bluuebunny/crossref_metadata_2025 huggingface dataset:
Cuneiform Neurons Activated during Cholinergically Induced Active Sleep in the Cat
Authors: Pose Inés , Sampogna Sharon , Chase Michael H. , Morales Francisco R.
Published: April 2018

In the present study, we report that the cuneiform (Cun) nucleus, a brainstem structure that before now has not been implicated in sleep processes, exhibits a large number of neurons that expressc-fosduring carbachol-induced active sleep (AS-carbachol). Compared with control (awake) cats, during AS-carbachol, there was a 671% increase in the number of neurons that expressedc-fosin this structure. Within the Cun nucleus, three immunocytochemically distinct populations of neurons were observed. One group consisted of GABAergic neurons, which predominantly did not expressc-fosduring AS-carbachol. Two other different populations expressedc-fosduring this state. One of the Fos-positive (Fos+) populations consisted of a distinct group of nitric oxide synthase (NOS)–NADPH-diaphorase (NADPH-d)-containing neurons; the neurotransmitter of the other Fos+population remains unknown. The Cun nucleus did not contain cholinergic, catecholaminergic, serotonergic, or glycinergic neurons. On the basis of neuronal activation during AS-carbachol, as indicated byc-fosexpression, we suggest that the Cun nucleus is involved, in an as yet unknown manner, in the physiological expression of active sleep. The finding of a population of NOS–NADPH-d containing neurons, which were activated during AS-carbachol, suggests that nitrergic modulation of their target cell groups is likely to play a role in active sleep-related physiological processes.
New Insights into the Hemodynamic Blood Oxygenation Level-Dependent Response through Combination of Functional Magnetic Resonance Imaging and Optical Recording in Gerbil Barrel Cortex
Authors: Hess Andreas , Stiller Detlef , Kaulisch Thomas , Heil Peter , Scheich Henning
Published: April 2018

Fast, low-angle shoot functional magnetic resonance imaging (fMRI), based on the blood oxygenation level-dependent (BOLD) effect, was combined with optical recording of intrinsic signals (ORIS) and 2-deoxyglucose labeling in gerbil barrel cortex. We observed over the activated barrel a positive BOLD signal and increased levels of deoxyhemoglobin and total hemoglobin during each period of prolonged (30 sec) D2 vibrissal stimulation. These data show that the hemodynamic basis of this fMRI signal is not necessarily a washout of deoxyhemoglobin, as generally assumed. Instead, they suggest that a positive BOLD signal can also be caused by a local increase of blood volume, even if deoxyhemoglobin levels are persistently elevated. We also show that this alternative interpretation is consistent with theoretical models of the BOLD signal. The changes in BOLD signal and blood volume, which are most tightly correlated with the periodic stimulation, peak at the site of neuronal activation. These results contribute to the understanding of the hemodynamic mechanisms underlying the BOLD signal and also suggest analysis methods, which improve the spatial localization of neuronal activation with both fMRI and ORIS.
Metaplasticity of Mossy Fiber Synaptic Transmission Involves Altered Release Probability
Authors: Goussakov Ivan V. , Fink Klaus , Elger Christian E. , Beck Heinz
Published: April 2018

Activity-dependent synaptic plasticity is a fundamental feature of CNS synapses. Intriguingly, the capacity of synapses to express plastic changes is itself subject to considerable activity-dependent variation, or metaplasticity. These forms of higher order plasticity are important because they may be crucial to maintain synapses within a dynamic functional range. In this study, we asked whether neuronal activity inducedin vivoby application of kainate can induce lasting changes in mossy fiber short- and long-term plasticity.

Several weeks after kainate-induced status epilepticus, the mossy fiber, but not the associational-commissural pathway, exhibits a marked loss of paired-pulse facilitation, augmentation, and long-term potentiation (LTP). Because the adenylyl cyclase–protein kinase A cascade is involved in mossy fiber LTP induction, we have tested the integrity of this key pathway by pharmacological activation of either adenylyl cyclase or protein kinase A. These treatments resulted in LTP in control, but not in kainate-treated animals, indicating that status-induced changes occur downstream of protein kinase A. To test whether altered neurotransmitter release might account for these changes, we measured the size of the releasable pool of glutamate in mossy fiber terminals. We find that the size of the releasable pool of glutamate was significantly increased in kainate-treated rats, indicating an increased release probability at the mossy fiber-CA3 synapse.

Therefore, we suggest that lasting changes in neurotransmitter release probability caused by neuronal activity may be a powerful mechanism for metaplasticity that modulates both short- and long-term plasticity in the mossy fiber-CA3 synapse after status epilepticus.
Modulation of Kv1.5 Currents by Src Tyrosine Phosphorylation: Potential Role in the Differentiation of Astrocytes
Authors: MacFarlane Stacey Nee , Sontheimer Harald
Published: April 2018

Using biophysical techniques, we previously have implicated outwardly rectifying potassium currents in the proliferation of cultured spinal cord astrocytes and have demonstrated that delayed rectifier potassium currents (IKd), in particular, are upregulated on entry into the cell cycle and downregulated with cell cycle exit and differentiation. In the present study, using specific antibodies and antisense oligodeoxynucleotides, we show that this proliferation-dependent potassium current is mediated by theShakerpotassium channel Kv1.5. Downregulation of Kv1.5 protein by antisense oligodeoxynucleotides reduces astrocyte proliferation by ∼50%, although no observed changes occur in Kv1.5 protein expression during spontaneous differentiation in culture. Tyrosine phosphorylation of Kv1.5, however, is downregulated markedly in differentiated cells but unaltered on cell cycle arrest. Using immunoprecipitation, we show that Kv1.5 is associated with Src family protein tyrosine kinases and that this association does not change with cell differentiation. Inhibition of kinase activity with the Src-specific inhibitor PP2 decreases Kv1.5 phosphorylation, reducesIKd, and inhibits astrocyte proliferation, specifically in the G0/G1phase of cell cycle. Conversely,IKdare potentiated when active Src is present in the pipette. Transfection of quiescent astrocytes with constitutively active Src (Src Y529F) causes marked upregulation of astrocyte proliferation. These data suggest that Kv1.5 is phosphorylated constitutively by Src kinases during growth and that downregulation of Src activity may underlie both astrocyte differentiation and the accompanying changes in delayed rectifier potassium channel activity.
Combined Lesions of Hippocampus and Subiculum Do Not Produce Deficits in a Nonspatial Social Olfactory Memory Task
Authors: Burton Stephen , Murphy David , Qureshi Uzma , Sutton Patrick , O'Keefe John
Published: April 2018

Rats transmit information to each other about which foods are safe to eat. If a rat smells a food odor on the breath of another rat, it is subsequently more likely to eat that food than an alternative. Work byGalef et al. (1988) has shown that the observer rat forms an association between two olfactory stimuli on the breath of the demonstrator rat that has eaten the food, the food odor and carbon disulphide, which is normally present in the rat breath. Bunsey and Eichenbaum (1995) claimed that the hippocampus/subicular region is required for the long-term retention of this nonspatial form of associative memory on the basis that combined lesions of the hippocampus and subiculum produced a deficit, but lesions of either structure alone did not. We report here a failure to repeat this finding. Rats with either combined lesions of the hippocampus and subiculum or with amygdala lesions were tested on their ability to remember this association either immediately (testing short-term memory) or after a 24 hr delay (testing long-term memory). Neither lesion group exhibited significant memory deficits on this nonspatial associative task at either test interval. In contrast, a deficit was observed on a spatial memory task (forced-choice alternation t-maze) for animals with combined lesions of the hippocampus and subiculum. These results contradict the findings of Bunsey and Eichenbaum (1995)and support the idea that the hippocampus/subicular region is not required for this nonspatial associative memory.
Activity-Dependent Maintenance of Long-Term Potentiation at Visual Cortical Inhibitory Synapses
Authors: Komatsu Yukio , Yoshimura Yumiko
Published: April 2018

Neural activity producing a transient increase in intracellular Ca2+concentration can induce long-term potentiation (LTP) at visual cortical inhibitory synapses similar to those seen at various excitatory synapses. Here we report that low-frequency neural activity is required to maintain LTP at these inhibitory synapses. Inhibitory responses of layer 5 cells evoked by layer 4 stimulation were studied in developing rat visual cortical slices under a pharmacological blockade of excitatory synaptic transmission using intracellular and whole-cell recording methods. Although LTP induced by high-frequency stimulation (HFS) persisted while test stimulation was applied at 0.1 Hz, it was not maintained in approximately two-thirds of cells after test stimulation was stopped for 30 min. In the rest of the cells, LTP seemed to be maintained by spontaneous presynaptic spikes, because presynaptic inhibitory cells discharged spontaneously in our experimental condition and because LTP was totally abolished by a temporary application of Na+channel blockers. Experiments applying various Ca2+channel blockers and Ca2+chelators after HFS demonstrated that LTP maintenance was mediated by presynaptic Ca2+entries through multiple types of high-threshold Ca2+channels, which activated Ca2+-dependent reactions different from those triggering transmitter release. The Ca2+entries associated with action potentials seemed to be regulated by presynaptic K+channels, presumably large-conductance Ca2+-activated K+channels, because the application of blockers for these channels facilitated LTP maintenance. In addition, noradrenaline facilitated the maintenance of LTP. These findings demonstrate a new mechanism by which neural activity regulates the continuation and termination of LTP at visual cortical inhibitory synapses.
G-Protein Types Involved in Calcium Channel Inhibition at a Presynaptic Nerve Terminal
Authors: Mirotznik Rukmini R. , Zheng Xu , Stanley Elis F.
Published: April 2018

The inhibition of presynaptic calcium channels via G-protein-dependent second messenger pathways is a key mechanism of transmitter release modulation. We used the calyx-type nerve terminal of the chick ciliary ganglion to examine which G-proteins are involved in the voltage-sensitive inhibition of presynaptic N-type calcium channels. Adenosine caused a prominent inhibition of the calcium current that was totally blocked by pretreatment with pertussis toxin (PTX), consistent with an exclusive involvement of Go/Giin the G-protein pathway. Immunocytochemistry was used to localize these G-protein types to the nerve terminal and its transmitter release face. We used two approaches to test for modulation by other G-protein types. First, we treated the terminals with ligands for a variety of G-protein-linked neurotransmitter receptor types that have been associated with different G-protein families. Although small inhibitory effects were observed, these could all be eliminated by PTX, indicating that in this terminal the Gifamily is the sole transmitter-induced G-protein inhibitory pathway. Second, we examined the kinetics of calcium channel inhibition by uncaging the nonselective and irreversible G-protein activator GTPγS, bypassing the receptors. A large fraction of the rapid GTPγS-induced inhibition persisted, consistent with a Go/Gi-independent pathway. Immunocytochemistry identified Gq, G11, G12, and G13as potential PTX-insensitive second messengers at this terminal. Thus, our results suggest that whereas neurotransmitter-mediated calcium channel inhibition is mainly, and possibly exclusively, via Go/Gi, other rapid PTX-insensitive G-protein pathways exist that may involve novel, and perhaps transmitter-independent, activating mechanisms.
Facial Visceral Motor Neurons Display Specific Rhombomere Origin and Axon Pathfinding Behavior in the Chick
Authors: Jacob John , Guthrie Sarah
Published: April 2018

In the chick embryo, facial motor neurons comprise branchiomotor and visceral motor subpopulations, which innervate branchial muscles and parasympathetic ganglia, respectively. Although facial motor neurons are known to develop within hindbrain rhombomere 4 (r4) and r5, the precise origins of branchiomotor and visceral motor neuron subpopulations are unclear. We investigated the organization and axon pathfinding of these motor neurons using axonal tracing and rhombomere transplantation in quail-chick chimeras. Our results show that a large majority of branchiomotor neurons originate in r4 but that a cohort of these neurons undergoes a caudal migration from r4 into r5. By contrast, visceral motor neurons develop exclusively in r5. We found that a striking property of facial visceral motor neurons is the ability of their axons to navigate back to appropriate ganglionic targets in the periphery after heterotopic transplantation. These results complement previous studies in which heterotopic facial branchiomotor neurons sent axons to their correct, branchial arch, target. By contrast, when trigeminal branchiomotor neurons were transplanted heterotopically, we found that they were unable to pathfind correctly, and instead projected to an inappropriate target region. Thus, facial and trigeminal motor neuron populations have different axon pathfinding characteristics.
A Transgenic Mouse Model for Inducible and Reversible Dysmyelination
Authors: Mathis Carole , Hindelang Colette , LeMeur Marianne , Borrelli Emiliana
Published: April 2018

Oligodendrocytes are glial cells devoted to the production of myelin sheaths. Myelination of the CNS occurs essentially after birth. To delineate both the times of oligodendrocyte proliferation and myelination, as well as to study the consequence of dysmyelinationin vivo, a model of inducible dysmyelination was developed. To achieve oligodendrocyte ablation, transgenic animals were generated that express the herpes virus 1 thymidine kinase (HSV1-TK) gene under the control of the myelin basic protein (MBP) gene promoter. The expression of the MBP-TK transgene in oligodendrocytes is not toxic on its own; however, toxicity can be selectively induced by the systemic injection of animals with nucleoside analogs, such as FIAU [1-(2-deoxy-2-fluoro-β-δ-arabinofuranosyl)-5-iodouracil]. This system allows us to control the precise duration of the toxic insult and the degree of ablation of oligodendrocytesin vivo.

We show that chronic treatment of MBP-TK mice with FIAU during the first 3 postnatal weeks triggers almost a total depletion of oligodendrocytes in the CNS. These effects are accompanied by a behavioral phenotype characterized by tremors, seizures, retarded growth, and premature animal death. We identify the period of highest oligodendrocytes division in the first 9 postnatal days. Delaying the beginning of FIAU treatments results in different degrees of dysmyelination. Dysmyelination in MBP-TK mice is always accompanied by astrocytosis. Thus, this transgenic line provides a model to study the events occurring during dysmyelination of various intensities. It also represents an invaluable tool to investigate remyelinationin vivo.
Phorbol Esters Potentiate Evoked and Spontaneous Release by Different Presynaptic Mechanisms
Authors: Waters Jack , Smith Stephen J
Published: April 2018

Phorbol esters enhance release from a variety of cell types. The mechanism by which phorbol esters potentiate presynaptic release from central neurons is unclear, although effects of phorbol esters both on the readily releasable pool of vesicles and on presynaptic calcium channels have been shown. Using confocal microscopy and the fluorescent styryl dye FM 1-43, we have examined the effects of phorbol-12,13-dibutyrate (PDBu) on presynaptic vesicle turnover at individually identified synapses in dissociated cultures obtained from neonatal rat hippocampus. Using different dye staining and destaining protocols we were able to resolve two effects of PDBu. Potentiation of evoked release by PDBu was insensitive to calcium channel antagonists, suggesting that this effect results from an increased number of vesicles in the readily releasable pool. Since we observed no effect of PDBu on the size of the total recycling vesicle pool, we conclude that phorbol esters alter the equilibrium between reserve and readily releasable pools. An additional effect of PDBu on spontaneous release was observed. This effect was antagonized by nifedipine but not ω-conotoxin GVIA or ω-agatoxin IVA. We conclude that PDBu influences spontaneous and evoked release by two different mechanisms: through L-type calcium channels and through an increase in the proportion of recycling vesicles in the readily releasable pool. In addition to further clarifying the mechanism of action of phorbol esters, these results suggest that phorbol esters may be a useful tool with which to probe the function of the readily releasable pool of presynaptic vesicles at CNS synapses.
Activation of Metabotropic Glutamate Receptor 5 Has Direct Excitatory Effects and Potentiates NMDA Receptor Currents in Neurons of the Subthalamic Nucleus
Authors: Awad Hazar , Hubert George W. , Smith Yoland , Levey Allan I. , Conn P. Jeffrey
Published: April 2018

The subthalamic nucleus (STN) is a key nucleus in the basal ganglia motor circuit that provides the major glutamatergic excitatory input to the basal ganglia output nuclei. The STN plays an important role in normal motor function, as well as in pathological conditions such as Parkinson's disease (PD) and related disorders. Development of a complete understanding of the roles of the STN in motor control and the pathophysiological changes in STN that underlie PD will require a detailed understanding of the mechanisms involved in regulation of excitability of STN neurons. Here, we report that activation of group I metabotropic glutamate receptors (mGluRs) induces a direct excitation of STN neurons that is characterized by depolarization, increased firing frequency, and increased burst-firing activity. In addition, activation of group I mGluRs induces a selective potentiation of NMDA-evoked currents. Immunohistochemical studies at the light and electron microscopic levels indicate that both subtypes of group I mGluRs (mGluR1a and mGluR5) are localized postsynaptically in the dendrites of STN neurons. Interestingly, pharmacological studies suggest that each of the mGluR-mediated effects is attributable to activation of mGluR5, not mGluR1, despite the presence of both subtypes in STN neurons. These results suggest that mGluR5 may play an important role in the net excitatory drive to the STN from glutamatergic afferents. Furthermore, these studies raise the exciting possibility that selective ligands for mGluR5 may provide a novel approach for the treatment of a variety of movement disorders that involve changes in STN activity.
Reduction in the Density and Expression, But Not G-Protein Coupling, of Serotonin Receptors (5-HT1A) in 5-HT Transporter Knock-Out Mice: Gender and Brain Region Differences
Authors: Li Qian , Wichems Christine , Heils Armin , Lesch Klaus-Peter , Murphy Dennis L.
Published: April 2018

The aim of the present study was to investigate the mechanisms underlying the desensitization of 5-HT1Areceptors in the dorsal raphe and hypothalamus of serotonin (5-HT) transporter knock-out mice (5-HTT −/−). The density of 5-HT1Areceptors in the dorsal raphe was reduced in both male and female 5-HTT −/− mice. This reduction was more extensive in female than in male 5-HTT −/− mice. 8-OH-DPAT-induced hypothermia was absent in female 5-HTT −/− and markedly attenuated in 5-HTT +/− mice. The density of 5-HT1Areceptors also was decreased significantly in several nuclei of the hypothalamus, amygdala, and septum of female 5-HTT −/− mice. 5-HT1Areceptor mRNA was reduced significantly in the dorsal raphe region, but not in the hypothalamus or hippocampus, of female 5-HTT +/− and 5-HTT −/− mice. G-protein coupling to 5-HT1Areceptors and G-protein levels in most brain regions were not reduced significantly, except that Goand Gi1proteins were reduced modestly in the midbrain of 5-HTT −/− mice. These data suggest that the desensitization of 5-HT1Areceptors in 5-HTT −/− mice may be attributable to a reduction in the density of 5-HT1Areceptors. This reduction is brain region-specific and more extensive in the female mice. The reduction in the density of 5-HT1Areceptors may be mediated partly by reduction in the gene expression of 5-HT1Areceptors in the dorsal raphe, but also by other mechanisms in the hypothalamus of 5-HTT −/− female mice. Finally, alterations in G-protein coupling to 5-HT1Areceptors are unlikely to be involved in the desensitization of 5-HT1Areceptors in 5-HTT −/− mice.
Regulation of AMPA Receptor GluR1 Subunit Surface Expression by a 4.1N-Linked Actin Cytoskeletal Association
Authors: Shen Lei , Liang Feng , Walensky Loren D. , Huganir Richard L.
Published: April 2018

The synaptic localization, clustering, and immobilization of neurotransmitter receptors and ion channels play important roles in synapse formation and synaptic transmission. Although several proteins have been identified that interact with AMPA receptors and that may regulate their synaptic targeting, little is known about the interaction of AMPA receptors with the cytoskeleton. In studies examining the interaction of the AMPA receptor GluR1 subunit with neuronal proteins, we determined that GluR1 interacts with the 4.1G and 4.1N proteins, homologs of the erythrocyte membrane cytoskeletal protein 4.1. Using the yeast two-hybrid system and a heterologous cell system, we demonstrated that both 4.1G and 4.1N bind to a membrane proximal region of the GluR1 C terminus, and that a region within the C-terminal domain of 4.1G or 4.1N is sufficient to mediate the interaction. We also found that 4.1N can associate with GluR1in vivoand colocalizes with AMPA receptors at excitatory synapses. Disruption of the interaction of GluR1 with 4.1N or disruption of actin filaments decreased the surface expression of GluR1 in heterologous cells. Moreover, disruption of actin filaments in cultured cortical neurons dramatically reduced the level of surface AMPA receptors. These results suggest that protein 4.1N may link AMPA receptors to the actin cytoskeleton.
A Cellular Mechanism for the Transformation of a Sensory Input into a Motor Command
Authors: Di Prisco Gonzalo Viana , Pearlstein Edouard , Le Ray Didier , Robitaille Richard , Dubuc Réjean
Published: April 2018

The initiation and control of locomotion largely depend on processing of sensory inputs. The cellular bases of locomotion have been extensively studied in lampreys where reticulospinal (RS) neurons constitute the main descending system activating and controlling the spinal locomotor networks. Ca2+imaging and intracellular recordings were used to study the pattern of activation of RS neurons in response to cutaneous stimulation. Pressure applied to the skin evoked a linear input/output relationship in RS neurons until a threshold level, at which a depolarizing plateau was induced, the occurrence of which was associated with the onset of swimming activity in a semi-intact preparation. The occurrence of a depolarizing plateau was abolished by blocking the NMDA receptors that are located on RS cells. Moreover, the depolarizing plateaus were accompanied by a rise in [Ca2+]i, and an intracellular injection of the Ca2+chelator BAPTA into single RS cells abolished the plateaus, suggesting that the latter are Ca2+dependent and rely on intrinsic properties of RS cells. The plateaus were shown to result from the activation of a Ca2+-activated nonselective cation current that maintains the cell in a depolarized state. It is concluded that this intrinsic property of the RS neuron is then responsible for the transformation of an incoming sensory signal into a motor command that is then forwarded to the spinal locomotor networks.
Insulysin Hydrolyzes Amyloid β Peptides to Products That Are Neither Neurotoxic Nor Deposit on Amyloid Plaques
Authors: Mukherjee Atish , Song Eun-suk , Kihiko-Ehmann Muthoni , Goodman Jack P. , Pyrek Jan St. , Estus Steven , Hersh Louis B.
Published: April 2018

Insulysin (EC. 3.4.22.11) has been implicated in the clearance of β amyloid peptides through hydrolytic cleavage. To further study the action of insulysin on Aβ peptides recombinant rat insulysin was used. Cleavage of both Aβ1–40and Aβ1–42by the recombinant enzyme was shown to initially occur at the His13-His14, His14-Gln15, and Phe19-Phe20bonds. This was followed by a slower cleavage at the Lys28-Gly29, Val18-Phe19, and Phe20-Ala21positions. None of the products appeared to be further metabolized by insulysin. Using a rat cortical cell system, the action of insulysin on Aβ1–40and Aβ1–42was shown to eliminate the neurotoxic effects of these peptides. Insulysin was further shown to prevent the deposition of Aβ1–40onto a synthetic amyloid. Taken together these results suggest that the use of insulysin to hydrolyze Aβ peptides represents an alternative gene therapeutic approach to the treatment of Alzheimer's disease.
Independent Anchoring and Assembly Mechanisms of INAD Signaling Complexes inDrosophilaPhotoreceptors
Authors: Tsunoda Susan , Sun Yumei , Suzuki Emiko , Zuker Charles
Published: April 2018

InDrosophilaphotoreceptors the multivalent PDZ protein INAD organizes the phototransduction cascade into a macromolecular signaling complex containing the effector PLC, the light-activated TRP channels, and a regulatory PKC. Previously, we showed that the subcellular localization of INAD signaling complexes is critical for signaling. Now we have examined how INAD complexes are anchored and assembled in photoreceptor cells. We find thattrpmutants, or transgenic flies expressinginaDalleles that disrupt the interaction between INAD and TRP, cause the mislocalization of the entire transduction complex. The INAD–TRP interaction is not required for targeting but rather for anchoring of complexes, because INAD and TRP can be targeted independently of each other. We also show that, in addition to its scaffold role, INAD functions to preassemble transduction complexes. Preassembly of signaling complexes helps to ensure that transduction complexes with the appropriate composition end up in the proper location. This may be a general mechanism used by cells to target different signaling machinery to the pertinent subcellular location.
Tonic Descending Facilitation from the Rostral Ventromedial Medulla Mediates Opioid-Induced Abnormal Pain and Antinociceptive Tolerance
Authors: Vanderah Todd W. , Suenaga Nova M. H. , Ossipov Michael H. , Malan T. Philip , Lai Josephine , Porreca Frank
Published: April 2018

Many clinical case reports have suggested that sustained opioid exposure can elicit unexpected, paradoxical pain. Here, we explore the possibility that (1) opioid-induced pain results from tonic activation of descending pain facilitation arising in the rostral ventromedial medulla (RVM) and (2) the presence of such pain manifests behaviorally as antinociceptive tolerance. Rats implanted subcutaneously with pellets or osmotic minipumps delivering morphine displayed time-related tactile allodynia and thermal hyperalgesia (i.e., opioid-induced “pain”); placebo pellets or saline minipumps did not change thresholds. Opioid-induced pain was observed while morphine delivery continued and while the rats were not in withdrawal. RVM lidocaine, or bilateral lesions of the dorsolateral funiculus (DLF), did not change response thresholds in placebo-pelleted rats but blocked opioid-induced pain. The intrathecal morphine antinociceptive dose–response curve (DRC) in morphine-pelleted rats was displaced to the right of that in placebo-pelleted rats, indicating antinociceptive “tolerance.” RVM lidocaine or bilateral DLF lesion did not alter the intrathecal morphine DRC in placebo-pelleted rats but blocked the rightward displacement seen in morphine-pelleted animals. The subcutaneous morphine antinociceptive DRC in morphine-pelleted rats was displaced to the right of that in placebo-pelleted rats; this right shift was blocked by RVM lidocaine. The data show that (1) opioids elicit pain through tonic activation of bulbospinal facilitation from the RVM, (2) increased pain decreases spinal opioid antinociceptive potency, and (3) blockade of pain restores antinociceptive potency, revealing no change in antinociceptive signal transduction. These studies offer a mechanism for paradoxical opioid-induced pain and allow the development of approaches by which the loss of analgesic activity of opioids might be inhibited.
Precise Burst Synchrony in the Superior Colliculus of the Awake Cat during Moving Stimulus Presentation
Authors: Pauluis Quentin , Baker Stuart N. , Olivier Etienne
Published: April 2018

This study aimed to characterize the synchrony that occurs between cell discharges in the superior colliculus of the awake cat. We trained cats to perform a visual fixation in the presence of a visual moving stimulus and then recorded 686 pairs of neighboring cells in the superior colliculus during task performance. A new method to assess the significance of precise discharge synchronization is described, which permits analysis of nonstationary data. Of 181 pairs with sufficient data for quantitative analysis, 125 showed a cross-correlation histogram (CCH) with features assessed as significant using this approach. CCHs frequently showed an isolated central peak (41 of 125) or a peak flanked by one or two troughs (68 of 125), and in a few cases an oscillatory pattern of ∼65 Hz (16 of 125). This is in contrast to the oscillation frequency reported for the visual cortex and shows that oscillations in the superior colliculus probably arise from a cortex-independent mechanism.

Our method also permits direct quantification of the correlation shift predictors, assessing precise time locking of spikes to the stimulus. Only 1 of 125 cross-correlation shift predictors had a significant central peak, meaning that most of the CCH features were not related to cell discharges time-locked to the stimulus presentation.

Further investigation using a burst-jittering method showed that synchrony in the superior colliculus is attributable to precise synchronization of short bursts of spikes. Such synchrony could be related to the network dynamics and the common inhibitory feedback from local interneurons, which would act as temporal selectors of the cells with greatest or fastest response.
Adenosine Receptor Subtypes Modulate Two Major Functional Pathways for Hippocampal Serotonin Release
Authors: Okada Motohiro , Nutt David J. , Murakami Takuya , Zhu Gang , Kamata Akihisa , Kawata Yuko , Kaneko Sunao
Published: April 2018

To clarify the mechanisms of interaction between adenosineA1receptor (A1-R) and adenosine A2receptor (A2-R) on neurotransmitter release, this study determined the functional interactions among adenosine receptors (AD-Rs), voltage-sensitive Ca2+channels (VSCCs), protein kinases (PKs), and synaptic proteins [N-ethylmaleimide-sensitive factor (NSF) attachment protein (SNAP) receptors] on hippocampal serotonin release usingin vivomicrodialysis in freely moving rat. Basal serotonin release was regulated by two functional complexes: N-type VSCC (N-VSCC)/calcium-phospholipid-dependent protein kinase (PKC)/syntaxin (major pathway) and P-type VSCC (P-VSCC)/cyclic AMP-dependent protein kinase (PKA)/synaptobrevin (minor pathway). However, K+-evoked serotonin release was regulated by N-VSCC/PKC/syntaxin (minor pathway) and P-VSCC/PKA/synaptobrevin (major pathway). A1-R antagonists increased basal serotonin release, which was reduced by inhibitors of N-VSCC, PKC, and syntaxin predominantly and by inhibitors of PKA and synaptobrevin weakly, but was not affected by P-VSCC inhibitor. In the presence of A1-R antagonist, A2-R agonists increased basal serotonin release, which was inhibited by inhibitors of P-VSCC, PKA, and synaptobrevin predominantly and reduced by inhibitors of N-VSCC, PKC, and syntaxin weakly. Under the condition of activation of adenylate cyclase in the absence of A1-R antagonists, A2-R agonists increased basal serotonin release. A1-R antagonist and A2-R agonist enhanced K+-evoked serotonin release, which was inhibited by inhibitors of P-VSCC, PKA, and synaptobrevin predominantly. These results suggest that an activation of A1-R suppresses serotonin release via inhibition of both N-VSCC/PKC/syntaxin and P-VSCC/PKA/synaptobrevin pathways, and an activation of A2-R stimulates serotonin release via enhancement of the P-VSCC/PKA/synaptobrevin pathway. Therefore, PKA activity plays an important role in the interaction between A1-R and A2-R on hippocampal serotonin release.
Differential Expression of KCNQ2 Splice Variants: Implications to M Current Function during Neuronal Development
Authors: Smith Jeffrey S. , Iannotti Claudia A. , Dargis Pauline , Christian Edward P. , Aiyar Jayashree
Published: April 2018

The KCNQ family of K+channels has been implicated in several cardiac and neurological disease pathologies. KCNQ2 (Q2) is a brain-derived gene, which in association with KCNQ3 (Q3) has been shown to provide a molecular basis for the neuronal M current. We have cloned a long (Q2L) and a short (Q2S) splice variant of the human KCNQ2 gene; these variants differ in their C-terminal tail. Northern blot analysis reveals that Q2L is preferentially expressed in differentiated neurons, whereas the Q2S transcript is prominent in fetal brain, undifferentiated neuroblastoma cells, and brain tumors. Q2L, transfected into mammalian cells, produces a slowly activating, noninactivating voltage-gated K+current that is blocked potently by tetraethylammonium (TEA; IC50, 0.14 mm). Q2S on the other hand produces no measurable potassium currents. Cotransfection of Q2S with either Q2L, Q3, or Q2L/Q3 heteromultimers results in attenuation of K+current, the suppression being most profound for Q3. Inclusion of Q2S in the heteromultimer also positively shifts the voltage dependence of current activation and alters affinity for the TEA block, suggesting that under these conditions, some Q2S subunits incorporate into functional channels on the plasma membrane. In view of the crucial role of M currents in modulating neuronal excitability, our findings provide important insight into the functional consequences of differential expression of KCNQ2 splice variants: dampened potassium conductances in the developing brain could shape firing repertoires to provide cues for proliferation rather than differentiation.
Functional Expression of the New Gap Junction Gene Connexin47 Transcribed in Mouse Brain and Spinal Cord Neurons
Authors: Teubner Barbara , Odermatt Benjamin , Güldenagel Martin , Söhl Goran , Degen Joachim , Bukauskas Feliksas F. , Kronengold Jack , Verselis Vytas K. , Jung Yong Tae , Kozak Christine A. , Schilling Karl , Willecke Klaus
Published: April 2018

A new mouse gap junction gene that codes for a protein of 46,551 Da has been identified and designated connexin47 (Cx47). It mapped as a single-copy gene to mouse chromosome 11. In human HeLa cells andXenopusoocytes, expression of mouse Cx47 or a fusion protein of Cx47 and enhanced green fluorescent protein induced intercellular channels that displayed strong sensitivity to transjunctional voltage. Tracer injections in Cx47-transfected HeLa cells revealed intercellular diffusion of neurobiotin, Lucifer yellow, and 4′,6-diamidino-2-phenylindole. Recordings of single channels yielded a unitary conductance of 55 pS main state and 8 pS substate. Cx47 mRNA expression was high in spinal cord and brain but was not found in retina, liver, heart, and lung. A low level of Cx47 expression was detected in ovaries.In situhybridizations demonstrated high expression in α motor neurons of the spinal cord, pyramidal cells of the cortex and hippocampus, granular and molecular layers of the dentate gyrus, and Purkinje cells of the cerebellum as well as several nuclei of the brainstem. This expression pattern is distinct from, although partially overlapping with, that of the neuronally expressed connexin36 gene. Thus, electrical synapses in adult mammalian brain are likely to consist of different connexin proteins depending on the neuronal subtype.
Ontogeny of Modulatory Inputs to Motor Networks: Early Established Projection and Progressive Neurotransmitter Acquisition
Authors: Le Feuvre Yves , Fénelon Valérie S. , Meyrand Pierre
Published: April 2018

Modulatory information plays a key role in the expression and the ontogeny of motor networks. Many developmental studies suggest that the acquisition of adult properties by immature networks involves their progressive innervation by modulatory input neurons. Using the stomatogastric nervous system of the European lobsterHomarus gammarus, we show that contrary to this assumption, the known population of projection neurons to motor networks, as revealed by retrograde dye migration, is established early in embryonic development. Moreover, these neurons display a large heterogeneity in the chronology of acquisition of their full adult neurotransmitter phenotype.

We performed retrograde dye migration to compare the neuronal population projecting to motor networks located in the stomatogastric ganglion in the embryo and adult. We show that this neuronal population is quantitatively established at developmental stage 65%, and each identified projection neuron displays the same axon projection pattern in the adult and the embryo. We then combined retrograde dye migration with FLRFamide-like, histamine, and GABA immunocytochemistry to characterize the chronology of neurotransmitter expression in individual identified projection neurons. We show that this early established population of projection neurons gradually acquires its neurotransmitter phenotype complement. This study indicates that (1) the basic architecture of the known population of projection inputs to a target network is established early in development and (2) ontogenetic plasticity may depend on changes in neurotransmitter phenotype expression within preexisting neurons rather than in the addition of new projection neurons or fibers.
The Inertial Anisotropy of the Arm Is Accurately Predicted during Movement Planning
Authors: Flanagan J. Randall , Lolley Sarah
Published: April 2018

An important theoretical concept in motor control is the idea that the CNS uses an internal model of the motor system and environment to predict the sensory consequences of motor commands. In arm movement control, a critical factor affecting the transformation from motor commands to sensory consequences is limb dynamics, including the inertial anisotropy of the arm, which refers to the fact that the inertial resistance of the arm depends on hand movement direction. Here we show that the CNS maintains an accurate internal model of the inertial anisotropy of the arm by demonstrating that the motor system can precisely predict direction-dependent variations in hand acceleration. Subjects slid an object, held beneath the index finger, across a frictionless horizontal surface to radially located targets. We recorded the normal (vertical) force exerted by the fingertip, as well as the tangential (horizontal) force proportional to hand acceleration. We found that normal force was precisely scaled in anticipation of tangential force, which, as expected, varied with direction. The peak rates of change of the normal and tangential forces, observed early in the movement, were highly correlated. Similar results were obtained regardless of whether the start position of the hand was located directly in front of the subject or rotated 45° to the right. Finally, we observed reduced force correlations under reaction time conditions. This suggests that the process of prediction, based on an internal model of the limb, is not fully completed within the reaction time interval.
Rapid Anatomical Plasticity of Horizontal Connections in the Developing Visual Cortex
Authors: Trachtenberg Joshua T. , Stryker Michael P.
Published: April 2018

Experience can dramatically alter the responses of cortical neurons. During a critical period in the development of visual cortex, these changes are extremely rapid, taking place in 2 d or less. Anatomical substrates of these changes have long been sought, primarily in alterations in the principal visual input from the thalamus, but the significant changes that have been found take 1 week. Recent results indicate that the initial physiological changes in the cortical circuit take place outside of the primary input layer. We now find that rapid plasticity of binocular responses in the upper layers of cortex is mirrored by similarly rapid anatomical changes in the horizontal connections between ocular dominance columns in the upper layers, which reorganize within 2 d.
Hypothalamic, Metabolic, and Behavioral Responses to Pharmacological Inhibition of CNS Melanocortin Signaling in Rats
Authors: Adage Tiziana , Scheurink Anton J. W. , de Boer Sietse F. , de Vries Koert , Konsman Jan Pieter , Kuipers Folkert , Adan Roger A. H. , Baskin Denis G. , Schwartz Michael W. , van Dijk Gertjan
Published: April 2018

The CNS melanocortin (MC) system is implicated as a mediator of the central effects of leptin, and reduced activity of the CNS MC system promotes obesity in both rodents and humans. Because activation of CNS MC receptors has direct effects on autonomic outflow and metabolism, we hypothesized that food intake-independent mechanisms contribute to development of obesity induced by pharmacological blockade of MC receptors in the brain and that changes in hypothalamic neuropeptidergic systems known to regulate weight gain [i.e., corticotropin-releasing hormone (CRH), cocaine–amphetamine-related transcript (CART), proopiomelanocortin (POMC), and neuropeptide Y (NPY)] would trigger this effect. Relative to vehicle-treated controls, third intracerebroventricular (i3vt) administration of the MC receptor antagonist SHU9119 to rats for 11 d doubled food and water intake (toward the end of treatment) and increased body weight (∼14%) and fat content (∼90%), hepatic glycogen content (∼40%), and plasma levels of cholesterol (∼48%), insulin (∼259%), glucagon (∼80%), and leptin (∼490%), whereas spontaneous locomotor activity and body temperature were reduced. Pair-feeding of i3vt SHU9119-treated animals to i3vt vehicle-treated controls normalized plasma levels of insulin, glucagon, and hepatic glycogen content, but only partially reversed the elevations of plasma cholesterol (∼31%) and leptin (∼104%) and body fat content (∼27%). Reductions in body temperature and locomotor activity induced by i3vt SHU9119 were not reversed by pair feeding, but rather were more pronounced. None of the effects found can be explained by peripheral action of the compound. The obesity effects occurred despite a lack in neuropeptide expression responses in the neuroanatomical range selected across the arcuate (i.e., CART, POMC, and NPY) and paraventricular (i.e., CRH) hypothalamus. The results indicate that reduced activity of the CNS MC pathway promotes fat deposition via both food intake-dependent and -independent mechanisms.
The Exocyst Complex Associates with Microtubules to Mediate Vesicle Targeting and Neurite Outgrowth
Authors: Vega Irving E. , Hsu Shu-Chan
Published: April 2018

During neuronal development, vesicles are targeted to the growth cone to promote neurite outgrowth and synaptogenesis. The Exocyst complex is an essential macromolecule in the secretory pathway that may play a role in vesicle targeting. Although it has been shown that this complex is enriched in rat brain, the molecular mechanism underlying its function is largely unknown. Here, we report that the Exocyst complex coimmunoprecipitates with microtubules from total rat brain lysate. Additionally, the Exocyst complex subcellular localization changes on neuronal differentiation. In undifferentiated pheochromocytoma (PC12) cells, this complex is associated with microtubules at the microtubule organizing center. However, in differentiated PC12 cells and cultured hippocampal neurons, the Exocyst complex and microtubules extend to the growing neurite and colocalize at the growth cone with synaptotagmin. Inhibition of the NGF-activated MAP kinase pathway blocks the Exocyst complex and microtubule redistribution, abolishing neurite outgrowth and promoting cytosolic accumulation of secretory vesicles. Consistently, the overexpression of Exocystsec10subunit mutant blocks neurite outgrowth. These results indicate that the Exocyst complex targets secretory vesicles to specific domains of the plasma membrane through its association with the microtubules, promoting neurite outgrowth.
Disruption of Retinogeniculate Pattern Formation by Inhibition of Soluble Guanylyl Cyclase
Authors: Leamey Catherine A. , Ho-Pao Chrystal L. , Sur Mriganka
Published: April 2018

During development of the visual system of the ferret, the terminals of retinal ganglion cell axons first segregate to form eye-specific layers and subsequently On-center and Off-center sublayers within the dorsal lateral geniculate nucleus (dLGN). Sublamination requires the activity of the afferent fibers, NMDA receptors, and nitric oxide synthase (NOS). We here report that soluble guanylyl cyclase (sGC), which in turn produces cGMP, is critically involved in the process of sublamination. cGMP expression is upregulated in both retinal terminals and postsynaptic dLGN cells during sublamination, and this expression is controlled by the activity of both NMDA receptors and NOS. Furthermore, the infusion of specific inhibitors of sGC or protein kinase G (PKG), a target of cGMP, prevents sublaminationin vivo. We conclude that the sGC–cGMP–PKG pathway acts downstream of NMDA receptors and nitric oxide as an effector of the activity-dependent refinement of connections at this level of the mammalian visual system.
The Role of Cortical Activity in Experience-Dependent Potentiation and Depression of Sensory Responses in Rat Barrel Cortex
Authors: Wallace Helen , Glazewski Stanislaw , Liming Katherine , Fox Kevin
Published: April 2018

The role of cortical activity in experience-dependent cortical plasticity was studied in the rat barrel cortex. Plasticity was induced by depriving every other whisker in a chessboard pattern, which is known to cause depression of responses to deprived whisker stimulation and potentiation of responses to spared whisker stimulation. Postsynaptic activity was blocked by muscimol released from elvax slow-release polymer located under the dura and over the barrel field. Spared whisker responses potentiated 2.5-fold in layer II/III and 2.9-fold in layer IV of the near-neighbor barrel in animals implanted with saline-elvax. In contrast, in whisker-deprived animals implanted with muscimol-elvax, responses were indistinguishable from those in undeprived animals. Similarly, in the spared barrel itself, spared whisker responses potentiated 1.3-fold in layer IV in animals implanted with saline-elvax but not at all in muscimol-treated animals. Whiskers that were deprived and then allowed to regrow showed depressed responses in saline-elvax-treated animals, in which 40% of the cells in layer II/III and 26% in layer IV were unresponsive to their principal whisker. These values fell to 17 and 3% for layers II/III and IV, respectively, in muscimol-treated animals, and the response magnitude distributions were indistinguishable from undeprived cases. Cortical activity block had no acute effect on the ventroposteriomedial nucleus responses and had a transient facilitatory effect after 4 d of muscimol treatment, which returned to baseline as the muscimol treatment wore off. We conclude from these studies that cortical activity is required for potentiation and depression of sensory responses in barrel cortex.