bluuebunny/crossref_metadata_2025_split huggingface dataset:
Subpial neuronal migration in the medulla oblongata of Pax‐6‐deficient rats
Authors: Horie Masao , Sango Kazunori , Takeuchi Kosei , Honma Shizuka , Osumi Noriko , Kawamura Koki , Kawano Hitoshi 
Published: March 2003

AbstractIn rat fetuses, neurons generated in the lower rhombic lip on embryonic day 14 (E14) specifically express the transcription factor Pax‐6 and migrate circumferentially in the subpial region along axons which are immunoreactive for TAG‐1, a neural cell adhesion molecule. These neurons ultimately settle from E17 in the contralateral medulla oblongata to form the precerebellar nuclei, the lateral reticular and external cuneate nuclei. We have examined this migratory process in rat small eye (rSey2) which has a mutation in the Pax‐6 gene. Both the migration and settlement of neurons labelled with 5‐bromo‐2′‐deoxyuridine (BrdU) at E14 delayed in the mutant. Furthermore, in the ventrolateral part of the E16 mutant medulla oblongata, cells both expressing Pax‐6 mRNA and prelabelled with BrdU at E14 were ectopically localized in the deep zone of the medullary parenchyma in addition to the normal subpial location. These ectopic neurons remained in close contact with ectopic TAG‐1‐immunoreactive axons. These results indicate that Pax‐6 plays a role in the migration of medullary precerebellar neurons, although neurons generated in the lower rhombic lip can nevertheless migrate and settle to form the external cuneate nucleus in the absence of Pax‐6.
The mouse VPAC2 receptor confers suprachiasmatic nuclei cellular rhythmicity and responsiveness to vasoactive intestinal polypeptide in vitro
Authors: Cutler David J. , Haraura Mai , Reed Helen E. , Shen Sanbing , Sheward W. John , Morrison Christine F. , Marston Hugh M. , Harmar Anthony J. , Piggins Hugh D. 
Published: March 2003

AbstractExpression of coherent and rhythmic circadian (≈ 24 h) variation of behaviour, metabolism and other physiological processes in mammals is governed by a dominant biological clock located in the hypothalamic suprachiasmatic nuclei (SCN). Photic entrainment of the SCN circadian clock is mediated, in part, by vasoactive intestinal polypeptide (VIP) acting through the VPAC2 receptor. Here we used mice lacking the VPAC2 receptor (Vipr2−/−) to examine the contribution of this receptor to the electrophysiological actions of VIP on SCN neurons, and to the generation of SCN electrical firing rate rhythms SCN in vitro. Compared with wild‐type controls, fewer SCN cells from Vipr2−/− mice responded to VIP and the VPAC2 receptor‐selective agonist Ro 25‐1553. By contrast, similar proportions of Vipr2−/− and wild‐type SCN cells responded to gastrin‐releasing peptide, arginine vasopressin or N‐methyl‐d‐aspartate. Moreover, VIP‐evoked responses from control SCN neurons were attenuated by the selective VPAC2 receptor antagonist PG 99‐465. In firing rate rhythm experiments, the midday peak in activity observed in control SCN cells was lost in Vipr2−/− mice. The loss of electrical activity rhythm in Vipr2−/− mice was mimicked in control SCN slices by chronic treatment with PG 99‐465. These results demonstrate that the VPAC2 receptor is necessary for the major part of the electrophysiological actions of VIP on SCN cells in vitro, and is of fundamental importance for the rhythmic and coherent expression of circadian rhythms governed by the SCN clock. These findings suggest a novel role of VPAC2 receptor signalling, and of cell‐to‐cell communication in general, in the maintenance of core clock function in mammals, impacting on the cellular physiology of SCN neurons.
PACAP and NGF regulate common and distinct traits of the sympathoadrenal lineage: effects on electrical properties, gene markers and transcription factors in differentiating PC12 cells
Authors: Grumolato Luca , Louiset Estelle , Alexandre David , Aït‐Ali Djida , Turquier Valérie , Fournier Alain , Fasolo Aldo , Vaudry Hubert , Anouar Youssef 
Published: March 2003

AbstractTo determine the possible role of pituitary adenylate cyclase‐activating polypeptide (PACAP) in the development of the sympathoadrenal cell lineage, we have examined the effects of this neurotrophic peptide, in comparison to nerve growth factor (NGF), on the morphology, electrophysiological properties, expression of neuronal and neuroendocrine marker genes, and activity of transcription factors during differentiation of sympathoadrenal‐derived cells, using the rat pheochromocytoma PC12 cell model. Both PACAP and NGF elicited rapid neurite outgrowth, which was accompanied by induction of cell excitability and the development of both sodium and calcium currents. Concurrently, PACAP and NGF increased the expression of a marker of synaptic vesicles. By contrast, PACAP, but not NGF, regulated the expression of different constituents of neuroendocrine large dense core vesicles in PC12 cells. Furthermore, PACAP and NGF differentially regulated the expression of mammalian achaete‐scute homologue and paired homeobox 2b genes, transcription factors instrumental for sympathoadrenal development. To compare downstream effectors activated by PACAP and NGF, we studied the effects of these factors on the binding activity of consensus 12‐O‐tetradecanoylphorbol‐13‐acetate‐ and cAMP‐responsive elements to nuclear extracts of differentiating PC12 cells. We found that both PACAP and NGF markedly increase the binding activity of these cis‐regulatory sequences and that PACAP preferentially recruits activator protein‐1‐like transcription factors to these elements. Taken together, these results show that PACAP and NGF exert common as well as different effects on neuronal and neuroendocrine traits in differentiating PC12 cells, strongly suggesting that these two trophic factors could play complementary roles in the development of the sympathoadrenal cell lineage.
Developmental and circadian changes in Ca2+ mobilization mediated by GABAA and NMDA receptors in the suprachiasmatic nucleus
Authors: Ikeda Masayuki , Yoshioka Tohru , Allen Charles N. 
Published: March 2003

AbstractThe hypothalamic suprachiasmatic nucleus (SCN) develops as the circadian pacemaker during postnatal life. Although both GABAA and NMDA receptors are expressed in the majority of SCN neurons, postnatal development of their functions has not been analysed. Thus, we studied the receptor‐mediated Ca2+ responses in mouse hypothalamic slices prepared on postnatal days (P) 6–16. The NMDA‐induced Ca2+ flux was prominent in the SCN and maximal Ca2+ responses in Mg2+‐free conditions had no day–night variations in P14–16 mice. At P6–7, extracellular Mg2+ reduced the NMDA‐induced Ca2+ flux irrespective of the circadian time whereas, after P9–10, Mg2+ produced a larger reduction at night than during the daytime. Muscimol also significantly increased Ca2+ in the developing SCN. Voltage‐sensitive Ca2+ channel blockers inhibited the muscimol‐induced Ca2+ increase whereas tetrodotoxin had no effect, suggesting that stimulation of postsynaptic GABAA receptors depolarizes SCN neurons to increase Ca2+. Macroscopic imaging analysis demonstrated a developmental reduction in the muscimol‐induced Ca2+ increase preferentially in the nighttime group older than P9–10. The day–night variation in the magnitude of the Ca2+ response was due to two cell populations, one of which exhibited an increase and the other a decrease in Ca2+ in response to muscimol. Because the critical developmental stages for exhibiting day–night variations in the receptor‐mediated Ca2+ responses overlapped the maturation of firing rhythms in SCN neurons, the Ca2+ signalling may be necessary for or regulated by the mature circadian clock.
Modulation of ACh release by presynaptic muscarinic autoreceptors in the neuromuscular junction of the newborn and adult rat
Authors: Santafé Manel M. , Salon Isabel , Garcia Neus , Lanuza M. Angel , Uchitel Osvaldo D. , Tomàs Josep 
Published: March 2003

AbstractWe studied the presynaptic muscarinic autoreceptor subtypes controlling ACh release and their relationship with voltage‐dependent calcium channels in the neuromuscular synapses of theLevator auris longusmuscle from adult (30–40 days) and newborn (3–6 and 15 days postnatal) rats. Using intracellular recording, we studied how several muscarinic antagonists affected the evoked endplate potentials. In some experiments we previously incubated the muscle with calcium channel blockers (nitrendipine, ω‐conotoxin‐GVIA and ω‐Agatoxin‐IVA) before determining the muscarinic response. In the adult, the M1 receptor‐selective antagonist pirenzepine (10 µm) reduced evoked neurotransmission (≈ 47%). The M2 receptor‐selective antagonist methoctramine (1 µm) increased the evoked release (≈ 67%). Both M1‐ and M2‐mediated mechanisms depend on calcium influx via P/Q‐type synaptic channels. We found nothing to indicate the presence of M3 (4‐DAMP‐sensitive) or M4 (tropicamide‐sensitive) receptors in the muscles of adult or newborn rats. In the 3–6‐day newborn rats, pirenzepine reduced the evoked release (≈ 30%) by a mechanism independent of L‐, N‐ and P/Q‐type calcium channels, and the M2 antagonist methoctramine (1 µm) unexpectedly decreased the evoked release (≈ 40%). This methoctramine effect was a P/Q‐type calcium‐channel‐dependent mechanism. However, upon maturation in the first two postnatal weeks, the M2 pathway shifted to perform the calcium‐dependent release‐inhibitory activity found in the adult. We show that the way in which M1 and M2 muscarinic receptors modulate neurotransmission can differ between the developing and adult rat neuromuscular synapse.
Glutamate transporters in the guinea‐pig cochlea: partial mRNA sequences, cellular expression and functional implications
Authors: Rebillard G. , Ruel J. , Nouvian R. , Saleh H. , Pujol R. , Dehnes Y. , Raymond J. , Puel J. L. , Devau G. 
Published: March 2003

AbstractIn the cochlea, glutamate plays a major role in synaptic transmission between the inner hair cell and the primary auditory neurons. Extracellular glutamate concentration must be regulated to prevent excitotoxicity. This regulation is mediated by excitatory amino acid transporters, membrane proteins that remove glutamate from the synaptic cleft. In this study, we investigated the distribution and activity of three excitatory amino acid transporters subtypes in the guinea‐pig cochlea: glutamate aspartate transporter, glutamate transporter and excitatory amino acid carrier. A partial messenger ribonucleic acid sequence was determined for each of these transporters, by polymerase chain reaction with degenerate primers, using guinea‐pig brain complementary deoxyribonucleic acid as the template. Primers specific for each transporter were then designed and used to screen a dissected organ of Corti complementary deoxyribonucleic acid library. The cellular distribution of each transporter was examined by immunocytochemistry. We investigated the functional consequences of inhibiting glutamate uptake by recording cochlear potentials during intracochlear perfusion with either l‐trans‐pyrrolidine‐2,4‐dicarboxylic acid or dihydrokainate. At the end of the electrophysiological session, cochleas were processed for electron microscopy. Only the glutamate aspartate transporter messenger ribonucleic acid was detected in the organ of Corti. Consistently, glutamate aspartate transporter protein was detected in the inner hair cell‐supporting cells and in the ganglion of Corti satellite cells. Glutamate transporter and excitatory amino acid carrier were found in the afferent auditory neurons. Only intracochlear perfusions with l‐trans‐pyrrolidine‐2,4‐dicarboxylic acid resulted in a dose‐dependent decrease in the amplitude of the cochlear compound action potential, leaving cochlear microphonic potential unaffected. After l‐trans‐pyrrolidine‐2,4‐dicarboxylic acid perfusion, cochleas displayed a swelling of the afferent endings typical of excitotoxicity. [(–)1‐(4‐aminophenyl)‐4‐methyl‐7,8‐methylenedioxy‐4,5‐dihydro‐3‐methylcarbamyl‐2,3‐benzodiazepine], a selective α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionic acid receptor antagonist protects the cochlea against l‐trans‐pyrrolidine‐2,4‐dicarboxylic acid effect.
Patterns of calcium‐binding proteins support parallel and hierarchical organization of human auditory areas
Authors: Chiry Oriana , Tardif Eric , Magistretti Pierre J. , Clarke Stephanie 
Published: March 2003

AbstractThe human primary auditory cortex (AI) is surrounded by several other auditory areas, which can be identified by cyto‐, myelo‐ and chemoarchitectonic criteria. We report here on the pattern of calcium‐binding protein immunoreactivity within these areas. The supratemporal regions of four normal human brains (eight hemispheres) were processed histologically, and serial sections were stained for parvalbumin, calretinin or calbindin. Each calcium‐binding protein yielded a specific pattern of labelling, which differed between auditory areas. In AI, defined as area TC [see C. von Economo and L. Horn (1930) Z. Ges. Neurol. Psychiatr.,130, 678–757], parvalbumin labelling was dark in layer IV; several parvalbumin‐positive multipolar neurons were distributed in layers III and IV. Calbindin yielded dark labelling in layers I–III and V; it revealed numerous multipolar and pyramidal neurons in layers II and III. Calretinin labelling was lighter than that of parvalbumin or calbindin in AI; calretinin‐positive bipolar and bitufted neurons were present in supragranular layers. In non‐primary auditory areas, the intensity of labelling tended to become progressively lighter while moving away from AI, with qualitative differences between the cytoarchitectonically defined areas. In analogy to non‐human primates, our results suggest differences in intrinsic organization between auditory areas that are compatible with parallel and hierarchical processing of auditory information.
Expression of the circadian clock gene Period 1 in neuroendocrine cells: an investigation using mice with a Per1::GFP transgene
Authors: Kriegsfeld Lance J. , Korets Ruslan , Silver Rae 
Published: March 2003

AbstractThe circadian clock located in the suprachiasmatic nuclei (SCN) of the hypothalamus regulates daily temporal organization in behaviour and neuroendocrine function. The molecular basis for circadian rhythm generation is an interacting transcriptional/translational feedback loop comprised of several ‘clock genes’ and their respective protein products. Clock genes are expressed not only in the SCN but also in numerous other locations throughout the brain, including regions rich in neuroendocrine cells. In order to investigate whether neuroendocrine cells function as autonomous oscillators, we used female transgenic mice in which an unstable, degradable jellyfish green fluorescent protein (GFP) gene is driven by a mouse Period 1 (Per1) gene promoter. Mice were injected (s.c.) with fluorogold (FG) in order to label neuroendocrine cells and brain sections were double‐labelled for either FG and Per1 mRNA (labelled by GFP immunostaining) or FG and PER1 protein using fluorescence immunocytochemistry. Mice were killed during either the day or night. Neuroendocrine cells contained Per1 mRNA and PER1 protein in several brain regions with the greatest proportion of double‐labelled cells occurring in the arcuate nucleus (Arc). The number of neuroendocrine cells labelled was not affected by the stage of the estrous cycle. Fewer FG‐labelled cells expressed Per1 message and protein during the night compared to the day. In the Arc, staining for tyrosine hydroxylase revealed that neuroendocrine cells expressing Per1 message and protein were dopaminergic. Together, these findings suggest that neuroendocrine cells contain the molecular machinery necessary to oscillate independently. It remains to be determined whether these cells actually function as autonomous oscillators or whether these rhythms are driven by signals from the SCN. These findings also indicate that the endocrine system represents an opportunity to study the interactions between central (SCN and neuroendocrine cells) and peripheral circadian (endocrine gland) oscillators.
Neurogenesis in explants from the walls of the lateral ventricle of adult bovine brain: role of endogenous IGF‐1 as a survival factor
Authors: Pérez‐Martín M. , Cifuentes M. , Grondona J. M. , J. Bermúdez‐Silva F. , Arrabal P. M. , Pérez‐Fígares J. M. , Jiménez A. J. , García‐Segura L. M. ,   P. Fernández‐Llebrez
Published: March 2003

AbstractPrevious studies have shown the existence of proliferating cells in explants from bovine (Bos Taurus) lateral ventricle walls that were maintained for several days in vitro in the absence of serum and growth factors. In this study we have characterized the nature of new cells and have assessed whether the insulin‐like growth factor‐1 (IGF‐1) receptor regulates their survival and/or proliferation. The explants were composed of the ependymal layer and attached subependymal cells. Ependymal cells in culture were labelled with glial markers (S‐100, vimentin, GFAP, BLBP, 3A7 and 3CB2) and did not incorporate bromodeoxiuridine when this molecule was added to the culture media. Most subependymal cells were immunoreactive for βIII‐tubulin, a neuronal marker, and did incorporate bromodeoxiuridine. Subependymal neurons displayed immunoreactivity for IGF‐1 and its receptor and expressed IGF‐1 mRNA, indicating that IGF‐1 is produced in the explants and may act on new neurons. Addition to the culture media of an IGF‐1 receptor antagonist, the peptide JB1, did not affect the incorporation of bromodeoxiuridine to proliferating subependymal cells. However, JB1 significantly increased the number of TUNEL positive cells in the subependymal zone, suggesting that IGF‐1 receptor is involved in the survival of subependymal neurons. In conclusion, these findings indicate that neurogenesis is maintained in explants from the lateral cerebral ventricle of adult bovine brains and that IGF‐1 is locally produced in the explants and may regulate the survival of the proliferating neurons.
Blockade of HMG‐CoA reductase activity causes changes in microtubule‐stabilizing protein tau via suppression of geranylgeranylpyrophosphate formation: implications for Alzheimer's disease
Authors: Meske V. , Albert F. , Richter D. , Schwarze J. , Ohm T. G. 
Published: March 2003

AbstractHistopathologically, Alzheimer's disease is characterized by plaques and tangles that develop progressively over time. Experimental data described a statin‐induced decrease in β‐amyloid production, a major constituent of the plaques. Others reported data on statin‐mediated changes in neuronal survival and cytoskeleton, including the microtubule‐associated protein tau, a major constituent of the tangles. However, these latter reports remain contradictory. To clarify and extend our knowledge on the effect of statin on the cytoskeleton, we challenged rat primary neuron cultures by lovastatin and determined the metabolite that is critical for structural integrity and survival of neurons. During the blockade of 3‐hydroxy‐3‐methylglutaryl‐coenzyme A reductase, the neuritic network was affected and eventually was completely destroyed. This process was not part of the execution phase of apoptosis and was marked by alterations in the microfilament and microtubule system. The distribution and phosphorylation of protein tau changed. Immunoblot analysis and indirect immunofluorescence revealed a transient increase in tau phosphorylation, which ceased during the execution of apoptosis. All of these effects could be linked to the lack of the geranylgeranylpyrophosphate intermediate. Inhibition of the geranylgeranylation of Rho family GTPases (geranylgeranyl‐transferase I) evoked similar changes in neurons. These data and our findings that statin treatment reduced the membrane‐bound fraction of RhoA‐GTPase in neurons suggest that reduced levels of functional small G proteins are responsible for the observed effects. Our data demonstrate that lovastatin concentrations able to suppress not only cholesterol but also geranylgeranylpyrophosphate formation may evoke phosphorylation of tau reminiscent of preclinical early stages of Alzheimer's disease and, when prolonged, apoptosis.
Regulation of tyrosine hydroxylase levels and activity and Fos expression during opioid withdrawal in the hypothalamic PVN and medulla oblongata catecholaminergic cell groups innervating the PVN
Authors: Benavides Marta , Laorden M. Luisa , García‐Borrón J. Carlos , Milanés M. Victoria 
Published: March 2003

AbstractMorphine withdrawal increases the hypothalamic–pituitary–adrenocortical (HPA) axis activity, which is dependent on an hyperactivity of noradrenergic pathways innervating the hypothalamic paraventricular nucleus (PVN). However, the possible adaptive changes that can occur in these pathways during morphine dependence are not known. We studied the alterations in tyrosine hydroxylase (TH; the rate‐limiting enzyme in catecholamines biosynthesis) immunoreactivity levels and TH enzyme activity in the rat NTS‐A2/VLM‐A1 noradrenergic cell groups and in the PVN during morphine withdrawal. In the same paradigm, we measured Fos expression as a marker of neuronal activation. TH and Fos immunoreactivity was determined by quantitative Western blot analysis, combined with immunostaining for TH and Fos for immunohistochemical identification of active neurons during morphine withdrawal. Dependence on morphine was induced by a 7‐day s.c. implantation of morphine pellets. Morphine withdrawal was precipitated on day 8 by an injection of naloxone (5 mg/kg s.c.). Morphine withdrawal induced the expression of Fos in the PVN and NTS/VLM, which indicates an activation of neurons in these nuclei. TH immunoreactivity in the NTS/VLM was increased 90 min after morphine withdrawal, whereas there was a decrease in TH levels in the PVN at the same time point. Following withdrawal, Fos immunoreactivity was present in most of the TH‐positive neurons of the A2 and A1 neurons. TH activity was measured in the PVN, a projection area of noradrenergic neurons arising from NTS‐A2/VLM‐A1. Morphine withdrawal was associated with an increase in the enzyme activity at different time points after naloxone‐precipitated morphine withdrawal. The present results suggest that an increase in TH protein levels and TH enzyme activity might contribute to the enhanced noradrenergic activity in the PVN in response to morphine withdrawal.
Impact of high and low anxiety on cognitive performance in a modified hole board test in C57BL/6 and DBA/2 mice
Authors: Ohl Frauke , Roedel Angelika , Binder Elke , Holsboer Florian 
Published: March 2003

AbstractWe investigated the interaction between behavioural dimensions and cognitive performance in the inbred mouse strains C57BL/6 and DBA/2, which have previously been found to differ in cognitive performance and emotionality. Because it has never been evaluated whether cognitive performance and emotional behaviour are interrelated in these strains, we analysed various behavioural dimensions and cognitive functions in parallel using the modified hole board test. We could show that naive BL6 and DBA mice distinctly differed in terms of anxiety‐related behaviour. Principal component analysis on the phenotyping data showed that anxiety‐related behaviour was described by identical parameters and was not correlated to locomotion in the two strains. During cognitive testing, DBA mice habituated faster and performed better than BL6 mice. Principal component analysis indicated a close correlation between anxiety‐related behaviour and cognitive performance in DBA mice, being associated with a highly successful cognitive performance. In BL6 mice, cognition was correlated to general exploration. This correlation turned out to be less successful in performing the modified hole board test. Our findings support the idea that high anxiety may interact with specific cognitive processing, thus offering a promising animal model for future preclinical research on the interaction of anxiety and cognition.