bluuebunny/crossref_metadata_2025 huggingface dataset:
Mossy Cells of the Rat Dentate Gyrus are lmmunoreactive for Calcitonin Gene‐related Peptide (CGRP)
Authors: Freund Tamás F. , Hájos Norbert , Acsády László , Górcs Tamás J. , Katona István
Published: April 2006

The neuropeptide calcitonin gene‐related peptide (CGRP) was localized in the hippocampus and dentate gyrus of the rat by immunocytochemistry at the light and electron microscopic levels. Without colchicine treatment only faint neuropil labelling was found in the inner molecular layer of the dentate gyrus. Following colchicine treatment, a large number of neurons with numerous complex spines along the proximal dendrites were visualized in the hilus of the dentate gyrus, particularly in the ventral areas, and, in addition, staining of the inner molecular layer became stronger. Several CA3c pyramidal cells located adjacent to the hilar region in the ventral hippocampus also appeared to be faintly positive, although in most cases only their axon initial segments were labelled. Outside this region, the subicular end of the CA1 subfield contained occasional CGRP‐positive non‐pyramidal cells. The hilar CGRP‐positive neurons were negative for parvalbumin, calretinin, cholecystokinin and somatostatin, whereas most of them were immunoreactive for GluR2/3 (the AMPA‐type glutamate receptor known to be expressed largely by principal cells). Correlated electron microscopy showed that the spines along the proximal dendritic shafts indeed correspond to thorny excrescences engulfed by large complex mossy terminals forming asymmetrical synapses. Pre‐embedding immunogold staining demonstrated that CGRP immunoreactivity in the inner molecular layer was confined to axon terminals that form asymmetrical synapses, and the labelling was associated with large dense‐core vesicles. The present data provide direct evidence that CGRP is present in mossy cells of the dentate gyrus and to a lesser degree in CA3c pyramidal cells of the ventral hippocampus. These CGRP‐containing principal cells terminate largely in the inner molecular layer of the dentate gyrus, and may release the neuropeptide in conjunction with their ‘classical’ neurotransmitter, glutamate.
Differential Effects of lntrastriatal Neurotensin(1–13) and Neurotensin(8–13) on Striatal Dopamine and Pallidal GABA Release. A Dual‐probe Microdialysis Study in the Awake Rat
Authors: Ferraro Luca , O'Connor William Thomas , Antonelli Tiziana , Fuxe Kjell , Tanganelli Sergio
Published: April 2006

In the present dual‐probe microdialysis study the effects of intrastriatal perfusion with the tridecapeptide neurotensin(1–13) [NT(1–13)] and its active fragment NT(8–13) on striatopallidal GABA and striatal dopamine release were investigated. The modulatory action of NT(1–13) on D2 receptor‐mediated inhibition of striatal and pallidal GABA release was also studied. Both intrastriatal NT(1–13) (100 nM) and NT(8–13) (100 nM) increased striatal (139 and 149% respectively) and pallidal (130 and 164%) GABA release, and this effect was antagonized by intrastriatal perfusion with the neurotensin receptor antagonist SR48692 (100 nM). A similar increase (155%) in striatal dopamine release was observed following intrastriatal NT(1–13) (100 nM), but not NT(8–13) (100 and 500 nM). However, at the highest concentration studied (1 μM) NT(8–13) was associated with a rapid increase (130%) in striatal dopamine release. In a second study intrastriatal NT(1–13) (10 nM) counteracted the inhibition of striatal and pallidal GABA release induced by pergolide (500 and 1500 nM). The inhibitory action of the D2 agonist was restored when SR48692 (100 nM) was added to the perfusion medium. These results suggest that in the neostriatum the neurotensin receptor located postsynaptically on the striatopallidal GABA neurons seems to differ from the neurotensin receptor located on dopaminergic terminals, as indicated by the relative lack of effect of NT(8–13) on striatal dopamine release. Furthermore, the ability of NT(1–13) to counteract the pergolide‐induced inhibition of both striatal and pallidal GABA release strengthens the evidence for antagonistic receptor‐receptor interaction between postsynaptic striatal neurotensin and D2 receptors located on striatopallidal GABA neurons.
Non‐synaptic Localization of the Glutamate Transporter EAACI in Cultured Hippocampal Neurons
Authors: Coco Silvia , Verderio Claudia , Trotti Davide , Rothstein Jeffrey D. , Volterra Andrea , Matteoli Michela
Published: April 2006

It has been postulated for several years that the high affinity neuronal glutamate uptake system plays a role in clearing glutamate from the synaptic cleft. Four different glutamate transporter subtypes are now identified, the major neuronal one being EAAC1. To be a good candidate for the reuptake of glutamate at the synaptic cleft, EAAC1 should be properly located at synapses, either at pre‐ or postsynaptic sites. We have investigated the distribution of EAAC1 in primary cultures of hippocampal neurons, which represent an advantageous model for the study of synaptogenesis and synaptic specializations. We have demonstrated that EAAC1 immunoreactivity is segregated in the somatodendritic compartment of fully differentiated hippocampal neurons, where it is localized in the dendritic shaft and in the spine neck, outside the area facing the active zone. No co‐localization of EAAC1 immunoreactivity with the stainings produced by typical presynaptic and postsynaptic markers was ever observed, indicating that EAAC1 is not to be considered a synaptic protein. Accordingly, the developmental pattern of expression of EAAC1 was found to be different from that of typical synaptic markers. Moreover, EAAC1 was expressed in the somatodendritic compartment of hippocampal neurons already at stages preceding the formation of synaptic contacts, and was also expressed in GABAergic interneurons with identical subcellular distribution. Taken together, these data rule against a possible role for EAAC1 in the clearance of glutamate from within the cleft and in the regulation of its time in the synapse. They suggest an unconventional non‐synaptic function of this high‐affinity glutamate carrier, not restricted to glutamatergic fibres.
Light‐induced c‐Fos Expression in the Mouse Suprachiasmatic Nucleus: Immunoelectron Microscopy Reveals Co‐localization in Multiple Cell Types
Authors: Castel Mona , Belenky Michael , Cohen Shulamith , Wagne Shlomo , Schwartz William J.
Published: April 2006

Although light is known to regulate the level of c‐fos gene expression in the suprachiasmatic nucleus (SCN), the site of an endogenous circadian clock, little is known about the identities of the photically activated cells. We used light‐microscopic immunocytochemistry and immunoelectron microscopy to detect c‐Fos protein in the SCN of Sabra mice exposed to brief nocturnal tight pulses at zeitgeber time 15–16. Stimulation with light pulses that saturated the phase‐shifting response of the circadian locomotor rhythm revealed an upper limit to the number of photo‐inducible c‐Fos cells at about one‐fifth of the estimated total SCN cell population. This functionally defined set was morphologically and phenotypically heterogeneous. About 24% could be labelled for vasoactive intestinal polypeptide, 13% for vasopressin‐neurophysin, and 7% for glial fibrillary acidic protein. The remaining 56% of c‐Fos‐positive cells were largely of unknown phenotype, although many were presumptive interneurons, some of which were immunoreactive for nitric oxide synthase.
Effect of Body Orientation with Respect to Gravity on Directional Accuracy of Human Pointing Movements
Authors: Smetanin B. N. , Popov K. E.
Published: April 2006

Errors in pointing to remembered target locations were measured in normal subjects in the upright posture and in a supine or prone lying position, three conditions that differed in the orientation of the moving arm with respect to gravity. Vertical errors, or, more strictly, errors along the body axis, were significantly larger in both supine and prone lying positions as compared with the vertical posture. Subjects’ orientation with respect to gravity produced a consistent error pattern, i.e. subjects pointed below the remembered target locations in the vertical posture and above them under the two lying conditions, in the body‐related co‐ordinates. On the contrary, variable error (the confidence ellipse) was differentially affected by the orientation of the movement trajectory with respect to gravity. In the supine body position the variable error was larger, and in the prone position it was smaller than in the upright posture. The finding of gravity‐related bias in pointing errors suggests that the motor programme generated in the lying position is not modified to adapt to an altered orientation with respect to gravity.
The Concerted Activity in Parallel Proprioceptive Pathways Controls the Initiation of Co‐activation in the Locust Kick Motor Programme
Authors: Jellema T. , Tait D. S. , Heitler W. J.
Published: April 2006

To jump and kick the locust uses a catapult mechanism implemented by a three‐stage motor programme: initial flexion of the hind tibiae, co‐activation of the antagonist flexor and extensor tibiae motor neurons and trigger inhibition of the flexor motorneurons. The transition from stage 1 to stage 2 thus involves a switch from the normal alternate activation to co‐activation of the antagonist tibiae motorneurons. However, co‐activation has never been observed when the central nervous system has been isolated from the leg. This led us to investigate the possibility that the transition from stage 1 to stage 2 is controlled by a proprioceptive signal. In the first set of experiments intracellular recordings were made in the flexor and extensor motorneurons while the position of the tendon of the femoral chordotonal organ (FCO), which signals tibial position and movement, was experimentally controlled. In these heavily dissected preparations, stretch of the FCO tendon (signalling tibial flexion) was a necessary condition for co‐activation. However, in minimally dissected preparations (in which merely EMG recordings were made), we found that co‐activation occurred even when the FCO was signalling tibial extension, suggesting the involvement of other proprioceptors. A series of experiments were then conducted on minimally dissected preparations to determine the relative contributions of each of the three main hind leg proprioceptors which might signal tibial flexion: the FCO, the lump receptor and Brünners organ. When all three proprioceptors were intact the chance of evoking co‐activation was largest, when all three were eliminated co‐activation could no longer be evoked, irrespective of the level of arousal. Various combinations of partial de‐afferentation showed that the FCO plays the major role, with the lump receptor and Brünners organ playing significant, but progressively less important, roles. We conclude that the three receptors act together as a permissive proprioceptive gate for the kick and jump motor programme, but with a hierarchy of the strengths of their effectiveness.
Adult Nestin‐expressing Subependymal Cells Differentiate to Astrocytes in Response to Brain Injury
Authors: Holmin Staffan , Almqvist Per , Lendahl Urban , Mathiesen Tiit
Published: April 2006

The adult brain contains a small population of central nervous system (CNS) cells in the subependyma which, like embryonic CNS progenitor cells, express the intermediate filament nestin. In this report, the differentiation capacity in vivo of these cells was analysed following a standardized trauma. Before the trauma, the subependymal cells expressed nestin but not the astrocytic and neuronal differentiation markers glial fibrillary acidic protein (GFAP) and neurofilament respectively. In response to injury, the majority of the subependymal cells coexpressed nestin and GFAP, but never nestin and neurofilament. Furthermore, cells coexpressing nestin and GFAP were found progressively further away from the subependyma and closer to the lesion at later time points after the injury, indicating that these cells migrate towards the lesion. Nestin was in addition re‐expressed in reactive astrocytes near the lesion and in non‐reactive astrocytes very far from the lesion throughout the ipsilateral cortex. In conclusion, our data indicate that the nestin‐positive subependymal cells are an in vivo source for the generation of new astrocytes but not neurons after injury, and that nestin re‐expression in astrocytes following traumatic stimuli can be used as a sensitive marker for astroglial activation.
Basolateral Amygdala Lesions Block the Memory‐enhancing Effect of Glucocorticoid Administration in the Dorsal Hippocampus of Rats
Authors: Roozendaal Benno , McGaugh James L.
Published: April 2006

These experiments examined the effects of bilateral amygdala nuclei lesions on modulation of memory storage induced by bilateral intrahippocampal microinfusions of glucocorticoids in male Sprague‐Dawley rats. Post‐training infusions of the glucocorticoid receptor (type II) agonist RU 28362 (3.0 or 10.0 ng) enhanced inhibitory avoidance retention, and infusions of the glucocorticoid receptor antagonist RU 38486 (3.0 or 10.0 ng) administered shortly before training in a water maze spatial task did not affect acquisition, but impaired retention. In both tasks, neurochemically induced lesions of the basolateral but not of the central amygdala blocked the memory‐modulatory effects of the intrahippocampal infusions of the drugs affecting glucocorticoid receptors. Lesions of the central amygdala alone impaired inhibitory avoidance retention, but basolateral amygdala lesions alone did not affect acquisition or retention in either task. These findings are consistent with previous evidence indicating that lesions of the basolateral amygdala block the memory‐modulatory effects of systemically administered glucocorticoids, and provide further evidence that the basolateral amygdala is a critical area involved in regulating glucocorticoid effects in other brain regions involved in memory storage.
5‐Hydroxytryptamine Induces TIS8/egr‐1 and c‐fos Expression in PC12 Cells. Involvement of Tyrosine Protein Phosphorylation
Authors: Humblot Nathalie , Esteve Laurent , Burgun Claude , Aunis Dominique , Zwiller Jean
Published: April 2006

The TIS8/egr‐1 gene is a member of the class of immediate early genes. Originally discovered as a mitogen induced gene, it can also be induced by synaptic activity. We report here the induction of the TIS8/egr‐1 gene by the neurotransmitter 5‐hydroxytryptamine (5‐HT) in cultured rat phaeochromocytoma PC12 cells. Induction was maximal 40 min after addition of 5‐HT to the cells, and declined very rapidly to reach the basal level after 90 min. The electrophoretic mobility‐shift assay showed that induction of the TIS8/egr‐1 gene by 5‐HT was accompanied by increased Egr‐1 protein binding to its DNA consensus sequence. We found an overall correlation of 5‐HT‐induced egr‐1 expression with that of c‐fos expression. The kinetics of the ability of both gene products to bind to their respective DNA consensus sequence was also similar. The 5‐HT‐induced activation in Egr‐1 binding was inhibited by ketanserin and mesulergine, indicating that 5‐HT exerted its action via a 5‐HT2 receptor subtype. The tyrosine protein kinase inhibitor genistein abolished induction of the TIS8/egr‐1 gene, suggesting that tyrosine kinase activity is required for the induction of early genes by 5‐HT. Genistein also inhibited 5‐HT‐induced Egr‐1 binding activity. The increase in phosphotyrosine content of focal adhesion kinase we noticed upon addition of 5‐HT to cells suggests that this cytoplasmic tyrosine protein kinase mediates the effect of 5‐HT in eliciting early gene induction.
Optical Imaging of Cat Auditory Cortex Cochleotopic Selectivity Evoked by Acute Electrical Stimulation of a Multi‐channel Cochlear Implant
Authors: Dinse Hubert R. , Godde Ben , Hilger Thomas , Reuter Gunter , Cords Sven M. , Lenarzl Thomas , von Seelen Werner
Published: April 2006

We measured reflectance changes by means of optical imaging of intrinsic signals to study the effects of acute electrical cochlear stimulation on the topography of the cat auditory cortex. After single‐pulse electrical stimulation at selected sites of a multichannel implant device, we found topographically restricted response areas representing mainly the high‐frequency range in Al. Systematic variation of the stimulation pairs and thus of the cochlear frequency sites revealed a systematic and corresponding shift of the response areas that matched the underlying frequency organization. Intensity functions were usually very steep. Increasingly higher stimulation currents evoked increasingly larger response areas, resulting in decreasing spatial, i.e. cochleotopic, selectivity; however, we observed only slight positional shifts of the focal zones of activity. Electrophysiological recordings of local field potential maps in the same individual animals revealed close correspondence of the locations of the cortical response areas. The results suggest that the method of optical imaging can be used to map response areas evoked by electrical cochlear stimulation, thereby maintaining a profound cochleotopic selectivity. Further experiments in chronically stimulated animals will shed more light on the degree of functional and reorganizational capacities of the primary auditory cortex and could be beneficial for our understanding of the treatment of profound deafness.
Loss of Nerve Endings in the Spinal Dorsal Horn After a Peripheral Nerve Injury. An Anatomical Study in Macaca fascicularis Monkeys
Authors: Liss Anders G. , Wiberg Mikael
Published: April 2006

In patients, the long‐term outcome of injuries to sensory nerves is poor. This is only partly due to mismatching of regenerating axons at the transection site. We found in the macaque monkey that 70% of the transganglionic labelling in the spinal dorsal horn was still significantly reduced 21 months after transection and suturing of the sensory radial nerve. The reduction was evenly distributed throughout the terminal field of nerve endings, which were labelled with a mixture of the intra‐axonal nerve tracer wheat germ agglutinin‐horseradish peroxidase conjugate and pure horseradish peroxidase.
Nitric Oxide Signalling is Required for the Generation of Anoxia‐induced Long‐term Potentiation in the Hippocampus
Authors: Huang Chiung‐Chun , Hsu Kuei‐Sen
Published: April 2006

The involvement of nitric oxide in anoxia‐induced long‐term potentiation (anoxic LTP) of synaptic transmission was investigated in CA1 neurons of rat hippocampal slices using intracellular recording techniques in vitro. In response to superfusion of an anoxic artificial cerebral spinal fluid saturated with 95% N2‐‐5% CO2, the excitatory postsynaptic potential (EPSP) generated in hippocampal CA1 neurons by stimulation of the Schaffer collateral/commissural afferent pathway was completely abolished within 10 min of anoxia. On return to reoxygenated medium, the EPSP returned to the control value within 10 min and was subsequently and progressively potentiated to reach a plateau 15–20 min after return to oxygen. This anoxia‐induced persistent increase in synaptic transmission lasted for more than 1 h. Application of the nitric oxide synthase inhibitors 7‐nitroindazole (7‐NI) or l‐NG‐nitroarginine (NOARG) produced no effects on the baseline EPSP amplitude, but effectively attenuated the anoxic LTP. The inhibitory effects of both 7‐NI and NOARG on the anoxic LTP were blocked by l‐arginine, a substrate for nitric oxide synthase. These results suggest that nitric oxide is required for the generation of anoxia‐induced LTP of glutamatergic synaptic transmission in the CA1 region of the rat hippocampus.
Characterization of a Putative Novel Type of Oligodendrocyte in Cultures from Rat Spinal Cord
Authors: Fanarraga M. L. , Milward E. A.
Published: April 2006

Oligodendrocytes originate in different neural tube domains, within boundaries of expression of a series of patterning genes which condition the diverse morphogenetic programme of each area. Although neuronal and astrocyte heterogeneity are widely accepted, and despite accumulating evidence for oligodendrocyte heterogeneity in vivo, oligodendrocytes in vitro are currently considered as a homogeneous cell population. The present investigation demonstrates that oligodendrocyte diversity can be detected in vitro and characterizes a novel morphological class of O4‐positive oligodendrocyte which is consistently identifiable in rat central nervous system cultures. These cells have a very characteristic epithelioid, unbranched and often lobulated morphology which enables their identification within 2 h of plating. lmmunostaining shows that this morphological type is sometimes positive for GD3, A2B5 and vimentin, and most of the time positive for Ranscht antibody, O1 and Rip but negative for glial fibrillary acidic protein, OX‐42, neuron‐specific enolase, nestin and erbB2. The apparent levels and/or distributions of (i) microtubules, (ii) surface glycolipids recognized by O4, O1 and Ranscht antibody, and (iii) the less specific marker carbonic anhydrase II, typically differ from those of nearby classical, branched oligodendrocytes. Cells with this epithelioid morphology also express myelin basic protein and O10 (a proteolipid protein epitope), both of which are markers for mature oligodendrocytes. Conversely, O4+/O1‐ cells with this membranous appearance were also seen. Although these atypical oligodendrocytes were most abundant in spinal cord cultures (representing >10% of the O4+ population), they were not exclusive to this region and occurred at a low frequency in neonatal optic nerve cultures.
Schwann Cells Modify Expression of Acetylcholinesterase and Butyrylcholinesterase at Rat Neuromuscular Junctions
Authors: Chapron J. , De La Porte S. , Delepine L. , Koenig J.
Published: April 2006

Using a monoclonal antibody (6.17) directed against a Schwann antigen, we have shown that Schwann cells synthesize a molecule implicated in a change of expression of synaptic cholinesterases, AChE and BChE, during muscle differentiation. In vitro, during synaptogenesis, the two enzymes are first present at developing synapses, and addition of Schwann cells to muscle‐neuron co‐cultures induces a disappearance of BChE, leaving only AChE activity as in the adult neuromuscular junction. This effect is inhibited by the 6.17 antibody. Thus, a molecule produced by Schwann cells is involved in the maturation of the neuromuscular synapse, in addition to the neuronal factors (CGRP, ARIA/heregulin, agrin), which are known to control the synthesis, maturation and accumulation of acetylcholine receptors and other synaptic components. In addition, in vivo, in the newborn rat, butyrylcholinesterase and acetylcholinesterase activities are initially present in equal amounts in the neural zone, but butyrylcholinesterase levels diminish sharply between 7 and 15 days after birth, the stage at which the synaptic Schwann cell membrane becomes juxtaposed with the muscle membrane.
Chondroitin/Dermatan Sulphate Promotes the Survival of Neurons from Rat Embryonic Neocortex
Authors: Kappler Joachim , Junghans Ulrich , Koops Antje , Stichel Christine C. , Hausser Heinz‐J. , Kresse Hans , Müller Hans Werner
Published: April 2006

Recently we have shown that biglycan, a small chondroitin sulphate proteoglycan of the extracellular matrix, supports the survival of cultured neurons from the developing neocortex of embryonic day 15 rats. Here we investigate the structure‐function relationship of this neurotrophic proteoglycan and show that chondroitin/dermatan sulphate chains are the active moieties supporting survival. Heparin, a highly sulphated glucosaminoglycan, is less active than the galactosaminoglycans (chondroitin‐4‐sulphate, chondroitin‐6‐sulphate and dermatan sulphate), whereas hyaluronic acid, an unsulphated glucosaminoglycan, does not support neuron survival. Galactosaminoglycans must be in direct contact with neurons to cause survival. Experiments with elevated potassium concentrations and antagonists of voltage‐gated calcium channels exclude the involvement of membrane depolarization. However, genistein and an erbstatin analogue, which are inhibitors of tyrosine kinases with low specificity, abolished neuron survival in the presence of chondroitin/dermatan sulphate, whereas a selective inhibitor of neurotrophin receptor kinases (K252a) had no suppressive effect. Thus, yet unidentified tyrosine kinases are involved in the chondroitin/dermatan sulphate‐dependent survival of neocortical neurons. In the embryonic stages of rat neocortical development chondroitin sulphate is mainly located in layers I, V and VI and the subplate. Chondroitin sulphate expression is maintained after birth, extends up to cortical layer IV on postnatal day 7, and is down‐regulated until postnatal day 21 concomitant with the period of naturally occurring cell death. The latter observation is consistent with a putative role of chondroitin sulphate in the control of neuron survival during cortical histogenesis.
Choline Acetyltransferase, Glutamate Decarboxylase, Tyrosine Hydroxylase, Calcitonin Gene‐related Peptide and Opioid Peptides Coexist in Lateral Efferent Neurons of Rat and Guinea‐pig
Authors: Safieddine Saaid , Prior Ana Maria Soto , Eybalin Michel
Published: April 2006

The lateral efferent (olivocochlear) innervation of the cochlea originates in the brainstem lateral superior olive. It is likely to use acetylcholine, γ‐aminobutyric acid, dopamine and various neuropeptides as neurotransmitters and/or neuromodulators. In order to determine the different coexistence patterns of these molecules in lateral efferent perikarya, we have used double and triple immunofluorescence co‐localization techniques to colocalize choline acetyltransferase, glutamate decarboxylase, tyrosine hydroxylase, calcitonin gene‐related peptide and enkephalins in single sections of the lateral superior olive. We also used a non‐radoactive in situ hybridization technique onto serial sections of this nucleus to confirm the immunofluorescence co‐localization data at the mRNA level. Whatever the pair or triplet of primary antibodies tested was, a high ratio of coexistence was observed in the immunofluorescence experiments. In triple co‐localization experiments, 90–93% of the choline acetyltransferase‐like immunoreactive neurons were also immunoreactive to the two other antigens investigated. The in situ hybridization co‐localization data, based on the use of biotin‐labelled oligoprobes, qualitatively confirmed these immunofluorescence data. In conclusion, it can be postulated that acetylcholine, γ‐aminobutyric acid, dopamine, calcitonin gene‐related peptide, enkephalins and dynorphins (whose coexistence with choline acetyltransferase and enkephalins has been previously described immunocytochemically) coexist in lateral efferent neurons. Based on these results, it is tempting to propose the lateral efferent innervation as a useful model with which the functional implications of the coexistence of neurotransmitters/neuromodulators can be investigated in vivo.
Photoreceptor Cells of the Pike Pineal Organ as Cellular Circadian Oscillators
Authors: Bolliet Valérie , Bégay Valérie , Taragnat Catherine , Ravault Jean Paul , Collin Jean Pierre , Falcón Jack
Published: April 2006

In the pike pineal, the rhythm of melatonin (MEL) secretion is driven by a population of cellular circadian oscillators, synchronized by the 24 h light/dark (LD) cycle. Because the pineal photoreceptor contains both the input and output pathways of the clock, this cell is likely to be a cellular circadian system by itself. To support this idea, we have dissociated and cultured pike pineal cells as well as purified photoreceptors. In culture, the pineal cells reassociated in follicles, surrounded by collagen fibres. At the electron microscopic level, they appeared well preserved. Total cells consisted mainly of photoreceptors and glia. Purified cells corresponded exclusively to photoreceptors. Under LD, MEL production was rhythmic. Under constant darkness (DD), the rhythm was well sustained for at least six 24 h cycles (τ= 24/27 h) with 1 × 106 total cells/well or below; with 2 × 106 total cells/well, a strong damping occurred towards high levels as soon as after the second cycle. At the density of 0.5 × 106 cells/well, purified photoreceptors produced less MEL than an equivalent amount of total cells. However, the pattern of the oscillations was similar to that observed with 2 × 106 total cells, i.e. a damping occurred rapidly. Decreasing the density to 0.125 × 106 photoreceptors/well resulted in a loss of homogeneity among replicates. The production of melatonin by single photoreceptors was monitored by means of the reverse haemolytic plaque assay. Both under LD and under DD, the number of photoreceptors releasing melatonin was higher during the (subjective) dark than during the (subjective) light. The results provide strong support to the idea that the pike pineal photoreceptor is a cellular circadian system. Expression of the oscillations seemed to depend on several factors, including cell to cell contacts between photoreceptors. There is indication that also MEL and glia might be involved.
Localization of CAM II Kinase‐α, GAD, GluR2 and GABAA Receptor Subunit mRNAs in the Human Entorhinal Cortex
Authors: Longson Damien , Longson Carole M. , Jones Edward G.
Published: April 2006

The human entorhinal cortex (ERC) is an important relay between neocortical association areas and the hippocampus. Pathology in this area, including disturbances in its unique cytoarchitecture and alterations in neurotransmitter receptor binding, has been implicated in several neuropsychiatric disorders but details of the patterns of gene expression for molecules involved in the major neurotransmitter systems in this cortex have been lacking. We used in situ hybridization histochemistry to localize the mRNAs for several proteins which are involved in excitatory and inhibitory neurotransmission in the human ERC. Labelling of mRNA for a glutamate receptor subunit (GluR2) and for a marker of glutamatergic cortical neurons (alpha type II calcium/calmodulin‐dependent protein kinase) were distributed in a laminar manner which matched the cellular packing seen on the Nissl sections, with particularly high levels of labelling in the layer II (pre‐á) cell clusters characteristic of this cortex. Cells labelled for the mRNA of 67 kDa glutamic acid decarboxylase, the synthesizing enzyme of GABA, were distributed diffusely throughout all layers, not concentrated in the cell clusters, and were present in higher numbers in layer Ill. The labelling of mRNAs for the α1, β2 and γ2 subunits of the GABAA receptor, however, was distributed in a laminar pattern similar to that for GluR2 and CAM II kinase mRNAs, implying a high concentration of inhibitory synapses on the excitatory cells which express these mRNAs.
Properties of Cloned Rat α1A Calcium Channels Transiently Expressed in the COS‐7 Cell Line
Authors: Berrow N. S. , Brice N. L. , Tedder I. , Page K. M. , Dolphin A. C.
Published: April 2006

The rat brain α1A calcium channel clone has been expressed in COS‐7 cells together with the neuronal accessory subunits p1b and α2‐δ. From reverse transcriptase polymerase chain reaction (RT‐PCR), immunocytochemistry and electrophysiology experiments, we have obtained no evidence that these cells contain any endogenous calcium channels. Transfected cells were identified by co‐expression of a cDNA for the reporter Green Fluorescent Protein. From immunocytochemical evidence, a high degree of co‐expression was obtained between Green Fluorescent Protein and individual calcium channel subunits. When all three calcium channel subunits (α1, α2‐δ and β1b) were co‐expressed, evidence was obtained that all subunits were present at the cell membrane. Voltage‐dependent calcium currents were observed between 24 and 72 h after transfection with the three calcium channel subunits. The current density for the combination α1A/α/β1ba24IPlb was 4.19 ± 0.69 pA.pF‐1 and the current produced was slowly inactivating. The time constant of inactivation of the maximum IBa was 332 ± 46 ms (n = 5). The voltage‐dependence of activation and steady‐state inactivation had voltages of half activation and inactivation of 9.5 ± 2.5 mV and ‐30.4 ± 1.5 mV respectively, and there was little overlap between the two curves. The α1A current was completely blocked by 100 μM Cd2+ and was also blocked by ω‐conotoxin MVIIC (500 nM). Dose‐inhibition curves and analysis of kon and kfor for ω‐agatoxin IVA both revealed apparent KD values of approximately 11 nM for α1A currents, with a kD of 7.8 × 104 M‐1s‐1. The results suggest that α1A expressed in these cells has some resemblance to the P type component of calcium current observed in native neurons, although it shows a somewhat greater degree of inactivation than native P current, more similar to the Q type current component. It also has an affinity for ω‐agatoxin IVA 2–5 fold lower than reported for P current, but approximately 9‐fold higher than reported for Q current.
Cable Properties of Dendrites in Hippocampal Neurons of the Rat Mapped by a Voltage‐sensitive Dye
Authors: Meyer Elisabeth , Müller Carsten O. , Fromherz Peter
Published: April 2006

Dendrites of pyramidal neurons from embryonic rat hippocampus are investigated in culture using a voltage‐sensitive fluorescent dye. The electrical response to somatic stimulation is observed as a time‐resolved map with a resolution of 0.9 μM at a time constant of 0.4 ms without signal averaging. The data are interpreted in terms of a tapering cable with Hodgkin‐Huxley parametrization. The spread of short hyperpolarizing transients is damped by capacitive shunting. The invasion of an action potential is boosted by voltage‐gated conductances of a low density. No irregularity is observed at a bifurcation. The passive cable parameters of internal resistance and membrane resistance at resting voltage are Ri= 300 ωcm and Rm= 40 kωcm2 respectively, at a maximum sodium conductance of ˜4.4 mS/cm2. The electrotonic length constant and the dynamic length constant at 1 kHz are 580 and 90 μm respectively. These results are compatible with electrophysiological data of dendrites in slices of adult hippocampus and with optical data of narrow processes of leech neurons in culture. The functional implications of boosting an action potential by voltage‐gated channels of low density are considered.
Effects of Noradrenaline on Frequency Tuning of Rat Auditory Cortex Neurons
Authors: Manunta Yves , Edeline Jean‐Marc
Published: April 2006

The selectivity of rat auditory cortex neurons for pure tone frequency was studied during and after ionophoretic application (5–40 nA) of noradrenaline in urethane‐anaesthetized rats. The dominant effect induced by noradrenaline was a significant decrease in spontaneous (93/268 cells) and evoked activity (1331268 cells) which outlasted the application. In the whole population of cells (n= 268) the signal‐to‐noise ratio, computed using as the signal either the mean evoked response or the response at the best frequency, was unchanged during noradrenaline application. It was significantly increased only for cells showing significantly decreased spontaneous activity, and was significantly decreased for cells showing increased spontaneous activity. Frequency selectivity was significantly increased for the whole population during and after noradrenaline application. It was also significantly increased for cells showing significantly decreased evoked activity, and was significantly decreased for cells showing increased evoked activity. The noradrenaline‐induced inhibition was not blocked by propranolol (β antagonist); it was blocked by prazosin (α1 antagonist) and partly mimicked by phenylephrine (α1 agonist). GABA, which also inhibited spontaneous and evoked activity, slightly increased the signal‐to‐noise ratio and significant increased frequency selectivity. However, when noradrenaline was ejected in the presence of bicuculline at doses that were able to block GABAergic inhibition, the inhibitory effects of noradrenaline on spontaneous and evoked activity were still observed. The possible function of noradrenaline‐induced inhibitions in sensory cortices is briefly discussed.
Neonatal γ‐Ray Irradiation Impairs Learning and Memory of an Olfactory Associative Task in Adult Rats
Authors: Chaillan F. A. , Devigne C. , Diabira D. , Khrestchatisky M. , Roman F. S. , Ben‐Ari Y. , Soumireu‐Mourat B.
Published: April 2006

Adult neonatally γ‐irradiated rats were compared with control animals in a non‐spatial olfactory associative task using two different procedures. Irradiation induced a clear reduction in the total mean area of the olfactory bulbs and hippocampus but not of the orbital prefrontal cortex, diagonal band and cell layers of the entorhinal and piriform cortex. The γ‐irradiation affected the granule cells of the olfactory bulbs and differentially altered the cell layers of the subfields of the ammonic fields and the dorsal and ventral blades of the dentate gyrus. In the CA1 ammonic field, dorsal and ventral blades of the dentate gyrus, the cellular loss was significant in comparison with control adult rats. The behavioural data indicated that irradiated rats were deeply disturbed in learning the odour‐reward association, and substantially impaired in a reversal experiment, but not in the discrimination of the odours per se. The cellular loss in the olfactory bulbs, in the CA1 and in the ventral blade of the gyrus dentatus was positively correlated with the deficit in behavioural performance. The data support the findings that the hippocampal system participates in the odour‐reward associations and facilitates the long‐term storage of associations after learning is achieved in this olfactory associative task.
Protection Against Oxidative Stress‐induced Neuronal Cell Death‐A Novel Role for RU486
Authors: Behl Christian , Trapp Thorsten , Skutella Thomas , Holsboer Florian
Published: April 2006

Free radicals and oxidative stress‐induced neuronal cell death have been implicated in a variety of neurological disorders. Therefore, neuroprotection is of primary interest in basic and preclinical neuroscience. Here it is shown that RU486 (mifepristone), a potent antagonist of progesterone and glucocorticoid receptors, protects rat primary hippocampal neurons, clonal mouse hippocampal cells and organotypic hippocampal slice cultures against oxidative stress‐induced neuronal cell death. 10‐5 M RU486 prevents intracellular peroxide accumulation and cell death induced by amyloid β protein, hydrogen peroxide and glutamate, neurotoxins that have been implicated in certain neurodegenerative disorders, including Alzheimer's disease. RU486 has a significant protective effect that is independent of the presence and activation of glucocorticoid or progesterone receptors. The neuroprotective activity of this well‐studied drug may have an impact on therapeutic interventions for neurodegenerative conditions which involve peroxidation processes. such as stroke and Alzheimer's disease.
Evidence for the Involvement of the Mammillary Bodies and Cingulum Bundle in Allocentric Spatial Processing by Rats
Authors: Neave N. , Nagle S. , Aggleton J. P.
Published: April 2006

Comparisons were made between the behavioural effects of lesions in three inter‐related limbic structures: the mammillary bodies, the fornix and the cingulum bundle/cingulate cortex. Cytotoxic lesions of the mammillary nuclei produced a marked deficit on reinforced T‐maze alternation, but performance gradually improved with practice. Subsequent tests in a cross‐maze and a radial‐arm maze showed that the animals with mammillary body lesions failed to use allocentric cues, but were able to perform normally in an egocentric discrimination. Three groups of rats with different patterns of either crossed or unilateral radio frequency lesions of the cingulate region were given the same tasks. The profile of results indicated that disruption of those fibres in the cingulum bundle connecting the anterior thalamic nuclei with the hippocampal/retrohippocampal region was responsible for the observed impairments to T‐maze alternation and radial‐arm maze performance. There was also evidence that disconnection of frontal connections in the cingulum bundle might affect perseverative behaviour, but not allocentric processing. The results add support to the notion of a functional circuit that involves projections from the hippocampus to the mammillary bodies and anterior thalamic nuclei, and from there back to hippocampal/ retrohippocampal regions via the cingulum bundle. This circuit appears to be vital for normal allocentric processing.
Lymphocyte Recruitment Following Spinal Cord Injury in Mice is Altered by Prior Viral Exposure
Authors: Schnell Lisa , Schneider Regula , Berman Monique A. , Perry V. Hugh , Schwab Martin E.
Published: April 2006

The inflammatory response induced by mechanical lesion of the spinal cord is known to include the recruitment of neutrophils and macrophages, while the involvement of lymphocytes has been largely ignored. We have studied the pattern of lymphocyte recruitment following partial transection of the mouse spinal cord. Using immunohistochemical techniques, all three types of lymphocytes (CD4‐positive T‐cells, CD8‐ positive T‐cells and B‐cells) were found in the vicinity of the lesion site within hours and persisted for up to 7 days. There was a predominance of B‐lymphocytes during the first 3 days. A second, late phase of cell infiltration, dominated by CD8‐positive T‐lymphocytes, occurred in mice that had been raised in a conventional breeding unit and had acquired antibody titres to a common murine virus (mouse hepatitis virus). In contrast, mice kept in specific pathogen‐free facilities did not show this late‐phase response. These findings suggest a possible role for lymphocytes in secondary tissue loss, local demyelination, scar formation, cytokine‐mediated inflammatory responses or trophic processes. They also provide evidence that a virus infection can significantly enhance the reaction of T‐cells to a spinal cord lesion.
Dopaminergic Phenotype Induced by Oestrogens in a Human Neuroblastoma Cell Line
Authors: Agrati P. , Ma Z. Q. , Patrone C. , Picotti G. B. , Pellicciari C. , Bondiolotti G. , Bottone M. G. , Maggi A.
Published: April 2006

Oestrogens are the key factor in the sexual differentiation of the mammalian brain and play an important role in the activity of selected areas of the mature brain. To pursue the study of oestrogen action on neural cells at the molecular level, we developed a human neuroblastoma cell line (SK‐ER3) expressing the oestrogen receptor (ER). Treatment of these cells with 17β‐oestradiol causes growth arrest and morphological and biochemical differentiation. The aim of the present study was to investigate whether oestrogen‐differentiated SK‐ER3 neuroblastoma cells acquire the ability to synthesize a specific neurotransmitter and whether the growth arrest previously reported can be ascribed to the blockage of the cells at a specific stage of the cell cycle. The results presented here indicate that oestrogens induce accumulation of SK‐ER3 cells in the GO phase of the cell cycle, underscoring the acquisition of a mature neural phenotype upon hormonal treatment. Most importantly, we show that in the differentiated cells the content of tyrosine hydroxylase and Na+‐dependent dopamine uptake is significantly augmented, proving that the oestrogen‐differentiated SK‐ER3 cells can synthesize and store a specific neurotransmitter. In addition, we prove that the dopamine accumulated in differentiated SK‐ER3 cells can be released. These studies therefore suggest that oestrogen treatment results in the acquisition of a fully functional dopaminergic phenotype of SK‐ER3 cells. Ample evidence shows a link between dopaminergic neurons and oestrogen activity in hypothalamic and non‐hypothalamic areas of the mammalian brain. Our study indicates that oestrogens might play a primary role in committing undifferentiated neuroblasts towards the dopaminergic phenotype.
Interaction Between Neurons in Different Laminae of the Dorsal Horn of the Spinal Cord. A Correlation Study in Normal and Neuropathic Rats
Authors: Biella Gabriele , Riva Lilette , Sotgiu Maria Luisa
Published: April 2006

Simultaneous recordings of 135 pairs of units, located respectively in the superficial (I‐110) and deep (V) laminae of the dorsal horn of the lumbar spinal cord of anaesthetized and paralysed animals, were performed both from normal (62 pairs) and from peripherally injured (chronically constricted sciatic nerve) rats (73 pairs). In each pair, one neuron was classified as nociceptive, responding only to noxious stimuli, and the other as a wide dynamic range neuron, responding to both non‐noxious and noxious stimuli. To understand if some interaction was present between diverse neurons modulated by noxious inputs, we used cross‐correlation techniques. The responses of simultaneously recorded pairs of units to suprathreshold (5 mA, 0.5 ms) electrical stimuli were used. A clearly delayed peak in the cross‐correlograms of recordings from normal animals was present, indicating connectivity of superficial and deep‐layer cells. This feature was not present in the cross‐correlograms obtained from nerve‐injured animals. Even if a specific pathway cannot be explicitly assigned to support these functional results, an overall connection between superficial and deep layers of the spinal cord is suggested. These connections are supposed to be either inactive or rearranged in the nerve‐injured rats, thus suppressing a well timed coordinated connectivity. This anomaly could underlie a reduced degree of functional coherence in the modulation of nociceptive spinal inputs in cases of chronic pain.
Magnetoencephalography May Help to Improve Functional MRI Brain Mapping
Authors: Beisteiner R. , Erdler M. , Teichtmeister C. , Diemling M. , Moser E. , Edward V. , Deecke L.
Published: April 2006

The validity of functional magnetic resonance imaging (FMRI) brain maps with respect to the sites of neuronal activation is still unknown. One source of localization error may be pixels with large signal amplitudes, since such pixels may be expected to overlie large vessels, running remote from the centre of neuronal activation. In this study, magnetoencephalography was used to determine the centre of neuronal activation in a simple finger tapping task. The localization accuracy of conventional FMRI depending on FMRI signal enhancement was investigated relative to the magnetoencephalography reference. The results show a deterioration of FMRI localization with increasing signal amplitude related to increased contributions from large vessels. We conclude that FMRI data analysis should exclude large signal amplitudes and that magnetoencephalography may help to improve FMRI brain mapping results in a multimethod approach.
The Perceptual Grouping Criterion of Colinearity is Reflected by Anisotropies of Connections in the Primary Visual Cortex
Authors: Schmidt Kerstin E. , Goebel Rainer , Löwel Siegrid , Singer Wolf
Published: April 2006

An important step in the processing of visual patterns is the segmentation of the retinal image. Neuronal responses evoked by the contours of individual objects need to be identified and associated for further joint processing. These grouping operations are based on a number of Gestalt criteria. Here we report that connections in the visual cortex of the cat exhibit a highly significant anisotropy, preferentially linking neurons activated by contours that have similar orientation and are aligned colinearly. These anatomical data suggest a close relation between the perceptual grouping criterion of colinearity and the topology of tangential intracortical connections. We propose that tangential intracortical connections support perceptual grouping by modulating the saliency of distributed cortical responses in a context‐dependent way. The present data are compatible with the hypothesis that the criteria for this grouping operation are determined by the architecture of the tangential connections.