bluuebunny/crossref_metadata_2025 huggingface dataset:
BDNF‐activated Sianal Transduction in Rat Cortical Glial Cells
Authors: Roback John D. , Marsh H. Nicholas , Downen Martha , Palfrey H. Clive , Wainer Bruce H.
Published: April 2006

Cortical glial cells in culture were found to be responsive to the neurotrophin brain‐derived neurotrophic factor (BDNF), as evidenced by activation of multiple signal transduction processes. BDNF produced an increase in mitogen‐activated protein (MAP) kinase tyrosine phosphorylation, MAP kinase activity, intracellular calcium concentration and c‐fos expression in the glial cells. Only a subset of the glial cells responded to BDNF, as reflected in single‐cell analysis of calcium transients and c‐fos expression. BDNF had no detectable effect on glial mitotic activity, as measured by DNA synthesis. In parallel studies, nerve growth factor and neurotrophin‐3 had no effect on signalling in these cultures. BDNF has previously been demonstrated to act via trkB receptors with a cytoplasmic tyrosine kinase domain (gp145trkB). Pretreatment of glial cultures with K252a, which at low concentrations specifically inhibits the trk tyrosine kinases, abolished BDNF effects on MAP kinase stimulation, suggesting that BDNF was acting through gp 145trkB. However, subsequent studies showed that gp 145trkB was expressed at extremely low levels in the cultures: gp145trkB mRNA transcripts could only be detected using the reverse transcription‐polymerase chain reaction, and gp 145trkB protein was not detected by either immunoblotting or immunocytochemistry. On the other hand, the glia expressed significantly higher levels of gp95trkB mRNA and protein, which represent truncated forms of trkB receptors lacking the tyrosine kinase domain. The results of these studies demonstrate that a subset of cultured CNS glia respond to BDNF with the activation of conventional signal transduction processes. The mechanism of BDNF‐initiated signal transduction in glial cells most likely involves a relatively small number of gp 145trkB receptors, but involvement of the more abundant truncated gp95trkB receptors cannot be excluded.
Acidic FGF and FGF Receptors are Specifically Expressed in Neurons of Developing and Adult Rat Dorsal Root Ganglia
Authors: Oellig Cornelia , Pirvola Ulla , Taylor Lesley , Elde Robert , Hökfelt Tomas , Pettersson Ralf F.
Published: April 2006

Employing complementary technical approaches, we have studied the expression of acidic fibroblast growth factor (aFGF) and FGF receptors in rat dorsal root ganglia. The results clearly showed that within spinal nerves aFGF and two high‐affinity FGF receptors, FGFR‐1 and FGFRQ, were prominently expressed in neurons, while expression in Schwann cells was undetectable. FGFR‐3 and FGFR‐4 were not expressed in dorsal root ganglia. Acidic FGF mRNA was detected in the majority of dorsal root ganglion neurons, including all size classes; FGFR‐1 and FGFR‐2 transcripts were only detected in subpopulations of mainly large and medium size neurons. In subcellular fractionation studies on dorsal root ganglion and spinal root tissue, aFGF was recovered in the soluble fraction and was thus not tightly associated with neuronal membranes. During development FGFR‐1 and FGFRQ mRNAs were found to be present at all stages examined (embryonic days 15–21 and postnatal days 1–120). Acidic FGF mRNA and protein were first detected at embryonic day 18, and their expression then increased progressively up to postnatal levels. In cultures of dorsal root ganglion neurons derived from day 15 embryos, aFGF expression was first detected 3 days after plating. The resulting neuron cultures continued to express aFGF in a Schwann cell‐independent manner. In combination, these results indicate that aFGF expression in dorsal root ganglia is initiated and maintained in postmitotic neurons. Furthermore, the data suggest that the physiological function of aFGF in the peripheral nervous system is connected to processes specific to the mature sensory (and motor) system, such as the maintenance and survival of peripheral nerve neurons.
The Effect of Barium on [3H]Noradrenalin Release from the Human Neuroblastoma SH‐SY5Y
Authors: Vaughan Peter F. T. , Kaye David F. , Ball Stephen G. , Reeve Helen L. , Peers Chris
Published: April 2006

Replacement of Ca2+ with Ba2+ in HEPES‐buffered saline stimulated [3H]noradrenalin release in the human neuroblastoma clone SH‐SY5Y by up to 20% of the cell content in the absence of other secretory stimuli. The Ba2+‐evoked release was inhibited by 85% by 3 μM tetrodotoxin and 95% by 5 μM nifedipine. Ba2+ also increased the potency of K+‐evoked release of [3H]noradrenalin, as maximal release was observed with 60 mM K+ compared with the 100 mM K+ necessary to achieve maximal release in the presence of Ca2+. In contrast, replacing Ca2+ with Ba2+ had little effect on carbachol‐ and bradykinin‐evoked release of [3H]noradrenalin. No evidence was obtained from studies on changes in [Ca2+]i (in response to 100 pM carbachol) using fura‐2 that Ba2+ could enter intracellular stores in SH‐SY5Y cells. Whole‐cell patch‐clamp studies showed that Ba2+ depolarizes SH‐SY5Y cells as well as enhancing inward Ca2+ channel currents and shifting their voltage dependence to more negative values. These results are discussed in terms of the hypothesis that Ba2+ blocks K+ channels, leading to depolarization followed by opening of voltage‐sensitive Na+ channels. This in turn opens voltage‐sensitive L‐type Ca2+ channels, which are coupled to the release of [3H]noradrenalin in SH‐SY5Y cells.
The Specification of Neuronal Fate: A Common Precursor for Neurotransmitter Subtypes in the Rat Cerebral Cortex In Vitro
Authors: Götz Magdalena , Williams Brenda P. , Bolz Jürgen , Price Jack
Published: April 2006

Neurotransmitter choice is a crucial step in neural development. In the cerebral cortex, pyramidal neurons use the excitatory neurotransmitter glutamate, whereas non‐pyramidal cells use the inhibitory neurotransmitter GABA. We are interested in how these two neuronal types are generated. We labelled precursor cells from embryonic rat cerebral cortex with a retroviral vector in dissociated cell cultures, and examined the neurotransmitter phenotype of their progeny immunohistochemically after 2 weeksin vitro.We discovered, first, that precursor cells in culture generate glutamatergic and GABAergic neurons in proportions similar to thosein vivo.Second, we found that neuronal precursor cells gave rise to both GABAergic and glutamatergic neurons. These results suggest that neuronal precursor cells in the cerebral cortex have the potential to generate both neuronal subtypes. Moreover, these data are consistent with a stochastic model of neurotransmitter specification.
Developmental Regulation of Full‐length trkC in the Rat Sciatic Nerve
Authors: Offenhäuser N. , Böhm‐Matthaei R. , Tsoulfas P. , Parada L. , Meyer M.
Published: April 2006

In order to gain insight into potential roles of neurotrophins in Schwann cell biology, the expression of neurotrophin receptors of the frk gene family was investigated in rat sciatic nerve development. This analysis revealed differential regulation of truncated and full‐length receptors. TrkA was undetectable even when analysed with a sensitive reverse transcriptase‐polymerase chain reaction (RT‐PCR) method. TrkB was present at the mRNA as well as protein level only in its truncated form. Surprisingly, multiple isoforms of trkC, including full‐length forms, were detected in early postnatal nerve. Specific antibodies detected truncated and full‐length trkC proteins in Western blotting, and RT‐PCR revealed the presence of two full‐length isoforms, one of them containing the 14 amino acid kinase insert. In situ hybridisation localized the expression of trkC to a subpopulation of Schwann cells. TrkC receptors are expressed already in nerves from day‐16 embryos. In contrast to early postnatal stages, full‐length trkC receptors are no longer expressed in adult nerves, which, however, maintain expression of truncated trkC transcripts. The presence of trkC kinases in peripheral nerve suggests a role for neurotrophin‐3, the only known trkC ligand, in peripheral nerve development.
Complex Deficits on Reaction Time Performance following Bilateral Intrastriatal 6‐OHDA Infusion in the Rat
Authors: Amalric M. , Moukhles H. , Nieoullon A. , Daszuta A.
Published: April 2006

The present study examined the ability of rats subjected to bilateral 6‐hydroxydopamine lesions of the terminal area of the nigrostriatal dopamine system to perform a prelearned reaction time task. This lesion model, the induction of a partial dopamine denervation of the striatum (74% depletion of dopamine striatal tissue content) with a retrograde degeneration of dopamine cell bodies in the substantia nigra, sparing the mesolimbic dopaminergic pathway, closely approximates the neuronal degeneration observed in human idiopathic Parkinson's disease. Rats were trained previously to release a lever, within a reaction time limit, after the presentation of a visual cue through reinforcement with food pellets. The onset of the light stimulus varied randomly after an unpredictable delay period of 0.25–1.0 s. Rats with dopaminergic lesions showed moderate to extensive performance deficits which were not compensated for the five postoperative weeks. More than half of the lesioned animals (64%) showed severe deficits, characterized by a concomitant increase in the number of anticipated (premature release of the lever before the visual cue) and delayed responses (lever release after the reaction time limit) with shortened reaction times in some cases. A smaller proportion (36%) of lesioned animals exhibited mild impairment of performance with a large increase in delayed responses and lengthening of reaction times but with no change in the number of anticipated responses. Asymmetric lesions had no effect on the reaction time performance. Examination of tyrosine hydroxylase immunostaining revealed that in the most impaired animals dopamine depletion was extensive in the medial striatum, whereas it was restricted to the dorsolateral striatum in the least impaired animals. Results suggest that a decrease in dopamine function at striatal level severely disrupts performance of a conditioned reaction time task. A partial dopamine depletion in the dorsolateral striatum induces motor initiation deficits (i.e. increases delayed response only). Larger striatal dopamine depletion may produce both motor and cognitive deficits (decrease in attentional control over response output and/or disruption of stimulus‐response associations) that could be related to similar events in Parkinson's disease.
Topographic Distribution of Fixation‐related Units in the Dorsomedial Frontal Cortex of the Rhesus Monkey
Authors: Lee Kyoungmin , Tehovnik Edward J.
Published: April 2006

Most cells in the dorsomedial frontal cortex of the rhesus monkey had activity related to saccadic eye movement and for visual fixation. This activity changed depending upon the position of a fixation target, which suggested coding for the target location in spatial coordinates. Further analysis of such activity revealed a topographical distribution of neurons: neurons in the rostral part of the area were more active with eyes to the contralateral position, while those in the caudal part were more active with eyes to the ipsilateral position; also, cells in the medial part of the area had higher activity with a downward fixation position, whereas those in the lateral part had higher activity with an upward fixation position. This distribution of units was in agreement with the map of termination zones of saccadic eye movements evoked by electrical stimulation of the same area. These observations provide evidence for the hypothesis that the dorsomedial frontal cortex is organized in spatial coordinates and is involved in specifying the position of visual fixation.
D1 and D2 Receptor Gene Expression in the Rat Frontal Cortex: Cellular Localization in Different Classes of Efferent Neurons
Authors: Gaspar Patricia , Bloch Bertrand , Le Moine Catherine
Published: April 2006

The dopaminergic input to the frontal cortex has an important role in motor and cognitive functions. These effects are mediated by dopamine receptors both of type D1 and of type D2, although the neural circuits involved are not completely understood. We used in situ hybridization to determine the cellular localization of D1 and D2 receptor mRNAs in the rat frontal cortex. Retrograde tracing was used in the same animals to identify the main cortical efferent populations. Fluorogold was injected into the different cortical targets of the frontal cortex and sections were hybridized with D1 and D2 35S‐labelled cRNA probes. D1 and D2 mRNA‐containing neurons were present in all the cortical areas investigated, with greater expression in the medial prefrontal, insular and cingulate cortexes and lower expression in the motor and parietal cortexes. Neurons containing D1 mRNA were most abundant in layer Vlb; they were also present in layers Vla and V of all cortical layers and in layer II of the medial prefrontal, cingulate and insular areas. Double labelling with fluorogold demonstrated that D1 mRNA was present in corticocortical, corticothalamic and corticostriatal neurons. Neurons containing D2 mRNA were essentially restricted to layer V, but only in corticostriatal and corticocortical neurons. Neither D1 nor D2 mRNA was found in corticospinal or corticopontine neurons. The present results demonstrate that D1 and D2 receptor genes are expressed in efferent cortical populations, with higher expression for D1. In spite of an overlap in some cortical layers, the expression of D1 and D2 receptor genes is specific for different categories of pyramidal neurons.
Ontogeny of a Photic Response in the Suprachiasmatic Nucleus in the Siberian Hamster (Phodopus sungorus)
Authors: Duffield Giles E. , Dickerson John M. , Alexander Iona H. M. , Ebling Francis J. P.
Published: April 2006

The ontogeny of photic responsiveness in the suprachiasmatic nucleus of the Siberian hamster (Phodopus sungorus) was studied using the enhanced expression of the immediate early gene c‐fos as a marker of neuronal activation. c‐fos expression was assessed by immunocytochemical localization of its protein product. Hamsters were kept on a 16 h light:8 h dark photocycle. The adult Siberian hamster showed a marked increase in the number of c‐fos‐immunoreactive (c‐fos‐ir) cells within the suprachiasmatic nuclei (SCN) in response to a 1 h light pulse delivered 1–3 h after lights off, in comparison to controls kept in the dark. This is consistent with previous studies in the Syrian hamster and rat. The development of the photic response was examined. The first study investigated the effects of a light pulse on c‐fos induction in pups at 5, 9, 12 and 24 postnatal days of age (PD). The suprachiasmatic region was identified by immunocytochemical localization of peptide‐histidine‐isoleucine in adjacent sections, a peptide expressed early in the development of the rodent SCN. The distribution of c‐fos‐ir cells was also compared with the location of retinal efferents, as determined by intraocular injection of the tract tracer cholera toxin B subunit 24 h previously. At PD 9, 12 and 24, significant increases in the number of c‐fos‐ir cells occurred in the light pulsed animals in comparison to age‐matched control animals which were moved within the non‐illuminated room to provide a ‘dark’ pulse. Induction of c‐fos mainly occurred in the ventrolateral region of the medial and caudal SCN, the region which receives the greatest density of retinal innervation. The second study focused on the earliest age at which light could induce c‐fos expression in the SCN by investigating the effects of light on c‐fos‐ir cells in pups at PD 2–4. Animals at PD 3 and 4 showed enhanced c‐fos expression in the ventrolateral region, whilst PD 2 animals showed no response. The number of c‐fos‐ir cells in the SCN region in light‐pulsed animals increased from PD 3 to adulthood. These results indicate that retinal input can activate cells in the SCN even before the eyelids open on PD 11, and the SCN can potentially be entrained by photic inputs as early as day 3 after birth.
Electrophysiology of the Neurons in the Area of the Enkephalinergic Magnocellular Dorsal Nucleus of the Guinea‐pig Hypothalamus, Studied by Intracellular and Whole‐cell Recordings
Authors: Niespodziany Isabelle , Poulain Pierre
Published: April 2006

The electrophysiological characteristics of 103 hypothalamic neurons in the area of the guinea‐pig enkephalinergic magnocellular dorsal nucleus were studied in a thick slice preparation with sharp microelectrodes (63 neurons) and patch pipettes for whole‐cell recordings (40 neurons). Of the sampled cells, 79.6% displayed tetrodotoxin‐resistant, calcium‐dependent slow‐depolarizing potentials when the membrane potential was hyperpolarized to ˜70 mV (type I neurons). Half of them showed robust slow depolarizing potentials, generating bursts of fast action potentials. In the remaining neurons, the slow‐depolarizing potentials did not cause burst‐firing action potentials but triggered single action potentials. The other class of neurons (20.4% of the sample: type II neurons) did not exhibit calcium‐dependent slow‐depolarizing potentials. Resting potential, input resistance and the membrane time constant did not distinguish among the two classes of neurons. Current‐voltage relationships were heterogeneous. A transient outward rectification was observed in the two classes. This was not totally blocked by 2 mM 4‐aminopyridine but was abolished when using perfusion with cobalt instead of calcium. Input resistance and the time constant were higher when measured in the whole‐cell mode but the other electrical parameters and the sampling of the recorded neurons were strikingly similar between the two methods of recording. Intracellular staining of 22 neurons retrogradely labelled from the lateral septum allowed confirmation of their location within the magnocellular dorsal nucleus. The study indicates that the electrical properties of these neurons did not differ from those of neurons found throughout the area explored. It also indicates the presence of distinct electrophysiological types of cells in the magnocellular dorsal nucleus, although the nucleus is composed of a single type of enkephalinergic neuron. It provides a basis for the study of the regulation of activity of the neurons at the origin of an enkephalinergic tractus which is involved in neuroendocrine, psychoneuroendocrine and immune processes.
Characterization of Nerve Growth Factor (NGF) Release from Hippocampal Neurons: Evidence for a Constitutive and an Unconventional Sodium‐dependent Regulated Pathway
Authors: Blöchl A. , Thoenen H.
Published: April 2006

We investigated the mechanism of neuronal nerve growth factor (NGF) release with regard to the potential function of NGF as a mediator of neuronal plasticity in the CNS. The analysis was performed in hippocampal slices and in primary cultures of hippocampal neurons, transiently transfected with an NGF cDNA construct to increase the level of NGF expression. In both systems there was activity‐dependent NGF release initiated by high potassium (KCl), veratridine, glutamate or carbachol. Replacement of 90% of sodium in the medium with N‐methyl‐glucamine strongly reduced this release. The KCl‐ and veratridine‐initiated NGF release was suppressed by tetrodotoxin; release by glutamate was less sensitive to tetrodotoxin but was sodium‐dependent. The glutamate effect could be inhibited by GYK152644, an antagonist of α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole propionic acid receptors, but not by MK‐801, an antagonist of NMDA receptors. The activity‐dependent release of NGF did not depend on extracellular Ca2+, but was sensitive to the intracellular Ca2+ chelator bis‐(o‐aminophenoxy)‐ethane‐N,N,N',N'‐tetraacetic acid tetra(acetoxymethyl)‐ester, and to depletion of intracellular calcium stores. Conversely, mobilization of Ca2+ from intracellular stores with caffeine and thapsigargin mimicked the effect of depolarization. Basal NGF release could be reduced by either temperature block (15°C) or tetrodotoxin to ˜50%. The combination of both treatments reduced NGF release to below the detection limit, suggesting that basal release has constitutive and regulated components, the latter presumably resulting from spontaneous activity of interconnected neurons.
Epileptiform Activity in the Guinea‐pig Neocortical Slice Spreads Preferentially along Supragranular Layers—Recordings with Voltage‐sensitive Dyes
Authors: Albowitz Birgit , Kuhnt Ulrich
Published: April 2006

The spread of epileptiform activity was monitored in guinea‐pig neocortical slices by the use of a voltage‐sensitive dye (RH795) and a fast optical recording technique. Epileptiform activity induced by bicuculline methiodide (10–20 μM) and single‐pulse stimulation spread from the stimulation site in layer I or in the white matter across most of the slice. Different lesions were made in the slice in order to specify the neuronal connections used for spread in the horizontal direction. In the slice, intracortical connections are necessary for the spread of epileptiform activity, as shown by vertical cuts through all cortical layers but sparing the white matter. Horizontal connections were interrupted by cuts parallel to the axis of pyramidal neurons through either supragranular or infragranular layers. Vertical connections were interrupted by cuts perpendicular to the axis of pyramidal neurons separating supragranular and infragranular layers. Spread of epileptiform activity in the horizontal direction was not hindered by horizontal cuts. Vertical cuts through infragranular layers also did not hinder the spread of epileptiform activity. In contrast, vertical cuts through supragranular layers either abolished completely (nine slices) or delayed significantly (ten slices) the spread of epileptiform activity. The mean delay at the supragranular lesion was 44 ms in layer III and 30 ms in layer V; at the infragranular lesion the mean delay was 2 ms in layer III and 6 ms in layer V. Also, with horizontal cuts, in three out of five slices the velocity of spread was significantly lower in infragranular as compared to supragranular layers. It is concluded that both supra‐ and infragranular layers if isolated possess the ability to initiate and propagate epileptiform activity independently. However, in the intact slice the influence of the supragranular networks on initiation and propagation of epileptiform activity appears to dominate.
Involvement of AMPA Receptors in Maintenance of Memory for a Passive Avoidance Task in Day‐old Domestic Chicks (Gallus domesticus)
Authors: Steele Robert J. , Stewart Michael G.
Published: April 2006

Day‐old chicks (Gallus domesticus) were trained on a one‐trial passive avoidance task where the aversive stimulus was an unpleasant tasting substance, methyl anthranilate. Chicks were killed 6.5 h after training. The kinetic parameters of [3H] α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid ([3H]AMPA) binding were determined using quantitative receptor autoradiography and Scatchard analyses in 15 discrete forebrain regions of trained and control (water‐trained) chicks, revealing two components of binding in each. KD
values showed some regional variation, but were 22.2 ± 1.1 nmol l‐1 for the high‐affinity component and 685 ± 25 nmol l‐1 for the low‐affinity component of binding to whole forebrain sections from control chicks. Analyses also revealed that Hill coefficients were significantly less than 1 in all regions measured. A significant decrease in KD for the low‐affinity component occurred bilaterally in the intermediate andmedial hyperstriatum ventrale (IMHV; left, 34.8%; right, 33.3%), a region that has previously been shown to be implicated in the processes of memory formation, following passive avoidance training. A significant decrease in KD for the high‐affinity component occurred in the right palaeostriatum augmentatum (19.5%). Significant decreases in Bmax accompanied the KD alterations in both cases. Additionally, bilateral intracerebral injections (administered 4.5‐5.5 h after training) into the IMHV of 500 nmol l‐1 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX), a selective antagonist of non‐NMDA glutamate receptors (particularly AMPA receptors), resulted in amnesia for one‐trial passive avoidance training in day‐old chicks tested 6.5 h after training. Unilateral injections administered 5.5 h after training had a significant but smaller effect. Injections administered before training or 5 min after training had no effect on learning or retention of memory for the task. These results show that the affinity of AMPA receptors increases at a time point after passive avoidance training at which their inhibition by CNQX blocks maintenance of long‐term memory for this task.
Subcellular Localization of the GABAA Receptor γ2 Subunit in the Rat Spinal Cord
Authors: Sur Cyrille , McKernan Ruth , Triller Antoine
Published: April 2006

The fine subcellular organization of the GABAA receptor complex in the adult rat spinal ventral horn was analysed by immunocytochemistry using a specific polyclonal antiserum raised against the γ subunit. This subunit confers benzodiazepine sensitivity on the chloride channel of the GABAA receptor. With both fluorescent and peroxidase staining, the immunoreactivity was mainly observed in the grey matter and more specifically in the dorsal and ventral horns on medium and large neurons. A high number of immunostained somata were clustered in regions corresponding to motor nuclei. On the neuronal surface, labelling appeared as fluorescent dots over the more diffuse staining that was present on the soma and proximal part of dendrites. At the ultrastructural level, peroxidase end product was in most cases associated with the internal side of postsynaptic differentiations facing terminal boutons enriched with pleiomorphic small clear vesicles. The positively stained synapses were encountered on proximal dendrites of neurons and throughout the neuropil of the ventral horn (layers VII‐IX). An immunoreactivity on the postsynaptic membrane was occasionally found to decorate large pieces of membrane not directly apposed to presynaptic active zones. In addition, presynaptic labelling was observed at axoaxonic contacts and at extrasynaptic sites on membranes within boutons, sometimes themselves apposed to γ2 immunoreactivity. Finally, we also observed γ2 immunoreactivity at the cytosolic face of the plasma membrane of some glial elements. These results give morphological evidence for the involvement of GABAA receptors in both post‐ and presynaptic inhibition in the rat spinal ventral horn. The presence of γ2 subunit immunoreactivity at these different synaptic contacts suggests that the two types of inhibition can be modulated by benzodiazepine drugs. The findings also provide anatomical evidence for the possible regulation of GABA release through an autoreceptor, and for GABAergic communication between neuronal and glial components.
Regional Distribution and Developmental Variation of the Glycine Transporters GLYT1 and GLYT2 in the Rat CNS
Authors: Zafra Francisco , Gomeza Jesús , Olivares Luis , Aragón Carmen , Giménez Cecilio
Published: April 2006

The high‐affinity glycine transporter in neurons and glial cells is the primary means of inactivating synaptic glycine. Previous molecular cloning studies have indicated heterogeneity of glycine transporters in the CNS. Here the distribution of glycine transporter GLYT1 and GLYT2 transcripts and proteins in different regions and developmental stages of the rat brain were analysed by Northern, Western and in situ hybridization techniques. Sequence‐specific riboprobes and two specific antibodies raised against fusion proteins were used, containing either 76 or 193 amino acids of the C or N terminus of the GLTY1 and GLYT2 transporters respectively. High levels of GLYT1 transcripts were found in the spinal cord, brainstem and cerebellum, and moderate levels in forebrain regions such as the cortex or hippocampus. GLYT2 transcripts are restricted to the spinal cord, brainstem and cerebellum. The onset of both GLYT1 and GLYT2 expression in the brainstem occurred in late fetal life, and full expression of these proteins was observed before weaning. There was a stepwise increase in the levels of mRNA and protein for these two transporters, reaching a maximum by the second postnatal week, followed by a slight decrease until adult values were reached by the fourth postnatal week. These data reveal interesting parallelism between the distribution of different glycine transporters and glycine receptor subunits, and suggest discrete roles for distinct glycine transporters.
Connections of the Lateral Reticular Nucleus to the Lateral Vestibular Nucleus in the Rat. An Anterograde Tracing Study with Phaseolus vulgaris Leucoagglutinin
Authors: Ruigrok T. J. H. , Cella F. , Voogd J.
Published: April 2006

Efferent projections from the lateral reticular nucleus in the rat were investigated with anterograde transport of Phaseolus vulgaris leucoagglutinin. Besides the well known mossy fibre connections to the cerebellar cortex and collaterals to the cerebellar nuclei, a substantial bilateral projection to the lateral vestibular nucleus was found. Terminal arborizations found within this nucleus appeared to detach from the reticulocerebellar fibres in the cerebellar white matter and enter the lateral vestibular nucleus from dorsally. This projection may have functional relevance for the control, by ascending spinal pathways, of the descending lateral vestibulospinal tract.
Differences in the Temporal Properties of Human Longwave‐ and Middlewave‐sensitive Cones
Authors: Whitmore A. V. , Bowmaker J. K.
Published: April 2006

In recent years a number of electrophysiological and psychophysical observations have suggested that the temporal properties of the human longwave‐ and middlewave‐sensitive cones might be different. However, until now the issue has remained unresolved, despite its obvious importance. We have succeeded in probing, electrophysiologically, the temporal properties of the two classes, under a range of adapting conditions, in a normal human observer. Here we present evidence that the temporal properties of these cone types are indeed different and that this difference is constant irrespective of the state of light adaptation, suggesting that light adaptation has little effect on the kinetics of transduction in human cones.
NMDA‐Dependent GABAA‐Mediated Polysynaptic Potentials in the Neonatal Rat Hippocampal CA3 Region
Authors: McLean H. A. , Rovira C. , Ben‐Ari Y. , Gaiarsa J.‐L.
Published: April 2006

Evoked inhibitory postsynaptic potentials (IPSPs) were studied in CA3 hippocampal neurons from brain slice preparations of rats ranging from 5 to 18 days of age (P5–18) using intracellular recording techniques. With KMeSO4‐filled electrodes the evoked inhibitory response consisted of fast and slow IPSPs mediated by GABAA and GABAB receptors respectively. In recordings obtained with electrodes filled with 2‐(triethylamino)‐N‐(2,6‐dimethylphenyl) acetamide and KMeSO4, electrical stimulation evoked monophasic IPSPs in mature slices (P10–18) and biphasic IPSPs with an early and a late phase in neonatal slices (P4–7). In neonates both the early and late phases of the IPSP were mediated by GABAA receptors. Pharmacological investigation revealed that the early phase arose from both direct and feedforward activation of GABAergic interneurons involving non‐NMDA receptors, while the late phase resulted from polysynaptic activation of GABAergic interneurons mediated by NMDA receptors.
Involvement of Substance P in Ultraviolet Irradiation‐induced Inflammation in Rat Skin
Authors: Eschenfelder Christoph C. , Benrath Justus , Zimmermann Manfred , Gillardon Frank
Published: April 2006

The possible involvement of substance P released from primary afferents in rat skin was investigated in cutaneous inflammation following ultraviolet (UV) irradiation. Recordings from c‐fibres innervating the UV‐exposed hindpaw skin showed long‐lasting low‐frequency (0.8–1.25 Hz) spontaneous activity. Spontaneously active c‐fibres increased to constitute 35.3% of the total population 72 h after UV exposure. Immunohisto‐chemical analysis of substance P‐containing nerve fibres in hindpaw skin revealed a significant increase in substance P immunoreactivity 24 h after UV irradiation. Average length of substance P‐immunolabelled nerve fibres was about two times higher in UV‐exposed compared to control skin. UV‐induced oedema was investigated in rat ears using an ear‐swelling test. Intradermal injection of either peptide (Spantide) or non‐peptide (CP‐96,345) substance P antagonists and epicutaneous application of CP‐96,345 reduced UV‐induced oedema significantly in the late phase of sunburn (>12 h after UV exposure). The UV‐induced increase in skin blood flow was investigated in hindpaw skin up to 72 h by the laser Doppler technique. Epicutaneous application of CP‐96,345 reduced erythema significantly between 12 and 72 h after UV exposure. Thus, our findings suggest the involvement of neurogenic substance P as a proinflammatory mediator in the late phase of UV‐induced cutaneous inflammation in rats.
The Entorhinal Cortex Entrains Fast CA1 Hippocampal Oscillations in the Anaesthetized Guinea‐pig: Role of the Monosynaptic Component of the Perforant Path
Authors: Charpak S. , Paré D. , Llinás R.
Published: April 2006

Entorhinal inputs reach the hippocampal CA1 field through a trisynaptic circuit involving dentate granule cells and CA3 pyramidal neurons, as well as through a monosynaptic path ending on the distal apical dendrites of CA1 pyramidal cells. The influence of monosynaptic entorhinal inputs onto CA1 operations is poorly understood. In this study, we characterized the involvement of the monosynaptic pathway in the generation of the fast CA1 oscillation bursts (30–60 Hz) that occur in the dorsal hippocampus of anaesthetized guinea‐pigs after partial cortex removal. Using multiple‐site extracellular and intracellular recording, we found that in this particular preparation, devoid of theta rhythm, fast oscillations are temporally coherent over a large portion of the CA1 region along the hippocampal septotemporal axis. Current source density analysis revealed that fast CA1 oscillations involve two dipoles reflecting synchronous synaptic activities in the stratum lacunosum‐moleculare of the hippocampus proper and in the stratum moleculare of the dentate gyrus. These layers constitute the two major termination zones of entorhinal afferents, suggesting that the entorhinal cortex entrains fast CA1 oscillations. This hypothesis was corroborated by the concomitant occurrence of fast oscillation bursts in the entorhinal cortex and CA1 region. Furthermore, fast CA1 oscillations were abolished by lidocaine or tetrodotoxin injections in the entorhinal cortex. Finally, acute interruption of the hippocampal trisynaptic loop did not affect the stratum lacunosum‐moleculare dipole recorded extracellularly, but also intracellularly, as high‐frequency postsynaptic potentials in CA1 pyramidal cells. These results indicate that the monosynaptic pathway is involved in the genesis of fast CA1 oscillations.
Comparison of Frequency‐specific c‐Fos Expression and Fluoro‐2‐deoxyglucose Uptake in Auditory Cortex of Gerbils (Meriones unguiculatus)
Authors: Zuschratter Werner , Gass Peter , Herdegen Thomas , Scheich Henning
Published: April 2006

Induction of c‐Fos in the auditory cortex of gerbils was investigated immunocytochemically 1 h after single, triple or 1 h continuous stimulation with a series of narrow band frequency‐modulated tone bursts. With single stimulation c‐Fos immunoreactive neurons were chiefly found in the primary auditory field (AI), where they formed a narrow frequency‐specific column across layers II‐VI. Side‐band‐like patterns adjacent to this column appeared characteristically with triple stimulation. Immunoreactive cell density in the anterior auditory field and the caudal fields was sparse and location not frequency specific with single or triple stimulation. Spatial comparisons of c‐Fos immunoreactive neuron density with 2‐deoxy‐2‐fluoro‐D‐glucose (FDG) autoradiography in the same animals after 1 h of stimulation revealed spreading of c‐Fos expression in neurons across the tonotopic maps of the Al and in the rostral and caudal fields of the auditory cortex. The pattern of the highest density of c‐Fos labelled cells in the Al still matched the peak labelling of FDG autoradiographs. The results show that the postsynaptic marker c‐Fos reflects the frequency representation in the Al with single or triple stimulation yet with a higher spatial resolution than the deoxyglucose technique. Longer stimulation causes non‐tonotopic intracortical spreading of the c‐Fos‐inducing message, a phenomenon potentially reflecting the effects of cooperativity in the maps.
Simultaneous Expression of Long‐term Depression of NMDA and Long‐term Potentiation of AMPA Receptor‐mediated Synaptic Responses in the CA1 Area of the Kainic Acid‐lesioned Hippocampus
Authors: Bernard Christophe L. , Wheal Howard V.
Published: April 2006

This study investigates the plasticity of the excitatory synapses in an experimental model of epilepsy, the kainic acid‐lesioned rat hippocampus. Stimulation of afferents in the CA1 area of lesioned hippocampi produced an epileptiform burst of action potentials, with an underlying synaptic potential composed of mixed α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionate (AMPA; 80%) and N‐methyl‐D‐aspartate (NMDA; 20%) receptor‐mediated components. Tetanic stimulation yielded a long‐term potentiation (LTP) of the mixed AMPA/NMDA receptor‐mediated population excitatory postsynaptic potentials. However, the same type of tetanus resulted in a long‐term depression (LTD) of pharmacologically isolated NMDA receptor‐mediated responses. This LTD occurred independently of the antagonism of AMPA receptors. This suggests that tetanic stimulation produced LTP of AMPA and LTD of NMDA receptor‐mediated responses simultaneously. Finally, both LTP and LTD were shown to be NMDA dependent. This property has profound functional implications for the control of excitatory networks in temporal lobe epilepsy. This work was supported by the Wellcome Trust and the Fondation Simone et Cino Del Duca.
β‐Adrenergic Receptor Activation Promotes Process Outgrowth in an Embryonic Rat Basal Forebrain Cell Line and in Primary Neurons
Authors: Kwon John H. , Eves Eva M. , Farrell Stephen , Segovia Jose , Tobin Allan J. , Wainer Bruce H. , Downen Martha
Published: April 2006

A clonal cell line, AS583‐8.E4.22, from the embryonic day 15 rat basal forebrain was established using retrovirus‐mediated transduction of a temperature‐sensitive mutant of the simian virus 40 (SV40) large tumour antigen. The cell line expresses cytoskeletal and neurotransmitter features indicative of neuronal commitment. In response to agents that increase intracellular CAMP, including forskolin and catecholamines, the cell line exhibits rapid process outgrowth and growth cone formation that does not require new gene expression or protein synthesis. The neurite outgrowth induced by catecholamines is mediated by β2‐adrenergic receptors and is characterized by a rapid, reversible redistribution of filamentous actin. Neurons from primary cultures of embryonic day 15 basal forebrain were also found to respond to β‐adrenergic receptor agonists by enhancing growth cone formation. These results suggest that catecholamines provide cues that induce cytoskeletal rearrangements leading to neuronal process outgrowth and growth cone formation in the developing basal forebrain and possibly other neuronal progenitor cell populations. The neuronal basal forebrain cell line provides an ideal model to study the signalling mechanisms underlying the catecholamine‐induced process outgrowth.
Pain Perception under Chronic High‐altitude Hypoxia
Authors: Noël‐Jorand M. C. , Bragard D. , Plaghki L.
Published: April 2006

Following studies of respiratory sensory functions during high‐altitude adaptation, pain perception investigations were carried out on European lowlanders during an expedition on the Bhrikuti peak, Himalaya (first ascent). Perception thresholds and discrimination performances of electrical stimuli applied to the skin were determined with a constant stimulus method. Additionally, Clark's Situational Pain Questionnaire was used to measure discriminability and response bias of the subjects' reports of pain. The tests were performed in the field under normoxic conditions, before and after ascent, and under hypoxic conditions at altitudes of 3500 and 5600 m. The tests were also performed in a control group under normoxic conditions and similar ambient temperatures. Under normoxic conditions, the expedition group differed from the control group and demonstrated a more stoic attitude and a lower pain threshold. At high altitudes, pain thresholds decreased through improved sensory discrimination performances. Hypoxia is supposed to be the main cause of this sensory adaptive reaction to altitude as psychological attitude remained unchanged and a decrease in ambient temperature was without effect on pain perception in the control group. Increased discrimination in pain perception may be a component of a general improvement in sensory processing during the early stages of altitude acclimatization.
The Projections of the Lateral Reticular Nucleus to the Deep Cerebellar Nuclei. An Experimental Analysis in the Rat
Authors: Parenti Rosalba , Cicirata Federico , Pantò Maria Rosita , Serapide Maria Francesca
Published: April 2006

The projections of the lateral reticular nucleus (LRN) to the cerebellar nuclei were studied using the retrograde axonal transport of tetramethyl rhodamine dextran amine (10% solution in 0.01 M neutral phosphate buffer) in 19 adult Wistar strain rats. The cerebellar nuclei receive topographically organized projections from the LRN. The projections are bilateral with an ipsilateral predominance and they are symmetrical. The contralateral component is progressively larger for projections to the nuclei interpositalis, to the nucleus lateralis and to the nucleus medialis. The projections to the various cerebellar nuclei arise from rostrocaudally oriented columns of neurons located in different (partly overlapping) areas of the magnocellular division of the LRN. The nucleus lateralis receives terminals from the dorsomedial area (mainly from the rostral level of the LRN), the nuclei interpositalis from the dorsolateral area (mainly from the central level) and the nucleus medialis from the intermedioventral area (mainly from the caudal level). Afferent fibres from the small subtrigeminal division were traced to the three cerebellar nuclei and from the parvocellular division to the nuclei interpositalis and medialis. The density of the projections from the LRN to the nuclei interpositalis increases progressively with the shift of the terminal field from the rostrolateral to the caudomedial part of the nucleus. The projections to the nucleus lateralis reach principally the dorsolateral hump, whereas only a few neurons project to the other divisions (parvo‐ and magnocellular). The projections to the various regions of the nucleus medialis show different densities. The highest density was found for projections to the caudal part, in particular to the dorsolateral protuberance and to the ventrolateral area of the middle division. Conversely, a low density of projections was found for the other areas of the middle division. The regions of the magnocellular division of the LRN which project to the nuclei lateralis (and are thus related to the cerebral cortex), interpositalis (related to the red nucleus) and medialis (related to the spinal cord) also receive afferent terminals from the cerebral cortex, the red nucleus and the spinal cord respectively, in addition to various afferent inputs. Thus, each of these areas is apparently concerned with integrating some spinal and supraspinal information in reverberating circuits.
Pre‐ and Post‐synaptic Actions of 5‐Hydroxytryptamine in the Rat Lumbar Dorsal Horn In Vitro: Implications for Somatosensory Transmission
Authors: Lopez‐Garcia J. A. , King A. E.
Published: April 2006

Since the relative contribution of pre‐ versus post‐synaptic actions of 5‐hydroxytryptamine (5‐HT) to modulation of somatosensory processing in the dorsal horn is not known, recordings fro m primary afferents and dorsal horn neurons from in vitro rat spinal cord were used to address this issue. 5‐HT produced a depression of spontaneous dorsal root potentials and a slow primary afferent depolarization (PAD): the PAD versus 5‐HT concentration‐response curve was bell shaped (maximum at 5 μM; 250±C 41.5 μV). In 28/40 dorsal horn neurons, 5‐HT elicited a slow depolarization not clearly associated with a specific input resistance change. Excitatory synaptic transmission from primary afferents to dorsal horn neurons was depressed by 5‐HT in 40/45 neurons. 5‐HT ≥ 5 μM significantly (P≤ 0.05) decreased the amplitude, shortened the total duration and half‐decay time of the excitatory post‐synaptic potential (EPSP). A dominant effect of 5‐HT on longer latency EPSP components was evident. There was no direct relationship between the magnitude of PAD and the reduction of the EPSP by 5‐HT. 5‐Carboxamidotryptamine, an agonist for 5‐HT1 receptors, mimicked the depression of neurotransmission in the dorsal horn without producing PAD. A sample of dorsal horn neurons (n= 8) was injected with biocytin and their morphology described. All had somata within laminae III‐VI. In five of these neurons 5‐HT depressed the EPSP but in one interneuron‐like and one unclassed neuron the EPSP was potentiated. These data suggest that whilst depression of synaptic transmission is the predominant effect of 5‐HT in the deep dorsal horn, this is not easily related to PAD or cellular actions of 5‐HT on dorsal horn neurons.