bluuebunny/crossref_metadata_2025 huggingface dataset:
Transient features of the thalamic reticular nucleus in the human foetal brain
Authors: Ulfig Norbert , Nickel Jens , Bohl Jürgen
Published: March 2003

The architectonic organization and neuronal types of the human foetal reticular nucleus (RN) – with special reference to transient characteristics – have been investigated using antisera against calretinin, parvalbumin and neurofilament epitopes of somata and dendrites (SMI 311). The RN consists of four subdivisions (clearly distinguishable in the 6/7th gestational month): The main portion appears as a prominent structure on account of its extension and high packing density of neurons which coexpress calretinin and parvalbumin. These two calcium‐binding proteins are also expressed by the perireticular nucleus forming a conspicuous grey within the internal capsule. Perireticular cells form clusters which are in continuity with the main portion, globus pallidus, ganglionic eminence and pregeniculate nucleus. In double‐labellings, a medial subnucleus stands out distinctly as it only expresses calretinin. SMI 311‐immunopreparations show neurons revealing a high degree of diversification and elaborated dendritic trees. Several transient characteristics become obvious: the perireticular nucleus, not visible in the adult, represents a distinct entity in the human foetal brain. The main portion and the pregeniculate nucleus appearing as prominent greys are dramatically reduced in size later on. The percentage of RN‐neurons expressing calretinin, the diversity of neuronal types and elaborated dendritic trees are reduced. The transient features can be correlated with the RN's putative functional roles in development: early RN‐afferents to the dorsal thalamus may represent pioneer fibres providing guiding cues for outgrowing axons from or into the thalamus. Moreover, the RN may serve as an intermediate target for growing axons which are sorted and directed towards different final targets.
β‐Actin is confined to structures having high capacity of remodelling in developing and adult rat cerebellum
Authors: Micheva Kristina D. , Vallée Annie , Beaulieu Clermont , Herman Ira M. , Leclerc Nicole
Published: March 2003

Neurons undergo complex morphological changes during differentiation and in cases of plasticity. A major determinant of cell morphology is the actin cytoskeleton, which in neurons is comprised of two actin isoforms, non‐muscle γ‐ and β‐actin. To better understand their respective roles during differentiation and plasticity, their cellular and subcellular localization was examined in developing and adult cerebellar cortex. It was observed that γ‐actin is expressed at a constant level throughout development, while the level of β‐actin expression rapidly decreases with age. At the light microscopic level, γ‐actin staining is ubiquitous and the only developmental change observed is a relative reduction of its concentration in cell bodies and white matter. In contrast, β‐actin staining almost completely disappears from the cytoplasm of cell bodies, primary dendrites and axons. In young cerebellar cultures, γ‐actin is found in the cell body, neurites and growth cones, while β‐actin is mainly found in growth cones, as previously reported in other primary neuronal culture systems [Kaech et al. (1997), J. Neuroscience, 17, 9565–9572; Bassell et al. (1998), J. Neuroscience, 18, 251–265]. Electron microscopy of post‐embedding immunogold‐labelled tissue confirms the widespread distribution of γ‐actin, and also reveals an increased concentration of γ‐actin in dendritic spines in the adult. During development, β‐actin accumulation is observed in actively growing structures, e.g. growth cones, filopodia, cell bodies and axonal tracts. In the adult cerebellar cortex, β‐actin is preferentially found in dendritic spines, structures which are known to retain their capacity for morphological modifications in the adult brain. This differential subcellular localization and developmental regulation of the two actin isoforms point to their different roles in neurons.
Acute phencyclidine neurotoxicity in rat forebrain: induction of haem oxygenase‐1 and attenuation by the antioxidant dimethylthiourea
Authors: Rajdev Sunita , Fix Andrew S. , Sharp Frank R.
Published: March 2003

Phencyclidine and otherN‐methyl‐d‐aspartate receptor antagonists are toxic to pyramidal neurons in the posterior cingulate/retrosplenial cortex of rat brain. Previous studies have shown induction of heat shock protein 70 in affected neurons. In this study, expression of haem oxygenase‐1, a heat shock protein induced by oxidative stress, was examined in rat forebrain after administration of a single intraperitoneal dose of phencyclidine (50 mg/kg). Northern and Western blot analyses of brain tissue extracts from phencyclidine‐treated rats revealed a marked induction of haem oxygenase‐1 mRNA and protein, respectively. Immunohistochemistry studies revealed that phencyclidine increased haem oxygenase‐1 immunoreactivity primarily in posterior cingulate/retrosplenial, piriform and entorhinal cortices, striatum and hippocampus. Haem oxygenase‐1 protein was induced in non‐neuronal cells, mainly astrocytes. Some microglia expressing haem oxygenase‐1 protein were also found in the posterior cingulate/retrosplenial cortex. Haem oxygenase‐1 immunoreactive astrocytes and microglia were present in close proximity to the heat shock protein 70‐positive neurons in the posterior cingulate/retrosplenial cortex following phencyclidine. Pretreatment of rats with 1,3‐dimethylthiourea, an antioxidant, significantly reduced haem oxygenase‐1 protein induction by phencyclidine. Thus, induction of haem oxygenase‐1 in glia by phencyclidine appears to be mediated mostly by oxidative stress. Experiments with the amino cupric silver stain for neuronal degeneration revealed phencyclidine‐induced neurotoxicity in the posterior cingulate/retrosplenial cortex. The number of affected neurons was significantly reduced after 1,3‐dimethylthiourea pretreatment. This suggests that the neurotoxicity ofN‐methyl‐d‐aspartate antagonists is due in part to the oxidative stress and may be amenable to therapeutic interventions.
Functional relationship between age‐related immunodeficiency and learning deterioration
Authors: Zhang Yongxiang , Moriguchi Toru , Saito Hiroshi , Nishiyama Nobuyoshi
Published: March 2003

Disordered immune responses are supposed to alter the function of the central nervous system through the neuroendocrine immunomodulation network. In this paper, we studied the influence of the immune function on learning performances from the angle of pharmacology using aged garlic extract (AGE), an immunomodulator. Splenocyte proliferation, induced by concanavalin A or lipopolysaccharide, and the antibody production response were declined in senescence accelerated mouse‐prone 8 (SAMP8) aged 12 months compared with age‐matched SAMR1 (SAM‐resistant 1). Chronic oral administration of AGE‐containing food (2%, w/w) significantly enhanced the immune responses of both SAMP8 and SAMR1. Male ddY mice were thymectomized 4 weeks after birth and fed AGE‐containing food after the operation until the experiments were finished. Learning performances, brain monoamine content and choline acetyltransferase (ChAT) activity, as well as the immune response were evaluated 10 months after the operation. Thymectomy resulted in not only immunodeficiency, but also deteriorated learning ability. AGE treatment prevented the reduction of the antibody production response induced by thymectomy and improved the thymectomy‐induced deterioration of learning behaviours in passive avoidance performance and in a spatial memory task. The contents of hypothalamic noradrenaline, 3,4‐dihydroxyphenylacetic acid and homovanillic acid, and the hypothalamic ChAT activity were increased in thymectomized mice compared to those of sham‐operated control, while AGE treatment restored them to the control levels. These results suggest that the improvement of immune function is closely related to the amelioration of age‐associated deterioration of learning and memory.
Development of the histaminergic neurons and expression of histidine decarboxylase mRNA in the zebrafish brain in the absence of all peripheral histaminergic systems
Authors: Eriksson Krister S. , Peitsaro Nina , Karlstedt Kaj , Kaslin Jan , Panula Pertti
Published: March 2003

The histamine‐storing neural system in adult and developing zebrafish (Danio rerio) was studied with immunocytochemical and chromatographical methods. Furthermore, the gene for histidine decarboxylase was partially cloned and its expression mapped with in situ hybridization. The histamine‐storing neurons were only seen in the caudal hypothalamus, around the posterior recess of the diencephalic ventricle. Almost all parts of the brain, except the cerebellum, contained at least some histamine‐immunoreactive fibres. The ascending projections had the rostral part of the dorsal telencephalon as a major target. Descending projections terminated in the torus semicircularis, central grey and inferior olive. A prominent innervation of the optic tectum, which has not been reported in other fish, was seen. The in situ hybridization gave a strong signal in cells with the same anatomical position as the histamine‐immunoreactive neurons. The first histamine‐immunoreactive neurons appeared in the ventral hypothalamus at about 85 h post‐fertilization, and at 90 h, immunoreactive fibres terminated in the dorsal telencephalon. The embryonic histamine production described in mammals was lacking in this species. Both immunocytochemical and chromatographical studies indicated that histamine is absent in all other parts of the zebrafish body, and no specific hybridization was seen in any other part of the fish than the hypothalamus. The zebrafish could therefore be a very useful model for pharmacological in vivo studies of the histaminergic system of the brain, since the powerful peripheral actions of histamine should be lacking in this species.
Different regions of the periaqueductal grey are involved differently in the expression and conditioned inhibition of fear‐potentiated startle
Authors: Fendt Markus
Published: March 2003

The fear‐potentiated startle paradigm is a useful model for investigating the neural systems underlying the mediation and modulation of fear and anxiety. A series of previous studies showed that the periaqueductal grey is involved in the expression and inhibition of fear‐potentiated startle, but it was uncertain whether the different columns of the periaqueductal grey play different roles. In the present study, picrotoxin, a GABAA (γ‐aminobutyric acid) chloride‐channel blocker, was injected into the dorsal, lateral and ventrolateral columns of the periaqueductal grey in order to examine the effects of neural disinhibition on expression and conditioned inhibition of fear‐potentiated startle. Picrotoxin injections into the lateral periaqueductal grey increase potentiation of the startle response by conditioned fear, injections into the ventrolateral periaqueductal grey block fear‐potentiated startle. Picrotoxin injections into the dorsal periaqueductal grey decreased conditioned inhibition but did not affect expression of fear‐potentiated startle. The baseline startle amplitude was not influenced by picrotoxin injections into the different columns of the periaqueductal grey. Picrotoxin injections into neighbouring brain areas did not have any effect on baseline startle amplitude nor did they have an effect on expression or conditioned inhibition of fear‐potentiated startle. Based on the present results, the possible pathways underlying the expression and conditioned inhibition of fear‐potentiated startle in rats are discussed.
Synaptic inhibition in the isolated respiratory network of neonatal rats
Authors: Brockhaus Johannes , Ballanyi Klaus
Published: March 2003

Gramicidin‐perforated patch‐clamp recording revealed phasic Cl–‐mediated hyperpolarizations in respiratory neurons of the brainstem–spinal cord preparation from newborn rats. The in vitro respiratory rhythm persisted after block of γ‐aminobutyric acid (GABA), i.e. GABAA, receptor‐mediated inhibitory postsynaptic potentials (IPSPs) with bicuculline and/or glycinergic IPSPs with strychnine. In one class of expiratory neurons, bicuculline unmasked inspiration‐related excitatory postsynaptic potentials (EPSPs), leading to spike discharge. Bicuculline also blocked hyperpolarizations and respiratory arrest due to bath‐applied muscimol, whereas strychnine antagonized similar responses to glycine. The reversal potential of respiration‐related IPSPs and responses to GABA, muscimol or glycine was not affected by CO2/HCO3–‐free solutions, but shifted from about −65 mV to values more positive than −20 mV upon dialysis of the cells with 144 instead of 4 mm Cl–. Impairment of GABA uptake with nipecotic acid or glycine uptake with sarcosine evoked a bicuculline‐ or strychnine‐sensitive decrease of respiratory frequency which could lead to respiratory arrest. Also, the GABAB receptor agonist baclofen led to reversible suppression of respiratory rhythm. This in vitro apnoea was accompanied by a K+ channel‐mediated hyperpolarization (reversal potential −88 mV) of tonic cells, whereas membrane potential of neighbouring respiratory neurons remained almost unaffected. Both baclofen‐induced hyperpolarization and respiratory depression were antagonised by 2‐OH‐saclofen, which did not affect respiration‐related IPSPs per se. The results show that synaptic inhibition is not essential for rhythmogenesis in the isolated neonatal respiratory network, although (endogenous) GABA and glycine have a strong modulatory action. Hyperpolarizing IPSPs mediated by GABAA and glycine receptors provide a characteristic pattern of membrane potential oscillations in respiratory neurons, whereas GABAB receptors rather appear to be a feature of non‐respiratory neurons, possibly providing excitatory drive to the network.
Proliferation, migration and differentiation of neuronal progenitor cells in the adult mouse subventricular zone surgically separated from its olfactory bulb
Authors: Jankovski A. , Garcia C. , Soriano E. , Sotelo C.
Published: March 2003

The subventricular zone of the adult mammalian forebrain contains progenitor cells that, by migrating along a restricted pathway called the ‘rostral migratory stream’ (RMS), add new neurons to the olfactory bulb throughout life. To determine the influence of the olfactory bulb on the development of these progenitor cells, we performed lesions that interrupt this pathway and separate the olfactory bulb from the rest of the forebrain. By labelling cells born at several survival times after the lesions with the thymidine analogue bromodeoxyuridine (BrdU), we found that disconnection from the bulb influences the rate of BrdU incorporation by the progenitor cells. The number of labelled cells in lesioned mice was almost half that found in control mice. In the disconnected migratory pathway, the number of neurons expressing calretinin was increased indicating that neuronal differentiation was enhanced: newly born neurons occurred within and around the RMS, most of them expressed calretinin and left the pathway starting about 2 weeks after the lesion. Thereafter, these neurons preserving their phenotype, spread for long distances, and accumulated ectopically in dorsal regions of the anterior olfactory nucleus and the frontal cortex. Finally, transplantation of adult subventricular cells into the lesioned pathway showed that the lesion neither prevents neuronal migration nor alters its direction. Thus, although the olfactory bulb appears to regulate the pace of the developmental processes, its disconnection does not prevent the proliferation, migration and phenotypic acquisition of newly generated bulbar interneurons that, since they cannot reach their terminal domains, populate some precise regions of the lesioned adult forebrain.
SHORT COMUNICATIONEarly sodium elevations induced by combined oxygen and glucose deprivation in pyramidal cortical neurons
Authors: Pisani Antonio , Calabresi Paolo , Tozzi Alessandro , Bernardi Giorgio , Knöpfel Thomas
Published: March 2003

We investigated the effects of oxygen (O2)/glucose deprivation on intracellular sodium concentration ([Na+]i) of cortical pyramidal cells in a slice preparation of rat frontal cortex. Intracellular recordings were combined with microfluorometric measurements of [Na+]i using the Na+‐sensitive dye sodium‐binding benzofuran isophthalate (SBFI). Deprivation of O2/glucose caused an initial membrane hyperpolarization that was followed by a slowly developing large depolarization. Levels of [Na+]i started to increase significantly during the phase of membrane hyperpolarization. Neither tetrodotoxin, a combination of ionotropic and metabotropic glutamate receptor antagonists (d‐amino‐phosphonovalerate, 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione plus S‐methyl‐4‐carboxyphenylglycine) nor bepridil, an inhibitor of the Na+/Ca2+‐exchanger, affected these responses to O2/glucose. The present results demonstrate that, in cortical neurons, O2/glucose deprivation induces an early rise in [Na+]i which cannot be ascribed to the activity of voltage gated Na+‐channels, glutamate receptors or of the Na+/Ca2+‐exchanger.
Shaping of the cat paw for food taking and object manipulation: an X‐ray analysis
Authors: Boczek‐Funcke A. , Kuhtz‐Buschbeck J. P. , Raethjen J. , Paschmeyer B. , Illert M.
Published: March 2003

The kinematics of the cat distal forelimb during food‐taking were analysed to obtain information on the movement processes within the paw before and during object taking in a species without monosynaptic cortico‐motoneuronal projections. The behaviour was investigated with two tests: either the table test (TT, food offered on a table located at ground level in a reaching distance of 22 and 28 cm) or the horizontal test (HT, food offered in a small container located at shoulder level, height 18–25 cm, reaching distance 6–12 cm). In five animals, the changes in configuration and the conjoint actions of the wrist, the metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints were assessed with three‐dimensional X‐ray cinematography (time resolution 20 ms, spatial resolution 1 mm) and video analysis.

While approaching the target, the digits were first extended and subsequently abducted. This ‘preshaping’ consisted of combined angular changes in the MCP and PIP joints, thereby attaining an adequate grip aperture. Each cat used a stable strategy, but different cats used different strategies. In the TT, preshaping involved an MCP extension and a PIP flexion. In the HT, predominant extension of the MCP, predominant extension of the PIP, or a combination of both were used, followed by MCP flexion and PIP flexion. The grip aperture started to decrease before object contact, earlier in the TT, later in the HT. Grasping was achieved by flexion of first the PIP and later the MCP.

The X‐ray analysis gave evidence for individuated digit movements. Correlation analysis of the angular position of the joints between the different phalanges showed that digits 3 and 4 acted in concert, as did digits 2 and 5, but with clear independence between the different pairs. Furthermore, the different phalanges served different purposes during the grasp. Digits 3, 4 established object contact, digits 2, 5 were mainly used to stabilize the paw onto the surface.

The cat distal forelimb displays a refined movement repertoire during the preshaping and grasping phase of food‐taking. During the preshaping phase, the kinematics resembled in some aspects the situation in humans. The results demonstrate the ability of the polysynaptic projections from the cortico‐motoneuronal system to organize differentiated distal limb movements, including individuated movements of the digits.
Acute inactivation of the inferior olive blocks associative learning
Authors: Welsh John P. , Harvey John A.
Published: March 2003

Can acute inactivation of the inferior olive block associative learning? We anaesthetized the inferior olive with lidocaine while rabbits simultaneously: (i) performed conditioned nictitating membrane responses to a flashing light to which they had already been trained; and (ii) underwent their first experience with classical conditioning of the same response to a tone. Inactivation of the inferior olive immediately and reversibly abolished the performance of conditioned responses and prevented learning during rabbits' initial conditioning with a tone‐conditioned stimulus. When olivary function was restored, rabbits showed no signs of having learned under olivary anaesthesia. The experiment demonstrates that an acute disruption in olivary function can block learning, in addition to severely degrading motor control. The results are interpreted to indicate the importance of the inferior olive in optimizing learning, perhaps through a general role in regulating temporal processing.
Stratum radiatum giant cells: a type of principal cell in the rat hippocampus
Authors: Gulyás A. I. , Tóth K. , McBain C. J. , Freund T. F.
Published: March 2003

Neurons of a distinct type in CA1 area stratum radiatum of the rat hippocampus have been found to express a direct cellular form of long‐term potentiation (LTP, Maccaferri & McBain, 1996, J. Neurosci.16, 5334), but their functional identity, i.e. whether interneuron or principal cell, remained unknown. Whole cell recording from hippocampal slices in vitro was combined with light and electron microscopy to answer this question. LTP was robustly induced by a pairing protocol and physiological properties were measured in radiatum giant cells (RGCs) using biocytin containing pipettes. Reconstruction of the cells' dendritic and axonal arbor revealed morphological properties similar to CA1 pyramidal cells with some characteristic differences. They typically had two large diameter apical dendrites, or when only one dendrite arose, it soon bifurcated. Apical dendrites formed a dendritic tuft in stratum lacunosum‐moleculare and the dendrites, but not the somata, were densely covered with conventional spines. The axon arose from the basal pole of the soma, descended to stratum oriens and emitted several axon terminals bearing collaterals that travelled horizontally, remaining in stratum oriens. The main, myelinated axon trunks turned towards the fimbria. In the electron microscope axon terminals were found to form asymmetrical synapses on postsynaptic dendritic shafts and dendritic spines in stratum oriens. The dendrites received asymmetrical synapses, mostly on their spines. The axon initial segments also received several synapses, a feature never observed on interneurons. All the above characteristics support the conclusion that RGCs are excitatory principal neurons.
European Neuroscience Association The changing pattern of fibre bundles that pass through the optic chiasm of mice
Authors: Colello S. J. , Guillery R. W.
Published: March 2003

The organization of retinofugal fibres in the developing and adult mouse has been studied with transmission electron microscopy, autoradiography and the Bodian silver method. It has previously been shown that all retinal ganglion cell axons are in glial‐wrapped bundles in the developing and adult optic nerve, but are not in similar bundles close to the chiasm. In the embryonic mouse this region shows a transition in glial morphology from an interfascicular to a radial type and here retinofugal fibres begin to form a new order related to their age. Growth cones become concentrated at the pial surface of the juxtachiasmatic nerve and older fibres are restricted to deeper regions. This same age‐related order is also evident in the optic tract. However, the age‐related order is lost within the chiasm, where growth cones, young and old fibres are again mingled in distinct bundles as they cross the mid‐line. This study is particularly concerned with the structure of the mid‐line bundles. These fibre bundles cross each other at right angles, and are recognizable in fetal and adult mice. In the adult, monocular injections of H3 proline followed by autoradiographic study show that the individual mid‐line bundles are monocular and that they fuse again, losing the fascicular structure as they leave the chiasm and enter the tract. In the fetus and in the adult, the bundles generally lack a complete glial wrapping so that growth cones can lie in intimate contact with two crossing bundles, one coming from the left eye, the other from the right. The interesting question about the mechanisms that keep growth cones from entering the wrong bundles when they are in this position remains to be addressed.
A purinergic component of the excitatory postsynaptic current mediated by P2X receptors in the CA1 neurons of the rat hippocampus
Authors: Pankratov Yuri , Castro Enrique , Miras‐Portugal Maria Teresa , Krishtal Oleg
Published: March 2003

The pyramidal neurons in the CA1 area of hippocampal slices from 17‐ to 19‐day‐old rats have been investigated by means of patch clamp. Excitatory postsynaptic currents (EPSCs) were elicited by stimulating the Schaffer collateral at a frequency below 0.2 Hz. It was found that inhibition of glutamatergic transmission by 20 μm 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX) and 100 μm 2‐amino‐5‐phosphonovaleric acid (D‐APV) left a small component of the EPSC uninhibited. The amplitude of this residual EPSC (rEPSC) comprised 25 ± 11% of the total EPSC when measured at a holding potential of −50 mV. The rEPSC was blocked by selective P2 blocker pyridoxal phosphate‐6‐azophenyl‐2′‐4′‐disulphonic acid (PPADS) 10 μm and bath incubation with non‐hydrolysable ATP analogues, ATP‐γ‐S and α,β‐methylene‐ATP at 50 and 20 μm, respectively. The rEPSC was dramatically potentiated by external Zn2+ (10 μm). In another series of experiments exogenous ATP was applied to the CA1 neurons in situ. An inward current evoked by ATP was inhibited by PPADS to the same extent as the rEPSC. It is concluded that, depending on membrane voltage, about one‐fifth to one‐quarter of the EPSC generated by the excitatory synaptic input to the hippocampal CA1 neurons of rat is due to the activity of P2X receptors.
Hippocampal synaptic density and glutamate immunoreactivity following transient cerebral ischaemia in the chick
Authors: Horner Catherine H. , Davies Heather A. , Stewart Michael G.
Published: March 2003

A transient ischaemic episode of 10 min duration was induced in 1‐day‐old chicks. After a 1‐week survival period, synapse density was assessed in the ventral hippocampus using the ‘disector’ technique. A significant decrease was observed in asymmetric synapses, markedly greater than that observed previously in the dorsal hippocampus. Because the effect occurred mainly on excitatory synapses, the distribution of glutamate in the ventral hippocampus was also assessed by a postembedding immunogold labelling technique. The density of gold particles was significantly greater in both boutons and neuropil in the ischaemic group compared to controls, lending support to the theory of excitotoxicity as an explanation for ischaemic neural degeneration.
Individual differences in stress‐induced dopamine release in the nucleus accumbens are influenced by corticosterone
Authors: Rougé‐Pont Françoise , Deroche Véronique , Moal Michel Le , Piazza Pier Vincenzo
Published: March 2003

Stressful experiences, glucocorticoids hormones and dopaminergic neurons seems to interact in determining a higher propensity to develop drug abuse. In this report, we studied the acute interaction between these three factors. For this purpose, we compared stress‐induced dopamine release in intact rats and in rats in which stress‐induced corticosterone secretion was experimentally blocked. Ten‐minute tail‐pinch was used as a stressor and dopamine release estimated in the nucleus accumbens by using the microdialysis technique. Individual differences were also taken into account by comparing rats identified as either predisposed (HRs) or resistant (LRs) to develop self‐administration of drugs of abuse, on the basis of their locomotor response to novelty. It was found that suppression of stress‐induced corticosterone secretion significantly decreased stress‐induced dopamine release. However, such an effect greatly differed between HR and LR rats. When corticosterone secretion was intact HR animals had a higher and longer dopamine release in response to stress than LRs. The blockade of stress‐induced corticosterone secretion selectively reduced the dopaminergic response of HRs that did not differ from LRs anymore. These findings strength the idea that glucocorticoids could be involved in determining propensity to develop drug self‐administration. In particular, these hormones could play a role in determining the higher dopaminergic activity that characterizes drug proned individuals.
Functional Expression Of GFP‐Tagged Kv1.3 And Kv1.4 Channels In HEK 293 Cells
Authors: Jürgen Kupper
Published: March 2003

Various types of voltage gated potassium channels (Kv) are responsible for setting the resting potential and shaping the membrane potential waveform in the subcellular domains of neurons. In order to visualize the expression behaviour of recombinant Kv channels, we have fused green fluorescent protein (GFP) to the N‐terminal of the α subunits Kv1.3 and Kv1.4. In transiently transfected HEK 293 cells the GFP‐Kv chimeras localize to the plasma membrane. Whole‐cell voltage clamp recordings demonstrate that they form functional potassium channels. Kinetic analysis reveals that the gating kinetics of GFP‐Kv1.3 are virtually indistinguishable from those displayed by its wild‐type correlate. For GFP‐Kv1.4 channels we find that their gating is modified in an expected manner. In response to short depolarizing voltage pulses they do not inactivate, indicating that the attached GFP interferes with the fast N‐type inactivation mechanism present in wild type Kv1.4 channels. We suggest that GFP tagging of Kv channels might be a useful tool to monitor the spatiotemporal distribution of recombinant potassium channels expressed in living neurons.
How does the human brain deal with a spinal cord injury?
Authors: Bruehlmeier M. , Dietz V. , Leenders K. L. , Roelcke U. , Missimer J. , Curt A.
Published: March 2003

The primary sensorimotor cortex of the adult brain is capable of significant reorganization of topographic maps after deafferentation and de‐efferentation. Here we show that patients with spinal cord injury exhibit extensive changes in the activation of cortical and subcortical brain areas during hand movements, irrespective of normal (paraplegic) or impaired (tetraplegic patients) hand function. Positron emission tomography ([15O]‐H2O‐PET) revealed not only an expansion of the cortical ‘hand area’ towards the cortical ‘leg area’, but also an enhanced bilateral activation of the thalamus and cerebellum. The areas of the brain which were activated were qualitatively the same in both paraplegic and tetraplegic patients, but differed quantitatively as a function of the level of their spinal cord injury. We postulate that the changes in brain activation following spinal cord injury may reflect an adaptation of hand movement to a new body reference scheme secondary to a reduced and altered spino‐thalamic and spino‐cerebellar input.
Prolonged expression of zinc finger immediate‐early gene mRNAs and decreased protein synthesis following kainic acid induced seizures
Authors: Honkaniemi Jari , Sharp Frank R.
Published: March 2003

In the present study in situ hybridization was used to study the effect of kainic acid induced seizures on the expression of the zinc finger immediate‐early genes (IEGs) NGFI‐A, NGFI‐B, NGFI‐C, egr‐2, egr‐3 and Nurr1. Kainic acid markedly induced these IEGs especially in hippocampus, cortex and amygdala by 30 min. This induction gradually decreased and returned to baseline by 24 h in most regions. However, in the CA1 and CA3 subfields of hippocampus known to be damaged by kainic acid the expression of all the IEGs except egr‐2 remained elevated for 24 h. NGFI‐A, NGFI‐B, NGFI‐C and to a lesser extent, Nurr1, remained elevated also in the subcortical region of the temporal lobe. By 24 h incorporation of 14C‐leucine decreased in the piriform cortex, amygdala, and in the CA1 and CA3 subfields, but not in CA2 and dentate gyrus. These areas showing decreased protein synthesis in the hippocampus by 24 h showed prolonged IEG induction, whereas IEG expression returned to control levels in areas showing normal protein synthesis. In the temporal lobe decreased protein synthesis coexisted with decreased IEG expression, whereas areas in the vicinity of the region showing decreased protein synthesis demonstrated elevated IEG expression. The decreased protein synthesis was localized in areas where extensive neuronal death has occurred. This prolonged IEG induction in the hippocampus, which has been linked with neuronal death, could solely represent a prolonged mRNA turnover caused by disrupted protein synthesis. The prolonged IEG expression in the temporal lobe appeared to be localized in regions where the cells are in stress, but still viable. The sustained IEG expression might therefore either represent a stress response by which the neurons are trying to protect themselves or, alternatively, the IEG response may be an early sign indicating that these cells are initiating a pathway leading to programmed cell death.
Nicotinic receptors in the rat prefrontal cortex: increase in glutamate release and facilitation of mediodorsal thalamo‐cortical transmission
Authors: Gioanni Y. , Rougeot C. , Clarke P. B. S. , Lepousé C. , Thierry A. M. , Vidal C.
Published: March 2003

The modulatory influence of nicotinic acetylcholine receptor (nAChRs) on thalamocortical transmission was characterized in the prelimbic area (PrL) of the rat prefrontal cortex. In the first experiment, rats received a unilateral excitotoxic lesion centred on the mediodorsal thalamic nucleus (MD), and were sacrificed 1 week later. The lesion resulted in a 40% reduction of 3H‐nicotine autoradiographic labelling in the ipsilateral prefrontal cortex, particularly in areas that are innervated by the MD. Electrophysiological experiments were subsequently performed in non‐lesioned anaesthetized animals, in order to study modulation of short‐ and long‐latency responses of PrL neurons evoked by electrical stimulation of the MD. The short‐latency responses result from activation of the MD–PrL pathway and are mediated via AMPA‐type glutamatergic receptors, whereas the long‐latency responses reflect activation of the recurrent collaterals of cortical pyramidal neurons. Iontophoretic application of nicotinic agonists (nicotine, DMPP) facilitated both types of response. Local application of the nAChR antagonists dihydro‐beta‐erythroidine, mecamylamine and methyllycaconitine, prevented both kinds of facilitation. Finally, intracerebral microdialysis experiments were performed in order to test for nicotinic modulation of extracellular glutamate concentrations in the PrL. Direct application of nicotine via the dialysis probe increased glutamate levels in a dose‐dependent manner. This effect was blocked by local perfusion of dihydro‐beta‐erythroidine. These findings therefore provide anatomical and functional evidence for nAChR‐mediated modulation of thalamocortical input to the prefrontal cortex. Such a mechanism may be relevant to the cognitive effects of nicotine and nicotinic antagonists.
Stimulus‐function, wind‐up and modulation by diffuse noxious inhibitory controls of responses of convergent neurons of the spinal trigeminal nucleus oralis
Authors: Dallel Radhouane , Duale Christian , Luccarini Philippe , Molat Jean‐Louis
Published: March 2003

Extracellular unitary recordings were made from 53 spinal trigeminal nucleus oralis (Sp5O) convergent neurons in halothane‐anaesthetized rats. The neurons had an ipsilateral receptive field including mainly oral or perioral regions. They responded to percutaneous electrical stimulation with two peaks of activation. The first had a short latency (4.3 ± 0.3 ms) and low threshold (0.35 ± 0.04 mA), whereas the second had a longer latency (68.1 ± 3.4 ms) and higher threshold (7.3 ± 0.5 mA). Intracutaneous injection of capsaicin (0.1%) produced a strong and rapid reduction of the long‐latency responses of Sp5O convergent neurons with little effect on the short‐latency responses. In most cases (73%), the long‐latency responses exhibited a wind‐up phenomenon during repetitive (0.66 Hz) suprathreshold electrical stimulation. These results suggest that C‐fibres mediate the long‐latency response of Sp5O convergent neurons. Regarding the C‐fibre‐evoked responses, a linear relationship between the intensity of the applied current and the magnitude of the response was found within the one to three times threshold range. The Sp5O convergent neurons also encoded the intensity of mechanical stimuli applied to the skin or mucosa in the 5–50 g ranges. The evoked activity of Sp5O convergent neurons could be suppressed by noxious heat applied to the tail (52 °C) and long‐lasting poststimulus effects followed this. These findings show that convergent neurons in the Sp5O resemble those in the deep laminae of the spinal dorsal horn and spinal trigeminal nucleus caudalis, and further support that the Sp5O plays a part in the processing of nociceptive information from the orofacial region.
Enhanced synaptic transmission and reduced threshold for LTP induction in fyn‐transgenic mice
Authors: Lu Y. ‐F. , Kojima N. , Tomizawa K. , Moriwaki A. , Matsushita M. , Obata K. , Matsui H.
Published: March 2003

To elucidate the physiological role of Fyn, we analysed the properties of synaptic transmission and synaptic plasticity in hippocampal slices of mice overexpressing either wild‐type Fyn (w‐Fyn) or its constitutively active mutant (m‐Fyn). These fyn‐transgenes were driven by the calcium/calmodulin‐dependent protein kinase IIα promoter which turned on in the forebrain neurons including hippocampal pyramidal cells and in late neural development. In the hippocampal slices expressing m‐Fyn the paired‐pulse facilitation was reduced and the basal synaptic transmission was enhanced. A weak theta‐burst stimulation, which was subthreshold for the induction of long‐term potentiation (LTP) in control slices, elicited LTP in CA1 region of the slices expressing m‐Fyn. When a relatively strong stimulation was applied, the magnitude of LTP in m‐Fyn slices was similar to that in control slices. By contrast, the basal synaptic transmission and the threshold for the induction of LTP were not altered in the slices overexpressing wild‐type Fyn. To examine the effect of expression of m‐Fyn on GABAergic inhibitory system, we applied bicuculline, a GABAA receptor blocker, to the hippocampal slices. The ability of bicuculline to enhance excitatory postsynaptic potentials was attenuated in slices expressing m‐Fyn, suggesting that the overexpression of m‐Fyn reduced the GABAergic inhibition. The enhancement of synaptic transmission and the reduction of GABAergic inhibition may contribute to the enhanced seizure susceptibility in the mice expressing m‐Fyn. Thus, these results suggest that regulation of Fyn tyrosine kinase activity is important for both synaptic transmission and plasticity.
Protective effects of idebenone and α‐tocopherol on β‐amyloid‐(1–42)‐induced learning and memory deficits in rats: implication of oxidative stress in β‐amyloid‐induced neurotoxicity in vivo
Authors: Yamada Kiyofumi , Tanaka Tomoko , Han Daiken , Senzaki Kouji , Kameyama Tsutomu , Nabeshima Toshitaka
Published: March 2003

Amyloid β‐peptide (Aβ), the major constituent of the senile plaques in the brains of patients with Alzheimer's disease, is cytotoxic to neurons and has a central role in the pathogenesis of the disease. Previous studies have suggested that oxidative stress is involved in the mechanisms of Aβ‐induced neurotoxicity in vitro. In the present study, we examined whether oxidative stress contributes to learning and memory deficits caused by continuous intracerebroventricular infusion of Aβ‐(1–42). In the Aβ‐(1–42)‐infused rats, spontaneous alternation behaviour in a Y‐maze and spatial memory in a water maze task were significantly impaired, as compared with Aβ‐(40–1)‐infused control rats. The retention of passive avoidance learning was also significantly impaired by treatment with Aβ‐(1–42). Potent antioxidants idebenone and α‐tocopherol prevented the behavioural deficits in Y‐maze and water maze, but not passive avoidance, tasks in Aβ‐(1–42)‐infused rats when they were repeatedly administered by mouth once a day from 3 days before the start of Aβ infusion to the end of behavioural experiments. Lipid peroxide levels in the hippocampus and cerebral cortex of Aβ‐(1–42)‐infused rats did not differ from those in control animals, and neither idebenone nor α‐tocopherol affected the lipid peroxide levels. These results suggest that treatment with antioxidants such as idebenone and α‐tocopherol prevents learning and memory deficits caused by Aβ.
Poly(ADP ribose) polymerase cleavage precedes neuronal death in the hippocampus and cerebellum following injury to the developing rat forebrain
Authors: Joashi U. C. , Greenwood K. , Taylor D. L. , Kozma M. , Mazarakis N. D. , Edwards A. D. , Mehmet H.
Published: March 2003

Transient unilateral forebrain hypoxia–ischaemia (HI) in 14‐day‐old rats produces infarction and delayed neuronal death in the frontal cortex. Cell death can also be observed in regions distant from the primary injury, a phenomenon known as diaschisis. While apoptosis is involved in selective neuronal death, its role in infarction and diaschisis remains poorly understood. Here, we have investigated the proteolytic cleavage of poly(ADP ribose) polymerase (PARP) and the occurrence of apoptosis in the hippocampus and the cerebellum following either HI or traumatic brain injury. We demonstrate that: (i) in vitro, PARP is cleaved during apoptosis but not necrosis in cultured neuronal (N1E) cells and Swiss 3T3 fibroblasts; (ii) following HI, apoptotic cells can be detected by 4 h after injury in the hippocampus; (iii) in the ipsilateral hippocampus the appearance of cells with apoptotic morphology is preceded by a dramatic increase in PARP cleavage in the same region, starting immediately following HI and persisting for 24 h; (iv) HI also induces apoptosis in the cerebellum and, as in the hippocampus, the appearance of cells with apoptotic morphology is preceded by PARP cleavage that is greater on the side Ipsilateral to forebrain injury; and (v) similarly, traumatic brain injury to the forebrain leads to PARP cleavage and apoptosis in the cerebellum. We conclude that HI injury or traumatic injury to the developing rat forebrain leads to PARP cleavage in directly affected areas and in sites distant from the primary injury that precedes the appearance of cells with apoptotic morphology. Our results are consistent with a role for apoptotic cell death in infarction and in diaschisis resulting from forebrain injury to the developing brain.
Glutamate receptor phenotypes in the auditory brainstem and mid‐brain of the developing rat
Authors: Caicedo Alejandro , Eybalin Michel
Published: March 2003

Glutamate receptors mediate most excitatory synaptic transmission in the adult vertebrate brain, but their activation in developing neurons also influences developmental processes. However, little is known about the developmental regulation of the subunits composing these receptors. Here we have studied age‐dependent changes in the expression of α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole (AMPA) andN‐methyl‐d‐aspartate (NMDA) receptor subunits in the cochlear nucleus complex (CN), the superior olivary complex (SOC), the nuclei of the lateral lemniscus, and the inferior colliculus of the developing rat. In the lateral superior olive, the medial nucleus of the trapezoid body, and the ventral nucleus of the lateral lemniscus, the distribution of AMPA receptor subunits changed drastically with age. While GluR1 and GluR2 subunits were highly expressed in the first 2 postnatal weeks, GluR4 staining was detectable only thereafter. GluR1 and GluR2 immunoreactivities rapidly decreased during the third postnatal week, with the GluR1 subunits disappearing from most neurons. In contrast, the adult pattern of the distribution of AMPA receptor subunits emerged gradually in most of the other auditory nuclei. Thus, progressive as well as regressive events characterized AMPA receptor development in some nuclei, while a monotonically maturation was seen in other regions. In contrast, the staining patterns of NMDA receptor subunits remained stable or only decreased during the same period. Although our data are not consistent with a generalized pattern of AMPA receptor development, the abundance of GluR1 subunits is a distinctive feature of early AMPA receptors. As similar AMPA receptors are present during plasticity periods throughout the brain, neurons undergoing synaptic and structural remodelling might have a particular need for these receptors.
The medullary dorsal reticular nucleus facilitates pain behaviour induced by formalin in the rat
Authors: Almeida A. , Størkson R. , Lima D. , Hole K. , Tjølsen A.
Published: March 2003

The influence of the dorsal reticular nucleus (DRt) on pain behaviour during the formalin test was studied in the rat by lesioning the nucleus through local application of electrical current or quinolinic acid. Animals in which the DRt was lesioned ipsilaterally to the paw injected with formalin spent less time in focused (licking, biting or scratching the injected paw) and total (focused pain behaviour plus protection of the injected paw during movements) pain behaviour, and showed paw‐jerks less frequently than non‐lesioned animals in both phases 1 and 2 of the test. Animals in which the DRt was lesioned contralaterally to the injected paw presented a decrease in total pain behaviour and number of paw‐jerks only during phase 2. The number of superficial (laminae I–II) and deep (laminae III–VI) spinal dorsal horn cells expressing the c‐fos proto‐oncogene 2 h after subcutaneous injection of formalin was reduced by 34% and 50%, respectively, in animals with an ipsilateral DRt lesion as compared to non‐lesioned rats. No differences in c‐fos expression were observed after lesioning the DRt contralateral to the formalin injection.

 The results indicate that the DRt is involved in the facilitation of nociception during the formalin test by enhancing the response capacity of dorsal horn neurons to noxious stimulation. It is suggested that the pronociceptive action of the DRt is mediated by the reciprocal connections it establishes with the spinal dorsal horn [Almeida et al. (1993) Neuroscience, 55, 1093].
Protein kinase C modulates field‐evoked transmitter release from cultured rat cerebellar granule cells via a dendrotoxin‐sensitive K+ channel
Authors: Cousin Michael A. , McLaughlin Mark , Nicholls David G.
Published: March 2003

The role of protein kinase C (PKC) in the control of neurotransmitter release from cultured rat cerebellar granule cells was investigated. Release of preloaded [3H]‐d‐aspartate which is incorporated into synaptic vesicles in this preparation was evoked by electrical field stimulation or elevated KCl. PKC activation by phorbol esters resulted in a large facilitation of field‐evoked Ca2+‐dependent [3H]‐d‐aspartate release and a lesser enhancement of KCl‐stimulated release. Inhibition of PKC by Ro 31‐8220 or staurosporine virtually abolished field‐evoked release but had no effect on KCl‐evoked release. Field‐evoked, but not KCl‐evoked, synaptic vesicle exocytosis monitored by the fluorescent vesicle probe FM2‐10 was inhibited by staurosporine. PKC was not directly modulating neurite Ca2+ channels coupled to release, as Ro 31‐8220 did not inhibit these channels. Activation or inhibition of PKC modulated field‐evoked plasma membrane depolarization, but had no effect on KCl‐evoked depolarization, consistent with a regulation of Na+ or K+ channels activated by field stimulation. No modulation of field‐evoked neurite Na+ influx was seen using phorbol esters. Phorbol ester‐induced facilitation of field‐evoked [3H]‐d‐aspartate release and neurite Ca2+ entry was non‐additive with that produced by the specific K+ channel antagonist dendrotoxin‐1, suggesting that PKC modulates transmitter release from field‐stimulated cerebellar granule cells by inhibiting a dendrotoxin‐1‐sensitive K+ channel.