bluuebunny/crossref_metadata_2025 huggingface dataset:
Involvement of the Prelimbic–Infralimbic Areas of the Rodent Prefrontal Cortex in Behavioral Flexibility for Place and Response Learning
Authors: Ragozzino Michael E. , Detrick Shauna , Kesner Raymond P.
Published: April 2018

The present experiments investigated the role of the prelimbic–infralimbic areas in behavioral flexibility using a place–response learning paradigm. All rats received a bilateral cannula implant aimed at the prelimbic–infralimbic areas. To examine the role of the prelimbic–infralimbic areas in shifting strategies, rats were tested on a place and a response discrimination in a cross-maze. Some rats were tested on the place version first followed by the response version. The procedure for the other rats was reversed. Infusions of 2% tetracaine into the prelimbic–infralimbic areas did not impair acquisition of the place or response discriminations. Prelimbic–infralimbic inactivation did impair learning when rats were switched from one discrimination to the other (cross-modal shift). To investigate the role of the prelimbic–infralimbic areas in intramodal shifts (reversal learning), one group of rats was tested on a place reversal and another group tested on a response reversal. Prelimbic–infralimbic inactivation did not impair place or response intramodal shifts. Some rats that completed testing on a particular version in the cross-modal and intramodal experiments were tested on the same version in a new room for 3 d. The transfer tests revealed that rats use a spatial strategy on the place version and an egocentric response strategy on the response version. Overall, these results suggest that the prelimbic–infralimbic areas are important for behavioral flexibility involving cross-modal but not intramodal shifts.
TrkB Isoforms with Distinct Neurotrophin Specificities Are Expressed in Predominantly Nonoverlapping Populations of Avian Dorsal Root Ganglion Neurons
Authors: Boeshore Kristen L. , Luckey Carol N. , Zigmond Richard E. , Large Thomas H.
Published: April 2018

Alternative splicing of the avian trkB receptor generates an extracellular deletion (ED) isoform missing 11 amino acids from the neurotrophin-binding domain of the full-length (FL) receptor. When expressed in fibroblasts, the ED isoform exhibited restricted neurotrophin specificity compared with that of the FL receptor. Brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and neurotrophin-4 (NT-4) activated the FL receptor, as determined by tyrosine phosphorylation. However, only BDNF was capable of significant activation of the ED isoform, although to a reduced level. Because positively charged residues in NT-3 are important for binding to trkB, two negatively charged aspartate residues within the 11 amino acid motif of FL trkB were mutated to examine the role of electrostatic interactions on ligand binding. As found for the ED isoform, the FL mutated receptor displayed a similar loss of NT-3- and NT-4-mediated activation, in addition to a diminished responsiveness to BDNF. Because of these profound effects on ligand specificity, reverse transcription-PCR was used to understand the expression of the FL and ED receptor isoforms at the level of single neurons. The predominant expression pattern of either FL or ED isoforms in single embryonic DRG neurons establishes the existence of two subpopulations exhibiting differential responsiveness to trkB ligands, indicating that regulated splicing of the extracellular domain of trkB may serve as a mechanism to restrict neuronal responsiveness to the neurotrophins.
Impairments in High-Frequency Transmission, Synaptic Vesicle Docking, and Synaptic Protein Distribution in the Hippocampus of BDNF Knockout Mice
Authors: Pozzo-Miller Lucas D. , Gottschalk Wolfram , Zhang Li , McDermott Kathryn , Du Jing , Gopalakrishnan Raj , Oho Chikara , Sheng Zu-Hang , Lu Bai
Published: April 2018

Brain-derived neurotrophic factor (BDNF) promotes long-term potentiation (LTP) at hippocampal CA1 synapses by a presynaptic enhancement of synaptic transmission during high-frequency stimulation (HFS). Here we have investigated the mechanisms of BDNF action using two lines of BDNF knockout mice. Among other presynaptic impairments, the mutant mice exhibited more pronounced synaptic fatigue at CA1 synapses during high-frequency stimulation, compared with wild-type animals. Quantitative analysis of CA1 synapses revealed a significant reduction in the number of vesicles docked at presynaptic active zones in the mutant mice. Synaptosomes prepared from the mutant hippocampus exhibited a marked decrease in the levels of synaptophysin as well as synaptobrevin [vesicle-associated membrane protein (VAMP-2)], a protein known to be involved in vesicle docking and fusion. Treatment of the mutant slices with BDNF reversed the electrophysiological and biochemical deficits in the hippocampal synapses. Taken together, these results suggest a novel role for BDNF in the mobilization and/or docking of synaptic vesicles to presynaptic active zones.
Gradual Emergence of Song Selectivity in Sensorimotor Structures of the Male Zebra Finch Song System
Authors: Janata Petr , Margoliash Daniel
Published: April 2018

Birdsong is a model system for understanding how motor and sensory information interact to coordinate behavior. Neurons in one potential site of sensorimotor integration, the forebrain nucleus HVc, have premotor activity during singing and auditory activity during playback of the bird’s own song. It is not known whether the high degree of selectivity for learned features of song observed during playback arises in HVc or also in structures afferent to HVc. We recorded in anesthetized adult zebra finches from two structures afferent to HVc: either the nucleus interfacialis (NIf) or the L1 subdivision of the field L complex, and simultaneously from a second electrode in HVc. Correlations in the bursting pattern of ongoing activity of HVc and NIf recordings were observed; these helped to localize the first electrode to NIf recording sites. Most NIf neurons exhibited song-selective responses, but as a population, they were less selective than were HVc neurons. Most L1 neurons were not song-selective. NIf neurons have also been reported to have premotor activity during singing; thus, NIf is another potential site of auditory–motor interactions in the song system. Evidence gathered to date suggests that those brain areas in the passerine forebrain that are recruited during song production also display the most selective learned auditory responses.
Association of Storage and Processing Functions in the Dorsolateral Prefrontal Cortex of the Nonhuman Primate
Authors: Levy Richard , Goldman-Rakic Patricia S.
Published: April 2018

The prominent role of the prefrontal cortex (PFC) in working memory (WM) is widely acknowledged both in nonhuman primates and in humans. However, less agreement exists on the issue of functional segregation within different subregions of the PFC with regard to the domains of spatial and nonspatial processing or involvement in simpler versus more complex aspects of WM, e.g., maintenance versus processing function. To address these issues, six monkeys were trained to perform four WM tasks that differed with respect to domain (spatial vs nonspatial) and level of WM demand (recall of one vs three items). The delayed response format was used to assess simple one-item memory, whereas self-ordering tasks were used to require the monkey to maintain and organize three items of information within WM. After training, the monkeys received bilateral PFC lesions in one of two different areas, Walker’s areas 9 and 8B (dorsomedial convexity;n= 3) or areas 46 and 8A (dorsolateral cortex,n= 3) and then tested postoperatively on all tasks.

Monkeys with lesions of the dorsomedial convexity were not impaired either on spatial or nonspatial WM tasks, whether the task required simple storage or sequential processing. By contrast, lesions of the dorsolateral cortex produced a significant and persistent impairment in both simple and complex spatial WM but no impairment in the two nonspatial WM tasks. These results support a functional segregation within the dorsolateral prefrontal cortex for WM: the dorsolateral prefrontal cortex (area 46/8A) is selectively involved in spatial WM, whereas the dorsomedial convexity (area 9/8B) is not critically engaged in either spatial or nonspatial working memory. Furthermore, the specific involvement of area 46/8A in spatial sequencing as well as in single-item storage WM tasks supports, in the nonhuman primate, an areal dissociation based on domain rather than on processing demand.
Subunit-Specific Association of Protein Kinase C and the Receptor for Activated C Kinase with GABA Type A Receptors
Authors: Brandon Nicholas J. , Uren Julia M. , Kittler Josef T. , Wang Hongbing , Olsen Richard , Parker Peter J. , Moss Stephen J.
Published: April 2018

GABA receptors (GABAA) are the major sites of fast synaptic inhibition in the brain and can be assembled from five subunit classes: α, β, γ, δ, and ε. Receptor function can be regulated by direct phosphorylation of β and γ2 subunits, but how kinases are targeted to GABAAreceptors is unknown. Here we show that protein kinase C-βII (PKC-βII) is capable of directly binding to the intracellular domain of the receptor β1 and β3 subunits, but not to those of the α1 or γ2 subunits. Moreover, associating PKC-βII is capable of specifically phosphorylating serine 409 in β1 subunit and serines 408/409 within the β3 subunit, key residues for modulating GABAAreceptor function. The receptor for activated C kinase (RACK-1) was found also to bind to the β1 subunit intracellular domain, but PKC binding appeared to be independent of this protein. Using immunoprecipitation, the association of PKC isoforms and RACK-1 with neuronal GABAAreceptors was seen. Furthermore, PKC isoforms associating with neuronal receptors were capable of phosphorylating the receptor β3 subunit.

Together, these observations suggest GABAAreceptors are intimately associated with PKC isoforms via a direct interaction with receptor β subunits. This interaction may serve to localize PKC activity to GABAAreceptors in neurons allowing the rapid regulation of receptor activity by cell-signaling pathways that modify PKC activity.
Targeted Deletion of a Cyclic Nucleotide-Gated Channel Subunit (OCNC1): Biochemical and Morphological Consequences in Adult Mice
Authors: Baker Harriet , Cummings Diana. M. , Munger Steven D. , Margolis Joyce W. , Franzen Linda , Reed Randall R. , Margolis Frank L.
Published: April 2018

The olfactory cyclic nucleotide-gated channel subunit 1 (OCNC1) is required for signal transduction in olfactory receptor cells. To further investigate the role of this channel in the olfactory system, the biochemical and morphological consequences of targeted disruption of OCNC1 were investigated in adult mice. Null as compared to wild-type mice had smaller olfactory bulbs, suggesting compromised development of the central target of the receptor cells. Ectopic olfactory marker protein (OMP)-stained fibers localized to the external plexiform layer reflected the relative immaturity of the olfactory bulb in the null mice. The olfactory epithelium of the knock-out mouse was thinner and showed lower expression of olfactory marker protein and growth-associated protein 43, indicating decreases in both generation and maturation of receptor cells. Tyrosine hydroxylase (TH) expression in the olfactory bulb, examined as a reflection of afferent activity, was reduced in the majority of periglomerular neurons but retained in atypical or “necklace” glomeruli localized to posterior aspects of the olfactory bulb. Double label studies demonstrated that the remaining TH-immunostained neurons received their innervation from a subset of receptor cells previously shown to express a phosphodiesterase that differs from that found in most receptor cells. These data indicate that expression of OCNC1 is required for normal development of the olfactory epithelium and olfactory bulb. The robust expression of TH in some periglomerular cells in the OCNC1-null mice suggests that receptor cells innervating these glomeruli may use an alternate signal transduction pathway.
Disruption of Laminin β2 Chain Production Causes Alterations in Morphology and Function in the CNS
Authors: Libby Richard T. , Lavallee Christopher R. , Balkema Grant W. , Brunken William J. , Hunter Dale D.
Published: April 2018

From the elegant studies of Ramon y Cajal (1909) to the current advances in molecular cloning (e.g., Farber and Danciger, 1997), the retina has served as an ideal model for the entire CNS. We have taken advantage of the well described anatomy, physiology, and molecular biology of the retina to begin to examine the role of the laminins, one component of the extracellular matrix, on the processes of neuronal differentiation and synapse formation in the CNS. We have examined the effect of the deletion of one laminin chain, the β2 chain, on retinal development. The gross development of retinas from laminin β2 chain-deficient animals appears normal, and photoreceptors are formed. However, these retinas exhibit several pathologies: laminin β2 chain-deficient mice display abnormal outer segment elongation, abnormal electroretinograms, and abnormal rod photoreceptor synapses. Morphologically, the outer segments are reduced by 50% in length; the outer plexiform layer of mutant animals is disrupted specifically, because only 7% of observed rod invaginating synapses appear normal, whereas the inner plexiform layer is undisturbed; finally, the rate of apoptosis in the mutant photoreceptor layer is twice that of control mice. Physiologically, the electroretinogram is altered; the amplitude of the b-wave and the slope of the b-wave intensity–response function are both decreased, consistent with synaptic disruption in the outer retina. Together, these results emphasize the prominence of the extracellular matrix and, in particular, the laminins in the development and maintenance of synaptic function and morphogenesis in the CNS.
The Fundamental Role of Pirouettes inCaenorhabditis elegansChemotaxis
Authors: Pierce-Shimomura Jonathan T. , Morse Thomas M. , Lockery Shawn R.
Published: April 2018

To investigate the behavioral mechanism of chemotaxis inCaenorhabditis elegans, we recorded the instantaneous position, speed, and turning rate of single worms as a function of time during chemotaxis in gradients of the attractants ammonium chloride or biotin. Analysis of turning rate showed that each worm track could be divided into periods of smooth swimming (runs) and periods of frequent turning (pirouettes). The initiation of pirouettes was correlated with the rate of change of concentration (dC/dt) but not with absolute concentration. Pirouettes were most likely to occur when a worm was heading down the gradient (dC/dt< 0) and least likely to occur when a worm was heading up the gradient (dC/dt> 0). Further analysis revealed that the average direction of movement after a pirouette was up the gradient. These observations suggest that chemotaxis is produced by a series of pirouettes that reorient the animal to the gradient. We tested this idea by imposing the correlation between pirouettes and dC/dton a stochastic point model of worm motion. The model exhibited chemotaxis behavior in a radial gradient and also in a novel planar gradient. Thus, the pirouette model ofC. eleganschemotaxis is sufficient and general.
Metabotropic Glutamate Receptor-Mediated Hippocampal Phosphoinositide Turnover Is Blunted in Spatial Learning-Impaired Aged Rats
Authors: Nicolle Michelle M. , Colombo Paul J. , Gallagher Michela , McKinney Michael
Published: April 2018

Maximal phosphoinositide (PI) turnover was examined in the hippocampus of young and aged Long–Evans rats that were behaviorally characterized for spatial learning in the Morris water maze. The type 1 metabotropic glutamate receptor (mGluR) agonist 1S,3R ACPD was used to stimulate PI turnover and to determine theEMAXfor each rat. Protein levels in hippocampus for type 1 mGluRs, Gαq11, and phospholipase Cβ-1 (PLCβ-1) were also measured by quantitative Western blotting. The results show that PI turnover mediated by the mGluRs was blunted in the aged rats. The magnitude of the decrement in PI turnover was also significantly correlated with age-related spatial memory decline. The decrease in mGluR-mediated PI turnover occurred without changes in the protein level of either the mGluRs or the G-protein coupled to those receptors, Gαq11. A significant decrease in the immunoreactivity of PLCβ-1, however, was observed in the hippocampus of aged rats; PLCβ-1 immunoreactivity was significantly correlated with spatial learning only when the young and aged rats were considered together. The decrement in mGluR-mediated signal transduction in the hippocampus that is related to cognitive impairment in aging may be attributable, at least in part, to a deficiency in the enzyme PLCβ-1. That deficiency may also contribute to a blunted response in muscarinic stimulation of hippocampal PI turnover that we previously found in this same study population. An age-related alteration in this signal transduction system may provide a functional basis for cognitive decline independent of any loss of neurons in the hippocampus.
Rapid Ischemic Cell Death in Immature Oligodendrocytes: A Fatal Glutamate Release Feedback Loop
Authors: Fern Robert , Möller Thomas
Published: April 2018

Ischemic injury of immature oligodendrocytes is a major component of the brain injury associated with cerebral palsy, the most common human birth disorder. We now report that cultured immature oligodendrocytes [O4+/galactoceramide (GC)−] are exquisitely sensitive to ischemic injury (80% of cells were dead after 25.5 min of oxygen and glucose withdrawal). This rapid ischemic cell death was mediated by Ca2+influx via non-NMDA glutamate receptors. The receptors were gated by the release of glutamate from the immature oligodendrocytes themselves via reverse glutamate transport and included a significant element of autologous feedback of glutamate from cells onto their own receptors. High (≥100 μm) extracellular glutamate was protective against ischemic injury as a result of non-NMDA glutamate receptor desensitization. Other potential pathways of Ca2+influx, such as voltage-gated Ca2+channels, NMDA receptors, or the Na+–Ca2+exchanger, did not significantly contribute to ischemic Ca2+influx or cell injury. Release of Ca2+from intracellular stores was also not an important factor. In agreement with previous studies, more mature oligodendrocytes (O4−/GC+) were found to be less sensitive to ischemic injury than were the immature cells studied here.
Developmental Changes in Calcium Channel Types Mediating Central Synaptic Transmission
Authors: Iwasaki Shinichi , Momiyama Akiko , Uchitel Osvaldo D. , Takahashi Tomoyuki
Published: April 2018

Multiple types of high-voltage-activated Ca2+channels trigger neurotransmitter release at the mammalian central synapse. Among them, the ω-conotoxin GVIA-sensitive N-type channels and the ω-Aga-IVA-sensitive P/Q-type channels mediate fast synaptic transmission. However, at most central synapses, it is not known whether the contributions of different Ca2+channel types to synaptic transmission remain stable throughout postnatal development. We have addressed this question by testing type-specific Ca2+channel blockers at developing central synapses. Our results indicate that N-type channels contribute to thalamic and cerebellar IPSCs only transiently during early postnatal period and P/Q-type channels predominantly mediate mature synaptic transmission, as we reported previously at the brainstem auditory synapse formed by the calyx of Held. In fact, Ca2+currents directly recorded from the auditory calyceal presynaptic terminal were identified as N-, P/Q-, and R-types at postnatal day 7 (P7) to P10 but became predominantly P/Q-type at P13. In contrast to thalamic and cerebellar IPSCs and brainstem auditory EPSCs, N-type Ca2+channels persistently contribute to cerebral cortical EPSCs and spinal IPSCs throughout postnatal months. Thus, in adult animals, synaptic transmission is predominantly mediated by P/Q-type channels at a subset of synapses and mediated synergistically by multiple types of Ca2+channels at other synapses.
Nicotinic Receptor Activation in Human Cerebral Cortical Interneurons: a Mechanism for Inhibition and Disinhibition of Neuronal Networks
Authors: Alkondon Manickavasagom , Pereira Edna F. R. , Eisenberg Howard M. , Albuquerque Edson X.
Published: April 2018

Cholinergic control of the activity of human cerebral cortical circuits has long been thought to be accounted for by the interaction of acetylcholine (ACh) with muscarinic receptors. Here we report the discovery of functional nicotinic receptors (nAChRs) in interneurons of the human cerebral cortex and discuss the physiological and clinical implications of these findings. The whole-cell mode of the patch-clamp technique was used to record responses triggered by U-tube application of the nonselective agonist ACh and of the α7-nAChR-selective agonist choline to interneurons visualized by means of infrared-assisted videomicroscopy in slices of the human cerebral cortex. Choline induced rapidly desensitizing whole-cell currents that, being sensitive to blockade by methyllycaconitine (MLA; 50 nm), were most likely subserved by an α7-like nAChR. In contrast, ACh evoked slowly decaying whole-cell currents that, being sensitive to blockade by dihydro-β-erythroidine (DHβE; 10 μm), were most likely subserved by an α4β2-like nAChR. Application of ACh (but not choline) to the slices also triggered GABAergic postsynaptic currents (PSCs). Evidence is provided that ACh-evoked PSCs are the result of activation of α4β2-like nAChRs present in preterminal axon segments and/or in presynaptic terminals of interneurons. Thus, nAChRs can relay inhibitory and/or disinhibitory signals to pyramidal neurons and thereby modulate the activity of neuronal circuits in the human cerebral cortex. These mechanisms, which appear to be retained across species, can account for the involvement of nAChRs in cognitive functions and in certain neuropathological conditions.
The Glial Cell Line-Derived Neurotrophic Factor Family Receptor Components Are Differentially Regulated within Sensory Neurons after Nerve Injury
Authors: Bennett David L. H. , Boucher Timothy J. , Armanini Mark P. , Poulsen Kris T. , Michael Gregory J. , Priestley John V. , Phillips Heidi S. , McMahon Stephen B. , Shelton David L.
Published: April 2018

Glial cell line-derived neurotrophic factor (GDNF) has potent trophic effects on adult sensory neurons after nerve injury and is one of a family of proteins that includes neurturin, persephin, and artemin. Sensitivity to these factors is conferred by a receptor complex consisting of a ligand binding domain (GFRα1–GFRα4) and a signal transducing domain RET. We have investigated the normal expression of GDNF family receptor components within sensory neurons and the response to nerve injury.

In normal rats, RET and GFRα1 were expressed in a subpopulation of both small- and large-diameter afferents projecting through the sciatic nerve [60 and 40% of FluoroGold (FG)-labeled cells, respectively]. GFRα2 and GFRα3 were both expressed principally within small-diameter DRG cells (30 and 40% of FG-labeled cells, respectively). Two weeks after sciatic axotomy, the expression of GFRα2 was markedly reduced (to 12% of sciatic afferents). In contrast, the proportion of sciatic afferents that expressed GFRα1 increased (to 66% of sciatic afferents) so that virtually all large-diameter afferents expressed this receptor component, and the expression of GFRα3 also increased (to 66% of sciatic afferents) so that almost all of the small-diameter afferents expressed this receptor component after axotomy. There was little change in RET expression.

The changes in the proportions of DRG cells expressing different receptor components were mirrored by alterations in the total RNA levels within the DRG. The changes in GFRα1 and GFRα2 expression after axotomy could be largely reversed by treatment with GDNF.
Destruction and Creation of Spatial Tuning by Disinhibition: GABAABlockade of Prefrontal Cortical Neurons Engaged by Working Memory
Authors: Rao Srinivas G. , Williams Graham V. , Goldman-Rakic Patricia S.
Published: April 2018

Local circuit neurons in the dorsolateral prefrontal cortex (dPFC) of monkeys have been implicated in the cellular basis of working memory. To further elucidate the role of inhibition in spatial tuning, we iontophoresed bicuculline methiodide (BMI) onto functionally characterized neurons in the dPFC of monkeys performing an oculomotor delayed response task. This GABAAblockade revealed that both putative interneurons and pyramidal cells possess significant inhibitory tone in the awake, behaving monkey. In addition, BMI application primarily resulted in the loss of previously extant spatial tuning in both cell types through reduction of both isodirectional and cross-directional inhibition. This tuning loss occurred in both the sensorimotor and mnemonic phases of the task, although the delay activity of prefrontal neurons appeared to be particularly affected. Finally, application of BMI also created significant spatial tuning in a sizable minority of units that were untuned in the control condition. Visual field analysis of such tuning suggests that it is likely caused by the unmasking of normally suppressed spatially tuned excitatory input. These findings provide the first direct evidence of directional inhibitory modulation of pyramidal cell and interneuron firing in both the mnemonic and sensorimotor phases of the working memory process, and they implicate a further role for GABAergic interneurons in the construction of spatial tuning in prefrontal cortex.
cAMP-Dependent Plasticity at Excitatory Cholinergic Synapses inDrosophilaNeurons: Alterations in the Memory MutantDunce
Authors: Lee Daewoo , O'Dowd Diane K.
Published: April 2018

It is well known that cAMP signaling plays a role in regulating functional plasticity at central glutamatergic synapses. However, in theDrosophilaCNS, where acetylcholine is thought to be a primary excitatory neurotransmitter, cellular changes in neuronal communication mediated by cAMP remain unexplored. In this study we examined the effects of elevated cAMP levels on fast excitatory cholinergic synaptic transmission in cultured embryonicDrosophilaneurons. We report that chronic elevation in neuronal cAMP (indunceneurons or wild-type neurons grown in db-cAMP) results in an increase in the frequency of cholinergic miniature EPSCs (mEPSCs). The absence of alterations in mEPSC amplitude or kinetics suggests that the locus of action is presynaptic. Furthermore, a brief exposure to db-cAMP induces two distinct changes in transmission at established cholinergic synapses in wild-type neurons: a short-term increase in the frequency of spontaneous action potential-dependent synaptic currents and a long-lasting, protein synthesis-dependent increase in the mEPSC frequency. A more persistent increase in cholinergic mEPSC frequency induced by repetitive, spaced db-cAMP exposure in wild-type neurons is absent in neurons from the memory mutantdunce. These data demonstrate that interneuronal excitatory cholinergic synapses inDrosophila,like central excitatory glutamatergic synapses in other species, are sites of cAMP-dependent plasticity. In addition, the alterations indunceneurons suggest that cAMP-dependent plasticity at cholinergic synapses could mediate changes in neuronal communication that contribute to memory formation.
Multiple G-Protein βγ Combinations Produce Voltage-Dependent Inhibition of N-Type Calcium Channels in Rat Superior Cervical Ganglion Neurons
Authors: Ruiz-Velasco Victor , Ikeda Stephen R.
Published: April 2018

Activation of several G-protein-coupled receptors leads to voltage-dependent (VD) inhibition of N- and P/Q-type Ca2+channels via G-protein βγ subunits (Gβγ). The purpose of the present study was to determine the ability of different Gβγ combinations to produce VD inhibition of N-type Ca2+channels in rat superior cervical ganglion neurons. Various Gβγ combinations were heterologously overexpressed by intranuclear microinjection of cDNA and tonic VD Ca2+channel inhibition evaluated using the whole-cell voltage-clamp technique. Overexpression of Gβ1–Gβ5, in combination with several different Gγ subunits, resulted in tonic VD Ca2+channel inhibition. Robust Ca2+channel modulation required coexpression of both Gβ and Gγ. Expression of either subunit alone produced minimal effects. To substantiate the apparent lack of Gβγ specificity, we examined whether heterologously expressed Gβγ displaced native Gβγ from heterotrimeric complexes. To this end, mutant Gβ subunits were constructed that differentially modulated N-type Ca2+and G-protein-gated inward rectifier K+channels. Results from these studies indicated that significant displacement does not occur, and thus the observed Gβγ modulation can be attributed directly to the heterologously expressed Gβγ combinations.
Application of Neutralizing Antibodies against NI-35/250 Myelin-Associated Neurite Growth Inhibitory Proteins to the Adult Rat Cerebellum Induces Sprouting of Uninjured Purkinje Cell Axons
Authors: Buffo Annalisa , Zagrebelsky Marta , Huber Andrea B. , Skerra Arne , Schwab Martin E. , Strata Piergiorgio , Rossi Ferdinando
Published: April 2018

The myelin-associated proteins NI-35/250 exert a powerful inhibition on axon regeneration, but their function exerted on intact neurons is still unclear. In the adult CNS these proteins are thought to regulate axon growth processes to confine plasticity within restricted regions and to prevent the formation of aberrant connections. We have recently shown that application of neutralizing IN-1 antibody Fab fragment against NI-35/250 proteins to the adult cerebellum induces the expression of injury/growth-associated markers in intact Purkinje cells. Here, we asked whether these cellular modifications are accompanied by growth phenomena of Purkinje neurites. A single intraparenchymal application of IN-1 Fab fragment to the adult cerebellum induces a profuse sprouting of Purkinje axons along their intracortical course. The newly formed processes spread to cover most of the granular layer depth. A significant axon outgrowth is evident 2 d after injection; it tends to increase at 5 and 7 d, but it is almost completely reversed after 1 month. No axonal modifications occur in control Fab-treated cerebella. The IN-1 Fab fragment-induced cellular changes and axon remodeling are essentially reproduced by applying affinity-purified antibody 472 raised against a peptide sequence of the recombinant protein NI-220, thus confirming the specificity of the applied treatments on these myelin-associated molecules. Functional neutralization of NI-35/250 proteins induces outgrowth from uninjured Purkinje neurites in the adult cerebellum. Together with previous observations, this suggests that these molecules regulate axonal plasticity to maintain the proper targeting of terminal arbors within specific gray matter regions.
Organization of Cortical Activities Related to Movement in Humans
Authors: Marsden J. F. , Werhahn K. J. , Ashby P. , Rothwell J. , Noachtar S. , Brown P.
Published: April 2018

The extent and function of synchronization of oscillatory elements in the human sensorimotor cortex during movement remains unclear. Here we determine whether synchronization is distributed in both the spatial and frequency domains and whether it changes according to task. Electrocorticographic (ECoG) signals were recorded from presumed nonpathological areas simultaneously with electromyographic (EMG) signals from upper limb muscles during isometric and phasic movement tasks in humans with subdural electrodesin situfor investigation of epilepsy. Functional mapping of the sensorimotor cortex was performed by previous electrical stimulation through the same ECoG electrodes used for recording. Significant coherence between ECoG and EMG was seen at discrete frequencies in the range of 7–100 Hz. There was no predilection for coherence within a given frequency band to be associated with cortical sites that had been functionally defined as producing contralateral arm motor responses on stimulation. However, coherence with muscle in the 7–14 and 15–30 Hz band tended to be associated with ECoG sites that lay close to or within the central sulcus as determined intraoperatively. The spatial pattern and frequency of coherence changed with different tasks, although similarities in the coherence pattern remained for tasks that shared common features. These findings provide support for the hypothesis that that synchronization at specific frequencies links cortical activities into a functional ensemble during voluntary movement.
Amphetamine Withdrawal Alters Bistable States and Cellular Coupling in Rat Prefrontal Cortex and Nucleus Accumbens Neurons RecordedIn Vivo
Authors: Onn Shao-Pii , Grace Anthony A.
Published: April 2018

Repeated amphetamine administration is known to produce changes in corticoaccumbens function that persist beyond termination of drug administration. We have found previously that long-term alteration in dopamine systems leads to changes in gap junction communication, expressed as dye coupling, between striatal neurons. In this study, the cellular bases of amphetamine-induced changes were examined usingin vivointracellular recordings and dye injection in ventral prefrontal–accumbens system neurons of control and amphetamine-treated rats. Rats that had been withdrawn from repeated amphetamine displayed a significant increase in the incidence of dye coupling in the prefrontal cortex and nucleus accumbens, which persisted for up to 28 d after withdrawal. The increased coupling was limited to projection neurons in both prefrontal cortical and accumbens brain regions, as identified by their axonal trajectory or the absence of interneuron-selective immunocytochemical markers. These changes occurred with no substantial loss of tyrosine hydroxylase-immunoreactive terminals in these cortical and accumbens regions, ruling out dopamine degeneration as a precipitating factor. Previous studies showed that nitric oxide plays a role in the regulation of coupling; however, amphetamine-withdrawn rats had fewer numbers of neurons and processes that stained for nitric oxide synthase immunoreactivity. In amphetamine-treated rats, a higher proportion of cortical cells fired in bursts, and a larger proportion of accumbens and prefrontal cortical neurons exhibited bistable membrane oscillations. By increasing corticoaccumbens transmission, amphetamine withdrawal may lead to neuronal synchronization via gap junctions. Furthermore, this adaptation to amphetamine treatment persists long after the drug is withdrawn.
Novel Role for the NMDA Receptor Redox Modulatory Site in the Pathophysiology of Seizures
Authors: Sanchez Russell M. , Wang Carl , Gardner Ginger , Orlando Lianna , Tauck David L. , Rosenberg Paul A. , Aizenman Elias , Jensen Frances E.
Published: April 2018

Redox-active compounds modulate NMDA receptors (NMDARs) such that reduction of NMDAR redox sites increases, and oxidation decreases, NMDAR-mediated activity. Because NMDARs contribute to the pathophysiology of seizures, redox-active compounds also may modulate seizure activity. We report that the oxidant 5,5′-dithio-bis(2-nitrobenzoic acid) (DTNB) and the redox cofactor pyrroloquinoline quinone (PQQ) suppressed low Mg2+-induced hippocampal epileptiform activityin vitro. Additionally, in slices exposed to 4–7 μmbicuculline, DTNB and PQQ reversed the potentiation of evoked epileptiform responses by the reductants dithiothreitol and Tris(2-carboxyethyl)phosphine (TCEP). NMDA-evoked whole-cell currents in CA1 neurons in slices were increased by TCEP and subsequently decreased by DTNB or PQQ at the same concentrations that modulated epileptiform activity. However, DTNB and PQQ had little effect on baseline NMDA-evoked currents in control medium, and PQQ did not alter NMDAR-dependent long-term potentiation. In contrast, in slices returned to control medium after low Mg2+-induced ictal activity, DTNB significantly inhibited NMDAR-mediated currents, indicating endogenous reduction of NMDAR redox sites under this epileptogenic condition. These data suggested that PQQ and DTNB suppressed spontaneous ictal activity by reversing pathological NMDAR redox potentiation without inhibiting physiological NMDAR function.In vivo, PQQ decreased the duration of chemoconvulsant-induced seizures in rat pups with no effect on baseline behavior. Our results reveal endogenous potentiation of NMDAR function via mass reduction of redox sites as a novel mechanism that may enhance epileptogenesis and facilitate the transition to status epilepticus. The results further suggest that redox-active compounds may have therapeutic use by reversing NMDAR-mediated pathophysiology without blocking physiological NMDAR function.
Isolation andIn VitroDifferentiation of Conditionally Immortalized Murine Olfactory Receptor Neurons
Authors: Barber Robert D. , Jaworsky Donna E. , Yau King-Wai , Ronnett Gabriele V.
Published: April 2018

Two major challenges exist in our understanding of the olfactory system. One concerns the enormous combinatorial code underlying odorant discrimination by odorant receptors. The other relates to neurogenesis and neuronal development in the olfactory epithelium. To address these issues, continuous cell cultures containing olfactory receptor neurons (ORNs) were obtained from olfactory epithelia of H-2Kb-tsA58 transgenic mice. ORNs were detected and characterized by immunocytochemistry, RT-PCR, and Western blot for the markers Gαolf, adenylyl cyclase III, the olfactory cyclic nucleotide-gated channel subunits, and olfactory marker protein. In culture, epidermal growth factor and nerve growth factor stimulated proliferation, and brain-derived neurotrophic factor and neurotrophin-3 induced cellular maturation.

Clonal cell lines were isolated by fluorescence-activated cell sorting with anti-neural cell adhesion molecule antibodies, and of 144 single cells plated, 39 clones were expanded, propagated, and stored in liquid nitrogen. All attempts at recovery of clonal lines from frozen stocks have been successful. The most thoroughly characterized clone, 3NA12, expressed ORN markers and responded to stimulation by single odorants. Each odorant activated ∼1% of cells in a clonal line, and this suggests that many different odorant receptors may be expressed by these clonal cells. Therefore, these cell lines and the method by which they have been obtained represent a significant advance in the generation of olfactory cell cultures and provide a system to investigate odorant coding and olfactory neurogenesis.
Convergent Inputs from Thalamic Motor Nuclei and Frontal Cortical Areas to the Dorsal Striatum in the Primate
Authors: McFarland Nikolaus R. , Haber Suzanne N.
Published: April 2018

Current models of basal ganglia circuitry primarily associate the ventral thalamic nuclei with relaying basal ganglia output to the frontal cortex. However, some studies have demonstrated projections from the ventral anterior (VA) and ventral lateral (VL) thalamic nuclei to the striatum, suggesting that these nuclei directly modulate the striatum. VA/VL nuclei have specific connections with primary, supplementary, premotor, and cingulate motor cortices indicating their involvement in motor function. These areas mediate different aspects of motor control such as movement execution, motor learning, and sensorimotor integration. Increasing evidence indicates that functionally related motor areas have convergent projections to the dorsal striatum, suggesting that integration of different aspects of motor control occur at the level of the striatum. This study examines the organization of VA/VL thalamic inputs to the dorsal “motor” striatum to determine how this afferent projection is organized with respect to corticostriatal afferents from motor, premotor, and cingulate motor areas. Motor cortical projections to specific dorsal striatal regions arose from multiple areas, including components from primary motor, premotor, supplementary, and cingulate motor areas. Diverse motor cortical projections to a given dorsal striatal region indicated convergence of functionally related corticostriatal motor pathways. Most dorsal striatal sites received dense thalamic inputs from the VL pars oralis nucleus. Additional thalamostriatal projections arose from VA, VL pars caudalis, and ventral posterior lateral pars oralis nuclei and Olszewski's Area X. Our results provide evidence for convergent striatal projections from interconnected ventral thalamic and cortical motor areas, suggesting that these afferents modulate the same striatal output circuits.
Heparan Sulfate Heterogeneity in Skeletal Muscle Basal Lamina: Demonstration by Phage Display-Derived Antibodies
Authors: Jenniskens Guido J. , Oosterhof Arie , Brandwijk Ricardo , Veerkamp Jacques H. , van Kuppevelt Toin H.
Published: April 2018

The basal lamina (BL) enveloping skeletal muscle fibers contains different glycoproteins, including proteoglycans. To obtain more information on the glycosaminoglycan moiety of proteoglycans, we have selected a panel of anti-heparan sulfate (HS) antibodies from a semisynthetic antibody phage display library by panning against glycosaminoglycan preparations derived from skeletal muscle. Epitope recognition by the antibodies is strongly dependent onO- andN-sulfation of the heparan sulfate. Immunostaining with these antibodies showed a distinct distribution of heparan sulfate epitopes in muscle basal lamina of various species. Clear differences in staining intensity were observed between neural, synaptic, and extrasynaptic basal laminae. Moreover, temporal and regional changes in abundancy of heparan sulfate epitopes were observed during muscle development bothin vitroandin vivo. Taken together, these data suggest a role for specific heparan sulfate domains/species in myogenesis and synaptogenesis. Detailed analysis of the functions of heparan sulfate epitopes in muscle morphogenesis has now become feasible with the isolation of antibodies specific for distinct heparan sulfate epitopes.
Upregulation of cAMP Response Element-Mediated Gene Expression during Experience-Dependent Plasticity in Adult Neocortex
Authors: Barth Alison L. , McKenna Mervyn , Glazewski Stanislaw , Hill Penelope , Impey Soren , Storm Daniel , Fox Kevin
Published: April 2018

Gene transcription is thought to be essential for memory consolidation and long-lasting changes in synaptic function. In particular, the signal transduction pathways that activate the transcription factor cAMP response element binding protein (CREB) have been implicated in the process of synaptic potentiation. To study the involvement of this pathway in neocortical plasticity within the barrel cortex, we have used a strain of mice carrying aLacZreporter gene with six cAMP response elements (CREs) upstream of a minimal promoter. Removal of all but one facial whisker results in the expansion of the spared whisker's functional representation within somatosensory cortex. Under the same conditions of whisker deprivation, we observed a strong (eightfold compared with baseline) and highly place-specific upregulation of CRE-mediated gene transcription in layer IV of the spared whisker barrel. Reporter gene upregulation occurred rapidly after deprivation (16 hr) and was only observed under experimental conditions capable of inducing whisker response potentiation.LacZexpression in layer IV was accompanied by an increase in responsiveness of a subpopulation of layers II/III cells to spared whisker stimulation as determined byin vivosingle-unit recording. Given that CREB is involved in the expression of plasticity in superficial layers (Glazewski et al., 1999), and yet CRE-mediated gene expression occurs in layer IV, it is likely that the molecular events initiating plasticity occur presynaptically to the cells that exhibit changes in their receptive field properties.
Evidence That Separate Neural Circuits in the Nucleus Accumbens Encode Cocaine Versus “Natural” (Water and Food) Reward
Authors: Carelli Regina M. , Ijames Stephanie G. , Crumling Alison J.
Published: April 2018

Electrophysiological recording procedures were used to examine nucleus accumbens (Acb) cell firing in rats trained to press a lever on a multiple schedule [ fixed ratio (FR)1, FR1] for either two “natural” reinforcers (food and water), or a natural reinforcer and intravenous self-administration of cocaine. Of 180 cells recorded during water and food reinforcement (n= 13 rats), 77 neurons were classified as phasically active, exhibiting one of three well-defined types of patterned discharges relative to the reinforced-response (Carelli and Deadwyler, 1994). Of the 77 phasic cells, the majority (68%) showed similar types of patterned discharges across the two natural reinforcer conditions. In contrast, of 127 neurons recorded during water and cocaine reinforcement (n= 8 rats), only 5 of 60 phasically active cells (8%) exhibited similar types of patterned discharges relative to water- and cocaine-reinforced responding. The remaining 55 phasic cells (92%) displayed patterned discharges relative to the cocaine-reinforced response (n= 26 cells), or relative to the water-reinforced response (n= 29 cells), but not both. For some rats (n= 3), food was substituted for water in the task. Again, the majority of phasic neurons (13 of 14 cells, 93%) exhibited nonoverlapping firing patterns across the drug and natural reinforcer conditions. These findings indicate that in the well-trained animal, cocaine activates a neural circuit in the Acb that is largely separate from the circuit that processes information about food and water reward.
Circadian and Homeostatic Control of Rapid Eye Movement (REM) Sleep: Promotion of REM Tendency by the Suprachiasmatic Nucleus
Authors: Wurts Sarah W. , Edgar Dale M.
Published: April 2018

The daily timing of rapid eye movement (REM) sleep reflects an interaction between the circadian pacemaker located in the suprachiasmatic nucleus of the hypothalamus (SCN) and a homeostatic process that induces compensatory REM sleep in response to REM sleep loss. Whether the circadian variation in REM sleep propensity is caused by active promotion, inhibition, or passive gating of REM sleep homeostasis by the SCN is unknown. To investigate these possibilities, compensatory responses to 24 hr REM sleep deprivation (RSD) were compared between SCN-lesioned (SCNx) and sham-lesioned rats at different times of day in constant dark. The attempts to enter REM sleep (REM tendency) increased during RSD in all rats and were modulated by circadian phase in sham-lesioned, but not SCNx rats. REM sleep homeostasis interacted with circadian time, such that REM tendency doubled during the rest phase in sham-lesioned rats relative to SCNx rats (F(6,93)= 17.9;p= 0.0001). However, REM tendency was indistinguishable between SCNx and sham-lesioned rats during the activity phase, suggesting the SCN does not inhibit REM tendency at this time. By contrast, the amount of compensatory REM sleep examined 2, 6, 12, or 24 hr after RSD did not depend on circadian phase. Thus, transitions into REM sleep are facilitated by the SCN during the rest phase, but the amount of REM sleep, once initiated, is determined primarily by homeostatic mechanisms. This work supports a role for the SCN in the active promotion of REM sleep at specific times of day.