bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chromogranin mRNA Levels in the Brain as a Marker for Acute and Chronic Changes in Neuronal Activity: Effect of Treatments Including Seizures, Osmotic Stimulation and Axotomy in the Rat
Authors: Shen P.‐J. , Gundlach A. L. 
Published: April 2006

AbstractChromogranin/secretogranins are a family of acidic, soluble proteins with a widespread distribution in secretory vesicles of endocrine and nervous tissues. The effects of experimental stimuli of differing duration and intensity on chromogranin B and secretogranin II mRNA levels in relevant areas of the rat brain were examined by in situ hybridization histochemistry using 35S‐labelled oligonucleotides. Effects of two ‘chronic stimulation’ paradigms were studied—the effect of 4 days of water or food deprivation on mRNA levels in the hypothalamus and the effect of unilateral cervical vagotomy on transcript levels in the dorsal vagal complex 1, 2 and 7 days after surgery. After 4 days of water deprivation secretogranin II mRNA was significantly increased in the supraoptic nucleus (366 ± 21% of control, P < 0.01), the magnocellular paraventricular nucleus (209 ± 20% of control, P < 0.01) and the parvocellular paraventricular nucleus (147 ± 6% of control, P < 0.01). Conversely, the level of secretogranin II mRNA in the supraoptic nucleus was decreased (61 ± 13% of control, P < 0.05) after 4 days of food deprivation. Seven days after unilateral cervical vagotomy, secretogranin II and chromogranin B mRNA levels were markedly decreased in the ipsilateral dorsal motor nucleus of the vagus (25 ± 4 and 47 ± 8% of contralateral values respectively, P < 0.01). Rapid changes in chromogranin mRNA were also detected following shorter duration ‘acute stimulation’—in the hypothalamus after hypertonic saline injection, in the hippocampus after electrical stimulation‐induced kindled seizures, and in the cerebral cortex after unilateral craniotomy. A large increase in secretogranin II mRNA was detected in the supraoptic nucleus (202 ± 25% of control, P < 0.01) and the magnocellular paraventricular nucleus (168 ± 29% of control, P < 0.05) 3 h after a single intraperitoneal injection of hypertonic (1.8 M) saline. Markedly increased levels of secretogranin II (125–160% of control) and chromogranin B (140–230% of control) mRNA were observed in granule cells of the dentate gyrus 0.5–2 h after amygdaloid stimulation‐induced seizures. A moderate increase in secretogranin II mRNA (144 ± 11% of contralateral side, P < 0.01) was found in the underlying cerebral cortex 2.5 h after unilateral craniotomy. These results indicate that measurement of changes in chromogranin mRNA, particularly secretogranin II, is a useful means of assessing both rapid and long‐lasting increases and decreases in neuronal activity and, in contrast to immediate early gene mRNA levels, may better reflect specific changes in neuronal secretory activity associated with transmitter/peptide release.
Differential Frequency Conditioning Enhances Spectral Contrast Sensitivity of Units in Auditory Cortex (Field Al) of the Alert Mongolian Gerbil
Authors: Ohl Frank W. , Scheich Henning 
Published: April 2006

AbstractDifferential aversive auditory conditioning in the awake Mongolian gerbil was performed during single‐ and multi‐unit recording in field Al of the primary auditory cortex. Presentations of pure tone stimuli of a given frequency (reinforced conditioned stimulus; CS+) paired with electrocutaneous stimulation (unconditioned stimulus) were combined with several other non‐reinforced tone stimuli (non‐reinforced conditioned stimulus; CS‐). Stimulus presentation during training and testing was optimized for constancy of the probability of occurrence of both the CS+ and the CS‐ stimulus. The paradigm led to a reorganization of both the spectral and temporal response characteristics of auditory cortical neurons with the following basic results. First, tone‐evoked responses of Al neurons recorded after multiple acoustic stimulation under these conditions varied statistically around a mean value (stationarity). Conditioning produced a shift in mean values of evoked responses. The altered tone responses were also stationary (stability of the plastic effects). Second, the frequency‐receptive fields (FRFs) of neurons were reorganized in a frequency‐specific way such that the CS+ frequency became located in a local minimum of the FRF after training. This resulted from a training‐induced increase in the responses to frequencies adjacent to the CS+ frequency in the FRF relative to the CS+ response. The effect can be interpreted as an enhancement of the ‘spectral contrast’ sensitivity of the unit in the CS+ neighbourhood. Third, apart from this frequency‐specific plastic effect, responses to other frequencies also underwent changes during training. The non‐frequency‐specific changes were not generally predictable but the post‐trial responses were stationary. Fourth, the analysis of the long‐term behaviour of FRF reorganization revealed the stability of plastic effects under retention training and the gradual re‐establishment of the pretrial FRF during extinction training. Fifth, not only the spectral characteristics but also the temporal structure of the tone‐evoked responses could be affected by the training. In most cases the training‐induced changes measured within the first tens of milliseconds of the response corresponded to the response changes obtained by integration over the total response period. There were some cases, however, in which the direction of the response change varied with time, indicating that excitatory and inhibitory influences on the temporal response pattern were differently affected by training.
Increased Expression of BDNF and trkB mRNA in Rat Facial Motoneurons after Axotomy
Authors: Kobayashi Nao R. , Bedard Annie M. , Hincke Maxwell T. , Tetzlaff Wolfram 
Published: April 2006

AbstractMotoneurons of the adult survive after axotomy even though they are deprived of putative target derived trophic factors. Alternative sources of trophic support may substitute. In this study we test the hypothesis that the immediate environment of the motoneuronal cell body or the cell body itself increases the production of trophic factors after axonal injury. Using in situ hybridization (ISH) and reverse transcription–polymerase chain reaction (RT‐PCR), we report that after axotomy, rat facial motoneurons increase the expression of mRNA for brainderived neurotrophic factor (BDNF) and its receptor trkB. After transection of the facial nerve, we measured a 2‐to 4‐fold increase in BDNF mRNA expression which had its onset between 3 and 8 h after injury. The BDNF mRNA levels peaked at ∼1–2 days and gradually declined thereafter to return to contralateral levels within 7 days of injury. Western blotting revealed a several‐fold increase in BDNF as early as 24 h, which subsequently reached a maximum in ∼5–7 days and was still sustained at 2 weeks post‐axotomy. Using exon‐specific primers, we determined that the increase in BDNF mRNA is largely due to an increased expression from the promoters of exons IV and III, and to a lesser extent from exons I and II. Analysing the mRNA expression for the BDNF receptor, trkB, we found a 2‐ to 3‐fold increase in full‐length trkB mRNA expression starting 2 days after axotomy which lasted for 2–3 weeks. These findings suggest that BDNF might act locally on axotomized motoneurons in an autocrine fashion, providing support for axotomized motoneurons during the first weeks after axotomy.
Effects of Substance P on Medial Vestibular Nucleus Neurons in Guinea‐pig Brainstem Slices
Authors: Vibert Nicolas , Serafin Maura , Vidal Pierre‐Paul , Mühlethaler Michel 
Published: April 2006

AbstractThe undecapeptide substance P (SP) has been recently implicated in the control of vestibular function. In particular, it seems to be co‐localized with glutamate in approximately half of the primary vestibular afferents in mammals. Using intracellular recordings in guinea‐pig brainstem slices, we have investigated the effects of SP and of several agonists of the three known tachykinin receptor subtypes (NK1, NK2 and NK3) on the three main types (A, B and B+LTS) of guinea‐pig medial vestibular nucleus neurons (MVNn) that we had previously described. SP could induce two distinct kinds of effects on all types of MVNn. Whereas around half of them were depolarized and had their membrane resistance increased by SP, ∼ 10% of all MVNn were in contrast hyperpolarized and inhibited while their membrane resistance was decreased. Both responses persisted under conditions of blockade of synaptic transmission, and were thus due to the activation of postsynaptic binding sites. The SP‐induced membrane depolarization could not be reproduced with any one of the specific agonists of the three tachykinin receptor subtypes, nor was it blocked by the specific NK1 receptor antagonists GR 82334 and CP 99994. This effect might therefore be due to the activation of a new, pharmacologically distinct, ‘NK1‐like’ receptor. Only the hyperpolarizing effects, which were in contrast mimicked by the specific NK1 receptor agonists GR 73632 and [Sar9, Met (O2)11]‐SP, would be mediated by the few typical NK1 receptors which have been demonstrated in the medial vestibular nucleus.
Evidence for Direct Connections between the Hand Region of the Supplementary Motor Area and Cervical Motoneurons in the Macaque Monkey
Authors: Rouiller Eric M. , Moret Véronique , Tanné Judith , Boussaoud Driss 
Published: April 2006

AbstractIn primates the corticospinal neurons of the hand representation of the primary motor cortex (M1) give rise to direct contacts with the cervical motoneurons that control distal forelimb muscles. We investigated, at the light‐microscopy level, whether corticospinal cells present in the hand area of the supplementary motor area (SMA) also establish direct connections with cervical motoneurons, particularly those innervating hand and finger muscles. The hand representation of the M1 (two monkeys) or SMA (two monkeys) was located using intracortical microstimulation and injected with the anterograde tracer biotinylated dextran amine to label corticospinal terminals. Forearm muscles acting on the wrist and hand as well as hand muscles acting on the thumb and index finger, thus including those activated by intracortical stimulation, were injected with the retrograde tracer cholera‐toxin B subunit, in order to label the motoneurons. A consistent zone of overlap between the two markers was found in the cervical cord. Close appositions between corticospinal axonal terminals and the somata or dendrites of motoneurons were found after injection in the M1, confirming previous observations. The new finding is the observation of similar close appositions after injection in the SMA, suggesting its control of hand movements in parallel with the M1.
Chronic NMDA Receptor Antagonism During Retinotopic Map Formation Depresses CaM Kinase II Differentiation in Rat Superior Colliculus
Authors: Scheetz A. J. , Prusky Glen T. , Constantine‐Paton Martha 
Published: April 2006

AbstractWe examined the effects of chronic NMDA receptor antagonism on the normal postnatal differentiation of calcium‐ and calmodulin‐dependent kinase II (CaM kinase II) in the rat superior colliculus. At postnatal day (P) zero, most CaM kinase II protein, as well as CaM kinase II activity, was detected in the soluble fraction. In vitro phosphorylation of P0 superior colliculus revealed several prominent substrates in both the particulate and soluble fractions. At P19 there was more particulate enzyme than soluble enzyme, and CaM kinase II activity in the particulate fraction was higher than in P0 particulate tissue. Additionally, in vitro phosphorylation of P19 superior colliculus revealed many more CaM kinase II substrates. Chronic NMDA receptor antagonism with 2‐amino‐5‐phosphonovalerate (DL‐AP5) caused CaM kinase II to retain many of the characteristics of the enzyme found in P0 untreated superior colliculus. In P19 superior colliculus treated with DL‐AP5 from birth, most of the protein was in the soluble fraction, CaM kinase II activity was largely restricted to the soluble fraction, and only a few substrates were observed by in vitro phosphorylation. These effects were not observed in tissue treated with the inactive isomer, L‐AP5. These results suggest that synaptic maturation is slowed by antagonism of NMDA receptors during retinotopic map formation.
Interactions between Associative Synaptic Potentials in the Piriform Cortex of the In Vitro Isolated Guinea Pig Brain
Authors: Biella Gerardo , Panzica Ferruccio , de Curtis Marco 
Published: April 2006

AbstractThe interaction between synaptic potentials generated by the activation of separate sets of associative fibres was investigated in the piriform cortex of an in vitro isolated guinea pig brain preparation. Restricted regions of the piriform cortex served by separate contingents of afferent fibres of the lateral olfactory tract were isolated surgically. The activity generated by these patches of cortex in response to afferent stimulation propagates to remote cortical regions along cortico‐cortical associative fibres. Current source density (CSD) analysis of field potential laminar profiles evoked by lateral olfactory tract stimulation confirmed that the synaptic sinks induced by distinct associative fibre contingents converge on the apical dendrites of piriform cortex neurons in the superficial lb layer. Pairing between potentials evoked by activation of two separate sets of associative fibres resulted in an almost linear summation when the two responses coincided. For interstimulus intervals of <100 ms, heterosynaptic pairing of independent associative inputs induced a facilitation of the conditioned associative potential, which correlated with an increase in the associative sink located in layer lb, as demonstrated by CSD analysis. The evaluation of the pairing intervals suggests that the heterosynaptic facilitation of the conditioned associative potentials may be due to the summation of local and remote associative synaptic events. It is concluded that separate associative inputs converge on the apical dendrites of piriform cortex pyramidal neurons to generate synaptic potentials through the activation of spatially close but independent synapses. The role of associative synaptic integration in the functional organization of the olfactory cortex is discussed.
Cortical Networks for Visual Reaching: Intrinsic Frontal Lobe Connectivity
Authors: Johnson Paul B. , Ferraina Stefano 
Published: April 2006

AbstractThe anatomical substrates of reaching to visual targets were studied in monkeys (Macaca nemestrina) by combining behavioural neurophysiology and neuroanatomy. An instructed‐delay reaching task was used to characterize the arm‐related regions of the dorsolateral frontal cortex. This task revealed gradients of signal‐, set‐, movement‐ and position‐related activity along the rostrocaudal extent of the frontal lobe. The frontal mesial projections to these physiologically defined gradients were studied through anatomical methods based on the retrograde transport of distinguishable tracers. The tangential distribution of the cells of origin of these projections displayed a gradient‐like arrangement similar to that defined physiologically in their terminal territory. These mesial projections to the dorsolateral frontal cortex may therefore be considered part of a cortical network wherein connections make only a limited contribution to the integration of different sources of information for the control of reaching movements. Further combination of such information must occur within each given cortical region by intrinsic local connections
Glutamate‐enriched Inputs from the Mesopontine Tegmentum to the Entopeduncular Nucleus in the Rat
Authors: Clarke N. P. , Bolam J. P. , Bevan M. D. 
Published: April 2006

AbstractIn order to clarify the origin and to examine the synaptology of the projection from the mesopontine tegmentum to the entopeduncular nucleus, rats received discrete deposits of anterograde tracers in different regions of the mesopontine tegmentum. Anterogradely labelled fibres in the entopeduncular nucleus were analysed at the light and electron microscopic levels. To determine the neurochemistry of the projection, the distributions of GABA and glutamate immunoreactivity in anterogradely labelled boutons in the entopeduncular nucleus were studied by postembedding immunocytochemistry. The morphological characteristics of anterogradely labelled structures were compared to those of choline acetyltransferase‐immunopositive structures. The anterograde tracing demonstrated that the projection to the entopeduncular nucleus arises from the area defined by the cholinergic neurons of the pedunculopontine region and from the more medial and largely non‐cholinergic, midbrain extrapyramidal area. The anterogradely labelled terminals formed asymmetrical synaptic contacts with dendritic shafts, cell bodies and more rarely spines in the entopeduncular nucleus, and they were significantly enriched in glutamate immunoreactivity compared to identified GABAergic terminals in the same region. The morphology, trajectory and synaptology of the anterogradely labelled fibres showed similarities to those of choline acetyltransferase‐immunopositive fibres and terminals, providing indirect evidence in support of previous suggestions that at least part of the projection is cholinergic. The structures postsynaptic to the anterogradely labelled boutons also received input from other classes of terminals that had the morphological and neurochemical characteristics of boutons derived from the neostriatum, globus pallidus and subthalamic nucleus. These findings imply that the mesopontine tegmentum sends a projection to the entopeduncular nucleus that is heterogeneous with respect to its origin and also possibly its neurochemistry. The synaptology of the projection underlies one route through which the mesopontine tegmentum can exert effects on movement by modulating the direct and indirect pathways of information flow through the basal ganglia.
The Glutamatergic Innervation of Oxytocin‐ and Vasopressin‐secreting Neurons in the Rat Supraoptic Nucleus and its Contribution to Lactation‐induced Synaptic Plasticity
Authors: Majdoubi M. El , Poulain D. A. , Theodosis D. T. 
Published: April 2006

AbstractThe present ultrastructural study analysed the distribution of glutamatergic synapses on oxytocin‐ and vasopressin‐secreting neurons in the rat supraoptic nucleus (SON) after post‐embedding immunogold labelling for glutamate and GABA, oxytocin or vasopressin. About 20% of SON axo—somatic synapses were enriched in glutamate immunoreactivity, visible over synaptic‐like vesicles, mitochondria and synaptic densities. Double labelling for glutamate and GABA showed that putative glutamatergic terminals were distinct from GABAergic terminals. In ultrathin sections stained for glutamate and either oxytocin or vasopressin, the proportion of glutamatergic synapses was similar on oxytocinergic and vasopressinergic somata in virgin rats under basal conditions of peptide release as well as in lactating rats, in which oxytocin secretion is enhanced. Cross‐sectional soma areas were significantly increased in lactating rats: oxytocinergic profiles were, on average, ˜40% larger than in virgin rats. However, the incidence of axo—somatic glutamatergic synapses (assessed as mean number of synapses per 100 μm of plasmalemma or proportion of somatic surface apposed to synaptic active zones) did not diminish, indicating that there was a compensatory increase of synapses during lactation. Also, we found an increase in the number of glutamatergic terminals making synaptic contact simultaneously onto two or more oxytocinergic elements in the same plane of section. Our observations therefore indicate that SON oxytocinergic and vasopressinergic neurons are innervated to a similar extent by a relatively large proportion of glutamatergic synapses. They reveal, moreover, that glutamatergic afferents participate in the lactation‐induced synaptic plasticity of the oxytocinergic system.
Regional Variation in Expression of Calbindin and Inositol 1,4,5‐trisphosphate Receptor Type 1 mRNAs in the Cerebellum of the Staggerer Mutant Mouse
Authors: Nakagawa Shin , Watanabe Masahiko , Inoue Yoshiro 
Published: April 2006

AbstractThe Purkinje cells in the staggerer mutant mouse have various cellular abnormalities, including reduced cell number, ectopia, smaller size and absence of dendritic spines. It is also known that some of these abnormalities exhibit regional variations in the cerebellum. In this paper we have investigated expression in the staggerer Purkinje cells of the calbindin and inositol 1,4,5‐trisphosphate receptor type 1 mRNAs by in situ hybridization. Although the transcription levels of both mRNAs were significantly reduced compared with the wild‐type cells, the reduction among the Purkinje cell populations was not even, varying greatly from region to region. Purkinje cells with different transcription levels were distributed in discrete regions and arranged alternately in the mediolateral direction. Moreover, the cell bodies with higher transcription levels were larger in size and aligned in a monolayer between the granular and molecular layers, whereas those with lower levels were smaller in size, fewer in number and dispersed throughout the granular layer. These findings suggest that there is a distinct mediolateral heterogeneity in the staggerer cerebellum with respect to transcription levels of these Purkinje cell‐specific molecules, which might correlate with some cytological phenotypes.
Subthalamic Nucleus Lesion in Rats Prevents Dopaminergic Nigral Neuron Degeneration After Striatal 6‐OHDA Injection: Behavioural and Immunohistochemical Studies
Authors: Piallat Brigitte , Benazzouz Abdelhamid , Benabid Alim Louis 
Published: April 2006

AbstractSeveral studies have shown that antagonists of N‐methyl‐D‐aspartate receptors provide protection of the dopaminergic nigrostriatal pathway in animal models of Parkinson's disease. Since the substantia nigra compacta receives a moderate glutamatergic innervation from the subthalamic nucleus, we tried to determine whether subthalamic nucleus lesion could prevent the toxicity of the selective dopaminergic neurotoxin 6‐hydroxydopamine (6‐OHDA). Experiments were carried out on four groups of rats. Group 1 (n= 10) received a unilateral injection of 6‐hydroxydopamine in the striatum and group 2 (n= 10) received kainic acid in the subthalamic nucleus. Group 3 (n= 10) received an injection of kainic acid in the subthalamic nucleus and 1 week later an injection of 6‐OHDA in the striatum. Group 4 (n= 5) received the same treatment but kainic acid was replaced by saline. Apomorphine induced an ipsilateral rotation in rats of groups 2 and 3 and a contralateral rotation in rats of groups 1 and 4. The number of tyrosine hydroxylase‐immunoreactive cells in the pars compacta of the substantia nigra was not significantly different between injected and non‐injected sides in rats of groups 2 and 3, but was significantly decreased on the side ipsilateral to 6‐OHDA striatal injection in rats of groups 1 and 4. These results show that subthalamic nucleus lesion provides neuroprotection of the dopaminergic nigrostriatal pathway against 6‐OHDA toxicity and opens a new way for slowing or stopping the progression of Parkinson's disease.