bluuebunny/crossref_metadata_2025_split huggingface dataset:
Host Brain Regulation of Fetal Locus Coeruleus Neurons Grafted to the Hippocampus in 6‐Hydroxydopamine‐Treated Rats. An Intracerebral Microdialysis Study
Authors: Kalén Peter , Cenci M. Angela , Lindvall Olle , Björklund Anders 
Published: April 2006

AbstractRelease properties of intrahippocampal transplants of noradrenergic neurons were monitored by microdialysis in awake and halothane‐anaesthetized rats. Fetal locus coeruleus neurons were implanted as a cell suspension into hippocampi deprived of their innate noradrenalin (NA) innervation by intraventricular 6‐hydroxydopamine treatment. Dialysis probes of the loop type were implanted into the dorsal hippocampus 1 ‐2 days before each experiment, i.e. 7–11 months after grafting. Age‐matched intact and lesion‐only animals served as controls. Microscopic analysis showed a graft‐derived tyrosine hydroxylase immunoreactive, presumably noradrenergic, fibre network throughout the dorsal hippocampal formation, surrounding the probe site. The innervation density varied from sub‐ to supranormal. The grafts restored baseline NA release in the graft‐reinnervated hippocampus to near‐normal levels both in awake and halothane‐anaesthetized animals. Potassium chloride (100 mM) in the perfusion fluid induced a dramatic increase in NA release that was similar in magnitude in the grafted and intact hippocampi. A NA uptake blocker (desipramine) added to the perfusion fluid at 5 μM induced a similar increase in NA output in the grafted and intact hippocampi, and the output was substantially reduced by tetrodotoxin, added at 1 μM in the presence of uptake blockade. Electrical stimulation of the lateral habenular nucleus (15 Hz, 0.5 mA) in halothane‐anaesthetized rats induced a significant increase in NA output both in the intact and grafted hippocampi. This effect was abolished by transection of the fasciculus retroflexus, which carries the efferent projections of the habenular complex. Behavioural activation through handling induced a consistent increase in NA release only in the intact animals, but in a few grafted rats (which also responded to habenular stimulation) the NA output was clearly elevated by handling. Forced immobilization induced a significant increase in NA output both in the intact and grafted hippocampi, but in the grafted ones the response was somewhat smaller and more transient. In the same set of animals, swimming in warm water (25–30°C) induced a sharp increase in NA output in the intact animals, whereas only one of the grafted rats responded by increased NA output. The results indicate that the locus coeruleus grafts, despite their ectopic location, can become functionally integrated with the host brain, and that the activity of the transplanted noradrenergic neurons can, under some circumstances, be modulated from the host brain in response to environmental challenges.
Specificity in the Development of Vertical Connections in Cat Striate Cortex
Authors: Katz Lawrence C. 
Published: April 2006

AbstractThe main efferent axons of pyramidal cells in layer 2/3 in the adult cat striate cortex make collateral connections specifically within layer 2/3 and layer 5 and avoid the intervening layer 4. Intracellular dye injections in vitro were used to determine how, during early postnatal development, this precise pattern of laminar connections was achieved. These investigations revealed that the pattern of collateral outgrowth was specific from the very earliest time that axons began sprouting collaterals. During the first postnatal week, sprouts were seen exclusively within layers 2/3 and 5; no evidence for a transient connection to layer 4 was observed. Furthermore, collaterals emerged simultaneously within layers 2/3 and 5, despite the large difference in the postmigratory ages of the two layers. By the end of the second postnatal week, the adult number of collaterals was achieved. Further elaboration of the local arbors occurred by repeated branching of already existing collaterals, rather than by addition of new collaterals to the main axon. These results demonstrate that the formation of local connections between cortical layers is highly specific, in contrast to the development of clustered horizontal connections by these same cells within layers 2/3 and 5, which involves extensive remodelling of local connections.
Cat Distal Forelimb Joints and Locomotion: An X‐ray Study
Authors: Caliebe F. , Häußler J. , Hoffmann P. , Illert M. , Schirrmacher J. , Wiedemann E. 
Published: April 2006

AbstractThe complex construction of the joint apparatus of the cat distal forelimb, which allows the paw three degrees of freedom, poses special requirements on the neural signals controlling the paw position. To understand the electromyography (emg) signals of the distal forelimb muscles during locomotion, it is necessary to know the kinematics of the forelimb joints in detail. As no such information is available, we used the pulsed X‐ray technique in trained cats during treadmill locomotion to analyse the angular excursions of the wrist, the metacarpophalangeal (MCP) and the proximal interphalangeal (PIP) joints. X‐ray illuminations were done in either the parasagittal or the frontal plane. At the beginning of the stance phase the wrist (WR) and the MCP joints extended slowly, and the PIP joints flexed. Whereas the WR and the PIP joints maintained a constant angular position of ∼200° and 60°, respectively, throughout the stance phase, extension continued in the MCP joints from 240° at touch‐down to 300° at the end of the stance phase. Slightly before lift‐off (100 ms) the WR and the MCP joints flexed rapidly. This flexion changed ∼150 ms after lift‐off into a slow extension. The PIP joints extended rapidly at the beginning and at the end of the swing phase, during the interposed period of the swing phase they displayed a slow flexion. Rotatory movements of the forelimb in the radioulnar joints were present during the swing and stance phases. During the swing phase the limb first supinated (starting 100 ms after lift‐off); pronation occurred immediately before ground contact. During the stance phase the supination angle was kept constant until 100 ms before lift‐off, when a short pronation was found. The paw was kept in an ulnar deviated position throughout the complete step cycle. Ulnar deviation decreased at the end of the swing and stance phases. The results of this study increase our understanding of how the body weight is transmitted on to the ground. They suggest four main functions for the skeletomotor apparatus and the underlying neural commands to secure the forward movement of the animal during the stance phase: (i) preparation and stabilization of a force‐transmitting platform; (ii) stabilization of the wrist and the carpal/metacarpal joints; (iii) stabilization of the supination angle; (iv) antigravity control of the extension in the MCP.
NMDA‐Receptor Antagonist Prevents Measles Virus‐induced Neurodegeneration
Authors: Andersson Tommy , Schultzberg Marianne , Schwarcz Robert , Löve Arthur , Wickman Charlotte , Kristensson Krister 
Published: April 2006

Abstract N‐methyl‐d‐aspartate (NMDA) receptors represent a major subtype of excitatory amino acid receptors in the mammalian brain. In addition to their physiological role, NMDA receptors have been linked to the occurrence of nerve cell death in several neurodegenerataive diseases. The hamster neurotropic (HNT) strain of measles virus causes non‐inflammatory encephalopathy in mice. This is associated with neuronal loss in areas CA1 and CA3 of the hippocampus. Systemic treatment with the non‐competitive NMDA receptor antagonist 5‐methyl‐10,11‐dihydro‐5H‐dibenzo(a,d)cyclo‐hepten‐5,10‐imine maleate (MK‐801) prevented this cellular necrosis. Thus, a virus may have indirect neurodegenerative effects in the brain due to activation of NMDA receptors.
Glutamate‐like Immunoreactivity in the Pigeon Optic Tectum and Effects of Retinal Ablation
Authors: Morino Patrizia , Bahro Marcel , Cuénod Michel , Streit Peter 
Published: April 2006

AbstractThe pattern of glutamate‐like immunoreactivity was investigated in the pigeon optic tectum. The most impressive aspect of the labelling pattern was an accumulation of immunoreactive terminal‐like elements restricted to those superficial tectal layers that correspond to the termination zone of the retinal afferents. These immunoreactive puncta occurred frequently in small clusters. At the level of electron microscopy, many of the labelled nerve endings showed the characteristics of retinal terminals. Moreover, following unilateral retinal ablation a drastic loss of immunoreactive terminal‐like puncta was observed in the retinorecipient layers of the tectum contralateral to the lesion. The remaining glutamate‐immunoreactive terminal‐like elements had the light and electron microscopic features typical of the afferents from the nucleus isthmi, pars parvocellularis (lpc). The relation between the latter result and the transmitter specificity of the afferents from this subtectal nucleus is unclear at present. On the other hand, the light and electron microscopic labelling patterns and the effect of retinal ablation suggest that afferents from retina and from lpc are the only major sources for glutamate‐immunoreactive terminals in the pigeon optic tectum. Furthermore, the results are well in line with previous data indicating glutamate as neurotransmitter at least in part of the retinal afferents to the pigeon optic tectum.
Inactivation of Delayed Potassium Current in Cultured Bovine Chromaffin Cells
Authors: Sala Salvador , Soria Bernat 
Published: April 2006

AbstractPotassium currents of cultured bovine chromaffin cells in the presence of CdCl2 (0.5 mM) or CoCl2 (2–4 mM) may be described as a component that follows an n4 kinetics over the first 100 ms. However, during prolonged voltage clamp steps (5–20 s) this current reaches a peak and then declines to a non‐zero steady‐state level. In the absence of potassium accumulation, slow decay has been attributed to slow inactivation of the K+ conductance. Slow inactivation of calcium‐independent potassium currents responds to the following: (i) the inactivation has a time course that may be fitted by a sum of two exponentials; (ii) inactivation is use‐dependent (increasing frequency or duration of depolarizing pulses increases the extent of inactivation). Use‐dependent inactivation does not appear when short (100 ms) hyperpolarizing prepulses are applied; (iii) at a membrane potential of −60 mV, approximately 20% of the channels are inactivated; (iv) recovery from inactivation is very slow. At a holding potential of −70 mV it takes about 20 s to reach the original value. The rate of inactivation recovery is voltage‐dependent. The more hyperpolarized the membrane potential, the faster the recovery. The presence of use‐dependent inactivation with slow recovery could be relevant for the stimulus–secretion coupling modulation in chromaffin cells.
Spatial and Temporal Patterns of Neurogenesis in the Chick Retina
Authors: Prada Carmen , Puga José , Pérez‐Méndez Luisa , López Rosario , Ramírez Galo 
Published: April 2006

AbstractChick embryo retinas were labelled in ovo by single injections of [3H]thymidine at selected times between days 2 and 12 of incubation. Embryos were later removed, at different stages of development, and the retinas processed for autoradiography of either serial sections or dissociated cell preparations. Analysis of unlabelled cells shows that neurogenesis starts, on day 2 of incubation, in a dorsotemporal area of the central retina, close to the posterior pole and to the optic nerve head. A gradient of neurogenesis spreads from this central area to the periphery, where neurogenesis ends, shortly after day 12, when the last few bipolar cells withdraw from the cell cycle. Additional dorsal‐to‐ventral and temporal‐to‐nasal gradients can be discerned in our autoradiographs. In all retinal sectors, ganglion cells start first to withdraw from the cell cycle, followed, with substantial overlapping, by amacrine, horizontal, photoreceptor plus Müller, and bipolar neuroblasts. Ganglion cells are also the first to reach the 50% level of unlabelled cells, followed this time by horizontal, photoreceptor, amacrine, Müller and bipolar cells. Finally, 100% levels of unlabelled cell populations are attained simultaneously by ganglion, horizontal and photoreceptor cells, followed by amacrine, then by Müller, and last by bipolar cells. Although all classes of neurons, in varying proportions, are being produced most of the time, our results also demonstrate that, in any given retinal area, the first cells leaving the cycle are determined to become ganglion cells, and the last ones bipolar cells, and not other types.
Calcitonin Gene‐related Peptide Stimulates the Induction of c‐fos Gene Expression in Rat Astrocyte Cultures
Authors: Haas Carola A. , Reddington Martin , Kreutzberg Georg W. 
Published: April 2006

AbstractThe action of calcitonin gene‐related pepide (CGRP) was studied on c‐fos gene expression in rat astrocyte cultures. A strong and transient increase in c‐fos mRNA was observed in cultured astrocytes after treatment with CGRP. Quantitative Northern blot analysis revealed an increase of c‐fos mRNA within 15 min, a peak after 30 min with a 10–15 fold increase over unstimulated cells and a subsequent decline. Induction of the c‐fos gene by CGRP was concentration‐dependent, half maximal stimulation of c‐fos mRNA being obtained with 100 nM CGRP. The CGRP effect appeared to be mediated by a CGRP receptor and calcitonin was found to mimic only weakly the action of CGRP on cultured astrocytes. Calcitonin transiently induced c‐fos gene expression with a similar time course to CGRP, but its effect was much less pronounced. Agents affecting the intracellular cyclic AMP level, forskolin and Ro 20–1724, stimulated c‐fos mRNA in a strong and transient fashion with a temporal sequence similar to the response to CGRP. Further, the phosphodiesterase inhibitor Ro 20–1724 potentiated the action of CGRP on c‐fos mRNA induction, suggesting a role for cyclic AMP in the action of CGRP. The present results indicate that CGRP may play a physiological role as a regulator of astrocyte gene expression.
AMPA Neurotoxicity in Rat Cerebellar and Hippocampal Slices: Histological Evidence for Three Mechanisms
Authors: Garthwaite Giti , Garthwaite John 
Published: April 2006

AbstractExcitatory amino acid‐induced death of central neurons may be mediated by at least two receptor types, the so‐called NMDA (N‐methyl‐d‐aspartate) and AMPA (α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazoleproprionate) receptors. We have studied the neurodegenerative mechanisms set in motion by AMPA receptor activation using incubated slices of 8‐day‐old rat cerebellum and hippocampus. In both preparations, AMPA induced a pattern of degeneration that differed markedly from the one previously shown to be elicited by NMDA. In cerebellar slices, AMPA induced the degeneration of most Purkinje cells together with a population of Golgi cells; in hippocampal slices the neurons were affected in the order CA3 > CA1 > dentate granule cells. Three mechanisms could be discerned: an acute one in which neurons (e.g. cerebellar Golgi cells) underwent a rapid degeneration; a delayed one in which the neurons (Purkinje cells and hippocampal neurons) appeared to be only mildly affected immediately after a 30 min exposure but then underwent a protracted degeneration during the postincubation period (1.5–3 h); and finally a slow toxicity, which took place during long (2 h) exposures to AMPA (3–30 μM). Although Purkinje cells were vulnerable in both cases, the efficacy of AMPA was higher for the delayed mechanism than for the slow one. The pathology displayed by the acutely destroyed Golgi neurons was a classical oedematous necrosis, whereas most neurons vulnerable to the delayed and slow mechanisms displayed a ‘dark cell degeneration’, whose cytological features bore a close resemblance to those of neurons irreversibly damaged by ischaemia, hypoglycaemia or status epilepticus in vivo.
Expression of Human Neurofilament‐light Transgene in Mouse Neurons Transplanted into the Brain of Adult Rats
Authors: Vidal‐Sanz Manuel , Villegas‐Pérez Maria P. , Carter David A. , Julien Jean‐Pierre , Peterson Alan , Aguayo Albert J. 
Published: April 2006

AbstractTo investigate the expression of nerve cell‐specific transgene products in neural transplants, we implanted into the hippocampus of immunosuppressed adult Sprague – Dawley rats cell suspensions obtained from the septal region of the fetal brain of mice that carry the human neurofilament‐light (hNF‐L) gene. In grafts examined between 3 weeks and 7 months after transplantation, axons and nerve cell somata immunoreacted to antibodies specific to the human NF‐L subunit. Thus, the hNF‐L protein appears to be a suitable marker of these grafted neurons. Transgenic mice bearing the hNF‐L gene may be a convenient source of donor tissue or be used as hosts for neural transplantation studies. Furthermore, the hNF‐L promoter/enhancer elements in this transgene may help direct neuronal expression of heterologous genes that could influence nerve cell responses in either the transplant or host tissues.
Pharmacological and Electrophysiological Properties of Recombinant GABAA Receptors Comprising the α3, β1 and γ2 Subunits
Authors: Knoflach F. , Backus K. H. , Giller T. , Malherbe P. , Pflimlin P. , Möhler H. , Trube G. 
Published: April 2006

AbstractTo assess the role of subunits for channel function and drug modulation in recombinant GABAA receptors, the α3β1γ2 subunits and the dual combinations α3β1, β1γ2 and α3γ2 were expressed by transfection of human embryonic kidney cells and by RNA injection in Xenopus oocytes (α3β1γ2 combination). GABA‐induced chloride currents were recorded using the whole‐cell configuration of the patch‐clamp technique (transfected cells) or the voltage‐clamp technique (oocytes). The currents recorded from the α3β1Γ2 subunit combination in transfected cells were reduced by bicuculline and picrotoxin, enhanced by flunitrazepam in a flumazenil‐sensitive manner and reduced by β‐carboline‐3‐carboxylic acid methyl ester (β‐CCM). The GABA‐induced current was reduced by β‐CCM in all combinations containing the γ2 subunit, but potentiation by flunitrazepam was only obtained when the 72 subunit was coexpressed in the presence of the α3 subunit (α3β1γ2 or α3γ2). The GABA sensitivities of the receptors were similar when the α3β1γ2 combination was expressed in oocytes (half‐maximum effective concentration = 240 μM) or in the kidney cell line (270 μM). However, the currents were less potentiated by flunitrazepam in oocytes (129% of controls) than in transfected cells (189%). These results suggest that the α3β1γ2 subunit combination, which is coexpressed in various brain regions as shown by in situ hybridization histochemistry, may represent a building block of functional GABAA receptors in situ.
The Critical Period for Experience‐dependent Plasticity in a System of Binocular Visual Connections in Xenopus laevis: Its Extension by Dark‐rearing
Authors: Grant S. , Dawes E. A. , Keating M. J. 
Published: April 2006

AbstractFollowing surgical rotation of an eye, the Xenopus‘intertectal’ system is capable of a vision‐dependent alteration of its connectivity, that restores spatial registration of binocular maps on the optic tectum. In the preceding paper (Keating and Grant, Eur. J. Neurosci., 4, 27–36, 1992), we reported that this capacity undergoes a progressive, age‐dependent restriction during a critical period around the time of metamorphosis, so that rotations produced in animals aged 3 months postmetamorphosis normally evoke no such alteration of the system. Here we examine whether this restriction is rigidly age‐dependent or whether vision can influence its profile. We report that in animals dark‐reared from embryonic stage 35 through the critical period to 3 months, 1 year or even 2 years after metamorphosis, rotations instituted at those ages now result in intertectal reorganization if a period of normal vision is allowed after the operation. Similarly, intertectal alteration was also seen in animals eye‐rotated at larval stage 58, then dark‐reared just for the duration of the critical period, and subsequently returned, at 3 months of age, to a normal visual environment. We conclude, therefore, that the normal developmental restriction in the plasticity of the Xenopus intertectal system is not strictly age‐dependent, but that vision contributes to the process by activating the underlying plasticity mechanisms.
Calbindin‐D28K (CaBP28k)‐like Immunoreactivity in Ascending Projections
Authors: Menètrey D. , de Pommery J. , Baimbridge K. G. , Thomasset M. 
Published: April 2006

AbstractThis study concerns the involvement of calbindin‐D28K (CaBP28k)‐containing neurons in the efferent projections of both the trigeminal nucleus caudalis and the dorsal vagal complex (nucleus of the solitary tract and area postrema) in rats. Recent evidence has shown that these projections are particularly important for the processing of visceroception and/or nociception at central levels. The trigeminal nucleus caudalis has dense projections to both the nucleus of the solitary tract and the parabrachial area; the dorsal vagal complex is intimately connected to the parabrachial area. CaBP28k is a calcium‐binding protein the function of which could be a determining factor in controlling the excitability of cells by acting on intrinsic calcium metabolism. CaBP28k content of projections was ascertained using a double labelling approach that combined the retrograde transport of a protein ‐ gold complex to identify projection cells and immunocytochemistry to identify CaBP28k‐positive cells. The trigeminal nucleus caudalis is rich in both CaBP28k‐immunoreactive cells and cells projecting to the parabrachial area or the nucleus of the solitary tract. Cells containing both the protein and the retrograde tracer, however, were mostly restricted to the superficial layers (laminae I and outer II) and to their rostral extensions, the dorsal paramarginal and paratrigeminal nuclei. These trigeminal subdivisions are targets for nociceptive, visceroceptive and thermal inputs of peripheral origins. The dorsal vagal complex is rich in CaBP28k. Dense populations of immunoreactive cells are observed in the ventrolateral part of the area postrema and all of the three main subdivisions of the nucleus of the solitary tract (rostral gustatory, ventrolateral respiratory and medial cardiovascular subregions). The subnucleus commissuralis, subnucleus centralis and dorsal subnuclei are particularly densely stained. The subnucleus centralis, which is involved in regulating food and water intake, does not project to the parabrachial area. The area postrema, subnucleus commissuralis and dorsal subnuclei, which are implicated in cardiovascular and/or ingestive behaviours, have dense projections to the parabrachial area, many of which contain CaBP28k. The present results demonstrate that CaBP28k‐containing cells form a major part of the solitary and trigeminal projection systems, including subregions that are involved in visceroception and/or nociception processing. The location of solitary nucleus projection cells overlaps those of some neuropeptidergic projecting populations, suggesting colocalization. Consequently, certain neuropeptidergic actions may be CaBP28k‐dependent.