sites were evaluated in the rat spinal cord following neonatal capsaicin treatment, dorsal rhizotomy and sciatic nerve section. The highest density of [125I]galanin binding sites in the normal rat spinal cord was particularly evident in the superficial layers of the dorsal horn whereas moderate to low amounts of labelling were associated with the deeper dorsal horn, areas around the central canal and the ventral horn. Capsaicin‐treated rats, compared to littermate controls, showed a significant bilateral increase in [125I]galanin binding in the superficial laminae of the dorsal horn. Similarly, unilateral dorsal rhizotomy evoked a significant increase in the density of [125I]galanin binding sites in the superficial dorsal horn ipsilateral to surgery. Section of the sciatic nerve, on the other hand, induced a significant depletion in [125I]galanin binding in laminae I and II of the ipsilateral dorsal horn. These results, in parallel to those reported for galanin immunoreactivity under similar conditions, suggest that [125I]galanin binding sites are preferentially located postsynaptically to the primary afferent fibre terminals in the dorsal horn of the spinal cord. Thus it seems that galanin, at the level of the dorsal spinal cord, regulates the processing of nociceptive information by acting on its own class of specific receptors located postsynaptically to primary sensory terminals.
Morphology of Callosal Axons Interconnecting Areas 17 and 18 of the Cat
Authors: Houzel Jean‐Christophe , Milleret Chantal , Innocenti Giorgio
Published: April 2006

Seventeen callosally projecting axons originating near the border between areas 17 and 18 in adult cats were anterogradely labelled with biocytin and reconstructed in 3‐D from serial sections. All axons terminated near the contralateral 17/18 border. However, they differed in their diameter, tangential and radial distributions, and overall geometry of terminal arbors. Diameters of reconstructed axons ranged between 0.45 and 2.25 μm. Most of the axons terminated in multiple terminal columns scattered over several square millimetres of cortex. Thus in general callosal connections are not organized according to simple, point‐to‐point spatial mapping rules. Usually terminal boutons were more numerous in supragranular layers; some were also found in infragranular layers, none in layer IV. However, a few axons were distributed only or mainly in layer IV, others included this layer in their termination. Thus, different callosal axons may selectively activate distinct cell populations. The geometry of terminal arbors defined two types of architecture, which were sometimes represented in the same axon: parallel architecture was characterized by branches of considerable length which supplied different columns or converged onto the same column; serial architecture was characterized by a tangentially running trunk or main branch with radial collaterals to the cortex. These architectures may relate to temporal aspects of inter‐hemispheric interactions. In conclusion, communication between corresponding areas of the two hemispheres appears to use channels with different morphological and probably functional properties.
Intracortical Regionality Represented by Specific Transcription for a Novel Protein, Latexin
Authors: Hatanaka Yumiko , Uratani Yoshihiko , Takiguchi‐Hayash Keiko , Omori Akira , Sato Kazuki , Miyamoto Mami , Arimatsu Yasuyoshi
Published: April 2006

The monoclonal antibody (mAb) PC3.1 recognizes a subset of neurons distributed in the infragranular layers of the lateral neocortex of the rat. Immunoaffinity chromatography with mAb PC3.1 showed that this antibody specifically binds a peptide epitope on a 29 kDa protein named latexin. To study the molecular details of the protein, we isolated four independent cDNA clones for latexin from cDNA libraries of the rat cerebral cortex and whole brain using the amino acid sequences of latexin fragments. Analysis of these cDNA clones showed that the predicted primary structure of latexin consists of 223 amino acids, and has no strict homology to any sequences so far known. Western and Northern blots demonstrated that the latexin and its mRNA were expressed predominantly in neural tissues with some expression in non‐neural tissues. The gene that encodes latexin in the rat appeared to have homologues in other mammalian species and in the chick. In situ hybridization showed that latexin mRNA is synthesized in a subset of neurons in the lateral but not the dorsal neocortex, and that the distribution profile of these neurons is quite similar to that of neurons expressing latexin. These results indicate that latexin is a novel class of neuronal protein which represents intracortical regionality, and suggest that the regional specification of the neocortex involves selective parcellation of neurons which express a particular gene.
Nerve‐evoked Electrical Activity Regulates Molecules and Cells With Immunological Function in Rat Muscle Tissue
Authors: Gundersen Kristian , Mæhlen Jan
Published: April 2006

Molecules coded by the major histocompatibility complex (MHC) are present on cell surfaces in most tissues, with the cells of the central nervous system and skeletal muscle as prominent exceptions. We show here that when rat skeletal muscles are rendered inactive by nerve impulse block, expression of MHC class I molecules occurs on the muscle fibres. In addition, the number of cells expressing MHC class II molecules in the muscle interstitium is increased by a factor of three after 2 weeks of impulse blockade. Similar effects obtained by denervation can be counteracted by direct electrical stimulation, Interferon‐γ‐like immunoreactivity accumulates in inactive muscle fibres, and interferon‐γ or a related cytokine could be a link between inactivity and MHC up‐regulation. These findings suggest that nerve‐evoked muscle activity influences not only the phenotype of the muscle cells themselves, but also processes in the interstitium that may increase the immunoreactivity of inactive muscle tissue.
Differential Stimulation of Noradrenaline Release by Reversal of the Na+/Ca2+Exchanger and Depolarization in Chromaffin Cells
Authors: Duarte Emília P. , Baltazar Graça , Carvalho Arsélio P.
Published: April 2006

We compared the effectiveness of Ca2+entering by Na+/Ca2+exchange with that of Ca2+entering by channels produced by membrane depolarization with K+in inducing catecholamine release from bovine adrenal chromaffin cells. The Ca2+influx through the Na+/Ca2+exchanger was promoted by reversing the normal inward gradient of Na+by preincubating the cells with ouabain to increase the intracellular Na+and then removing Na+from the external medium. In this way we were able to increase the cytosolic free Ca2+concentration ([Ca2+]c) by Na+/Ca2+exchange to 325 ± 14 nM, which was similar to the rise in [Ca2+]cobserved upon depolarization with 35 mM K+of cells not treated with ouabain. After incubating the cells with ouabain, K+depolarization raised the [Ca2+]cto 398 ± 31 nM, and the recovery of [Ca2+]cto resting levels was significantly slower. Reversal of the Na+gradient caused an −6‐fold increase in the release of noradrenaline or adrenaline, whereas K+depolarization induced a 12‐fold increase in noradrenaline release but only a 9‐fold increase in adrenaline release. The ratio of noradrenaline to adrenaline release was 1.24 ± 0.23 upon reversal of the Na+/Ca2+exchange, whereas it was 1.83 ± 0.19 for K+depolarization. Reversal of the Na+/Ca2+exchange appeared to be as efficient as membrane depolarization in inducing adrenaline release, in that the relation of [Ca2+]cto adrenaline release was the same in both cases. In contrast, we found that for the same average [Ca2+]c, the Ca2+influx through voltage‐gated channels was much more efficient than the Ca2+entering through the Na+/Ca2+exchanger in inducing noradrenaline release from chromaffin ceils. This greater effectiveness of membrane depolarization in stimulating noradrenaline release suggests that there is a pool of noradrenaline vesicles which is more accessible to Ca2+entering through voltage‐gated Ca2+channels than to Ca2+entering through the Na+/Ca2+exchanger, whereas the adrenaline vesicles do not distinguish between the source of Ca2+.
Control of Impulse Conduction in Long Range Branches of Afferents by Increases and Decreases of Primary Afferent Depolarization in the Rat
Authors: Wall Patrick D.
Published: April 2006

It has been shown previously that impulses in axons of the descending branches of myelinated afferents in rat dorsal columns may suffer a blockade of transmission along their course in the dorsal columns. This paper tests the effect of the mechanism of primary afferent depolarization on the orthodromic movement of impulses in descending dorsal column primary afferent axons originating in the L1 dorsal root. Orthodromic impulses were recorded in the L5 and 6 dorsal columns after stimulation of the L1 dorsal root. Twenty‐seven out of 82 axons (33%) suffered a temporary transmission block if primary afferent depolarization had been induced by L5 stimulation before the L1 stimulus. The tendency to block peaked at 10–15 ms and persisted for up to 30–40 ms. The number of single unit orthodromic impulses originating from the L1 root and recorded during a search of the dorsal columns 15 mm caudal to L1 increased by a factor of 3.1 after the systemic administration of bicuculline (1 mg/kg). The number of single unit orthodromic impulses originating from the L1 root and recorded in axons descending in the dorsal columns 20 mm caudal to the root increased by a factor of 8.7 after the systemic administration of picrotoxin (5 mg/kg). It is concluded that the transmission of impulses in the long range caudally running axons from dorsal roots to dorsal columns may be blocked during primary afferent depolarization and that conduction may be restored by the administration of GABA antagonists.
Archistriatal Lesions Impair the Acquisition of Filial Preferences During Imprinting in the Domestic Chick
Authors: Lowndes M. , Davies D. C. , Johnson M. H.
Published: April 2006

The avian archistriatum has been demonstrated to play a role in agonistic behaviours and avoidance learning. However, the extent of its role in learning is unknown. The involvement of the archistriatum in the learning process of filial imprinting was therefore investigated in day‐old chicks. Bilateral archistriatal lesions, lateral cerebral area lesions or sham archistriatal penetrations were made in dark‐reared, day‐old chicks, which were subsequently exposed to either a rotating red box or blue cylinder for 2 × 1 h training sessions. Three hours later, the approach of chicks to their training object and to the other, novel object was measured. Chicks with archistriatal lesions ran a similar distance towards each stimulus and therefore failed to display a preference for their training object. However, chicks with sham archistriatal penetrations or lateral cerebral area lesions exhibited a significant preference for the object they had been trained upon. These results demonstrate that the archistriatum is essential for the expression of an imprinted preference. All chicks approached their training object significantly more on their second compared to their first training exposure, suggesting that some aspects of imprinting behaviour remain intact in chicks with archistriatal lesions. Taken together with the results of previous work, the current data suggest that the archistriatum may be involved in retention of significant aspects of the imprinting experience, or in motivation to approach imprinting objects.
X‐Ray Study of the Cat Hindlimb During Treadmill Locomotion
Authors: Kuhtz‐Buschbeck J. P. , Boczek‐Funcke A. , Illert M. , Weinhardt C.
Published: April 2006

With pulsed X‐ray cinematography we have analysed the angular excursions of the distal hindlimb joints (proximal interphalangeal, PIP; metatarsophalangeal, MTP; ankle) in cats walking on a treadmill. These distal joints transmit the body weight and the dynamic forces onto the ground. We have included the knee and hip joints in the analysis to relate the angular excursions of the proximal and distal joints and to verify the data previously obtained with external markers on the kinematics of the proximal joints. At the beginning of the stance phase the PIP joints flexed rapidly, the MTP joints extended slowly and the ankle and knee yielded under body weight. Whereas the PIP joints maintained a rather constant angular position of −75° throughout the stance phase, extension continued in the MTP joints from −230° at touch‐down to −270° at the end of the stance phase. Around 50 ms before lift‐off the MTP joints flexed rapidly. Early (−30 ms) after lift‐off this flexion changed into a slow extension. The PIP joints extended swiftly at the stance‐swing transition and moderately at the end of the swing phase. During the middle part of the swing phase they flexed slowly. Small rotatory movements around the long axis of the foot took place in the last 100 ms of the swing phase. The results of this study on the distal joints are discussed in relation to the placing of the paw, to the translation of forward propulsion into a MTP movement and to the lifting of the paw (conventionally described as toe curling). They show a differentiated mechanical interaction between the different distal limb joints during these different phases, which must be known in detail to interpret the corresponding electromyographic data and to understand how the hip is moved forward over the MTP joints which serve as the final pivot during stance.
Comparison of Stress‐induced Changes in Noradrenergic and Serotonergic Neurons in the Rat Hippocampus Using Microdialysis
Authors: Vahabzadeh Abdolvahab , Fillenz Marianne
Published: April 2006

The effects of stress on the serotonergic and noradrenergic projection to the hippocampus were compared in freely moving rats using microdialysis. Stress‐induced changes in 5‐hydroxytryptamine (5‐HT), noradrenaline and their metabolites 5‐hydroxyindoleacetic acid (5‐HIAA) and 3,4‐dihydroxyphenylacetic acid (DOPAC) were measured in the presence of their respective uptake blockers. Local infusion of tetrodotoxin and replacement of Ca2+ with Cd2+ were used to test dependence on impulse traffic. A 5 min tail pinch or 10 min restraint stress increased 5‐HT, 5‐HIAA, noradrenaline and DOPAC levels. A subcutaneous saline injection produced an increase in 5‐HT and DOPAC but not noradrenaline or 5‐HIAA. Although α2 adrenoceptor agonists and antagonists produced changes in the baseline values of noradrenaline and DOPAC, they had little or no effect on stress‐induced changes. Both the abolition of impulse traffic and its enhancement by stress had a greater effect on transmitter than on metabolite levels. Although the responses to stress of the noradrenergic and serotonergic pathway showed many similarities, there was evidence for their activation by separate pathways.
Rat Oligodendrocytes Express Muscarinic Receptors Coupled to Phosphoinositide Hydrolysis and Adenylyl Cyclase
Authors: Cohen R. I. , Almazan G.
Published: April 2006

Muscarinic receptors expressed by rat oligodendrocyte primary cultures were examined by measuring changes in second messengers following exposure to carbachol, an acetylcholine analog, and by polymerase chain reaction. Inositol phosphate levels were measured in [3H]myo‐inositol‐labelled young oligodendrocyte cultures following stimulation with carbachol. Atropine, a specific muscarinic antagonist, prevented the carbachol‐induced accumulation of inositol phosphates. The formation of inositol trisphosphate was concentration‐ and time‐dependent, with the peak at 100 μM carbachol and 10 min. Carbachol increased intracellular calcium levels, which were dependent both on the mobilization of intracellular stores and influx of extracellular calcium. In initial experiments with more selective antagonists, the mobilization of intracellular calcium was preferentially inhibited by pirenzepine, a selective M1 antagonist, but not methoctramine, a selective M2 antagonist, suggesting M1 muscarinic receptor involvement. A role for protein kinase C in the regulation of carbachol‐stimulated inositol phosphate formation and intracellular calcium mobilization was demonstrated, as acute pretreatment with phorbol‐12, 13‐myristate acetate abolished the formation of both second messengers. Pretreatment with 100 μM carbachol abolished the 40% increase in the cyclic AMP accumulation stimulated by isoproterenol, a specific β‐adrenergic agonist. In turn, the inhibition was alleviated by pretreatment with atropine, suggesting muscarinic receptor involvement. Polymerase chain reaction carried out with specific ml and m2 muscarinic receptor oligonucleotide primers, confirmed that these cells express, at least, the two muscarinic receptor subtypes. Without excluding the expression of other subtypes, these results suggest that developing oligodendrocytes express ml (M1) and m2 (M2) muscarinic receptors capable of mediating phosphoinositide hydrolysis, mobilization of intracellular calcium and the attenuation of β‐adrenergic stimulation of cyclic AMP formation.