bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Situ Hybridization of trkB and trkC Receptor mRNA in Rat Forebrain and Association with High‐affinity Binding of [125I]BDNF, [125I]NT‐4/5 and [125I]NT‐3
Authors: Altar C. Anthony , Siuciak Judith A. , Wright Paul , Ip Nancy Y. , Lindsay Ronald M. , Wiegand Stanley J. 
Published: April 2006

AbstractThe TrkB and TrkC receptor tyrosine kinases have been identified as high‐affinity receptors for the neurotrophic factors brain‐derived neurotrophic factor (BDNF) and neurotrophin‐4/5 (NT‐4/5) and NT‐3 respectively. These receptor classes were identified and mapped by the in situ hybridization of antisense riboprobes complementary to portions of the intracellular (tyrosine kinase) or extracellular (ligand‐binding) domains of trkB and trkC mRNA, and by the distribution of high‐affinity [125I]BDNF, [125I]NT‐4/5 and [125I]NT‐3 binding sites in adjacent rat brain sections. Both methods showed that TrkB and TrkC receptors are abundant and widely expressed throughout the brain. Kinase or extracellular domain trkC probes labelled neuronal somata in a qualitatively similar manner in virtually every major area of the forebrain. Neither trkC probe labelled non‐neuronal cells except for elements within cerebral arteries and arterioles. The kinase domain trkB probe hybridized exclusively to neurons. Neurons expressing trkB were even more widely distributed than those expressing trkC. The extracellular domain trkB probe labelled neurons with the same relative distribution as the trkB kinase domain probe, but also hybridized extensively with non‐neural cells, particularly astrocytes, ependyma and choroid epithelium cells. The distribution of [125I]NT‐3 binding sites generally resembled that of trkC hybridization, particularly in the neocortex, striatum and thalamus. [125I]BDNF and [125I]NT‐4/5 binding sites were more widely distributed and denser than those for [125I]NT‐3, and resembled the trkB hybridization pattern. These patterns are consistent with the preferential binding in the brain of TrkC receptors by [125I]NT‐3 and of TrkB receptors by [125I]BDNF and [125I]NT‐4/5. That the predominantly neuronal patterns of hybridization obtained with kinase and extracellular domain probes for trkC are qualitatively indistinguishable suggests that truncated and full‐length forms of TrkC are expressed within extensively overlapping populations of neurons. In marked contrast to TrkC, expression of the full‐length and truncated forms of TrkB appears to be largely segregated, being expressed principally on neurons and non‐neuronal cells respectively. The abundant and widespread neuronal distribution of full‐length, signal‐transducing forms of TrkB and TrkC predict that their cognate ligands, BDNF, NT‐4/5 and NT‐3, may exert direct effects on a large proportion of neurons within the mature brain.
Preserved Recognition Memory for Small Sets, and Impaired Stimulus Identification for Large Sets, Following Rhinal Cortex Ablations in Monkeys
Authors: Eacott M. J. , Gaffan D. , Murray E. A. 
Published: April 2006

AbstractSeven cynomolgus monkeys (Macaca fascicularis) performed a series of tasks designed to assess their visual memory and their ability to identify visual stimuli. Preoperatively they were trained and tested in delayed and simultaneous matching‐to‐sample, both with a large stimulus set and with a small stimulus set; there were ∼500 million possible stimuli in the large set, which effectively means that stimuli were trial‐unique with this set, while in the small set there were only four stimuli, which appeared repeatedly in every session of training with the small set. Three of the monkeys then had the cortex within and adjacent to the rhinal sulcus removed bilaterally, while the other four served as an unoperated control group. Postoperatively, the animals with ablation of the rhinal cortex showed severe impairment in delayed matching‐to‐sample with the large set. With the large set they were also impaired, however, in matching‐to‐sample with no delay between sample and test (0 s delay) and in simultaneous matching‐to‐sample, in which the sample and the two choice patterns were simultaneously present for inspection. The impairment in simultaneous matching‐to‐sample was particularly clear when the task was made more difficult by reducing the physical discriminability of the trial‐unique stimuli. With the small set of four stimuli, the animals with rhinal cortex ablation were not significantly impaired in overall performance level in delayed matching‐to‐sample, though their level was on average below that of the normal control animals. The stimulus set was then further restricted, so that there were now only two stimuli used throughout; in this condition, the animals with rhinal cortex ablation performed delayed matching‐to‐sample without any suggestion of impairment, showing indistinguishable performance levels from those of the control animals over a range of forgetting intervals. Subsequently, the animals were trained in trial‐unique non‐matching‐to‐sample with 0 s delay, which required reversal of the matching‐to‐sample rule they had previously learned; animals with rhinal cortex ablation showed a clear impairment in this rule‐reversal learning. The final experimental task was a concurrent discrimination learning task in which 20 pairs of stimuli were presented once per session; the animals with rhinal cortex ablation learned more slowly than the control animals on average, but the difference between the groups did not attain statistical significance. Overall, this pattern of deficits and of preserved abilities is clearly inconsistent with the idea that rhinal cortex ablation produces an impairment in all forms of visual recognition memory, and only in visual recognition memory. Instead, the present results indicate a general impairment in the capacity for knowledge about visual stimuli.
Cortical Layer‐specific Effects of the Metabotropic Glutamate Receptor Agonist 1S,3R‐ACPD in Rat Primary Somatosensory Cortex In Vivo
Authors: Cahusac Peter M. B. 
Published: April 2006

AbstractThe effects of iontophoretically applied (1S,3R)‐1‐aminocyclopentane‐1,3‐dicarboxylic acid (1S,3R‐ACPD), a metabotropic glutamate receptor (mGluR) agonist, were studied on extracellularly recorded neurons throughout the depth of the primary somatosensory cortex in the anaesthetized adult rat. Distinct excitatory effects were found almost exclusively in neurons recorded in layer V. Postsynaptic depressant effects dominated neurons recorded in layers I–IV. In layer VI, neurons were equally divided as to excitation and depression. Both the excitatory and postsynaptic depressant effects could be antagonized by the mGluR antagonist (RS)‐α‐methyl‐4‐carboxyphenylglycine (MCPG). Experiments using bicuculline and several lines of analysis suggested that the postsynaptic depressant effects were mediated directly, rather than through disfacilitation. In a proportion of neurons 1S,3R‐ACPD selectively depressed synaptically evoked responses (produced by vibrissa deflections), with little or no effect on the postsynaptic level of firing. Comparing the depressant effects of 1S,3R‐ACPD with those of GABA supported a presynaptic mGluR site. Responses to centre and surround receptive field stimulation were depressed to the same extent, suggesting that thalamocortical and intracortical axon terminals are equally endowed with presynaptic receptors. In contrast to previous studies, the actions of l‐2‐amino‐4‐phosphonobutyric acid (L‐AP4) were shown to be qualitatively different to those of 1S,3R‐ACPD, in particular suggesting that the presynaptic depression produced by 1S,3R‐ACPD is not mediated by l‐AP4‐type receptors. The functional implications of different mGluR actions in the primary somatosensory cortex are discussed.
Uptake of Acetylcholinesterase by Neurons in the Substantia Nigra
Authors: Dickie B. G. M. , Budd T. C. , Vaux D. , Greenfield S. A. 
Published: April 2006

AbstractIt is known that acetylcholinesterase is secreted by the dopaminergic neurons of the substantia nigra and has a subsequent action independent of cholinergic transmission. Although non‐cholinergic actions of this protein have been demonstrated, the subsequent fate of acetylcholinesterase is unknown. One possibility is that acetylcholinesterase is taken up following secretion into the extracellular space. This hypothesis has been tested in vivo, in both conscious and anaesthetized guinea‐pigs. Exogenous acetylcholinesterase (2–20 pM) was infused via a push‐pull cannula implanted into either the substantia nigra or the surrounding extranigral regions; the amount subsequently recovered in the perfusate was then compared with control values. Only when the push‐pull cannulae were implanted in the substantia nigra was there a marked decrease in the amount of acetylcholinesterase recovered; this selective retention was abolished when the perfusion medium was cooled to 4°C or when the experiment was performed post mortem. Direct visualization of immunocytochemically identified nigral dopaminergic cells revealed co‐localized deposits of labelled, exogenous acetylcholinesterase. Moreover, when exogenous acetylcholinesterase was boiled to prevent detection by the assay system and to eliminate any classical enzymatic action, an enhancement in perfusate levels of endogenous acetylcholinesterase was observed from nigral but not from extranigral sites, indicating that endogenous and exogenous acetylcholinesterases were in competition. These results suggest that, within the substantia nigra, secreted acetylcholinesterase may be subject to a temperature‐ and energy‐dependent uptake mechanism.
Clearance of Myelin Constituents and Axonal Sprouting in the Transected Postcommissural Fornix of the Adult Rat
Authors: Stichel Christine C. , Wunderlich Gilbert , Schwab Martin E. , Müller Hans Werner 
Published: April 2006

AbstractFollowing transection of the postcommissural fornix in the adult rat, fibres retract from the lesion zone but then start to regrow within their former pathway up to the lesion site, where they terminate. The fibres neither penetrate nor bypass this region. In order to define the molecular mechanisms that cause regenerative failure at the lesion site, we analysed the spatiotemporal relationship between clearance/re‐expression of myelin constituents and axon sprouting. Using immunocytochemical methods, we investigated the distribution of myelin‐associated growth inhibitor (Nl‐35/250) and myelin basic protein after transection of the postcommissural fornix. In the studies described here we demonstrate the sequential removal of neurofilaments and myelin constituents in a perilesion zone and at the lesion site. The removal of myelin constituents was followed by the extensive regrowth of fornix fibres in the proximal segment. However, these fibres stopped at the lesion site, an area that lacked immunostaining for Nl‐35/250 and. In the distal stump we observed the disappearance of neurofilament along the entire fornix segment but spatial differences in the removal of myelin constituents. While both NI‐35/250 and myelin basic protein disappeared in the perilesion zone, they persisted in the more distal segment for at least 28 months after lesion. In conclusion, our study indicates that the onset of axon sprouting is correlated with the removal of myelin basic protein and NI‐35/250. Furthermore, we suggest that it seems unlikely that the myelin growth inhibitor NI‐35/250 constitutes the stop signal of the axon growth barrier in the transected fornix.
The Effects of Early Postnatal Modification of Body Shape on the Somatosensory—Visual Organization in Mouse Superior Colliculus
Authors: Benedetti F. , Ferro I. 
Published: April 2006

AbstractDifferent regions of the body of an animal have their own shape and location within visual space. Accordingly, in the superior colliculus there are somatosensory‐visual bimodal neurons receiving tactile and visual input from the same region of space. In newborn mice, we changed the position of some body parts within visual space in order to see what happened to the alignment of the somatosensory and visual receptive fields of superior colliculus bimodal neurons. To do this, we modified the shape of the head by displacing the superior vibrissae and the ears, normally in the superior portion of visual space, into the inferior visual space. Analogously, we bent the inferior vibrissae into the superior visual space. At the sixth postnatal week we recorded from somatosensory‐visual bimodal neurons of the deep layers of the superior colliculus and found that the tactile and visual receptive fields were aligned. Neurons receiving tactile input from the downward‐displaced superior vibrissae and ears showed visual receptive fields in the inferior portion of visual space, whereas neurons receiving input from the upward‐displaced inferior vibrissae showed visual receptive fields in the superior visual space. These results show that an experience‐dependent interaction between visual and somatosensory inputs occurs during development, and that early exposure to abnormal visual‐somatosensory experience modifies the organization of multisensory neurons in the superior colliculus.
Postnatal Development of GABA Neurons in the Rat Somatosensory Barrel Cortex: A Quantitative Study
Authors: Micheva Kristina D. , Beaulieu Clemont 
Published: April 2006

AbstractAs an estimate of the numerical importance of GABA‐containing neurons during development, their quantitative distribution was analysed in the primary somatosensory cortex of rats between postnatal days (P) 5 and 60, using the disector method and GABA postembedding immunocytochemistry. In relation to the overall number of neurons in the barrel field cortex, the proportion of GABA neurons showed an early significant decrease between P5 and P10 from 14 to 11%, most likely due to termination of transient expression of GABA by some cells. It then remained stable until P20, after which it started slowly but steadily to increase, reaching 14% of the total at P60. The absolute number of GABA neurons also increased by nearly 50% during that period, whereas the number of all neurons remained constant. These changes are seemingly due to a subpopulation of neurons, shown to be of small size, which express GABA late in development. Thus, anatomical adjustments of the cortical GABA system may be observed at least until the end of the second postnatal month, reflecting both delayed maturation and adaptation of this inhibitory circuitry. We suggest the existence of three subpopulations of cortical GABA neurons depending on the time of onset and the regulation of their GABA expression: (i) neurons which express GABA before completion of migration and thus provide for its neurotrophic influence. (ii) neurons which express GABA immediately after completion of migration and build up the cortical inhibitory circuitry, and (iii) neurons which express GABA later in development and represent a substrate of experience dependent plasticity.
Temporal Coding of Amplitude and Frequency Modulation in the Rat Auditory Cortex
Authors: Gaese Bernhard H. , Ostwald Joachim 
Published: April 2006

AbstractThe rat primary auditory cortex was explored for neuronal responses to pure tones and sinusoidally amplitude‐modulated (SAM) and frequency‐modulated (SFM) stimuli. Units showed phase‐locked responses to SAM stimulation (55%) and SFM stimulation (80%), with modulation frequencies up to 18 Hz. Tuning characteristics to the modulation frequency were mainly band‐pass with best modulation frequencies (BMFs) between 4 and 15 Hz. Units with synchronized activity to SFM stimulation showed three response types with respect to the direction of the frequency modulation: 52% were selective to the upward direction, 30% to the downward direction, and 18% had no preference. Triangular frequency modulations were used to test if units were tuned to specific modulation frequencies or to specific rates of frequency change. In the vast majority of units tested the response characteristics were strongly influenced by varying the modulation frequency, whereas varying the rate of frequency change had little effect in the stimulus range used. Units that showed phase‐locked responses to SAM and SFM stimulation had similar activity patterns in response to both types of stimuli. BMFs for SAM and SFM stimulation were significantly correlated. Intrinsic oscillations of up to 20 Hz could be seen in the spontaneous activity and after the stimuli independent of the stimulus type. Oscillation frequencies were significantly correlated with the BMFs of the respective units. The results are discussed in terms of a mechanism for periodicity detection based on a temporal code. This could be important for the recognition of complex acoustic signals.
Nerve‐Dependent Plasticity of the Golgi Complex in Skeletal Muscle Fibres: Compartmentalization Within the Subneural Sarcoplasm
Authors: Jasmin Bernard J. , Antony Claude , Changeux Jean‐Pierre , Cartaud Jean 
Published: April 2006

AbstractSeveral recent reports have highlighted the plasticity of the Golgi apparatus during myogenesis, yet the organization of this specialized organelle in innervated skeletal muscle fibres remains poorly understood. Using four bona fide anti‐Golgi antibodies, directed against a 210 kDa protein, a 160 kDa sialoglycoprotein, the small GTP‐binding protein rabop, and TGN38, the localization of which covers the various compartments of the Golgi complex, we show by immunofluorescence microscopy that the Golgi complex undergoes considerable reorganization in the course of myogenic differentiation and motor endplate formation in the rat. Unlike the typical perinuclear distribution of the Golgi stacks associated with every nucleus in myotubes, a striking subneural compartmentalization is observed in adult innervated myofibres. In short‐term denervated adult muscle fibres, we noticed the presence of the perinuclear Golgi apparatus in extrajunctional regions, a pattern reminiscent of that of developing myotubes. At variance with anti‐Golgi antibodies, antibodies to the rough endoplasmic reticulum label structures dispersed throughout the entire sarcoplasm, hence suggesting that it is not the entire membrane/secretory protein synthesis machinery which is compartmentalized, but only the Golgi apparatus. Also, an unexpected lack of immunoreactivity with the TGN38 and α‐mannosidase II antibodies points to biochemical differentiation of the subneural Golgi apparatus at the adult motor endplate. These new data extend our previous observations on the compartmentalization of the Golgi apparatus in the postsynaptic sarcoplasm of chick muscle fibres, and further illustrate the plasticity of the Golgi apparatus in muscle cells. The specialization of the Golgi apparatus within the subneural compartment provides this particular region with a compartmentalized secretory pathway, and these observations highlight the notion that the level of differentiation of this domain is not only maintained via transcriptional regulation but also by post‐translational control mechanisms
Ectopic Substance P and Calcitonin Gene‐related Peptide Immunoreactive Fibres in the Spinal Cord of Transgenic Mice Over‐expressing Nerve Growth Factor
Authors: Ma Weiya , Ribeiro‐da‐Silva A. , Noel G. , Julien J.‐P. , Cuello A. Claudio 
Published: April 2006

AbstractThe aim of this study was to investigate the in vivo effects of CNS over‐expression of nerve growth factor (NGF) on primary sensory neurons. To achieve this objective a transgenic mouse model was generated which bore a chick NGF gene driven by the myelin basic protein promoter. Northern blot analysis demonstrated that high levels of NGF mRNA were detected in the spinal cord of adult transgenic mice. Using immunocytochemistry NGF‐immunoreactive (IR) oligodendrocytes were observed throughout the white matter. Furthermore, numerous ectopic substance P (SP)‐ and calcitonin gene‐related peptide (CGRP)‐IR fibres were detected in the white matter of the spinal cord of transgenic mice. NGF‐IR oligodendrocytes and ectopic SP‐ and CGRP‐ fibres were entirely absent from control mice. In the cervical and lumbar dorsal root ganglia, the percentages of SP‐IR neurons were significantly higher in transgenic mice when compared with controls. At the electron microscope level, ectopic SP‐ and CGRP‐IR fibres were characterized as unmyelinated axons and axonal boutons. SP co‐localized with CGRP in some of those axonal boutons and fibres. Capsaicin treatment of adult mice completely abolished the ectopic SP‐IR fibres, confirming their primary sensory origin. Our results indicate that primary sensory neurons are responsive to NGF over‐expression in the CNS. Ectopic SP‐ and CGRP‐IR fibres in the white matter are likely to represent collateral sprouts of the central processes of the dorsal root ganglion cells which were triggered by NGF over‐expressed in the myelinating oligodendrocytes in the spinal cord of transgenic mice.
Interactive Events Subserving the Pupillary Light Reflex in Pigmented and Albino Rats
Authors: Chan K. M. C. , Young Michael J. , Lund Raymond D. 
Published: April 2006

AbstractThe consensual pupilloconstrictor response requires the intensity information that is delivered to each eye to be integrated to produce an averaged response such that the pupillary diameter in each eye is equal. Here we have examined how luminance information from each eye is integrated in the rat and where the integration occurs, using a pupillometry system to record pupillary diameter after illumination of one or both eyes. In albino rats the size of the uncrossed optic pathway to the pupilloconstrictor centre, the olivary pretectal nucleus, is reduced three‐fold and there is a concomitant but less dramatic reduction in the size of the consensual response. Unilateral lesions of the olivary pretectal nucleus in pigmented rats restrict all optic input to the opposite pretectum. Stimulation of one or both eyes in these animals suggests that integration occurs not only at the level of the olivary pretectal nucleus, but also downstream in the Edinger‐Westphal nucleus. Parallels with human studies and the opportunity to perform secondary lesions suggests the rat may provide a good model in which to study the substrates of the pupilloconstrictor response and mechanisms of integration of convergent parallel inputs in general.