bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Vivo Regulation of Amyloid Precursor Protein Secretion in Rat Neocortex by Cholinergic Activity
Authors: Rossner Steffen , Ueberham Uwe , Yu Juan , Kirazov Ludmil , Schliebs Reinhard , Perez‐Polo J. Regino , Bigl Volker 
Published: April 2006

AbstractThe proteolytic cleavage of the amyloid precursor protein (APP) has been shown to be modulated through specific muscarinic receptor activation in vitro in both transfected cell lines and native brain slices, whereas a demonstration of receptor‐mediated control of APP processing under in vivo conditions is still lacking. To simulate alterations in muscarinic receptor stimulation in vivo, we have (i) specifically reduced the cortical cholinergic innervation in rats using partial immunolesions with 192lgG–saporin, and (ii) restored cholinergic function in lesioned rats by transplantation of nerve growth factor producing fibroblasts. While total APP levels in cortical homogenates were unaffected by cholinergic deafferentation, we observed a significant reduction in the abundance of secreted APP and a concomitant increase in membrane‐bound APP. These changes were reversed in immunolesioned rats with nerve growth factor‐producing fibroblasts. There was a strong positive correlation between the ratio of secreted APP to membrane‐bound APP and the activity of choline acetyltransferase and M1 muscarinic acetylcholine receptor density (measured by [3H]pirenzepine binding) in experimental groups. Additionally, we observed a transient decrease in the ratio of cortical APP transcripts containing the Kunitz protease inhibitor domain (APP 770 and APP 751) versus APP 695 in rats with cholinergic hypoactivity. The data presented suggest that cortical APP processing is under basal forebrain cholinergic control, presumably mediated through M1 muscarinic acetylcholine receptors on cholinoceptive cortical target cells.
Neuropeptide Y and the Calcitonin Gene‐related Peptide Attenuate Learning Impairments Induced by MK‐801 via a Sigma Receptor‐related mechanism
Authors: Bouchard Pascale , Maurice Tangui , St‐Pierre Serge , Privat Alain , Quirion Rémi 
Published: April 2006

AbstractIt has been shown recently that low doses of sigma (σ) receptor ligands like 1,3‐di‐(2‐tolyl)guanidine (DTG), (+)N‐allylnormetazocine [(+)SKF 10 047] and (+)pentazocine can antagonize learning impairments induced by dizocilpine (MK‐801), a non‐competitive antagonist at the NMDA receptor channel. This antagonism has been proposed to involve σ receptor sites since it is blocked by the administration of purported o antagonists such as NE‐100 and BMY‐14802. It has also been demonstrated that peptides of the neuropeptide Y (NPY) and calcitonin gene‐related peptide (CGRP) families modulate, in vivo, é labelling and electrophysiological effects in the hippocampal formation. Accordingly, we investigated if NPY‐ and CGRP‐related peptides modulate cognitive processes by interacting with σ sites in mice. In order to test this hypothesis, a step‐down passive avoidance task was used. Interestingly, similarly to various σ agonists, NPY, peptide YY (PYY) and the Y1 agonist [Leu31Pro34]NPY (but not NPY13–36, a purported Y2 agonist), as well as hCGRPα and the purported CGRP2 agonist [CyS(ACM)2–7]hCGRPα (but not CGRP8–37, a CGRP1 receptor antagonist), significantly attenuated learning impairments induced by MK‐801. Furthermore, the effects of NPY, [Leu31 Pro34]NPY, hCGRPα and [CYS(ACM)2–7]hCGRPα were blocked by the administration of the σ antagonist, BMY‐14802. The present data suggest that NPY‐ and CGRP‐related peptides can indirectly interact in vivo with σ receptors to modulate cognitive processes associated with NMDA receptor function.
TrkA Expression Levels of Sympathetic Neurons Correlate with NGF‐dependent Survival During Development and After Treatment with Retinoic Acid
Authors: Holst Alexander V. , Lefcort Frances , Rohrer Hermann 
Published: April 2006

AbstractSympathetic neurons depend on the classical neurotrophin nerve growth factor (NGF) for survival by the time they innervate their targets, but not before. The acquisition of NGF responsiveness is thought to be controlled by environmental cues in sympathetic neurons. We have investigated the expression of the signal transducing NGF receptor trkA on mRNA and protein level during development of chick sympathetic neurons obtained from lumbosacral, paravertebral chain ganglia between embryonic days (E) 6.5 and 10. We demonstrate that trkA mRNA levels increase between E6.5 and E10, whereas the levels of trkC and p75 do not change. We also observed a similar increase in trkA protein during this time period. This increase correlates with the increase in NGF‐dependent survival of sympathetic neurons from the corresponding stages in vitro. To define the correlation between trkA expression and NGF‐mediated survival in more detail, trkA expression was adjusted to different levels by treatment with increasing concentrations of retinoic acid. We observed that small changes of trkA mRNA expression levels, below one order of magnitude, are decisive for the ability of immature sympathetic neurons to survive in the presence of NGF. A small and transient increase in trkA mRNA expression was also elicited in vivo by application of retinoids. These data provide evidence that sympathetic neurons upregulate the NGF receptor trkA and in this way acquire NGF‐dependency.
ω‐Agatoxin IVA, a P‐Type Calcium Channel Antagonist, Reduces Nociceptive Processing in Spinal Cord Neurons with Input From the Inflamed But Not From the Normal Knee Joint — An Electrophysiological Study in the Rat In Vivo
Authors: Nebe J. , Vanegas H. , Neugebauer V. , Schaible H.‐G. 
Published: April 2006

AbstractHigh threshold voltage‐dependent P‐ and Q‐type calcium channels are involved in neurotransmitter release. In order to investigate the role of P‐ and Q‐type calcium channels in the mechanosensory (nociceptive) processing in the spinal cord, their participation in the responses of spinal wide‐dynamic‐range neurons to innocuous and noxious mechanical stimulation of the knee and ankle joints was studied in 30 anaesthetized rats. The knee was either normal or acutely inflamed by kaolin/carrageenan. During the topical application of ω‐agatoxin IVA (P‐type channel antagonist, 0.1 μM) onto the dorsal surface of the spinal cord, the responses to innocuous and noxious pressure applied to the normal knee were increased to respectively 124 ± 42% and 114 ± 23% of predrug values (mean ± SD, P < 0.05, 14 neurons). By contrast, in rats with an inflamed knee, the responses to innocuous and noxious pressure applied to the knee were reduced to respectively 72 ± 19 and 73 ± 22% of baseline (mean ± SD, P < 0.01, 13 neurons). In the same neurons, ω‐agatoxin IVA slightly increased the responses to pressure on the non‐inflamed ankle whether the knee was normal or inflamed. Thus P‐type calcium channels seem to acquire a predominant importance in the excitation of spinal cord neurons by mechanosensory input from inflamed tissue and hence in the generation of inflammatory pain. By contrast, the Q‐type channel antagonist, ω‐conotoxin MVllC (1 or 100 μM), had no significant effect upon responses to innocuous or noxious pressure applied to either normal or inflamed knees (25 neurons).
AMPA Receptors in Cultured Vestibular Ganglion Neurons: Detection and Activation
Authors: Rabejac Denis , Devau Gina , Raymond Jacqueline 
Published: April 2006

AbstractThe presence and the activity of α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole propionic acid (AMPA) glutamate receptors were investigated in mouse cultured vestibular ganglion neurons using immunocytochemistry and measurement of intracellular calcium concentration ([Ca2+],) by spectrofluorimetry. Cultures of dissociated vestibular ganglia from 18 gestation day mouse embryos were grown in vitro for 3–4 days. lmmunocytochemical labelling of AMPA receptor subunits GluR2/R3 and GluR4 was detected in neuron cell bodies and proximal neurites and more lightly in glial cells. There was no clear selective subcellular localization of the different subunits. For the GluR1 subunit a signal was observed only in some neurons and neurites and was weak. Vestibular ganglion neurons responded to fast application of 1 mM glutamate and 10 mM aspartate through unknown receptors by a transient increase in [Ca2+]i. The mean amplitude of this rapid increase was about nine times the resting level and recovery was complete within 30–45 s after the application. If separated by an interval of at least 10 min, consecutive applications produced similar calcium responses. AMPA (1 mM) application induced the same type of responses. Five minutes prior to the AMPA exposure, the application of a specific AMPA antagonist, 6, 7‐dinitroquinoxaline‐2, 3‐dione (DNQX, 1.5 mM), in the external medium inhibited the response to AMPA. Chelation of external calcium by EGTA (1.5 mM) abolished the responses to drug applications, indicating that an influx of external calcium is involved in the [Ca2+]i increase. These observations suggest that heteromeric AMPA receptors are expressed in vestibular ganglion neurons in culture and play a functional role in their glutamate‐induced depolarization. Experiments are in progress using specific AMPA and NMDA antagonists to characterize the participation of the two types of ionotropic glutamate receptors in the glutarnate/aspartate‐induced intracellular calcium response.
Effects of Inferior Temporal Lesions on Two Types of Orientation Discrimination in the Macaque Monkey
Authors: Vogels Rufin , Saunders Richard C. , Orban Guy A. 
Published: April 2006

AbstractRhesus monkeys with transection of the forebrain commissures were trained in two different tasks in which grating orientation was the discriminandum. In the temporal same—different task, the monkeys had to judge whether or not two successively presented gratings differed in orientation. In the identification task, we measured how well the monkey could judge the orientation of the grating. The performance in any task was affected neither by a unilateral anterior temporal cortical area lesion nor by a subsequent posterior temporal cortical area lesion in the same hemisphere resulting in a two‐stage inferior temporal (IT) lesion. However, a single stage IT (combined anterior and posterior temporal cortical areas) lesion of the other hemisphere severely disrupted the performance in the temporal same‐different task, but only barely increased just noticeable differences in orientation in the identification task. This indicates that the impairment in a temporal comparison task after an IT lesion is not due to a perceptual coding deficit, but is related to the temporal comparison per se. Thus, IT is involved in the temporal comparison of successively presented stimuli. On the other hand, the two IT lesions, each having a different history (single versus two stage) had dramatically different behavioural effects, suggesting an important role for adult brain plasticity in determining the behavioural outcome of a brain lesion.
Human Brain Activity Related to Orientation Discrimination Tasks
Authors: Orban Guy A. , Dupont Patrick , Vogels Rufin , Bormans Guy , Mortelmans Luc 
Published: April 2006

AbstractIn order to relate regional activity in the human brain to the different components of discrimination tasks, we compared regional cerebral blood flow, measured with positron emission tomography, under four conditions: successive orientation discrimination, orientation identification, detection and passive viewing. By adding successive discrimination and passive viewing at a second, lower rate we were able to investigate the main effects and interaction between task and presentation rate. Four occipital regions—the posterior calcarine region bilaterally, the right lingual gyrus and the right inferior occipital cortex‐displayed a main effect of presentation rate. Two regions—a right posterolateral occipital region and a right posterior fusiform region—displayed a significant main effect of task. The involvement of this posterior fusiform region in successive discrimination was also revealed by the subtraction of detection from successive discrimination, as was that of the right middle fusiform gyrus. Finally, a more anterior right middle fusiform region was differentially active in successive discrimination compared to identification, suggesting that activity in this region is related to the temporal comparison of orientation.
Positive Correlations Between Cerebral Protein Synthesis Rates and Deep Sleep in Macaca mulatta
Authors: Nakanishi Hajime , Sun Yun , Nakamura Richard K. , Mori Kentaro , Ito Masanori , Suda Sumio , Namba Hiroki , Storch Fredric I. , Dang Thao P. , Mendelson Wallace , Mishkin Mortimer , Kennedy Charles , Gillin J. Christian , Smith Carolyn Beebe , Sokoloff Louis 
Published: April 2006

AbstractLocal rates of cerebral protein synthesis (ICPSleu), were determined with the autoradiographic L‐[1‐14C]leucine method in seven awake and seven asleep, adult rhesus monkeys conditioned to sleep in a restraining chair in a darkened, ventilated chamber while EEG, EOG, and EMG were monitored. Prior to the period of measurement all animals slept for 1–4 h. Controls were awakened after at least one period of rapid‐eye‐movement (REM) sleep. Experimental animals were allowed to remain asleep, and they exhibited non‐REM sleep for 71–99% of the experimental period. Statistically significant differences in ICPSleu between control and experimental animals were found in four of the 57 regions of brain examined, but these effects may have occurred by chance. In the sleeping animals, however, correlations between ICPSleu, and percent time in deep sleep were positive in all regions and were statistically significant (P≤ 0.05) in 35 of the regions. When time in deep sleep was weighted for the integrated specific activity of leucine in grey matter, positive correlations were statistically significant (P≤ 0.05) in 18 regions in the experimental animals. These results suggest that rates of protein synthesis are increased in many regions of the brain during deep sleep compared with light sleep.
Activation of the GABAA Receptor Inhibits the Proliferative Effects of bFGF in Cortical Progenitor Cells
Authors: Antonopoulos J. , Pappas I. S. , Parnavelas J. G. 
Published: April 2006

AbstractRecent studies have localized γ‐aminobutyric acid (GABA)‐containing neurons and identified cells that express subunits of the GABAA receptor in the proliferative zone of the developing cerebral cortex and have demonstrated a role for GABA in cortical neurogenesis. We examined here the interactions between a number of neurotrophic factors, known to be involved in cortical cell proliferation and differentiation, and the GABAergic system (GABA and GABAA receptors) in the regulation of cell production in dissociated cortical cell cultures. We found that basic fibroblast growth factor (bFGF) increased the number of cells labelled for the α1 subunit of the GABAA receptor but not for the α2, α3 or α5 subunits. The α1 subunit was expressed by the majority of proliferating neuroepithelial cells as well as by differentiated neurons. We also found that activation of the GABAA receptor by GABA or muscimol inhibited the proliferative effects of bFGF on cortical progenitors, leading to an increased number of differentiated neurons. These results suggest that bFGF stimulates cell proliferation and GABAA receptor expression in cultured progenitor cells of the developing neocortex, and that GABA regulates cell production by providing a feedback signal that terminates cell division.
The Effects of Light Reversals on Photoreceptor Synaptogenesis in the Fly Musca domestica
Authors: Rybak J. , Meinertzhagen I. A. 
Published: April 2006

AbstractThe short‐term influence of visual experience was studied in the first‐order tetrad synapses of the first optic neuropil, or lamina, underlying the compound eye in the housefly (Musca domestica). We report the effects of single light reversals, in which flies reared in constant darkness were exposed to light or those in constant light were exposed to darkness, on this defined population of synapses. The synaptic population was characterized by quantitative electron microscopic methods using three parameters: (i) the number of synaptic contacts per photoreceptor terminal; (ii) the size of these synapses, given by the mean platform width of their presynaptic ribbons; and (iii) the proportion (up to ˜20%) of small synapses—those having a ribbon platform less than 0.17 μm wide. The effects of light exposures in'flies reared in constant darkness include decreased mean synaptic size and increased numbers of synapses. These effects are seen in flies of all ages (to 10 days). Long light exposures (2–6 h) are much less effective than short exposures (down to 20 s), with maximum effects obtained at 15 min (up to 45% more synapses). Small synapses are reasoned to be new junctions formed only recently; the decreased mean synaptic size and the increased number of synapses seen after short light exposures are both interpreted to result from a recent burst of synaptogenesis in the adult lamina. The effects of dark exposure in flies reared in constant light are the reciprocal of those seen in dark‐reared flies exposed to light, but they are less pronounced. Although the function of such changes is not yet known, they may form part of the light adaptation mechanism of the photoreceptor, and occur along with a redistribution of other organelles involving membrane invaginations into its terminal. These changes occur against a background trend for control flies reared under constant conditions to have fewer, larger synapses with increasing age up to 10 days, an effect that is most pronounced in constant darkness, when synaptic number decreases by 21% and size increases by 13%.
Significance of the Paralemniscal Tegmental Area for Audio‐motor Control in the Moustached Bat, Pteronotus p. parnellii: The Afferent and Efferent Connections of the Paralemniscal Area
Authors: Schuller G. , Fischer S. , Schweizer H. 
Published: April 2006

AbstractThe paralemniscal tegmental area has been determined in the brain of the New World moustached bat, Pteronotus p. parnellii, by electrical microstimulation eliciting echolocation calls and pinna movements. It is located in the dorsal tegmentum rostral and medial to the dorsal nucleus of the lateral lemniscus and is characterized by medium sized and large neurons. Tracer injections (WGA‐HRP) showed that the most intense input to the paralemniscal tegmental area originates in the intermediate and deep layers of the homolateral superior colliculus. The strong projections from the ipsi‐ and contralateral nucleus praepositus hypoglossus most probably contributes vestibular information. Further inputs in descending order of intensity are from the substantia nigra, the contralateral paralemniscal tegmental area, the putamen, the ventral reticular formation in its lateral portions, the medial cerebellar nucleus and the dorsal reticular formation. Efferent projections of the paralemniscal tegmental area reach the putamen bilaterally, the nucleus accumbens and other parts of the basal ganglia, the pretectal area, the substantia nigra, the intermediate and deep layers of the superior colliculus bilaterally and the tegmental area ventral to it. Connections to the dorsal part of the periaqueductal grey, the cuneiform nucleus and the parabrachial region are important in the context of vocal control, whereas projections to the medial portion of the contralateral facial nucleus may interfere with the control of pinna movement. The findings suggest that the paralemniscal tegmental area is involved in audio‐motor control of vocalization and pinna movements in bats; connectional and functional similarities and disparities to tegmental regions described in other mammals are discussed.
Localization, Differential Expression and Retrograde Axonal Transport Suggest Physiological Role of FGF‐2 in Spinal Autonomic Neurons of the Rat
Authors: Blottner Dieter , Stapf Christian , Meisinger Christof , Grothe Claudia 
Published: April 2006

AbstractFibroblast growth factor‐2 (FGF‐2) has marked pharmacological neurotrophic effects on lesioned spinal autonomic neurons following target removal of the adrenal medulla, yet expression and axonal transport in autonomic neurons remain to be shown. We show here FGF‐2 and FGF receptor type 1 (FGFR1) protein and mRNA expression in preganglionic intermediolateral neurons of the rat thoracic spinal cord. While immunoreactivity of both FGF‐2 and FGFR1 co‐localize to intermediolateral neurons, mRNA transcripts of FGFR1, but not of FGF‐2, are detectable in intermediolateral preparations by RNase protection analysis, suggesting protein translocation in viva Unilateral microinjection of 125iodinated FGF‐2 into the adrenal medulla (a major target of intermediolateral neurons) results in significant accumulation of specific radioactivity in thoracic spinal cord tissue, including the intermediolateral neurons, and the ipsilateral splanchnic nerve. Emulsion autoradiography demonstrated labelling over ipsilateral intermediolateral neurons only. Neuronal co‐localization of FGF‐2/FGFR1 protein, differential mRNA expression, specific retrograde axonal transport and the known neurotrophic actions in vivo, strongly suggest unique physiological roles of FGF‐2 in the autonomic nervous system.
Representations of Graphomotor Trajectories in the Human Parietal Cortex: Evidence for Controlled Processing and Automatic Performance
Authors: Seitz Rüdiger J. , Canavan Anthony G. M. , Yágüez Lidia , Herzog Hans , Tellmann Lutz , Knorr Uwe , Huang Yanxiong , Hömberg Volker 
Published: April 2006

AbstractThe aim of this study was to identify the cerebral areas activated during kinematic processing of movement trajectories. We measured regional cerebral blood flow (rCBF) during learning, performance and imagery of right‐hand writing in eight right‐handed volunteers. Compared with viewing the writing space, increases in rCBF were observed in the left motor, premotor and frontomesial cortex, and in the right anterior cerebellum in all movement conditions, and the increases were related to mean tangential writing velocity. No rCBF increases occurred in these areas during imagery. Early learning of new ideomotor trajectories and deliberately exact writing of letters both induced rCBF increases in the cortex lining the right intraparietal sulcus. In contrast, during fast writing of overlearned trajectories and in the later phase of learning new ideograms the rCBF increased bilaterally in the posterior parietal cortex. Imagery of ideograms that had not been practised previously activated the anterior and posterior parietal areas simultaneously. Our results provide evidence suggesting that the kinematic representations of graphomotor trajectories are multiply represented in the human parietal cortex. It is concluded that different parietal subsystems may subserve attentive sensory movement control and whole‐field visuospatial processing during automatic performance.