bluuebunny/crossref_metadata_2025 huggingface dataset:
Different Subthreshold Mechanisms Underlie Song Selectivity in Identified HVc Neurons of the Zebra Finch
Authors: Mooney Richard
Published: April 2018

Songbirds learn and maintain their songs via auditory experience. Neurons in many telencephalic nuclei important to song production and development are song selective, firing more to forward auditory playback of the bird's own song (BOS) than to reverse BOS or conspecific songs. Elucidating circuits that generate these responses can localize where auditory experience influences vocalization, bridging cellular and systems analyses of song learning. Song-selective responses in many song nuclei, including the vocal premotor nucleus robustus archistriatalis (RA) and the basal ganglia homolog area X, are thought to originate in nucleus HVc (used as a proper name), which contains interneurons and relay cells that innervate either RA or area X. Previous studies indicated that only X-projecting neurons have auditory responses, leaving open the source of RA's auditory input and the degree to which song selectivity may be refined in HVc. Here,in vivointracellular recordings from morphologically and electrophysiologically identified HVc neurons revealed that both relay cell types fire song-selectively. However, their firing arises via markedly different subthreshold processes, and only X-projecting neurons appear to be sites for auditory refinement. RA-projecting neurons exhibited purely depolarizing subthreshold responses that were highly song selective and that were excitatory. In contrast, subthreshold responses of X-projecting neurons included less-selective depolarizing and highly selective hyperpolarizing components. Within individual birds, these BOS-evoked hyperpolarizations closely matched interneuronal firing, suggesting that HVc interneurons make restricted inputs onto X-projecting neurons. Because of the two relay cell types' subthreshold differences, factors affecting their resting membrane potentials could enable them to transmit distinct song representations to their targets.
Regulation of Rat Cortex Function by D1 Dopamine Receptors in the Striatum
Authors: Steiner Heinz , Kitai Stephen T.
Published: April 2018

Interactions between the basal ganglia and the cerebral cortex are critical for normal goal-directed behavior. In the present study, we used immediate-early genes (c-fos,zif 268) as functional markers to investigated how basal ganglia output altered by stimulation/blockade of D1 dopamine receptors in the striatum affects cortical function. Systemic administration of the mixed D1/D2 receptor agonist apomorphine (3 mg/kg) increased immediate-early gene expression in the striatum and throughout most of the cortex. Unilateral intrastriatal infusion of the selective D1 receptor antagonist SCH-23390 (0.5–10 μg) blocked this response bilaterally in striatum and cortex in a dose-dependent manner. Even apparently regionally restricted blockade of striatal D1 receptors attenuated gene expression throughout striatum and cortex in both hemispheres. Intrastriatal administration of the D1 antagonist inhibited apomorphine-induced sniffing/whisking, whereas other motor behaviors were unaffected. To determine whether such changes in cortical gene expression could reflect altered cortical function, we examined the effects of blocking striatal D1 receptors on whisker stimulation-evoked immediate-early gene expression in the sensorimotor cortex. Apomorphine increased sensory stimulation-evoked gene expression in the barrel cortex, and intrastriatal infusion of SCH-23390 attenuated this effect. These results suggest that stimulation of D1 dopamine receptors in the striatum exerts a widespread facilitatory effect on cortical function.
The Midbrain Precommand Nucleus of the Mormyrid Electromotor Network
Authors: von der Emde Gerhard , Sena Leonel Gómez , Niso Rafaella , Grant Kirsty
Published: April 2018

The functional role of the midbrain precommand nucleus (PCN) of the electromotor system was explored in the weakly electric mormyrid fishGnathonemus petersii, using extracellular recording of field potentials, single unit activity, and microstimulationin vivo.

Electromotor-related field potentials in PCN are linked in a one-to-one manner and with a fixed time relationship to the electric organ discharge (EOD) command cycle, but occur later than EOD command activity in the medulla. It is suggested that PCN electromotor-related field potentials arise from two sources: (1) antidromically, by backpropagation across electrotonic synapses between PCN axons and command nucleus neurons, and (2) as corollary discharge-driven feedback arriving from the command nucleus indirectly, via multisynaptic pathways.

PCN neurons can be activated by electrosensory input, but this does not necessarily activate the whole motor command chain. Microstimulation of PCN modulates the endogenous pattern of electromotor command in a way that can mimic the structure of certain stereotyped behavioral patterns. PCN activity is regulated, and to a certain extent synchronized, by corollary discharge feedback inhibition. However, PCN does not generally function as a synchronized pacemaker driving the electromotor command chain. We propose that PCN neurons integrate information of various origins and individually relay this to the command nucleus in the medulla. Some may also have intrinsic, although normally nonsynchronized, pacemaker properties. This descending activity, integrated in the electromotor command nucleus, will play an important modulatory role in the central pattern generator decision process.
Timing Mechanisms in the Cerebellum: Testing Predictions of a Large-Scale Computer Simulation
Authors: Medina Javier F. , Garcia Keith S. , Nores William L. , Taylor Nichole M. , Mauk Michael D.
Published: April 2018

We used large-scale computer simulations of eyelid conditioning to investigate how the cerebellum generates and makes use of temporal information. In the simulations the adaptive timing displayed by conditioned responses is mediated by two factors: (1) different sets of granule cells are active at different times during the conditioned stimulus (CS), and (2) responding is not only amplified at reinforced times but also suppressed at unreinforced times during the CS. These factors predict an unusual pattern of responding after partial removal of the cerebellar cortex that was confirmed using small, electrolytic lesions of cerebellar cortex. These results are consistent with timing mechanisms in the cerebellum that are similar to Pavlov's “inhibition of delay” hypothesis.
A Cholecystokinin-Mediated Pathway to the Paraventricular Thalamus Is Recruited in Chronically Stressed Rats and Regulates Hypothalamic-Pituitary-Adrenal Function
Authors: Bhatnagar Seema , Viau Victor , Chu Alan , Soriano Liza , Meijer Onno C. , Dallman Mary F.
Published: April 2018

Chronic stress alters hypothalamic-pituitary-adrenal (HPA) responses to acute, novel stress. After acute restraint, the posterior division of the paraventricular thalamic nucleus (pPVTh) exhibits increased numbers of Fos-expressing neurons in chronically cold-stressed rats compared with stress-naı̈ve controls. Furthermore, lesions of the PVTh augment HPA activity in response to novel restraint only in previously stressed rats, suggesting that the PVTh is inhibitory to HPA activity but that inhibition occurs only in chronically stressed rats. In this study, we further examined pPVTh functions in chronically stressed rats. We identified afferent projections to the pPVTh using injection of the retrograde tracer fluorogold. Of the sites containing fluorogold-labeled cells, neurons in the lateral parabrachial, periaqueductal gray, and dorsal raphe containing fluorogold also expressed cholecystokinin (CCK) mRNA. We then examined whether these CCKergic inputs to the pPVTh were involved in HPA responses to acute, novel restraint after chronic stress. We injected the CCK-B receptor antagonist PD 135,158 into the PVTh before restraint in control and chronically cold-stressed rats. ACTH responses to restraint stress were augmented by PD 135,158 only in chronically stressed rats but not in controls. In addition, CCK-B receptor mRNA expression in the pPVTh was not altered by chronic cold stress. We conclude that previous chronic stress specifically facilitates the release of CCK into the pPVTh in response to acute, novel stress. The CCK is probably secreted from neurons in the lateral parabrachial, the periaqueductal gray, and/or the dorsal raphe nuclei. Acting via CCK-B receptors in pPVTh, CCK then constrains facilitated ACTH responses to novel stress in chronically stressed but not naı̈ve rats. These results demonstrate clearly that chronic stress recruits a new set of pathways that modulate HPA responsiveness to a novel stress.
Light and Glutamate-Induced Degradation of the Circadian Oscillating Protein BMAL1 during the Mammalian Clock Resetting
Authors: Tamaru Teruya , Isojima Yasushi , Yamada Takashi , Okada Masato , Nagai Katsuya , Takamatsu Ken
Published: April 2018

Recently discovered mammalian clock genes are believed to compose the core oscillator, which generates the circadian rhythm. BMAL1/CLOCK heterodimer is the essential positive element that drives clock-related transcription and self-sustaining oscillation by a negative feedback mechanism. We examined BMAL1 protein expression in the rat suprachiasmatic nuclei (SCN) by immunoblot analysis. Anti-BMAL1 antiserum raised against rBMAL1 recognized 70 kDa mBMAL1b and detected a similar immunoreactivity (IR) as a major band in rat brains. Robust circadian BMAL1-IR oscillations with nocturnal peaks were detected in the SCN during a light/dark cycle and under constant darkness. A short duration light exposure at night acutely reduced BMAL1-IR in the SCN during photoentrainment. This might be attributable to the degradation of BMAL1 protein. Application of glutamate and NMDA to the SCN slices at projected night, a procedure mimicking photic phase delay shift, also acutely reduced BMAL1-IR in a similar manner. A rapid decrease of BMAL1 protein suggests that BMAL1 protein might be implicated in the light-transducing pathway within the SCN.
The Excitatory Neuronal Network of Rat Layer 4 Barrel Cortex
Authors: Petersen Carl C. H. , Sakmann Bert
Published: April 2018

Sensory whiskers are mapped to rodent layer 4 somatosensory cortex as discrete units termed barrels, which can be visualized at high resolution in living brain slices. Both anatomical and physiological properties of the layer 4 neuronal network can thus be investigated in the context of the functional boundaries of this sensory map. Large-scale confinement of neuronal arbors to single barrels was suggested by restricted lateral diffusion of DiI across septa between barrels. Morphological analysis of dendritic and axonal arborizations of individual excitatory neurons showed that neuronal processes remain within the barrel of origin through polarization toward the center of the barrel. Functionally, the large-scale properties of the neuronal network were investigated through mapping the spatial extent of field EPSPs, which were found to attenuate at barrel borders. This ensemble property of a layer 4 barrel was further investigated by analyzing the connectivity of pairs of excitatory neurons with respect to the locations of the somata. Approximately one-third of the excitatory neurons within the same barrel were synaptically coupled. At the septum between adjacent barrels the connectivity dropped rapidly, and very few connections were found between neurons located in adjacent barrels. Each layer 4 barrel is thus composed of an excitatory neuronal network, which to a first order approximation, acts independently of its neighbors.
CD45 Opposes β-Amyloid Peptide-Induced Microglial Activation via Inhibition of p44/42 Mitogen-Activated Protein Kinase
Authors: Tan Jun , Town Terrence , Mori Takashi , Wu Yajuan , Saxe Michael , Crawford Fiona , Mullan Mike
Published: April 2018

Reactive microglia have been suggested to play a role in the Alzheimer's disease (AD) process, and previous studies have shown that expression of CD45, a membrane-bound protein-tyrosine phosphatase (PTP), is elevated in microglia in AD brain compared with controls. To investigate the possible role of CD45 in microglial responsiveness to β-amyloid (Aβ) peptides, we first co-treated primary cultured microglia with a tyrosine phosphatase inhibitor [potassium bisperoxo (1,10-phenanthroline) oxovanadate (phen), 5 μm] and freshly solubilized Aβ peptides (1000 nm). Data show synergistic induction of microglial activation as evidenced by tumor necrosis factor α (TNF-α) production and nitric oxide (NO) release, both of which we show to be dependent on activation of p44/42 mitogen-activated protein kinase (MAPK). Furthermore, co-treatment with phen and Aβ peptides results in microglia-induced neuronal cell injury. Stimulation of microglial CD45 by anti-CD45 antibody markedly inhibits these effects via inhibition of p44/42 MAPK, suggesting that CD45 is a negative regulator of microglial activation. Accordingly, primary cultured microglia from CD45-deficient mice demonstrate hyper-responsiveness to Aβ, as evidenced by TNF-α release, NO production, and neuronal injury after stimulation with Aβ peptides. As a validation of these findingsin vivo, brains from a transgenic mouse model of AD [transgenic Swedish APP-overexpressing (Tg APPsw) mice] deficient for CD45 demonstrate markedly increased production of TNF-α compared with Tg APPswmice. Taken together, these results suggest that therapeutic agents that stimulate the CD45 PTP signaling pathway may be effective in suppressing microglial activation associated with AD.
Impairment of Long-term Potentiation and Associative Memory in Mice That Overexpress Extracellular Superoxide Dismutase
Authors: Thiels Edda , Urban Nathan N. , Gonzalez-Burgos Guillermo R. , Kanterewicz Beatriz I. , Barrionuevo German , Chu Charleen T. , Oury Tim D. , Klann Eric
Published: April 2018

Reactive oxygen species, including superoxide, generally are considered neurotoxic molecules whose effects can be alleviated by antioxidants. Different from this view, we show that scavenging of superoxide with an antioxidant enzyme is associated with deficits in hippocampal long-term potentiation (LTP), a putative neural substrate of memory, and hippocampal-mediated memory function. Using transgenic mice that overexpress extracellular superoxide dismutase (EC-SOD), a superoxide scavenger, we found that LTP was impaired in hippocampal area CA1 despite normal LTP in area CA3. The LTP impairment in area CA1 could be reversed by inhibition of EC-SOD. In addition, we found that EC-SOD transgenic mice exhibited impaired long-term memory of fear conditioning to contextual cues despite exhibiting normal short-term memory of the conditioning experience. These findings strongly suggest that superoxide, rather than being considered exclusively a neurotoxic molecule, should also be considered a signaling molecule necessary for normal neuronal function.
Enhanced Spinal Nociceptin Receptor Expression Develops Morphine Tolerance and Dependence
Authors: Ueda Hiroshi , Inoue Makoto , Takeshima Hiroshi , Iwasawa Yoshikazu
Published: April 2018

The tolerance and dependence after chronic medication with morphine are thought to be representative models for studying the plasticity, including the remodeling of neuronal networks. To test the hypothesis that changes in neuronal plasticity observed in opioid tolerance or dependence are derived from increased activity of the anti-opioid nociceptin system, the effects of chronic treatments with morphine were examined using nociceptin receptor knock-out (NOR−/−) mice and a novel nonpeptidic NOR antagonist, J-113397, which shows a specific and potent NOR antagonist activity inin vitro[35S]GTPγS binding assay andin vivoperipheral nociception test. The NOR−/−mice showed marked resistance to morphine analgesic tolerance without affecting morphine analgesic potency in tail-pinch and tail-flick tests. The NOR−/−mice also showed marked attenuation of morphine-induced physical dependence, manifested as naloxone-precipitated withdrawal symptoms after repeated morphine treatments. Similar marked attenuation of morphine tolerance was also observed by single subcutaneous (10 mg/kg) or intrathecal (1 nmol) injection of J-113397, which had been given 60 min before the test in morphine-treated ddY mice. However, the intracerebroventricular injection (up to 3 nmol) did not affect the tolerance. On the other hand, morphine dependence was markedly attenuated by J-113397 that had been subcutaneously given 60 min before naloxone challenge. There was also observed a parallel enhancement of NOR gene expression only in the spinal cord during chronic morphine treatments. Together, these findings suggest that the spinal NOR system develops anti-opioid plasticity observed on morphine tolerance and dependence.
Emotional Responses to Pleasant and Unpleasant Olfactory, Visual, and Auditory Stimuli: a Positron Emission Tomography Study
Authors: Royet Jean-P. , Zald David , Versace Rémy , Costes Nicolas , Lavenne Frank , Koenig Olivier , Gervais Rémi
Published: April 2018

Neural correlates of responses to emotionally valenced olfactory, visual, and auditory stimuli were examined using positron emission tomography. Twelve volunteers were scanned using the water bolus method. For each sensory modality, regional cerebral blood flow (rCBF) during presentation of both pleasant and unpleasant stimuli was compared with that measured during presentation of neutral stimuli. During the emotionally valenced conditions, subjects performed forced-choice pleasant and unpleasant judgments. During the neutral conditions, subjects were asked to select at random one of a two key-press buttons. All stimulations were synchronized with inspiration, using an airflow olfactometer, to present the same number of stimuli for each sensory modality. A no-stimulation control condition was also performed in which no stimulus was presented. For all three sensory modalities, emotionally valenced stimuli led to increased rCBF in the orbitofrontal cortex, the temporal pole, and the superior frontal gyrus, in the left hemisphere. Emotionally valenced olfactory and visual but not auditory stimuli produced additional rCBF increases in the hypothalamus and the subcallosal gyrus. Only emotionally valenced olfactory stimuli induced bilateral rCBF increases in the amygdala. These findings suggest that pleasant and unpleasant emotional judgments recruit the same core network in the left hemisphere, regardless of the sensory modality. This core network is activated in addition to a number of circuits that are specific to individual sensory modalities. Finally, the data suggest a superior potency of emotionally valenced olfactory over visual and auditory stimuli in activating the amygdala.
Hypocretin-1 Modulates Rapid Eye Movement Sleep through Activation of Locus Coeruleus Neurons
Authors: Bourgin Patrice , Huitrón-Reséndiz Salvador , Spier Avron D. , Fabre Véronique , Morte Beatriz , Criado José R. , Sutcliffe J. Gregor , Henriksen Steven J. , de Lecea Luis
Published: April 2018

The hypocretins (hcrts), also known as orexins, are two recently identified excitatory neuropeptides that in rat are produced by ∼1200 neurons whose cell bodies are located in the lateral hypothalamus. The hypocretins/orexins have been implicated in the regulation of rapid eye movement (REM) sleep and the pathophysiology of narcolepsy. In the present study, we investigated whether the locus coeruleus (LC), a structure receiving dense hcrtergic innervation, which is quiescent during REM sleep, might be a target for hcrt to regulate REM sleep. Local administration of hcrt1 but not hcrt2 in the LC suppressed REM sleep in a dose-dependent manner and increased wakefulness at the expense of deep, slow-wave sleep. These effects were blocked with an antibody that neutralizes hcrt binding to hcrt receptor 1.In situhybridization and immunocytochemistry showed the presence of hcrt receptor 1 but not the presence of hcrt receptor 2 in the LC. Iontophoretic application of hcrt1 enhanced the firing rate of LC neuronsin vivo, and local injection of hcrt1 into the LC induced the expression of c-fosin the LC area. We propose that hcrt receptor 1 in the LC is a key target for REM sleep regulation and might be involved in the pathophysiological mechanisms of narcolepsy.
High-frequency Synchronization of Neuronal Activity in the Subthalamic Nucleus of Parkinsonian Patients with Limb Tremor
Authors: Levy Ron , Hutchison William D. , Lozano Andres M. , Dostrovsky Jonathan O.
Published: April 2018

It has been hypothesized that in Parkinson's disease (PD) there is increased synchronization of neuronal firing in the basal ganglia. This study examines the discharge activity of 121 pairs of subthalamic nucleus (STN) neurons in nine PD patients undergoing functional stereotactic mapping. Four patients had a previous pallidotomy. A double microelectrode setup was used to simultaneously record from two neurons separated by distances as small as 250 μm. In the six patients who had limb tremor during the recording session (n= 76 pairs), the discharge pattern of 12 pairs of tremor cells (TCs) was found to be coherent at the frequency of the limb tremor. Both in-phase and out-of-phase relationships were observed between TCs. Interestingly, in these six patients, 63/129 single neurons displayed 15–30 Hz oscillations, whereas 36/76 pairs were coherent in this frequency range. Although the oscillatory frequencies were variable between patients, they were highly clustered within a patient. The phase difference between these pairs was found to be close to 0. High-frequency synchronization was observed during periods of limb tremor as well as during intermittent periods with no apparent limb tremor. In contrast, in the three patients without limb tremor during the recording session, only 1/84 neurons had high-frequency oscillatory activity, and no TCs or synchronous high-frequency oscillatory activity was observed (n= 45 pairs). These findings demonstrate that in PD patients with limb tremor, many STN neurons display high-frequency oscillations with a high degree of in-phase synchrony. The results suggest that high-frequency synchronized oscillatory activity may be associated with the pathology that gives rise to tremor in PD patients.
Selective Blockade of P/Q-Type Calcium Channels by the Metabotropic Glutamate Receptor Type 7 Involves a Phospholipase C Pathway in Neurons
Authors: Perroy Julie , Prezeau Laurent , De Waard Michel , Shigemoto Ryuichi , Bockaert Joel , Fagni Laurent
Published: April 2018

Although presynaptic localization of mGluR7 is well established, the mechanism by which the receptor may control Ca2+channels in neurons is still unknown. We show here that cultured cerebellar granule cells express native metabotropic glutamate receptor type 7 (mGluR7) in neuritic processes, whereas transfected mGluR7 was also expressed in cell bodies. This allowed us to study the effect of the transfected receptor on somatic Ca2+channels. In transfected neurons, mGuR7 selectively inhibited P/Q-type Ca2+channels. The effect was mimicked by GTPγS and blocked by pertussis toxin (PTX) or a selective antibody raised against the G-protein αo subunit, indicating the involvement of a Go-like protein. The mGuR7 effect did not display the characteristics of a direct interaction between G-protein βγ subunits and the α1A Ca2+channel subunit, but was abolished by quenching βγ subunits with specific intracellular peptides. Intracellular dialysis of G-protein βγ subunits did not mimic the action of mGluR7, suggesting that both G-protein βγ and αo subunits were required to mediate the effect. Inhibition of phospholipase C (PLC) blocked the inhibitory action of mGluR7, suggesting that a coincident activation of PLC by the G-protein βγ with αo subunits was required. The Ca2+chelator BAPTA, as well as inhibition of either the inositol trisphosphate (IP3) receptor or protein kinase C (PKC) abolished the mGluR7 effect. Moreover, activation of native mGluR7 induced a PTX-dependent IP3formation. These results indicated that IP3-mediated intracellular Ca2+release was required for PKC-dependent inhibition of the Ca2+channels. Possible control of synaptic transmission by the present mechanisms is discussed.
Developmental Changes in Synaptic AMPA and NMDA Receptor Distribution and AMPA Receptor Subunit Composition in Living Hippocampal Neurons
Authors: Pickard Lisa , Noël Jacques , Henley Jeremy M. , Collingridge Graham L. , Molnar Elek
Published: April 2018

AMPA and NMDA receptors mediate most excitatory synaptic transmission in the CNS. We have developed antibodies that recognize all AMPA or all NMDA receptor variants on the surface of living neurons. AMPA receptor variants were identified with a polyclonal antibody recognizing the conserved extracellular loop region of all four AMPA receptor subunits (GluR1–4, bothflipandflop), whereas NMDA receptors were immunolabeled with a polyclonal antibody that binds to an extracellular N-terminal epitope of the NR1 subunit, common to all splice variants. In non-fixed brain sections these antibodies gave labeling patterns similar to autoradiographic distributions with particularly high levels in the hippocampus. Using these antibodies, in conjunction with GluR2-specific and synaptophysin antibodies, we have directly localized and quantified surface-expressed native AMPA and NMDA receptors on cultured living hippocampal neurons during development. Using a quantitative cell ELISA, a dramatic increase was observed in the surface expression of AMPA receptors, but not NMDA receptors, between 3 and 10 d in culture. Immunocytochemical analysis of hippocampal neurons between 3 and 20 din vitroshows no change in the proportion of synapses expressing NMDA receptors (∼60%) but a dramatic increase (∼50%) in the proportion of them that also express AMPA receptors. Furthermore, over this period the proportion of AMPA receptor-positive synapses expressing the GluR2 subunit increased from ∼67 to ∼96%. These changes will dramatically alter the functional properties of hippocampal synapses.
Novel SCAMPs Lacking NPF Repeats: Ubiquitous and Synaptic Vesicle-Specific Forms Implicate SCAMPs in Multiple Membrane-Trafficking Functions
Authors: Fernández-Chacón Rafael , Südhof Thomas C.
Published: April 2018

In vertebrates, secretory carrier membrane proteins (SCAMPs) 1–3 constitute a family of putative membrane-trafficking proteins composed of cytoplasmic N-terminal sequences with NPF repeats, four central transmembrane regions (TMRs), and a cytoplasmic tail. SCAMPs probably function in endocytosis by recruiting EH-domain proteins to the N-terminal NPF repeats but may have additional functions mediated by their other sequences. We now demonstrate that SCAMPs form a much larger and more heterogeneous protein family than envisioned previously, with an evolutionary conservation extending to invertebrates and plants. Two novel vertebrate SCAMPs (SCAMPs 4 and 5), single SCAMP genes inCaenorhabditis elegansandDrosophila melanogaster, and multiple SCAMPs inArabidopsis thalianawere identified. Interestingly, the novel SCAMPs 4 and 5 lack the N-terminal NPF repeats that are highly conserved in all other SCAMPs. RNA and Western blotting experiments showed that SCAMPs 1–4 are ubiquitously coexpressed, whereas SCAMP 5 is only detectable in brain where it is expressed late in development coincident with the elaboration of mature synapses. Immunocytochemistry revealed that SCAMP 5 exhibits a synaptic localization, and subcellular fractionations demonstrated that SCAMP 5 is highly enriched in synaptic vesicles. Our studies characterize SCAMPs as a heterogeneous family of putative trafficking proteins composed of three isoforms that are primarily synthesized outside of neurons (SCAMPs 2–4), one isoform that is ubiquitously expressed but highly concentrated on synaptic vesicles (SCAMP 1), and one brain-specific isoform primarily localized to synaptic vesicles (SCAMP 5). The conservation of the TMRs in all SCAMPs with the variable presence of N-terminal NPF repeats suggests that in addition to the role of some SCAMPs in endocytosis mediated by their NPF repeats, all SCAMPs perform a “core” function in membrane traffic mediated by their TMRs.
Mice with Combined Gene Knock-Outs Reveal Essential and Partially Redundant Functions of Amyloid Precursor Protein Family Members
Authors: Heber Sabine , Herms Jochen , Gajic Vladan , Hainfellner Johannes , Aguzzi Adriano , Rülicke Thomas , Kretzschmar Hans , von Koch Cornelia , Sisodia Sangram , Tremml Phillippe , Lipp Hans-Peter , Wolfer David P. , Müller Ulrike
Published: April 2018

The amyloid precursor protein (APP) involved in Alzheimer's disease is a member of a larger gene family including amyloid precursor-like proteins APLP1 and APLP2. We generated and examined the phenotypes of mice lacking individual or all possible combinations of APP family members to assess potential functional redundancies within the gene family. Mice deficient for the nervous system-specific APLP1 protein showed a postnatal growth deficit as the only obvious abnormality. In contrast to this minor phenotype, APLP2−/−/APLP1−/−and APLP2−/−/APP−/−mice proved lethal early postnatally. Surprisingly, APLP1−/−/APP−/−mice were viable, apparently normal, and showed no compensatory upregulation of APLP2 expression. These data indicate redundancy between APLP2 and both other family members and corroborate a key physiological role for APLP2. This view gains further support by the observation that APLP1−/−/APP−/−/APLP2+/−mice display postnatal lethality. In addition, they provide genetic evidence for at least some distinct physiological roles of APP and APLP2 by demonstrating that combinations of single knock-outs with the APLP1 mutation resulted in double mutants of clearly different phenotypes, being either lethal, or viable. None of the lethal double mutants displayed, however, obvious histopathological abnormalities in the brain or any other organ examined. Moreover, cortical neurons from single or combined mutant mice showed unaltered survival rates under basal culture conditions and unaltered susceptibility to glutamate excitotoxicityin vitro.
Constitutive Endocytosis of GABAAReceptors by an Association with the Adaptin AP2 Complex Modulates Inhibitory Synaptic Currents in Hippocampal Neurons
Authors: Kittler Josef T. , Delmas Patrick , Jovanovic Jasmina N. , Brown David A. , Smart Trevor G. , Moss Stephen J.
Published: April 2018

Type A GABA receptors (GABAA) mediate the majority of fast synaptic inhibition in the brain and are believed to be predominantly composed of α, β, and γ subunits. Although changes in cell surface GABAAreceptor number have been postulated to be of importance in modulating inhibitory synaptic transmission, little is currently known on the mechanism used by neurons to modify surface receptor levels at inhibitory synapses. To address this issue, we have studied the cell surface expression and maintenance of GABAAreceptors. Here we show that constitutive internalization of GABAAreceptors in hippocampal neurons and recombinant receptors expressed in A293 cells is mediated by clathrin-dependent endocytosis. Furthermore, we identify an interaction between the GABAAreceptor β and γ subunits with the adaptin complex AP2, which is critical for the recruitment of integral membrane proteins into clathrin-coated pits. GABAAreceptors also colocalize with AP2 in cultured hippocampal neurons. Finally, blocking clathrin-dependant endocytosis with a peptide that disrupts the association between amphiphysin and dynamin causes a large sustained increase in the amplitude of miniature IPSCs in cultured hippocampal neurons. These results suggest that GABAAreceptors cycle between the synaptic membrane and intracellular sites, and their association with AP2 followed by recruitment into clathrin-coated pits represents an important mechanism in the postsynaptic modulation of inhibitory synaptic transmission.
NMDA But Not Non-NMDA Excitotoxicity is Mediated by Poly(ADP-Ribose) Polymerase
Authors: Mandir Allen S. , Poitras Marc F. , Berliner Adam R. , Herring William J. , Guastella Daniel B. , Feldman Alicia , Poirier Guy G. , Wang Zhao-Qi , Dawson Ted M. , Dawson Valina L.
Published: April 2018

Poly(ADP-ribose) polymerase (PARP-1), a nuclear enzyme that facilitates DNA repair, may be instrumental in acute neuronal cell death in a variety of insults including, cerebral ischemia,1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced parkinsonism, and CNS trauma. Excitotoxicity is thought to underlie these and other toxic models of neuronal death. Different glutamate agonists may trigger different downstream pathways toward neurotoxicity. We examine the role of PARP-1 in NMDA- and non-NMDA-mediated excitotoxicity. NMDA and non-NMDA agonists were stereotactically delivered into the striatum of mice lacking PARP-1 and control mice in acute (48 hr) and chronic (3 week) toxicity paradigms. Mice lacking PARP-1 are highly resistant to the excitoxicity induced by NMDA but are as equally susceptible to AMPA excitotoxicity as wild-type mice. Restoring PARP-1 protein in mice lacking PARP-1 by viral transfection restored susceptibility to NMDA, supporting the requirement of PARP-1 in NMDA neurotoxicity. Furthermore, Western blot analyses demonstrate that PARP-1 is activated after NMDA delivery but not after AMPA administration. Consistent with the theory that nitric oxide (NO) and peroxynitrite are prominent in NMDA-induced neurotoxicity, PARP-1 was not activated in mice lacking the gene for neuronal NO synthase after NMDA administration. These results suggest a selective role of PARP-1 in glutamate excitoxicity, and strategies of inhibiting PARP-1 in NMDA-mediated neurotoxicity may offer substantial acute and chronic neuroprotection.
Regeneration of Lesioned Corticospinal Tract Fibers in the Adult Rat Induced by a Recombinant, Humanized IN-1 Antibody Fragment
Authors: Brösamle Christian , Huber Andrea B. , Fiedler Markus , Skerra Arne , Schwab Martin E.
Published: April 2018

Axons in the CNS of higher vertebrates generally fail to regenerate after injury. This lack of regeneration is crucially influenced by neurite growth inhibitory protein constituents of CNS myelin. We have shown previously that a monoclonal antibody (mAb IN-1) capable of binding and neutralizing Nogo-A, a myelin-associated inhibitor of neurite growth, can induce long-distance axonal regeneration and increased structural plasticity with improved functional recovery in rat models of CNS injury. In this paper we demonstrate that a partially humanized, recombinant Fab fragment (rIN-1 Fab) derived from the original mAb IN-1, was able to promote long-distance regeneration of injured axons in the spinal cord of adult rats. When infused into a spinal cord injury site, regrowth of corticospinal fibers in 11 of 18 animals was observed after a survival time of 2 weeks. Regenerating fibers grew for >9 mm beyond the lesion site and arborized profusely in the distal cord. Regenerated fibers formed terminal arbors with varicosities in the spinal cord gray matter, strongly resembling synaptic points of contact to neurons in the spinal cord distal to the lesion. In animals that had received a bovine serum albumin solution or a recombinant IN-1 fragment that had been mutated in the antigen binding site (mutIN-1 Fab), no significant growth beyond normal lesion-induced sprouting was observed. Neutralization of endogenous nerve growth inhibitors represents a novel use of recombinant antibody technology with potential therapeutic applications after traumatic CNS lesions.
Potassium-Coupled Chloride Cotransport Controls Intracellular Chloride in Rat Neocortical Pyramidal Neurons
Authors: DeFazio R. Anthony , Keros Sotirios , Quick Michael W. , Hablitz John J.
Published: April 2018

Chloride (Cl−) homeostasis is critical for many cell functions including cell signaling and volume regulation. The action of GABA at GABAAreceptors is primarily determined by the concentration of intracellular Cl−. Developmental regulation of intracellular Cl−results in a depolarizing response to GABA in immature neocortical neurons and a hyperpolarizing or shunting response in mature neocortical neurons. One protein that participates in Cl−homeostasis is the neuron-specific K+–Cl−cotransporter (KCC2). Thermodynamic considerations predict that in the physiological ranges of intracellular Cl−and extracellular K+concentrations, KCC2 can act to either extrude or accumulate Cl−. To test this hypothesis, we examined KCC2 function in pyramidal cells from rat neocortical slices in mature (18–28 d postnatal) and immature (3–6 d postnatal) rats. Intracellular Cl−concentration was estimated from the reversal potential of whole-cell currents evoked by local application of exogenous GABA. Both increasing and decreasing the extracellular K+concentration resulted in a concomitant change in intracellular Cl−concentration in neurons from mature rats. KCC2 inhibition by furosemide caused a change in the intracellular Cl−concentration that depended on the concentration of pipette Cl−; in recordings with low pipette Cl−, furosemide lowered intracellular Cl−, whereas in recordings with elevated pipette Cl−, furosemide raised intracellular Cl−. In neurons from neonatal rats, manipulation of extracellular K+had no effect on intracellular Cl−concentration, consistent with the minimal KCC2 mRNA levels observed in neocortical neurons from immature animals. These data demonstrate a physiologically relevant and developmentally regulated role for KCC2 in Cl−homeostasis via both Cl−extrusion and accumulation.
Transmitter–Receptor Interactions between Growth Cones of IdentifiedLymnaeaNeurons Determine Target Cell SelectionIn Vitro
Authors: Spencer Gaynor E. , Lukowiak Ken , Syed Naweed I.
Published: April 2018

In addition to their involvement in transsynaptic communication in the adult nervous system, neurotransmitters also participate in many developmental events, such as neurite initiation and outgrowth. Although growth cones can release transmitters and are themselves sensitive to exogenously applied neurotransmitters, a direct causal relationship between the release of transmitter from one growth cone and its effect on another has not yet been demonstrated. In this study, we provide evidence that dopamine release from the growth cones of an identifiedLymnaeaneuron, right pedal dorsal 1 (RPeD1), differentially regulates the growth cone behavior of itsin vivotarget and nontarget neuronsin vitro. In coculture, RPeD1 growth cones enhanced the rate of growth cone advance from target cells and synaptic connections developed immediately after contact. In contrast, RPeD1 growth cones not only inhibited the rate of growth cone advance from nontarget cells but they also induced growth cone collapse. Using a “sniffer cell” approach, we demonstrated that both RPeD1 growth cones and somata released dopamine, which can be detected at a distance of several hundred micrometers. RPeD1 somata were used to demonstrate that spontaneous release of dopamine also acted as a chemoattractant for target growth cones but as a chemorepellent for nontarget growth cones. These effects were mimicked by exogenous dopamine application, and both RPeD1 growth cone and soma-induced effects were also blocked in the presence of dopamine receptor antagonists. This study emphasizes the importance of transmitter–receptor interactions between growth cones in target cell selection.
Long-Term Optical Imaging and Spectroscopy Reveal Mechanisms Underlying the Intrinsic Signal and Stability of Cortical Maps in V1 of Behaving Monkeys
Authors: Shtoyerman Eran , Arieli Amos , Slovin Hamutal , Vanzetta Ivo , Grinvald Amiram
Published: April 2018

Explorations of learning and memory, other long-term plastic changes, and additional cognitive functions in the behaving primate brain would greatly benefit from the ability to image the functional architecture within the same patch of cortex, at the columnar level, for a long period of time. We developed methods for long-term optical imaging based on intrinsic signals and repeatedly visualized the same functional domains in behaving macaque cortex for a period extending over 1 year. Using optical imaging and imaging spectroscopy, we first explored the relationship between electrical activity and hemodynamic events in the awake behaving primate and compared it with anesthetized preparations. We found that, whereas the amplitude of the intrinsic signal was much larger in the awake animal, its temporal pattern was similar to that observed in the anesthetized animals. In both groups, deoxyhemoglobin concentration reached a peak 2–3 sec after stimulus onset. Furthermore, the early activity-dependent increase in deoxyhemoglobin concentration (the “initial dip”) was far more tightly colocalized with electrical activity than the delayed increase in oxyhemoglobin concentration, known to be associated with an increase in blood flow. The implications of these results for improvement of the spatial resolution of blood oxygenation level-dependent functional magnetic resonance imaging are discussed. After the characterization of the intrinsic signal in the behaving primate, we used this new imaging method to explore the stability of cortical maps in the macaque primary visual cortex. Functional maps of orientation and ocular dominance columns were found to be stable for a period longer than 1 year.
Activation of ERK/MAP Kinase in the Amygdala Is Required for Memory Consolidation of Pavlovian Fear Conditioning
Authors: Schafe Glenn E. , Atkins Coleen M. , Swank Michael W. , Bauer Elizabeth P. , Sweatt J. David , LeDoux Joseph E.
Published: April 2018

Although much has been learned about the neurobiological mechanisms underlying Pavlovian fear conditioning at the systems and cellular levels, relatively little is known about the molecular mechanisms underlying fear memory consolidation. The present experiments evaluated the role of the extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) signaling cascade in the amygdala during Pavlovian fear conditioning. We first show that ERK/MAPK is transiently activated–phosphorylated in the amygdala, specifically the lateral nucleus (LA), at 60 min, but not 15, 30, or 180 min, after conditioning, and that this activation is attributable to paired presentations of tone and shock rather than to nonassociative auditory stimulation, foot shock sensitization, or unpaired tone–shock presentations. We next show that infusions of U0126, an inhibitor of ERK/MAPK activation, aimed at the LA, dose-dependently impair long-term memory of Pavlovian fear conditioning but leaves short-term memory intact. Finally, we show that bath application of U0126 impairs long-term potentiation in the LAin vitro. Collectively, these results demonstrate that ERK/MAPK activation is necessary for both memory consolidation of Pavlovian fear conditioning and synaptic plasticity in the amygdala.
Visual Responses in Monkey Areas V1 and V2 to Three-Dimensional Surface Configurations
Authors: Bakin Jonathan S. , Nakayama Ken , Gilbert Charles D.
Published: April 2018

The visual system uses information about the relative depth of contours and surfaces to link and segment elements of visual scenes. The integration of form and depth information was studied in areas V1 and V2 of the alert macaque. Neurons in area V2 used contextual depth information to integrate occluded contours, signal the presence of object boundaries, and segment surfaces: (1) Amodal contour completion occurs when a contour passes behind an occluder. The basis of contour completion, the facilitation of neuronal responses to stimuli located within their receptive fields (RFs) by contextual lines lying outside their RFs, was blocked by orthogonal lines intersecting the contours but was recovered when the orthogonal line was placed in the near depth plane. (2) An illusory contour will modally complete separated elements located across an isoluminant field if the elements are placed in the near depth plane. V2 neurons responded when line segments were placed outside the RF in the near depth plane and a field of uniform luminance covered the RF. (3) Texture elements within a surface will “capture” the perceived depth consistent with the disparity of the surface's boundary, even when given no disparity themselves. V2 neurons responded to the center elements of a grating as if they contained disparity, even though disparity was present only for the grating's end elements located beyond the RF borders. These results, which were more common in V2 than in V1, demonstrate a role for V2 in the three-dimensional representation of surfaces in space.
Neural Correlates of Olfactory Recognition Memory in the Rat Orbitofrontal Cortex
Authors: Ramus Seth J. , Eichenbaum Howard
Published: April 2018

The orbitofrontal cortex (OF) is strongly and reciprocally connected with the perirhinal (PR) and entorhinal areas of the medial temporal lobe and plays an important role in odor recognition memory. This study characterized firing patterns of single neurons in the OF of rats performing a continuous odor-guided delayed nonmatch to sample (DNMS) task. Most OF neurons fired in association with one or more task events, including the initiation of trials, the sampling of odor stimuli, and the consumption of rewards. OF neurons also exhibited sustained odor-selective activity during the memory delay, and a large proportion of OF cells had odor-specific enhanced or suppressed responses on stimulus repetition. Most OF neurons were activated during several task events, or associated with complex behavioral states. The incidence of cells that fired in association with the critical match/non-match judgement was increased as the DNMS rule was learned, and was higher in OF than in perirhinal and entorhinal cortex. Furthermore, the classification of match and nonmatch trials was correlated with accuracy in performance of that judgement. These findings are consistent with the view that OF is a high order association cortex that plays a role both in the memory representations for specific stimuli and in the acquisition and application of task rules.
The Status of Voltage-Dependent Calcium Channels in α1EKnock-Out Mice
Authors: Wilson Scott M. , Toth Peter T. , Oh Seog Bae , Gillard Samantha E. , Volsen Steven , Ren Dongjun , Philipson Louis H. , Lee E. Chiang , Fletcher Colin F. , Tessarollo Lino , Copeland Neal G. , Jenkins Nancy A. , Miller Richard J.
Published: April 2018

It has been hypothesized that R-type Ca currents result from the expression of the α1Egene. To test this hypothesis we examined the properties of voltage-dependent Ca channels in mice in which the α1ECa channel subunit had been deleted. Application of ω-conotoxin GVIA, ω-agatoxin IVA, and nimodipine to cultured cerebellar granule neurons from wild-type mice inhibited components of the whole-cell Ba current, leaving a “residual” R current with an amplitude of ∼30% of the total Ba current. A minor portion of this R current was inhibited by the α1E-selective toxin SNX-482, indicating that it resulted from the expression of α1E. However, the majority of the R current was not inhibited by SNX-482. The SNX-482-sensitive portion of the granule cell R current was absent from α1Eknock-out mice. We also identified a subpopulation of dorsal root ganglion (DRG) neurons from wild-type mice that expressed an SNX-482-sensitive component of the R current. However as with granule cells, most of the DRG R current was not blocked by SNX-482. We conclude that there exists a component of the R current that results from the expression of the α1ECa channel subunit but that the majority of R currents must result from the expression of other Ca channel α subunits.