bluuebunny/crossref_metadata_2025 huggingface dataset:
Glycinergic Inhibition Contributes to the Generation of Rostral Scratch Motor Patterns in the Turtle Spinal Cord
Authors: Currie Scott N. , Lee Steven
Published: April 2018

Cutaneous stimulation within the rostral scratch receptive field in a low spinal-immobilized turtle elicits a fictive rostral scratch reflex characterized by robust rhythmic motor output from ipsilateral hindlimb muscle nerves and weaker, alternating motor discharge in contralateral nerves. Simultaneous bilateral stimulation elicits bilateral rostral scratch motor patterns in which activity on the right and left sides alternates.

We investigated the role of glycinergic inhibition in the generation and coordination of fictive rostral scratch motor patterns. Glycine (2 or 5 mm) and strychnine (5–50 μm), a glycine antagonist, were superfused over the anterior spinal hindlimb enlargement while fictive rostral scratch motor output was recorded bilaterally from hindlimb muscle nerves in the form of electroneurograms (ENGs). Although glycine reduced rostral scratch burst frequencies, strychnine tended to increase burst frequency. Strychnine also changed the shape of hip flexor ENG bursts, resulting in more abrupt burst onsets, indicating an earlier recruitment of motor neurons with large ENG spikes. During bilateral stimulation, strychnine increased the variability of interlimb phase values (left vs right hip flexor bursts) but did not abolish right-left alternation.

These results indicate that glycinergic neurons in or near the anterior hindlimb enlargement contribute to the overall timing of the rostral scratch rhythm and to the recruitment timing of individual hip flexor motor neurons within each scratch burst. Our data also indicate that glycinergic mechanisms contribute to, but are not critically important for, maintaining an alternating interlimb coordination during bilateral scratch motor patterns.
Isoforms of Na,K-ATPase α and β Subunits in the Rat Cerebellum and in Granule Cell Cultures
Authors: Peng Liang , Martin-Vasallo Pablo , Sweadner Kathleen J.
Published: April 2018

There are multiple isoforms of the Na,K-ATPase in the nervous system, three isoforms of the α subunit, and at least two of the β subunit. The α subunit is the catalytic subunit. The β subunit has several roles. It is required for enzyme assembly, it has been implicated in neuron-glia adhesion, and the experimental exchange of β subunit isoforms modifies enzyme kinetics, implying that it affects functional properties. Here we describe the specificities of antibodies against the Na,K-ATPase β subunit isoforms β1 and β2. These antibodies, along with antibodies against the α subunit isoforms, were used to stain sections of the rat cerebellum and cultures of cerebellar granule cells to ascertain expression and subcellular distribution in identifiable cells. Comparison of α and β isoform distribution with double-label staining demonstrated that there was no preferential association of particular α subunits with particular β subunits, nor was there an association with excitatory or inhibitory neurotransmission modes. Isoform composition differences were seen when Purkinje, basket, and granule cells were compared. Whether β1 and β2 are specific for neurons and glia, respectively, has been controversial, but expression of both β subunit types was seen here in granule cells. In rat cerebellar astrocytes, in sections and in culture, α2 expression was prominent, yet the expression of either β subunit was low in comparison. The complexity of Na,K-ATPase isoform distribution underscores the subtlety of its regulation and physiological role in excitable cells.
TrkB Signaling Is Required for Postnatal Survival of CNS Neurons and Protects Hippocampal and Motor Neurons from Axotomy-Induced Cell Death
Authors: Alcántara Soledad , Frisén Jonas , del Rı́o José Antonio , Soriano Eduardo , Barbacid Mariano , Silos-Santiago Inmaculada
Published: April 2018

Newborn mice carrying targeted mutations in genes encoding neurotrophins or their signaling Trk receptors display severe neuronal deficits in the peripheral nervous system but not in the CNS. In this study, we show thattrkB (−/−) mice have a significant increase in apoptotic cell death in different regions of the brain during early postnatal life. The most affected region in the brain is the dentate gyrus of the hippocampus, although elevated levels of pyknotic nuclei were also detected in cortical layers II and III and V and VI, the striatum, and the thalamus. Furthermore, axotomized hippocampal and motor neurons oftrkB (−/−) mice have significantly lower survival rates than those of wild-type littermates. These results suggest that neurotrophin signaling through TrkB receptors plays a role in the survival of CNS neurons during postnatal development. Moreover, they indicate that TrkB receptor signaling protects subpopulations of CNS neurons from injury- and axotomy-induced cell death.
Brain-Derived Neurotrophic Factor Mediates the Activity-Dependent Regulation of Inhibition in Neocortical Cultures
Authors: Rutherford Lana C. , DeWan Andrew , Lauer Holly M. , Turrigiano Gina G.
Published: April 2018

The excitability of cortical circuits is modulated by interneurons that release the inhibitory neurotransmitter GABA. In primate and rodent visual cortex, activity deprivation leads to a decrease in the expression of GABA. This suggests that activity is able to adjust the strength of cortical inhibition, but this has not been demonstrated directly. In addition, the nature of the signal linking activity to GABA expression has not been determined. Activity is known to regulate the expression of the neurotrophin brain-derived neurotrophic factor (BDNF), and BDNF has been shown to influence the phenotype of GABAergic interneurons. We use a culture system from postnatal rat visual cortex to test the hypothesis that activity is regulating the strength of cortical inhibition through the regulation of BDNF. Cultures were double-labeled against GABA and the neuronal marker MAP2, and the percentage of neurons that were GABA-positive was determined. Blocking spontaneous activity in these cultures reversibly decreased the number of GABA-positive neurons without affecting neuronal survival. Voltage-clamp analysis of inhibitory currents demonstrated that activity blockade also decreased GABA-mediated inhibition onto pyramidal neurons and raised pyramidal neuron firing rates. All of these effects were prevented by incubation with BDNF during activity blockade, but not by neurotrophin 3 or nerve growth factor. Additionally, blockade of neurotrophin signaling mimicked the effects of activity blockade on GABA expression. These data suggest that activity regulates cortical inhibition through a BDNF-dependent mechanism and that this neurotrophin plays an important role in the control of cortical excitability.
Structural Abnormalities and Deficient Maintenance of Peripheral Nerve Myelin in Mice Lacking the Gap Junction Protein Connexin 32
Authors: Anzini Patrizia , Neuberg Dirk H.-H. , Schachner Melitta , Nelles Eric , Willecke Klaus , Zielasek Jürgen , Toyka Klaus V. , Suter Ueli , Martini Rudolf
Published: April 2018

Mutations affecting the connexin 32 (Cx32) gene are associated with the X-linked form of the hereditary peripheral neuropathy Charcot–Marie–Tooth disease (CMTX). We show that Cx32-deficient mice develop a late-onset progressive peripheral neuropathy with abnormalities comparable to those associated with CMTX, thus providing proof of the critical role of Cx32 in the maintenance of peripheral nerve myelin and an animal model for CMTX. Frequently observed features include abnormally thin myelin sheaths, cellular onion bulb formation reflecting myelin degeneration-induced Schwann cell proliferation, and enlarged periaxonal collars while nerve conductance properties are altered only slightly. These observations are consistent with earlier hypotheses suggesting a function of Cx32 as a channel-forming protein that facilitates the communication between the abaxonal and adaxonal aspects of Schwann cell cytoplasm.
Neuronal Dopamine Subpopulations Maintained in Hypothalamic Slice Explant Cultures Exhibit Distinct Tyrosine Hydroxylase mRNA Turnover Rates
Authors: Maurer Jennifer A. , Wray Susan
Published: April 2018

Changes in mRNA stability have been shown to regulate critical intracellular processes. In this investigation, we studied tyrosine hydroxylase (TH) mRNA turnover in functionally and anatomically distinct dopaminergic (DA) populations of the rat hypothalamus. To this end, long-term slice explant cultures from postnatal, preoptic area/hypothalami, containing three anatomically discrete DA populations, were generated and maintained under defined conditions. The organotypic cultures were treated with the transcription inhibitors 5,6-dichloro-1-D-ribofuranosylbenzimidazole or actinomycin D and processed forin situhybridization histochemistry. Relative TH mRNA content per cell was quantitated. Single-cell analysis showed marked differences in basal TH mRNA turnover rates between DA neuronal populations. Anterior and midhypothalamic DA neurons exhibited half-time turnovers of 9–12 and 11–23 hr, respectively. In contrast, in the caudal hypothalamus, DA neurons of the arcuate nucleus had a significantly lower baseline level and more rapid turnover (6–7 hr) of TH mRNA. This investigation shows that basal turnover of a phenotypic mRNA, TH mRNA in DA neurons, isnotan intrinsic property of the phenotypic marker. Furthermore, we found that destabilization of TH mRNA in the caudal hypothalamus corresponds to the known rhythmic output displayed by arcuate DA cells and, as such, may be critical for normal function of this population. We propose that intrinsic differences in the post-transcriptional regulation of TH permits neuronal subpopulations, which subserve different physiological functions, an additional mechanism to control DA biosynthesis in response to their unique needs.
Identification and Functional Characterization of a K+Channel α-Subunit with Regulatory Properties Specific to Brain
Authors: Castellano Antonio , Chiara Maria D. , Mellström Britt , Molina Antonio , Monje Francisco , Naranjo José R. , López-Barneo José
Published: April 2018

The physiological diversity of K+channels mainly depends on the expression of several genes encoding different α-subunits. We have cloned a new K+channel α-subunit (Kv2.3r) that is unable to form functional channels on its own but that has a major regulatory function. Kv2.3r can coassemble selectively with other α-subunits to form functional heteromultimeric K+channels with kinetic properties that differ from those of the parent channels. Kv2.3r is expressed exclusively in the brain, being concentrated particularly in neocortical neurons. The functional expression of this regulatory α-subunit represents a novel mechanism without precedents in voltage-gated channels, which might contribute to further increase the functional diversity of K+channels necessary to specify the intrinsic electrical properties of individual neurons.
Regional Cerebral Blood Flow Changes as a Function of Delta and Spindle Activity during Slow Wave Sleep in Humans
Authors: Hofle Nina , Paus Tomás , Reutens David , Fiset Pierre , Gotman Jean , Evans Alan C. , Jones Barbara E.
Published: April 2018

In the present study, we investigated changes in regional cerebral blood flow (rCBF) in humans during the progression from relaxed wakefulness through slow wave sleep (SWS). These changes were examined as a function of spindle (12–15 Hz) and δ (1.5–4.0 Hz) electroencephalographic (EEG) activity of SWS. rCBF was studied with positron emission tomography (PET) using the H215O bolus method. A maximum of six 60 sec scans were performed per subject during periods of wakefulness and stages 1–4 of SWS, as determined by on-line EEG monitoring. Spectral analysis was performed off-line on the EEG epochs corresponding to the scans for computation of activity in specific frequency bands. The relationship between EEG frequency band activity and normalized rCBF was determined by means of a voxel-by-voxel analysis of covariance. δ activity covaried negatively with rCBF most markedly in the thalamus and also in the brainstem reticular formation, cerebellum, anterior cingulate, and orbitofrontal cortex. After the effect of δ was removed, a significant negative covariation between spindle activity and the residual rCBF was evident in the medial thalamus. These negative covariations may reflect the disfacilitation and active inhibition of thalamocortical relay neurons in association with δ and spindles, as well as the neural substrates underlying the progressive attenuation of sensory awareness, motor responsiveness, and arousal that occur during SWS. δ activity covaried positively with rCBF in the visual and auditory cortex, possibly reflecting processes of dream-like mentation purported to occur during SWS.
Fetal Transplants Alter the Development of Function after Spinal Cord Transection in Newborn Rats
Authors: Miya Dorene , Giszter Simon , Mori Futoshi , Adipudi Vijayalakshmi , Tessler Alan , Murray Marion
Published: April 2018

Pieces of fetal spinal tissue were transplanted into the site of complete midthoracic spinal transections in neonatal rat pups (transplant rats). The development of locomotion in these animals was compared with that of unoperated control rats and rats that received spinal transections alone (spinal rats). Reflex, treadmill and overground locomotion, staircase descent, and horizontal ladder crossing for a water reward were tested in control, spinal, and transplant rats from 3 weeks to adulthood. All tests were readily performed by control animals. Most spinal rats were unable to make many linked weight-supported steps on these tasks. Transplant rats were variable in their locomotor capabilities, but a subset of rats were able to demonstrate coordinated and adaptable locomotion on these tasks. Some transplant rats performed better on more challenging tasks, suggesting that motor strategies for these tasks used different information, perhaps from descending systems. Transplanted tissue survived, and in most cases there was immunocytochemical staining of serotonergic fibers passing into and caudal to the transplant, supporting the conclusion that descending systems grew through the transplanted tissue. Integration with the host tissue was often poor, suggesting that nonspecific or trophic effects of the transplant might also contribute to the development of locomotor function. Therefore several mechanisms may contribute to the repair of injured spinal cord provided by transplants that permit the development of useful locomotion.
Chronic Fos-Related Antigens: Stable Variants of ΔFosB Induced in Brain by Chronic Treatments
Authors: Chen Jingshan , Kelz Max B. , Hope Bruce T. , Nakabeppu Yusaku , Nestler Eric J.
Published: April 2018

Fos family transcription factors are believed to play an important role in the transcriptional responses of the brain to a variety of stimuli. Previous studies have described 35 and 37 kDa Fos-like proteins, termed chronic Fos-related antigens (FRAs), that are induced in brain in a region-specific manner in response to several chronic perturbations, including chronic electroconvulsive seizures, psychotropic drug treatments, and lesions. We show in this study that the chronic FRAs are isoforms of ΔFosB, a truncated splice variant of FosB that accumulate in brain after chronic treatments because of their stability. ΔFosB cDNA encodes the expression of 33, 35, and 37 kDa proteins that arise from a single AUG translation start site. The 35 and 37 kDa proteins correspond to the chronic FRAs that are induced in brain by chronic treatments, whereas the 33 kDa protein corresponds to a Fos-like protein that is induced in brain by acute treatments, findings based on migration on one- and two-dimensional Western blots with anti-FRA and anti-FosB antibodies. Using cells in which ΔFosB or FosB expression is under the control of a tetracycline-regulated gene expression system, we show that the 37 kDa ΔFosB protein exhibits a remarkably long half-life, the 35 kDa ΔFosB protein exhibits an intermediate half-life, and the 33 kDa ΔFosB protein and all FosB-derived proteins exhibit relatively short half-lives. Moreover, we show that the 33 kDa ΔFosB protein is the first to appear after activation of ΔFosB expression. Finally, ΔFosB proteins are shown to possess DNA-binding activity and to exert potent transactivating effects in reporter gene assays. Together, these findings support a scheme wherein ΔFosB, expressed as a 33 kDa protein, is modified to form highly stable isoforms of 35 and 37 kDa. As a result, these stable isoforms gradually accumulate in the brain with repeated treatments to mediate forms of long-lasting neural and behavioral plasticity.
Adenosine A1Receptor-Mediated Activation of Phospholipase C in Cultured Astrocytes Depends on the Level of Receptor Expression
Authors: Biber Knut , Klotz Karl-Norbert , Berger Mathias , Gebicke-Härter Peter J. , van Calker Dietrich
Published: April 2018

Adenosine A1receptors induce an inhibition of adenylyl cyclase via G-proteins of the Gi/ofamily. In addition, simultaneous stimulation of A1receptors and of receptor-mediated activation of phospholipase C (PLC) results in a synergistic potentiation of PLC activity. Evidence has accumulated that Gβγ subunits mediate this potentiating effect. However, an A1receptor-mediated increase in extracellular glutamate was suggested to be responsible for the potentiating effect in mouse astrocyte cultures. We have investigated the synergistic activation of PLC by adenosine A1and α1adrenergic receptors in primary cultures of astrocytes derived from different regions of the newborn rat brain. It is reported here that (1) adenosine A1receptor mRNA as well as receptor protein is present in astrocytes from all brain regions, (2) A1receptor-mediated inhibition of adenylyl cyclase is of similar extent in all astrocyte cultures, (3) the A1receptor-mediated potentiation of PLC activity requires higher concentrations of agonist than adenylyl cyclase inhibition and is dependent on the expression level of A1receptor, and (4) the potentiating effect on PLC activity is unrelated to extracellular glutamate.

Taken together, our data support the notion that βγ subunits are the relevant signal transducers for A1receptor-mediated PLC activation in rat astrocytes. Because of the lower affinity of βγ, as compared with α subunits, more βγ subunits are required for PLC activation. Therefore, only in cultures with higher levels of adenosine A1receptors is the release of βγ subunits via Gi/oactivation sufficient to stimulate PLC. It is concluded that variation of the expression level of adenosine A1receptors may be an important regulatory mechanism to control PLC activation via this receptor.
Motor Pattern Selection via Inhibition of Parallel Pathways
Authors: Blitz Dawn M. , Nusbaum Michael P.
Published: April 2018

Motor pattern selection from a multifunctional neural network often results from direct synaptic and modulatory actions of different projection neurons onto neural network components. Less well documented is the presence and function of interactions among distinct projection neurons innervating the same network. In the stomatogastric nervous system of the crabCancer borealis, several distinct projection neurons that influence the pyloric and gastric mill rhythms have been studied. These rhythms are generated by overlapping subsets of identified neurons in the stomatogastric ganglion (STG). One of these identified projection neurons is the modulatory proctolin neuron (MPN). We showed previously that MPN stimulation excites the pyloric rhythm by its excitatory actions on STG neurons. In contrast to its excitatory actions on the pyloric rhythm, we have now found that MPN inhibits the gastric mill rhythm. This inhibition does not occur within the STG, but instead results from MPN-mediated inhibition of two previously identified projection neurons within the commissural ganglia. These projection neurons innervate the STG and, via their actions on STG neurons, they elicit the gastric mill rhythm as well as modify the pyloric rhythm in a manner distinct from MPN. By inhibiting these projection neurons, MPN removes excitatory drive to gastric mill neurons and elicits an MPN-specific pyloric rhythm. Motor pattern selection by MPN therefore results from both a direct modulation of STG network activity and an inhibition of competing pathways.
Appican Expression Induces Morphological Changes in C6 Glioma Cells and Promotes Adhesion of Neural Cells to the Extracellular Matrix
Authors: Wu Anfan , Pangalos Menelas N. , Efthimiopoulos Spiros , Shioi Junichi , Robakis Nikolaos K.
Published: April 2018

Appicans are secreted or cell-associated brain chondroitin sulfate proteoglycans produced by glia cells and containing Alzheimer amyloid precursor protein (APP) as a core protein. Here, we report that rat C6 glioma cells transfected with appican displayed a dramatic change in their phenotypic appearance compared with untransfected cells or cells transfected with APP. Appican-transfected cells lost the round appearance of the untransfected control C6 cells, acquired a flat morphology, and elaborated more processes than control cells. Untransfected, or APP-transfected C6, cells were completely dissociated from their substrate after 40 min of treatment with cell dissociation solution. Under the same conditions, however, <20% of the appican-transfected C6 cells were dissociated from their substrate, suggesting that the appican-transfected glia cells attach more avidly to their substrate than do untransfected or APP transfected control cells. In contrast, appican-transfected fibroblast cells showed no morphological changes and dissociated from their substrate similarly to untransfected fibroblast cells. Extracellular matrix (ECM) prepared from appican-transfected C6 cell cultures contained high levels of appican and was a significantly better substrate for the attachment of C6 cells than ECM from either untransfected or APP-transfected cultures. Furthermore, cell adhesion to ECM was independent of the level of appican expression of the plated cells. ECM from appican-transfected C6 cultures stimulated adhesion of other neural cells including primary astrocytes, Neuro2a neuroblastoma, and PC12 pheochromocytoma, but not fibroblast cells. Conditioned media from appican-transfected C6 cultures failed to promote cell adhesion. Together, these data suggest that secreted appican incorporates into ECM and promotes adhesion of neural cells. Furthermore, our data suggest that the chondroitin sulfate chain engenders APP with novel biological functions.
Stretch Hyperreflexia of Triceps Surae Muscles in the Conscious Cat after Dorsolateral Spinal Lesions
Authors: Taylor J. S. , Friedman R. F. , Munson J. B. , Vierck Jr C. J.
Published: April 2018

Resistive force and electromyograms from triceps surae muscles were measured during dorsiflexion of both ankles of awake cats before and after interruption of one dorsolateral funiculus (DLF). DLF lesions produced ipsilateral increases in dynamic and static reflex force that persisted over 66 weeks. The increase in dynamic reflex force was velocity sensitive, as demonstrated by a greater effect for 60°/sec than for 10°/sec dorsiflexion. Also, the lesions increased dynamic force to a greater extent than static force (increased dynamic index). Background force (recorded immediately before each reflex response) was elevated ipsilaterally. However, increases in reflex force were observed when preoperative and postoperative background forces were matched within 10% and were associated with equivalent resting levels of electromyographic (EMG) activity. Resistive reflex force was significantly correlated with EMG responses to dorsiflexion and was not determined by nonreflexive mechanical stiffness of the muscles. Contralateral background and reflex force and associated EMG activity were decreased slightly, comparing preoperative and postoperative records.

Clinical testing revealed ipsilateral postoperative increases in extensor tone, increased resistance to hindlimb flexion, hypermetria during positive support responses, and appearance of the Babinski reflex. However, the most reliable tests of DLF lesion effects were the quantitative measures of dynamic and static reflex amplitude. The enhancement of stretch reflexes is suggestive of spasticity. However, hyperactive stretch reflexes, hypertonicity, and the Babinski reflex were observed soon after interruption of the ipsilateral DLF, in contrast to a gradual development of positive signs that is characteristic of a more broadly defined spastic syndrome from large spinal lesions. Also, other signs that often are included in the spastic syndrome, including clonus, increased flexor reflex activity, and flexor spasms, did not result from DLF lesions. Thus, unilateral DLF lesions provide a model of spasticity but produce only several components of a more inclusive spastic syndrome.
Neuronally Restricted RNA Splicing Regulates the Expression of a Novel GABAAReceptor Subunit Conferring Atypical Functional Properties
Authors: Whiting Paul J. , McAllister George , Vassilatis Demetrios , Bonnert Timothy P. , Heavens Robert P. , Smith David W. , Hewson Louise , O’Donnell Ruth , Rigby Michael R. , Sirinathsinghji Dalip J. S. , Marshall George , Thompson Sally A. , Wafford Keith A.
Published: April 2018

We report the isolation and characterization of a cDNA encoding a novel member of the GABA receptor gene family, ε. This polypeptide is 506 amino acids in length and exhibits its greatest amino acid sequence identity with the GABAAreceptor γ3 subunit (47%), although this degree of homology is not sufficient for it to be classified as a fourth γ subunit. The ε subunit coassembles with GABAAreceptor α and β subunits inXenopus laevisoocytes and transfected mammalian cells to form functional GABA-gated channels. α1β1ε GABAAreceptors, like α1β1γ2s receptors, are modulated by pentobarbital and the steroid 5α-pregnan-3α-ol-20-one but, unlike α1β1γ2s receptors, are insensitive to flunitrazepam. Additionally, α1β1ε receptors exhibit rapid desensitization kinetics, as compared with α1β1 or α1β1γ2s. Northern analysis demonstrates widespread expression of a large ε subunit transcript in a variety of non-neuronal tissues and expression of a smaller transcript in brain and spinal cord. Sequence analysis demonstrated that the large transcript contained an unspliced intron, whereas the small transcript represents the mature mRNA, suggesting regulation of expression of the ε subunit via neuronally restricted RNA splicing.In situhybridization and immunocytochemistry reveal a pattern of expression in the brain restricted primarily to the hypothalamus, suggesting a role in neuroendocrine regulation, and also to subfields of the hippocampus, suggesting a role in the modulation of long term potentiation and memory.
Diverse Expression and Distribution ofShakerPotassium Channels during the Development of theDrosophilaNervous System
Authors: Rogero Oscar , Hämmerle Barbara , Tejedor Francisco J.
Published: April 2018

The spatio-temporal expression ofShaker(Sh) potassium channels (Kch) in the developing and adult nervous system ofDrosophilahas been studied at the molecular and histological level using specific antisera.ShKch are distributed in most regions of the nervous system, but their expression is restricted to only certain populations of cells.ShKch have been found in the following three locations: in synaptic areas of neuropile, in axonal fiber tracks, and in a small number of neuronal cell bodies. This wide subcellular localization, together with a diverse distribution, implicatesShKch in multiple neuronal functions.

Experiments performed withShmutants that specifically eliminate a few of theShKch splice variants clearly demonstrate an abundant differential expression and usage of the wide repertoire ofShisoforms, but they do not support the idea of extensive segregation of these isoforms among different populations of neurons.ShKch are predominantly expressed at late stages of postembryonic development and adulthood. Strikingly, wide changes in the repertoire ofShsplice isoforms occur some time after the architecture of the nervous system is complete, indicating that the expression ofShKch contributes to the final refinements of neuronal differentiation. These late changes in the expression and distribution ofShKch seem to correlate with activity patterns suggesting thatShKch may be involved in adaptative mechanisms of excitability.
NMDA Receptor and the Tyrosine Phosphorylation of Its 2B Subunit in Taste Learning in the Rat Insular Cortex
Authors: Rosenblum Kobi , Berman Diego E. , Hazvi Shoshi , Lamprecht Raphael , Dudai Yadin
Published: April 2018

We demonstrate that the NMDA receptor is involved in taste learning in the insular cortex of the behaving rat and describe two facets of this involvement. Blockage of the NMDA receptor in the insular cortex by the reversible antagonist APV during training in a conditioned taste aversion (CTA) paradigm impaired CTA memory, whereas blockage of the NMDA receptor in an adjacent cortex or before a retrieval test had no effect. When rats sampled an unfamiliar taste and hence learned about it, either incidentally or in the context of CTA training, the tyrosine phosphorylation of the NMDA receptor subunit 2B (NR2B) in the insular cortex was specifically increased. The level of tyrosine phosphorylation on NR2B was a function of the novelty of the taste stimulus and the quantity of the taste substance consumed, properties that also determined the efficacy of the taste stimulus as a conditioned stimulus in CTA; however, blockage of the NMDA receptor by APV during training did not prevent tyrosine phosphorylation of NR2B. We suggest that tyrosine phosphorylation of NR2B subserves encoding of saliency in the insular cortex during the first hours after an unfamiliar taste is sampled and that this encoding is independent of another, necessary role of NMDA receptors in triggering experience-dependent modifications in the insular cortex during taste learning. Because a substantial fraction of the NR2B protein in the insular cortex seems to be expressed in interneurons, saliency and the tyrosine phosphorylation of NR2B correlated with it may modulate inhibition in cortex.
Synaptic Connections of Calretinin-Immunoreactive Neurons in the Human Neocortex
Authors: del Rı́o Marı́a R. , DeFelipe Javier
Published: April 2018

Previous immunocytochemical studies in the cerebral cortex of various species have shown that the calcium-binding protein calretinin (CR) labels specific subpopulations of nonspiny nonpyramidal cells (interneurons). The present study attempts to characterize morphologically and chemically the microcircuitry of CR-immunoreactive (CR-ir) neurons in the human temporal neocortex. Postembedding immunocytochemistry for CR and GABA and combination immunocytochemistry for CR and nonphosphorylated neurofilament protein (NPNFP) or for CR and the calcium-binding proteins parvalbumin (PV) and calbindin (CB) showed CR multiterminal endings frequently innervating the distal apical dendrite or the cell body and proximal dendrites of NPNFP-ir or CB-ir pyramidal cells, respectively. Cell bodies of interneurons immunoreactive for CB or PV were innervated only occasionally by CR multiterminal endings, whereas certain GABA neurons were surrounded by them. Furthermore, CR-ir axon terminals formed either symmetrical (the majority) or asymmetrical synapses with a variety of postsynaptic elements. These results indicate that different subpopulations of CR interneurons exist that are specialized for selective innervation of somatic or dendritic regions of certain pyramidal and nonpyramidal neurons.
Memory Representation within the Parahippocampal Region
Authors: Young Brian J. , Otto Tim , Fox Gregory D. , Eichenbaum Howard
Published: April 2018

The activity of 378 single neurons was recorded from areas of the parahippocampal region (PHR), including the perirhinal and lateral entorhinal cortex, as well as the subiculum, in rats performing an odor-guided delayed nonmatching-to-sample task. Nearly every neuron fired in association with some trial event, and every identifiable trial event or behavior was encoded by neuronal activity in the PHR. The greatest proportion of cells was active during odor sampling, and for many cells, activity during this period was odor selective. In addition, odor memory coding was reflected in two general ways. First, a substantial proportion of cells showed odor-selective activity throughout or at the end of the memory delay period. Second, odor-responsive cells showed odor-selective enhancement or suppression of activity during stimulus repetition in the recognition phase of the task. These data, combined with evidence that the PHR is critical for maintaining odor memories in animals performing the same task, indicate that this cortical region mediates the encoding of specific memory cues, maintains stimulus representations, and supports specific match–nonmatch judgments critical to recognition memory. By contrast, hippocampal neurons do not demonstrate evoked or maintained stimulus-specific codings, and hippocampal damage results in little if any decrement in performance on this task. Thus it becomes increasingly clear that the parahippocampal cortex can support recognition memory independent of the distinct memory functions of the hippocampus itself.
Role of Neural Cell Adhesion Molecule and Polysialic Acid in Mouse Circadian Clock Function
Authors: Shen Huaming , Watanabe Michiko , Tomasiewicz Henry , Rutishauser Urs , Magnuson Terry , Glass J. David
Published: April 2018

The suprachiasmatic nuclei (SCN) express the highly polysialylated form of the neural cell adhesion molecule (NCAM) that has been proposed to promote plasticity in the adult brain. To investigate a role for NCAM in SCN circadian clock function, we examined the daily locomotor rhythm of mice homozygous for a mutation,Ncamtm1Cwr, which results in deletion of the NCAM-180 isoform that in brain carries polysialic acid (PSA). Mutant mice entrained well to a 12 hr light/dark cycle but exhibited a significantly shortened free-running period and longer activity duration under constant darkness (DD) than did wild-type mice. By the third week of DD treatment, circadian rhythmicity in the mutant was abolished. Immunocytochemical analyses of the mutant SCN revealed an abnormal number and distribution of vasoactive intestinal polypeptide-producing neurons, suggesting a developmental effect of the mutant phenotype; however, a direct physiological effect of the mutation on clock function was indicated by the fact that removal of PSA from adult wild-type SCN by microinjection of endoneuraminidase shortened the free-running period to a similar extent as in the mutant. Together, these data indicate critical roles for NCAM and PSA in the development and physiology of the mammalian SCN circadian clock.
Lesions in Medial Preoptic Area and Bed Nucleus of Stria Terminalis: Differential Effects on Copulatory Behavior and Noncontact Erection in Male Rats
Authors: Liu Yian-Cheng , Salamone John D. , Sachs Benjamin D.
Published: April 2018

The goal of these studies was to assess the regulatory roles of the medial preoptic area (MPOA) and the bed nucleus of the stria terminalis (BST) in sexual arousal, inferred from noncontact erection (NCE) evoked in male rats by remote cues from estrous females. NCE and copulatory behavior were recorded before and after quinolinic acid or radiofrequency (RF) lesions were made in the MPOA (Experiments 1–3) or RF lesions were made in the BST (Experiment 4). All males with MPOA lesions, particularly in the rostral region, displayed severe deficits in copulation but little or no decrement in NCE. In contrast, BST lesions caused relatively moderate deficits in copulation, but they severely impaired NCE. Animals with larger BST lesions, including rostral and caudal medial regions, had more deficits in both copulatory behavior and NCE than did males with smaller lesions confined to the rostral medial BST. These results suggest that (1) the MPOA is critical for copulatory behavior but not for NCE, (2) males that stop copulating after MPOA lesions are still sexually aroused by estrous females, and (3) the BST plays an important role in mediating NCE.
A Postsynaptic Interaction between Dopamine D1and NMDA Receptors Promotes Presynaptic Inhibition in the Rat Nucleus Accumbens via Adenosine Release
Authors: Harvey Jenni , Lacey Michael G.
Published: April 2018

The mechanism underlying dopamine D1receptor-mediated attenuation of glutamatergic synaptic input to nucleus accumbens (NAcc) neurons was investigated in slices of rat forebrain, using whole-cell patch-clamp recording. The depression by dopamine of EPSCs evoked by single-shock cortical stimulation was stimulus-dependent. Synaptic activation of NMDA-type glutamate receptors was critical for this effect, because dopamine-induced EPSC depressions were blocked by the competitive NMDA receptor antagonistd/l-2-amino-5-phosphonopentanoate (AP5). Application of NMDA also depressed the EPSC, and both this effect and the dopamine depressions were blocked by the A1receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), implicating adenosine release in the EPSC depression. A1receptor agonists also depressed EPSCs by a presynaptic action, causing increased paired-pulse facilitation, but this was insensitive to AP5. Activation of D1receptors enhanced both postsynaptic inward currents evoked by NMDA application and the isolated NMDA receptor-mediated component of synaptic transmission. The biochemical processes underlying the dopamine-induced EPSC depression did not involve either protein kinase A or the production of cAMP and its metabolites, because this effect was resistant to the protein kinase inhibitors H89 and H7 and the cAMP-specific phosphodiesterase inhibitor rolipram. We conclude that activation of postsynaptic D1receptors enhances the synaptic activation of NMDA receptors in nucleus accumbens neurons, thereby promoting a transsynaptic feedback inhibition of glutamatergic synaptic transmission via release of adenosine. Unusually for D1receptors, this phenomenon occurs independently of adenylyl cyclase stimulation. This process may contribute to the locomotor stimulant action of dopaminergic agents in the NAcc.
The Neurotrophin Receptor p75 Binds Neurotrophin-3 on Sympathetic Neurons with High Affinity and Specificity
Authors: Dechant Georg , Tsoulfas Pantelis , Parada Luis F. , Barde Yves-Alain
Published: April 2018

High-affinity neurotrophin-3 (NT3) receptors have been identified on nerve growth factor (NGF)-dependent sympathetic neurons, but their occupancy by NT3 does not lead to neuronal survival. The molecular nature of these NT3 binding sites was investigated in this study. With freshly dissociated embryonic day 11 (E11) chick sympathetic neurons, cross-linking experiments revealed that the main receptor responsible for high-affinity specific binding was the neurotrophin receptor p75 (p75NTR), with only a small fraction corresponding to trkC. When E11 sympathetic neurons were cultured in the presence of NGF,trkCtranscripts became undetectable, but high-affinity specific NT3 binding persisted. Cross-linking and antibody inhibition experiments indicated that p75NTRwas the only detectable NT3 receptor protein. These characteristics were not observed when p75NTRwas expressed in transformed cells. We conclude that p75NTRcan exist in neurons in a confirmation conferring hitherto unrecognized properties to this receptor.
Nerve Growth Factor Accelerates Seizure Development, Enhances Mossy Fiber Sprouting, and Attenuates Seizure-Induced Decreases in Neuronal Density in the Kindling Model of Epilepsy
Authors: Adams Beth , Sazgar Mona , Osehobo Philip , Van der Zee Catharina E. E. M. , Diamond Jack , Fahnestock Margaret , Racine Ronald J.
Published: April 2018

Recurrent seizure activity induced during kindling has been reported to produce a functional synaptic reorganization of the mossy fibers in the hippocampus. To date, it is unclear whether this kindling-induced growth is secondary to decreases in hilar neuron density, which are presumed to reflect hilar neuronal cell loss, or whether it is related specifically to an activation-dependent plasticity. We recently demonstrated that blocking nerve growth factor (NGF) biological activity retards seizure development and inhibits the sprouting of mossy fibers. We now demonstrate that intraventricular administration of NGF itself accelerates the progression of kindling epileptogenesis, increases mossy fiber sprouting in the CA3 region and in the inner molecular layer (IML), but reduces seizure-induced decreases in hilar cell density. These findings provide support for a role of NGF in kindling and kindling-induced mossy fiber sprouting. In addition, the results dissociate this form of epileptogenesis from hilar cell loss or decreases in hilar cell density attributable to increases in hilar area, thereby supporting seizure-induced mossy fiber sprouting as being primarily attributable to the combined effects of neuronal activation and the activation-induced upregulation of growth factors.
ATP P2XReceptors Mediate Fast Synaptic Transmission in the Dorsal Horn of the Rat Spinal Cord
Authors: Bardoni Rita , Goldstein Peter A. , Lee C. Justin , Gu Jianguo G. , MacDermott Amy B.
Published: April 2018

ATP has been proposed to mediate synaptic transmission in the spinal cord dorsal horn, particularly in the pathway carrying nociceptive information. Using transverse spinal cord slices from postnatal rats, we show that EPSCs mediated by P2Xreceptors, and presumably activated by synaptically released ATP, are evoked in a subpopulation of spinal cord lamina II neurons, a region known to receive strong input from nociceptive primary afferents. The P2Xreceptors on acutely dissociated dorsal horn neurons are nondesensitizing, insensitive to αβ methylene ATP, and show strong but variable sensitivity to the antagonists suramin and pyridoxal-phosphate-6-azophenyl-2′,4′-disulfonic acid (PPADS). These characteristics are consistent with a heterogeneous population of P2Xreceptors, the composition of which includes P2X2, P2X4, and P2X6receptor subtypes. Our results suggest that ATP-activated P2Xreceptors in lamina II of the rat spinal cord may play a role in transmitting or modulating nociceptive information.
Postsynaptic Inhibitors of Calcium/Calmodulin-Dependent Protein Kinase Type II Block Induction But Not Maintenance of Pairing-Induced Long-Term Potentiation
Authors: Otmakhov Nikolai , Griffith Leslie C. , Lisman John E.
Published: April 2018

The role of postsynaptic kinases in the induction and maintenance of long-term potentiation (LTP) was studied in the CA1 region of the rat hippocampal slice. A peptide inhibitor for the catalytic domain of calcium/calmodulin-dependent protein kinase type II (CaM-kinase) was applied through a perfused patch pipette. The inhibitor completely blocked both the short-term potentiation and LTP induced by a pairing protocol. This indicates that the kinase or kinases affected by the peptide are downstream from depolarization in the LTP cascade. The ability to block LTP required that measures be taken to interfere with degradation of the peptide kinase inhibitor by endogenous proteases; either addition of protease inhibitors or modifications of the peptide itself greatly enhanced the effectiveness of the peptide. Protease inhibitors by themselves or control peptide did not block LTP induction. To study the effect of kinase inhibitor on LTP maintenance, we induced LTP in one pathway. Subsequent introduction of the kinase inhibitor blocked the induction of LTP in a second pathway, but it did not affect maintenance of LTP in the first. The implications for the role of kinases in LTP maintenance are discussed.
Nerve Growth Factor Stimulates the Accumulation of β1 Integrin at the Tips of Filopodia in the Growth Cones of Sympathetic Neurons
Authors: Grabham Peter W. , Goldberg Daniel J.
Published: April 2018

Addition of nerve growth factor (NGF) to sympathetic neurons that have been starved of it causes a rapid induction of growth cone motility and the resumption of neurite growth. Using immunofluorescence staining, we show that within 10 min, NGF stimulated the accumulation of dense aggregates of β1 integrin [a receptor for extracellular matrix (ECM) proteins] at most of the tips of either newly extended or preexisting filopodia. This effect occurred in the absence of ECM proteins and in the presence of 1 mg/ml Arg-Gly-Asp-Ser peptide, which blocks ECM binding to integrin, indicating that occupation of the integrin receptor is not necessary for tip localization. In fact, addition of either laminin or fibronectin caused a rapid withdrawal of β1 integrin aggregates from filopodial tips at a rate comparable to that of the rearward flow of actin filaments in the periphery of the growth cone. Surface labeling of the extracellular domain of β1 integrin while aggregated at the tips of filopodia or withdrawing in response to ECM proteins showed that the receptor is positioned within the membrane. The drug butanedione monoxime, an inhibitor of myosins, blocked the accumulation of β1 integrin at the tips of filopodia without inhibiting the formation of filo-podia, suggesting the involvement of a myosin motor in β1 integrin transport. These results provide the first evidence of NGF-mediated accumulation of ECM receptors to sensory elements of the growth cone and suggest one mechanism whereby soluble and substrate-bound cues coordinate to produce directed neurite growth.
Effects of Regional Anesthesia on Phantom Limb Pain Are Mirrored in Changes in Cortical Reorganization
Authors: Birbaumer Niels , Lutzenberger Werner , Montoya Pedro , Larbig Wolfgang , Unertl Klaus , Töpfner Stephanie , Grodd Wolfgang , Taub Edward , Flor Herta
Published: April 2018

The causes underlying phantom limb pain are still unknown. Recent studies on the consequences of nervous system damage in animals and humans reported substantial reorganization of primary somatosensory cortex subsequent to amputation, and one study showed that cortical reorganization is positively correlated with phantom limb pain. This paper examined the hypothesis of a functional relationship between cortical reorganization and phantom limb pain. Neuroelectric source imaging was used to determine changes in cortical reorganization in somatosensory cortex after anesthesia of an amputation stump produced by brachial plexus blockade in six phantom limb pain patients and four pain-free amputees. Three of six phantom limb subjects experienced a virtual elimination of current phantom pain attributable to anesthesia (mean change: 3.8 on an 11-point scale;Z= −1.83;p< 0.05) that was mirrored by a very rapid elimination of cortical reorganization in somatosensory cortex (change = 19.8 mm;t(2)= 5.60;p< 0.05). Cortical reorganization remained unchanged (mean change = 1.6 mm) in three phantom limb pain amputees whose pain was not reduced by brachial plexus blockade and in the phantom pain-free amputation controls. These findings suggest that cortical reorganization and phantom limb pain might have a causal relationship. Methods designed to alter cortical reorganization should be examined for their efficacy in the treatment of phantom limb pain.