bluuebunny/crossref_metadata_2025_split huggingface dataset:
Noradrenergic Control of Thalamic Oscillation: the Role of α‐2 Receptors
Authors: Buzsáki G. , Kennedy B. , Solt V. B. , Ziegler M. 
Published: April 2006

AbstractThe effects of α‐adrenergic drugs on neocortical high voltage spike and wave spindles (HVS), reflecting thalamic oscillation, was investigated in freely moving rats. HVS occurred spontaneously in the awake but immobile animal. Peripheral administration of the α‐1 antagonist, prazosin and α‐2 agonists, xylazine and clonidine increased the incidence and duration of HVS in a dose‐dependent manner. The α‐2 antagonist, yohimbine and the tricyclic antidepressants, desipramine and amitriptyline, significantly decreased the incidence of the neocortical HVS. Bilateral microinjections of the α‐2 agonists into the nucleus ventralis lateralis area of the thalamus, but not into the hippocampus or corpus callosum, was as effective as peripheral injection of these drugs. Xylazine was most effective in Fischer 344 rats that display high spontaneous rate of HVS and less effective in the Sprague – Dawley and Buffalo strains. The HVS‐promoting effect of clonidine was antagonized by prior intrathalamic injection of the α‐2 antagonist, yohimbine. The amplitude of the HVS was increased by picomole amounts of unilaterally‐injected clonidine. Neurotoxic destruction of the thalamopetal noradrenergic afferents by intracisternal or intrathalamic injection of 6‐hydroxydopamine, but not by peripheral administration of DSP‐4, increased the incidence of HVS. Importantly, intrathalamic administration of xylazine continued to induce HVS after destroying the thalamic noradrenergic terminals. Following downregulation of the α‐2 adrenoceptors by chronic administration (3 weeks) of amitriptylene the incidence of HVS decreased and the effectiveness of intrathalamic xylazine on the induction of HVS was significantly reduced. Based on these findings, we suggest that a major action of α‐2 adrenergic drugs on thalamic oscillation may be mediated by postsynaptic α‐2 adrenoceptors located on the thalamocortical neurons. We hypothesize that noradrenaline in the thalamus has a dual effect on the relay cells: blocking and promoting thalamic oscillation via α‐1 and α‐2 receptors, respectively. The final physiological effect is assumed to be a function of the relative density and affinity of these adrenergic receptor subtypes.
The Neural Cell Adhesion Molecule (N‐CAM) Modulates K+ Channels in Cultured Glial Precursor Cells
Authors: Sontheimer Harald , Kettenmann Helmut , Schachner Melitta , Trotter Jacqueline 
Published: April 2006

AbstractApplication of antibodies against the neural cell adhesion molecule (N‐CAM) to O4‐positive murine glial precursor cells in vitro results in a reduction of two distinct K+ currents measured using the whole cell patch clamp technique. Both the A‐type and delayed rectifier K+ currents are reduced in amplitude within a few minutes of the application of poly‐ or monoclonal antibodies against N‐CAM. This effect is not due to the binding of any antibody to the surface of the glial precursor cells because monoclonal antibody directed against the O4 surface antigen, or polyclonal antibodies directed against liver cell membranes (which also bind to the surface of glial precursor cells), do not affect membrane currents. Activators of protein kinase C, such as phorbol esters or diacylglycerol, also induce changes in potassium currents that appear, both in magnitude and kinetics, to be similar to those induced by antibodies against N‐CAM. In contrast, activation of G proteins upregulates K+ currents. Glial precursor cells thus respond to triggering of N‐CAM by altering channel properties. These observations suggest that adhesive events between neural cells can influence the intracellular ionic milieu.
Differential Distribution of Somatostatin‐like Immunoreactivity in the Visual Sector of the Thalamic Reticular Nucleus in Galago
Authors: Conley Michael , Schmechel Donald E. , Diamond Irving T. 
Published: April 2006

AbstractImmunocytochemical methods were used to compare the distributions of somatostatin‐14 (SOM) and glutamic acid decarboxylase (GAD) in the medial and lateral tiers of the visual sector of the thalamic reticular nucleus in the bushbaby, Galago. As expected, all of the neurons in the visual sector were immunoreactive for GAD, the synthesizing enzyme for GABA, but the distribution of SOM‐immunoreactive cells was not uniform. It appeared that every cell in the medial tier was immunoreactive for SOM, but that very few cells in the lateral tier contained this neuropeptide. The significance of the difference in reticular neuron SOM content could be related to the functional differences between the dorsal lateral geniculate nucleus, which is connected reciprocally with the lateral tier, and the pulvinar nucleus, which is connected reciprocally with the medial tier.
Origins of Spinal Ascending Pathways that Reach Central Areas Involved in Visceroception and Visceronociception in the Rat
Authors: Menétrey D. , de Pommery J. 
Published: April 2006

AbstractThe location of spinal cells projecting rostrally to central areas that process visceroception and visceronociception were studied in rat using the retrograde transport of a protein‐gold complex. Origins of afferents to the nucleus tractus solitarius (the spinosolitary tract), the parabrachial area (the spinoparabrachial tract), the hypothalamus (the spinohypothalamic tract) and the amygdala (the spinoamygdalar tract) were studied at thoracic, lumbar and sacral levels, where spinal visceroceptive areas are concentrated. All of the afore‐mentioned pathways have common origins in the lateral spinal nucleus and in the reticular formation of the neck of the dorsal horn at all the levels studied, and also in the dorsal grey commissure and adjacent areas at sacral levels. The spinosolitary and the spinoparabrachial tracts are dense pathways, both of which are also characterized by afferents from the superficial layers of the dorsal horn at all the levels studied and from cells lying in close proximity to some autonomie spinal areas. These autonomie areas are the central autonomie nucleus (dorsal commissural nucleus) of lamina X at thoracolumbar levels and the parasympathetic column at sacral levels; some projections from the intermediolateral cell column at thoracic levels were also noted. Projections from all these autonomie structures to the parabrachial area have not yet been recognized. Thus, the origin of the spinoparabrachial tract closely resembles that of the spinomesencephalic tract that reaches the periaquaductal grey and adjacent areas. The spinohypothalamic and the spinoamygdalar tracts are smaller pathways. Direct spinal connections to the amygdala have not been reported previously. Both the hypothalamus and amygdala receive projections from lamina VII cells at low thoracic and upper lumbar levels in a pattern that resembles that of the preganglionic cells of the intercalated nucleus. Hypothalamic projections from the sacral parasympathetic area were also noted. The use of c‐fos as a functional marker to identify spinal neurons that are activated by noxious visceral stimulation suggests that both the spinoparabrachial and the spinosolitary tracts contribute significantly to the central transmission of visceronociceptive messages. Most of the visceronociceptive ascending projections in these pathways issued from lamina I cells. The results presented here confirm previous observations regarding the spinosolitary and the spinohypothalamic tracts and also demonstrate, for the first time, the complex origin of the spinoparabrachial tract and the existence of direct spinal afferents to the amygdala. These findings suggest that rostral transmission and central integration of visceral inputs require several parallel routes. The spinosolitary and spinoparabrachial tracts clearly play a role in conveying information regarding visceronociception.
Behavioural Correlates of the Release and Subsequent Action of Acetylcholinesterase Secreted in the Substantia Nigra
Authors: Jones S. A. , Greenfield S. A. 
Published: April 2006

AbstractAcetylcholinesterase is secreted in the central nervous system (independently of cholinergic transmission) in a non‐classic, non‐enzymatic capacity. A light‐emitting reaction has recently been established that demonstrates release of this protein from the substantia nigra of a guinea pig with a temporal resolution corresponding to real time, i.e. ‘on‐line’. In this study the technique has been applied to investigate the significance of this novel phenomenon in the generation of specific types of movement. During locomotion a ‘pulsatile’ release of acetylcholinesterase occurs much more frequently than in other situations. However, these pulses of released acetylcholinesterase are of shorter duration than the respective periods of locomotion that caused them. Furthermore, as episodes of movement are repeated, the release of acetylcholinesterase becomes less likely. These observations suggest that the phenomenon does not simply reflect ongoing movement. Indeed, chewing behaviour is frequently initiated when acetylcholinesterase release occurs during locomotor activity. Hence, acetylcholinesterase released in association with locomotion may favour the onset of further types of movement.
Sensory Excitatory Postsynaptic Potentials Mediated by NMDA and non‐NMDA Receptors in the Thalamus in vivo
Authors: Salt T. E. , Eaton S. A. 
Published: April 2006

AbstractExcitatory amino acid neurotransmitters, such as l‐glutamate, act at several receptors in the brain, which are sometimes referred to as N‐methyl‐d‐aspartate (NMDA) and non‐NMDA receptors. Extensive in vitro work indicates that both NMDA receptors and non‐NMDA receptors contribute to excitatory postsynaptic potentials (epsps). The contribution of NMDA receptors to epsps in vivo under physiological conditions is, however, almost unknown. The receptors that mediate the epsps evoked in thalamic relay cells by natural stimulation of sensory afferents have been investigated in anaesthetized rats, and we report the first pharmacological characterization of an excitatory amino acid receptor‐mediated epsp in vivo involving both non‐NMDA receptors and, in particular, NMDA receptors.
Regeneration of Lesioned Septohippocampal Acetylcholinesterase‐positive Axons is Improved by Antibodies Against the Myelin‐associated Neurite Growth Inhibitors NI‐35/250
Authors: Cadelli D. , Schwab M. E. 
Published: April 2006

AbstractTwo oligodendrocyte membrane proteins, NI‐35 and NI‐250, have been shown to be highly inhibitory for neurite growth. Upon neutralization of these components with the specific monoclonal antibody IN‐1, lesioned corticospinal tract fibres were able to regenerate over long distances. In the present study, we have investigated the behaviour of regenerating cholinergic septohippocampal tract fibres. Large fimbria/fornix aspiration lesions were bridged by human amnion extracellular matrix material containing nerve growth factor, and the inhibitor‐neutralizing antibody IN‐1 or a control antibody were applied. After 3–5 weeks survival time, acetylcholinesterase (AchE)‐positive fibres had crossed the bridge and, upon entering the hippocampus, had developed a profuse fibre plexus. In the controls (antibody against peroxidase) the fibre growth within the hippocampal tissue remained limited to maximally 1 mm in the caudal and lateral directions. In the presence of the antibody IN‐1, however, AchE‐positive fibres were seen to grow for 2–4 mm both in the caudal and lateral directions. Interestingly, the regenerated fibres preferably grew to their original terminal areas in the infra‐ and suprapyramidal layers of the hippocampus proper and the hilus, and in the supragranular layer of the dentate gyrus. These data show that the neurite growth inhibitors severely impede regenerative axon growth also for the cholinergic fibres in the hippocampus, and that their neutralization increases axon growth and leads to partial reconstitution of the original anatomical fibre distribution.
Loss of Calbindin‐28K Immunoreactivity in Hippocampal Slices from Aged Rats: a Role for Calcium?
Authors: Dutar P. , Potier B. , Lamour Y. , Emson P. C. , Senut M. C. 
Published: April 2006

AbstractCalbindin‐28K (CaBP) is a calcium‐binding protein widely distributed in the brain. This protein appears to be involved in the sequestration and the translocation of intracellular free calcium. In this study, we have examined the distribution pattern of the structures immunoreactive for CaBP in the hippocampal formation from slices of young (4 months) and aged (24–27 months) rats previously submitted to electrophysiological measurements. We demonstrated a marked loss in the number of pyramidal cells immunoreactive for CaBP in aged rats as compared to young rats. A consistent decrease in the staining intensity was also revealed by optical density measurements. Some experiments have suggested that calcium homeostasis is modified in hippocampal neurons of aged rats. The loss of CaBP‐like immunoreactivity (CaBP‐LI) labelling could result from an increase in intracellular calcium concentrations. To support this hypothesis, we showed that in young rats (i) the CaBP‐LI was enhanced in pyramidal neurons when the slice was preincubated in a calcium‐free medium, and (ii) CaBP‐LI was strongly decreased when the slice was preincubated in a high‐calcium medium (5 mM) and when the entry of calcium into the cell was increased by a short application of an excitatory amino acid in the medium. Our results suggest that the loss of CaBP‐LI in the hippocampus of aged rats could be due to an increase in intracellular calcium concentration. Preliminary observations of hippocampal slices at different times after induction of long‐term potentiation (LTP) failed to show significant changes in CaBP immunoreactivity, suggesting that this calcium‐binding protein is not directly involved in LTP processes.
Long‐term Potentiation of NMDA Receptor‐mediated EPSP in Guinea‐pig Hippocampal Slices
Authors: Berretta N. , Berton F. , Bianchi R. , Brunelli M. , Capogna M. , Francesconi W. 
Published: April 2006

AbstractHippocampal slices from guinea‐pigs were used to examine the long‐term potentiation (LTP) of the N‐methyl‐D‐aspartate (NMDA)‐mediated excitatory postsynaptic potential (EPSP). lntracellular recordings were performed from CA1 pyramidal neurons in the presence of 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX, 5–10 μM) and picrotoxin (50 μM). In these experimental conditions test stimuli applied at low frequency (0.1 Hz) to the Schaffer collateral ‐ commissural pathway evoked a prolonged EPSP (150–200 ms). To obtain this CNQX‐resistant EPSP, stimulus intensities had to be raised above the level required to evoke an EPSP of comparable amplitude in physiological solution. Tetanic stimulation (two trains of 100 Hz, 1 s every 20 s) led to a potentiation of the CNQX‐resistant EPSP, and this potentiated response was abolished with d‐(‐)‐2‐amino‐5‐phosphonovaleric acid (50μM). The potentiation of the NMDA receptor‐mediated EPSP was more pronounced for strong than for weak test stimuli, and was suppressed when test EPSPs were evoked during membrane hyperpolarization. These results suggest that NMDA receptor‐mediated responses can undergo LTP, and hence can contribute to the maintenance of LTP.
In Vitro Development of Rat Cerebellar Neurons of Early Embryonic Origin. An Anatomical and Electrophysiological Study
Authors: Hamon Brigitte , Condé Françoise , Jaillard Danielle , Thomasset Monique , Crépel Francis 
Published: April 2006

AbstractThe development of the major morphological and electrophysiological properties of presumptive Purkinje cells (PCs) was studied in primary cultures of rat cerebellum dissociated on the 14th embryonic day, when PCs are minimally differentiated and migrate in vivo PCs were identified with a specific antibody to calbindin D‐28K (CaBP), which allowed visualization of the different morphological types of PCs between 3 and 29 days in vitro (DIV). CaBP‐immunopositive cells were first detected at 3 DIV. Thereafter, the shape of these cells resembled some of those described in viva After 20 DIV, 95% of the CaBP‐immunopositive cells had characteristic PC dendritic trees, although they were very atrophic. Glial cells immunopositive for the glial fibrillary acidic protein (GFAP) were first seen at 3 DIV. Thereafter GFAP‐immunopositive cells resembled Bergmann cells or velate astrocytes. Neurons regarded as PCs were studied electrophysiologically using the patch‐clamp whole‐cell configuration. Voltage‐dependent, tetrodotoxin‐sensitive fast inward currents were virtually absent at 2–4 DIV, but increased between 7 and 14 DIV to reach two‐thirds of the amplitude obtained after 15 DIV. These currents were large enough to give rise to overshooting spikes as early as 7 DIV in the current‐clamp mode. This time schedule is in keeping with that of PCs developed in situ. The tetraethylammonium‐sensitive, slowly inactivating outward currents had reached two‐thirds of the amplitude obtained after 15 DIV by 3–4 DIV. Their amplitude remained stable between 4 and 7 DIV, and increased to their maximal value during 7–14 DIV, with a marked shortening of action potentials. 4‐Aminopyridine‐sensitive, fast‐inactivating outward currents might also be associated with development, since they were present in 66% of the cells between 7 and 14 DIV but in only 39% from 15 to 29 DIV; however, their amplitude did not vary with time. Presumptive PCs bore l‐glutamate‐activated receptors, which preceded the emergence of kynurenate‐sensitive, spontaneous synaptic currents at 7 DIV. These currents were sometimes intermingled with inhibitory currents, although presumptive PCs were sensitive to γ‐aminobutyrate at 7 DIV. The present model represents some unequivocal features of PC development, although the PCs used had undergone minimal differentiation in vivo and were cultured in a very disturbed cellular environment.
Projections from the Cerebral Cortex to the Red Nucleus of the Guinea‐pig. A Retrograde Tracing Study
Authors: Giuffrida R. , Aicardi G. , Rapisarda C. 
Published: April 2006

AbstractThe origin and the topographic distribution of corticorubral (CR) projections in the guinea‐pig were studied by using the retrograde axonal transport of a tracer, colloidal gold‐labelled, enzymatically inactive horseradish peroxidase conjugated to wheat‐germ agglutinin (WGAapoHRP‐Au), which was injected in the red nucleus (RN). It was found that the bulk of the CR projections arise from layer V neurons of the agranular frontal cortex in both its medial (Agm) and lateral (Agl) subdivisions; in the Agm labelled neurons are preferentially located in the upper part of layer V, whereas in the Agl they are more concentrated in the central band of the layer. Fewer projections originate from areas of the granular parietal and the agranular cingulate and retrobulbar cortices. CR projections have a bilateral origin, with a large ipsilateral predominance. The pattern of retrograde cortical labelling observed after injection of WGAapoHRP‐Au in different portions of the RN indicates that CR projections are distributed throughout the entire rostrocaudal extent of the nucleus, but are slightly more concentrated in the rostral parvocellular area. The morphological arrangement of CR projections in the guinea‐pig, as demonstrated in the present study, shows several analogies with other mammals. The functional characteristics of the cortical areas in which CR neurons are located indicate that CR projections may play a significant role in the central organization of movement.
Down‐regulation of GAP‐43 During Oligodendrocyte Development and Lack of Expression by Astrocytes In Vivo: Implications for Macroglial Differentiation
Authors: Curtis Rory , Hardy Rebecca , Reynolds Richard , Spruce Barbara A. , Wilkin Graham P. 
Published: April 2006

AbstractThe discovery of molecular markers which are selectively expressed during the development of specific classes of rat central nervous system macroglia has greatly advanced our understanding of how these cells are related. In particular, it has been shown in tissue culture that oligodendrocytes and some astrocytes (type‐2) may be derived from a common progenitor cell (O‐2A progenitor). However, the existence of type‐2 astrocytes in vivo has yet to be unequivocally established. Recently, it has been reported that the neural‐specific growth‐associated protein‐43 (GAP‐43, otherwise known as 8–50, F1, pp46 and neuromodulin) may be expressed by cells of the O‐2A lineage in vitro. We set out to examine the cellular specificity of GAP‐43 in O‐2A progenitors and their descendants in vitro and in vivo. Using a polyclonal antiserum against a GAP‐43 fusion protein we have shown the presence of immunoreactive GAP‐43 in the membranes of bipotential O‐2A glial progenitor cells and type‐2 astrocytes by Western blotting and immunocytochemistry of cells in culture. In contrast to previous studies, double labelling with mature oligodendrocyte markers showed that GAP‐43 is down‐regulated during oligodendrocyte differentiation in vitro. Immunohistochemical staining of sections of developing rat brain demonstrated the same developmental regulation of GAP‐43, suggesting that oligodendrocytes only express GAP‐43 at immature stages. In addition, normal and reactive astrocytes in tissue sections were not labelled with GAP‐43.
Distribution of mRNAs for Chromogranins A and B and Secretogranin II in Rat Brain
Authors: Mahata S. K. , Mahata M. , Marksteiner J. , Sperk G. , Fischer‐Colbrie R. , Winkler H. 
Published: April 2006

AbstractThe mRNA distribution of chromogranins A and B and secretogranin II was determined in rat brain. In Northern blots the oligonucleotide probes used hybridized with single mRNA species of the expected sizes. With tissue hybridization the mRNA signals for these three proteins were found throughout the brain. However, each of the three messages had a distinct distribution, which was exemplified by the fact that in the various regions either all three proteins, a combination of two or only one of them were apparently synthesized. Significant levels of all three mRNAs were found in several regions of the hippocampus and of the amygdala, in some thalamic nuclei and in the pyriform cortex. On the other hand the subiculum contained only the message for chromogranin A, the granule cell layer of the cerebellum only that for chromogranin B, and in posterior intralaminar thalamic and medial geniculate nuclei and in the nucleus of the solitary tract only secretogranin II mRNA was found. The distinct distributions of mRNAs for the chromogranins in various brain regions support the concept that these proteins are propeptides giving rise to functionally active components.
The Desheathed Periphery of Aplysia Giant Neuron. Fine Structure and Measurement of [Ca2+]o Fluctuations with Calcium‐selective Microelectrodes
Authors: Keicher E. , Bilbaut A. , Maggio K. , Hernandez‐Nicaise M. L. , Nicaise G. 
Published: April 2006

AbstractThe visceral ganglion of Aplysia was mechanically desheathed after protease softening of the connective tissue to permit the positioning of ion‐selective electrodes in the vicinity of the neuronal membrane. The effects of this treatment on satellite glia and neuronal cytology were observed by electron microscopy. The intracellular alterations were not suggestive of serious membrane damage but the cohesion between glial and neuronal membranes was affected—the glial processes appeared to retract from the trophospongium and in some cases the neuronal membrane was completely naked. The external calcium activity [Ca2+]o at the surface of identified giant neuron, R2, was measured using double‐barrelled calcium‐selective microelectrodes. A decrease of ∼1 mM in [Ca2+]o could be recorded only during trains of action potentials induced by intracellular depolarizing current injection, and when the electrode was pushed firmly against the neuron surface. A recovery from this decrease in [Ca2+]o could sometimes, but not always, be observed during the phase of induced neuronal activity.