bluuebunny/crossref_metadata_2025 huggingface dataset:
Blockade of Tetrahydrobiopterin Synthesis Protects Neurons after Transient Forebrain Ischemia in Rat: A Novel Role for the Cofactor
Authors: Cho Sunghee , Volpe Bruce T. , Bae Youngmee , Hwang Onyou , Choi Hyun J. , Gal Judit , Park Larry C. H. , Chu Chung K. , Du Jinfa , Joh Tong H.
Published: April 2018

The generation of nitric oxide (NO) aggravates neuronal injury. (6R)-5,6,7,8-Tetrahydro-l-biopterin (BH4) is an essential cofactor in the synthesis of NO by nitric oxide synthase (NOS). We attempted to attenuate neuron degeneration by blocking the synthesis of the cofactor BH4usingN-acetyl-3-O-methyldopamine (NAMDA).In vitrodata demonstrate that NAMDA inhibited GTP cyclohydrolase I, the rate-limiting enzyme for BH4biosynthesis, and reduced nitrite accumulation, an oxidative metabolite of NO, without directly inhibiting NOS activity. Animals exposed to transient forebrain ischemia and treated with NAMDA demonstrated marked reductions in ischemia-induced BH4levels, NADPH-diaphorase activity, and caspase-3 gene expression in the CA1 hippocampus. Moreover, delayed neuronal injury in the CA1 hippocampal region was significantly attenuated by NAMDA. For the first time, these data demonstrate that a cofactor, BH4, plays a significant role in the generation of ischemic neuronal death, and that blockade of BH4biosynthesis may provide novel strategies for neuroprotection.
Lectin-Induced Inhibition of Desensitization of the Kainate Receptor GluR6 Depends on the Activation State and Can Be Mediated by a Single Native or Ectopic N-Linked Carbohydrate Side Chain
Authors: Everts Inga , Petroski Robert , Kizelsztein Pablo , Teichberg Vivian I. , Heinemann Stephen F. , Hollmann Michael
Published: April 2018

The ionotropic glutamate receptor GluR6 exhibits strongly and rapidly desensitizing current responses. Treatment of heterologically expressed GluR6 with the lectin concanavalin A (ConA) inXenopusoocytes as well as in human embryonic kidney-293 cells results in a considerable increase of the steady-state current, presumably by inhibiting receptor desensitization. In the present study, we investigated the molecular basis of this effect using a systematic mutagenesis approach. We found that although N-glycosylation is an absolute prerequisite for the lectin-mediated inhibition of desensitization, no single one of the nine extracellular consensus sites for N-glycosylation of GluR6 is required. Rather, each of the nine N-linked carbohydrate side chains is independently capable of modulatory interaction with the lectin. Moreover, even artificially introduced N-glycosylation sites can substitute for native sites. Thus, the specific site of the lectin binding does not appear to be important for its desensitization-inhibiting action. Furthermore, we show that the extent of the receptor’s ConA sensitivity depends on its state of activation, because the desensitized GluR6 exhibits significantly lower lectin sensitivity than the nondesensitized receptor. We conclude that binding of ConA “locks” the receptor in the activatable state, thereby inhibiting conformational changes required to shift the receptor to the desensitized state.
Functional Properties of Two Bombesin-Like Peptide Receptors Revealed by the Analysis of Mice Lacking Neuromedin B Receptor
Authors: Ohki-Hamazaki Hiroko , Sakai Yasushi , Kamata Katsuo , Ogura Hiroo , Okuyama Shigeru , Watase Kei , Yamada Kazuyuki , Wada Keiji
Published: April 2018

The neuromedin B-preferring receptor (NMB-R) is one of the members of the bombesin (BN)-like peptide receptor subfamily in mammals. Previously, we have generated and characterized mice with targeted disruption of the two other BN-like peptide receptors, bombesin receptor subtype-3 (BRS-3) and gastrin-releasing peptide-preferring receptor (GRP-R). Here we describe the generation and analysis of NMB-R-deficient mice to investigate how NMB-R differs from BRS-3 and GRP-R. Compensation for NMB-R deficiency by overexpression of GRP-R and/or BRS-3 was not detected. Although the hypothermic effect of NMB was reduced by 50% in NMB-R-deficient mice, the effect of GRP infusion was comparable to the wild-type mice. In contrast, fundic smooth muscle contraction on stimulation with NMB or GRP was normal in NMB-R-deficient mice. Administration of GRP but not NMB suppressed glucose intake in both normal and NMB-R-deficient mice. These results suggest that the NMB-R has an essential role in thermoregulation, but not for smooth muscle contraction of the fundus or for the suppression of feeding behavior. In addition, the behavioral phenotypes of GRP-R-deficient mice were not observed in NMB-R-deficient mice. These data show that the functions of NMB-R and GRP-R are distinct, with only partial overlap.
Protein Kinase C Modulation of Recombinant NMDA Receptor Currents: Roles for the C-Terminal C1 Exon and Calcium Ions
Authors: Logan Stephen M. , Rivera Felix E. , Leonard John P.
Published: April 2018

Protein kinase C (PKC) positively modulates NMDA receptor (NMDAR) currents. In contrast to previous reports, this study determines the importance of individual exons in the mechanism underlying the potentiation process by examining the complete set of eight naturally occurring splice variants expressed inXenopusoocytes both as homomers and as heteromeric NR1/NR2A or NR1/NR2B complexes. After PKC stimulation, homomeric currents demonstrated a high level of potentiation (∼500% of untreated baseline currents) that reduced to a lower level (∼300% of baseline) in variants containing the first C-terminal exon (C1). An ANOVA showed that only C1 and no other exon or interaction of exons determined the degree of NMDAR current modulation by PKC. When recordings were performed in solutions in which barium replaces calcium, only the lower form of potentiation was observed, regardless of the splice variant exon composition. This suggested an important role for calcium in the PKC modulation of homomeric NMDA splice variant currents in which the C1 exon also participates. The effectiveness of the C1 exon to reduce the higher form of potentiation is modulated by heteromeric assemblies with NR2A heteromers yielding smaller levels of potentiation and a larger C1 exon effect compared with NR2B heteromers. The heteromers demonstrated the higher form of potentiation even in the absence of calcium. Furthermore, calcium had different effects in the potentiation of the heteromers depending on the NR2 subunit. This study refines the region of the NR1 subunit involved in a modulation crucial to the function of NMDA receptors and provides evidence that the NR2A and NR2B subunits realize this modulation differentially.
The 69 bp Circadian Regulatory Sequence (CRS) Mediatesper-Like Developmental, Spatial, and Circadian Expression and Behavioral Rescue inDrosophila
Authors: Hao Haiping , Glossop Nick R. J. , Lyons Lisa , Qiu Jan , Morrish Bronwyn , Cheng Yuzhong , Helfrich-Förster Charlotte , Hardin Paul
Published: April 2018

Theperiod(per) gene is an essential component of the circadian timekeeping mechanism inDrosophila. This gene is expressed in a circadian manner, giving rise to a protein that feeds-back to regulate its own transcription. A 69 bp clock regulatory sequence (CRS) has been identified previously upstream of theperiodgene. The CRS confers wild-type mRNA cycling when used to drive alacZreporter gene in transgenic flies. To determine whether the CRS also mediates proper developmental and spatial expression and behavioral rescue, we used the CRS to drive eitherlacZorperin transgenic flies. The results show that the CRS is able to activate expression in pacemaker neuron precursors in larvae and essentially all tissues that normally expressperin pupae and adults. The CRS is sufficient to rescue circadian feedback loop function and behavioral rhythms inper01flies. However, the period of locomotor activity rhythms shortens if a stronger basal promoter is used. This study shows that regulatory elements sufficient for clock-dependent and tissue-specificperexpression in larvae, pupae, and adults are present in the CRS and that the period of adult locomotor activity rhythms is dependent, in part, on the overall level ofpertranscripts.
Different Contributions of the Hippocampus and Perirhinal Cortex to Recognition Memory
Authors: Wan Huimin , Aggleton John P. , Brown Malcolm W.
Published: April 2018

Brain regions involved in visual recognition memory, including the hippocampus, have been investigated by measuring differential neuronal activation produced by novel and familiar pictures. Novel and familiar pictures were presented simultaneously, one to each eye, using a paired viewing procedure. Differential neuronal activation was determined using immunohistochemistry for the protein products of c-fos as an imaging technique. The results establish that the regions of the rat brain associated with discriminating the novelty or familiarity of an individual item (such as a single object) differ from those responding to a spatial array of items (such as a scene). Perirhinal cortex and area TE of the temporal lobe are activated significantly more by pictures of novel than of familiar individual objects, but the hippocampus is not differentially activated. In contrast, pictures of novel arrangements of familiar items produce significantly greater activation than familiar arrangements of these items in postrhinal cortex and subfield CA1 of the hippocampus but significantly less activation in the dentate gyrus and subiculum; perirhinal cortex and area TE are not differentially activated. Thus, the hippocampus is importantly involved in processing information essential to recognition memory concerning the relative familiarity of arrangements of items, as needed for episodic memory of scenes, whereas the perirhinal cortex processes such information for individual items.
Molecular Dynamics of the Sodium Channel Pore Vary with Gating: Interactions between P-Segment Motions and Inactivation
Authors: Bénitah Jean-Pierre , Chen Zhenhui , Balser Jeffrey R. , Tomaselli Gordon F. , Marbán Eduardo
Published: April 2018

Disulfide trapping studies have revealed that the pore-lining (P) segments of voltage-dependent sodium channels undergo sizable motions on a subsecond time scale. Such motions of the pore may be necessary for selective ion translocation. Although traditionally viewed as separable properties, gating and permeation are now known to interact extensively in various classes of channels. We have investigated the interaction of pore motions and voltage-dependent gating in μ1 sodium channels engineered to contain two cysteines within the P segments. Rates of catalyzed internal disulfide formation (kSS) were measured in K1237C+W1531C mutant channels expressed in oocytes. During repetitive voltage-clamp depolarizations, increasing the pulse duration had biphasic effects on thekSS, which first increased to a maximum at 200 msec and then decreased with longer depolarizations. This result suggested that occupancy of an intermediate inactivation state (IM) facilitates pore motions. Consistent with the known antagonism between alkali metals and a component of slow inactivation,kSSvaried inversely with external [Na+]o. We examined the converse relationship, namely the effect of pore flexibility on gating, by measuring recovery from inactivation in Y401C+E758C (YC/EC) channels. Under oxidative conditions, recovery from inactivation was slower than in a reduced environment in which the spontaneous YC/EC cross-link is disrupted. The most prominent effects were slowing of a component with intermediate recovery kinetics, with diminution of its relative amplitude. We conclude that occupancy of an intermediate inactivation state facilitates motions of the P segments; conversely, flexibility of the P segments alters an intermediate component of inactivation.
Neural Mapping of Direction and Frequency in the Cricket Cercal Sensory System
Authors: Paydar Sussan , Doan Caitlin A. , Jacobs Gwen A.
Published: April 2018

Primary mechanosensory receptors and interneurons in the cricket cercal sensory system are sensitive to the direction and frequency of air current stimuli. Receptors innervating long mechanoreceptor hairs (>1000 μm) are most sensitive to low-frequency air currents (<150 Hz); receptors innervating medium-length hairs (900–500 μm) are most sensitive to higher frequency ranges (150–400 Hz). Previous studies demonstrated that the projection pattern of the synaptic arborizations of long hair receptor afferents form a continuous map of air current direction within the terminal abdominal ganglion (Jacobs and Theunissen, 1996). We demonstrate here that the projection pattern of the medium-length hair afferents also forms a continuous map of stimulus direction. However, the afferents from the long and medium-length hair afferents show very little spatial segregation with respect to their frequency sensitivity. The possible functional significance of this small degree of spatial segregation was investigated, by calculating the relative overlap between the long and medium-length hair afferents with the dendrites of two interneurons that are known to have different frequency sensitivities. Both interneurons were shown to have nearly equal anatomical overlap with long and medium hair afferents. Thus, the differential overlap of these interneurons with the two different classes of afferents was not adequate to explain the observed frequency selectivity of the interneurons. Other mechanisms such as selective connectivity between subsets of afferents and interneurons and/or differences in interneuron biophysical properties must play a role in establishing the frequency selectivities of these interneurons.
Cerebellar Purkinje Cell Simple Spike Discharge Encodes Movement Velocity in Primates during Visuomotor Arm Tracking
Authors: Coltz J. D. , Johnson M. T. V. , Ebner T. J.
Published: April 2018

Pathophysiological, lesion, and electrophysiological studies suggest that the cerebellar cortex is important for controlling the direction and speed of movement. The relationship of cerebellar Purkinje cell discharge to the control of arm movement parameters, however, remains unclear. The goal of this study was to examine how movement direction and speed and their interaction—velocity—modulate Purkinje cell simple spike discharge in an arm movement task in which direction and speed were independently controlled. The simple spike discharge of 154 Purkinje cells was recorded in two monkeys during the performance of two visuomotor tasks that required the animals to track targets that moved in one of eight directions and at one of four speeds. Single-parameter regression analyses revealed that a large proportion of cells had discharge modulation related to movement direction and speed. Most cells with significant directional tuning, however, were modulated at one speed, and most cells with speed-related discharge were modulated along one direction; this suggested that the patterns of simple spike discharge were not adequately described by single-parameter models. Therefore, a regression surface was fitted to the data, which showed that the discharge could be tuned to specific direction–speed combinations (preferred velocities). The overall variability in simple spike discharge was well described by the surface model, and the velocities corresponding to maximal and minimal discharge rates were distributed uniformly throughout the workspace. Simple spike discharge therefore appears to integrate information about both the direction and speed of arm movements, thereby encoding movement velocity.
RNA Oxidation Is a Prominent Feature of Vulnerable Neurons in Alzheimer’s Disease
Authors: Nunomura Akihiko , Perry George , Pappolla Miguel A. , Wade Ramon , Hirai Keisuke , Chiba Shigeru , Smith Mark A.
Published: April 2018

In this study we used anin situapproach to identify the oxidized nucleosides 8-hydroxydeoxyguanosine (8OHdG) and 8-hydroxyguanosine (8OHG), markers of oxidative damage to DNA and RNA, respectively, in cases of Alzheimer’s disease (AD). The goal was to determine whether nuclear and mitochondrial DNA as well as RNA is damaged in AD. Immunoreactivity with monoclonal antibodies 1F7 or 15A3 recognizing both 8OHdG and 8OHG was prominent in the cytoplasm and to a lesser extent in the nucleolus and nuclear envelope in neurons within the hippocampus, subiculum, and entorhinal cortex as well as frontal, temporal, and occipital neocortex in cases of AD, whereas similar structures were immunolabeled only faintly in controls. Relative density measurement showed that there was a significant increase (p< 0.0001) in 8OHdG and 8OHG immunoreactivity with 1F7 in cases of AD (n= 22) as compared with senile (n= 13), presenile (n= 10), or young controls (n= 4). Surprisingly, the oxidized nucleoside was associated predominantly with RNA because immunoreaction was diminished greatly by preincubation in RNase but only slightly by DNase. This is the first evidence of increased RNA oxidation restricted to vulnerable neurons in AD. The subcellular localization of damaged RNA showing cytoplasmic predominance is consistent with the hypothesis that mitochondria may be a major source of reactive oxygen species that cause oxidative damage in AD.
The Distribution of Neurons Expressing Calcium-Permeable AMPA Receptors in the Superficial Laminae of the Spinal Cord Dorsal Horn
Authors: Engelman Holly S. , Allen Thomas B. , MacDermott Amy B.
Published: April 2018

The superficial dorsal horn is a major site of termination of nociceptive primary afferents. Fast excitatory synaptic transmission in this region is mediated mainly by release of glutamate onto postsynaptic AMPA and NMDA receptors. NMDA receptors are known to be Ca2+-permeable and to provide synaptically localized Ca2+signals that mediate short-term and long-term changes in synaptic strength. Less well known is a subpopulation of AMPA receptors that is Ca2+-permeable and has been shown to be synaptically localized on dorsal horn neurons in culture (Gu et al., 1996) and expressed by dorsal horn neuronsin situ(Nagy et al., 1994; Engelman et al., 1997). We used kainate-induced cobalt uptake as a functional marker of neurons expressing Ca2+-permeable AMPA receptors and combined this with markers of nociceptive primary afferents in the postnatal rat dorsal horn. We have shown that cobalt-positive neurons are located in lamina I and outer lamina II, a region strongly innervated by nociceptors. These cobalt-positive neurons colocalize with afferents labeled by LD2, and with the most dorsal region of capsaicin-sensitive and IB4- and LA4-positive afferents. In contrast, inner lamina II has a sparser distribution of cobalt-positive neurons. Some lamina I neurons expressing the NK1 receptor, the receptor for substance P, are also cobalt positive. These neurons are likely to be projection neurons in the nociceptive pathway. On the basis of all of these observations, we propose that Ca2+-permeable AMPA receptors are localized to mediate transmission of nociceptive information.
Brain-Derived Neurotrophic Factor Prevents Low-Frequency Inputs from Inducing Long-Term Depression in the Developing Visual Cortex
Authors: Kinoshita Shuichiro , Yasuda Hiroki , Taniguchi Nobuaki , Katoh-Semba Ritsuko , Hatanaka Hiroshi , Tsumoto Tadaharu
Published: April 2018

Brain-derived neurotrophic factor (BDNF) is reported to enhance synaptic transmission and to play a role in long-term potentiation in hippocampus and neocortex. If so, a shortage or blockade of BDNF might lead to another form of synaptic plasticity, long-term depression (LTD). To test this possibility and to elucidate mechanisms if it is the case, EPSCs evoked by test stimulation of layer IV were recorded from layer II/III neurons in visual cortical slices of young rats in the whole-cell voltage-clamp mode. LTD was induced by low-frequency stimulation (LFS) at 1 Hz for 10–15 min if each pulse of the LFS was paired with depolarization of neurons to −30 mV but was not induced if their membrane potentials were kept at −70 mV. Such an LTD was blocked by exogenously applied BDNF, probably through presynaptic mechanisms. Suppression of endogenous BDNF activity by the anti-BDNF antibody or an inhibitor for BDNF receptors made otherwise ineffective stimuli (LFS without postsynaptic depolarization) effective for LTD induction, suggesting that endogenous BDNF may prevent low-frequency inputs from inducing LTD in the developing visual cortex.
Orphanin-FQ/Nociceptin (OFQ/N) Modulates the Activity of Suprachiasmatic Nucleus Neurons
Authors: Allen Charles N. , Jiang Zhi-Gen , Teshima Koji , Darland Tristan , Ikeda Masayuki , Nelson Cole S. , Quigley Denise I. , Yoshioka Tohru , Allen Richard G. , Rea Michael A. , Grandy David K.
Published: April 2018

Neurons in the suprachiasmatic nucleus (SCN) constitute the principal circadian pacemaker of mammals.In situhybridization studies revealed expression of orphanin-FQ/nociceptin (OFQ/N) receptor (NOR) mRNA in the SCN, whereas no expression of mRNA for preproOFQ/N (ppOFQ/N) was detected. The presence of OFQ/N peptide in the SCN was demonstrated by radioimmunoassay. SCN neurons (88%) responded dose-dependently to OFQ/N with an outward current (EC50= 22.3 nm) that was reduced in amplitude by membrane hyperpolarization and reversed polarity near the theoretical potassium equilibrium potential. [Phe1ψ(Ch2-NH)Gly2]OFQ/N(1–13)NH2(3 μm), a putative NOR antagonist, activated a small outward current and significantly reduced the amplitude of the OFQ/N-stimulated current. OFQ/N reduced the NMDA receptor-mediated increase in intracellular Ca2+. When injected unilaterally into the SCN of Syrian hamsters housed in constant darkness, OFQ/N (1–50 pmol) failed to alter the timing of the hamsters’ wheel-running activity. However, injection of OFQ/N (0.1–50 pmol) before a brief exposure to light during the midsubjective night significantly attenuated the light-induced phase advances of the activity rhythm. These data are consistent with the interpretation that OFQ/N acting at specific receptors modulates the activity of SCN neurons and, thereby, the response of the circadian clock to light.
Concurrent Inhibition and Excitation of Phrenic Motoneurons during Inspiration: Phase-Specific Control of Excitability
Authors: Parkis M. A. , Dong X.-W. , Feldman J. L. , Funk G. D.
Published: April 2018

The movements that define behavior are controlled by motoneuron output, which depends on the excitability of motoneurons and the synaptic inputs they receive. Modulation of motoneuron excitability takes place over many time scales. To determine whether motoneuron excitability is specifically modulated during the active versus the quiescent phase of rhythmic behavior, we compared the input–output properties of phrenic motoneurons (PMNs) during inspiratory and expiratory phases of respiration.

In neonatal rat brainstem–spinal cord preparations that generate rhythmic respiratory motor outflow, we blocked excitatory inspiratory synaptic drive to PMNs and then examined their phase-dependent responses to superthreshold current pulses. Pulses during inspiration elicited fewer action potentials compared with identical pulses during expiration. This reduced excitability arose from an inspiratory-phase inhibitory input that hyperpolarized PMNs in the absence of excitatory inspiratory inputs. Local application of bicuculline blocked this inhibition as well as the difference between inspiratory and expiratory firing. Correspondingly, bicuculline locally applied to the midcervical spinal cord enhanced fourth cervical nerve (C4) inspiratory burst amplitude. Strychnine had no effect on C4 output. Nicotinic receptor antagonists neither potentiated C4 output nor blocked its potentiation by bicuculline, further indicating that the inhibition is not from recurrent inhibitory pathways. We conclude that it is bulbospinal in origin.

These data demonstrate that rapid changes in motoneuron excitability occur during behavior and suggest that integration of overlapping, opposing synaptic inputs to motoneurons is important in controlling motor outflow. Modulation of phasic inhibition may represent a means for regulating the transfer function of PMNs to suit behavioral demands.
Synchronized Paroxysmal Activity in the Developing Thalamocortical Network Mediated by Corticothalamic Projections and “Silent” Synapses
Authors: Golshani Peyman , Jones Edward G.
Published: April 2018

In mouse thalamocortical slicesin vitro, the potassium channel blocker 4-AP and GABAAreceptor antagonist bicuculline together induced spontaneous prolonged depolarizations in layer VI neurons from postnatal day 2 (P2), in ventroposterior nucleus neurons (VP) from P7, and in reticular nucleus neurons (RTN) from P8. Dual whole-cell recordings revealed that prolonged bursts were synchronized in layer VI, VP, and RTN. Bursts were present in cortex isolated from thalamus, but not in thalamus isolated from cortex, indicating that bursts originated in cortex and propagated to thalamus. Prolonged bursts were synchronized in layer VI when vertical cuts extended from pia mater through layers IV or V, but were no longer synchronized when cuts extended through layer VI and white matter.

In voltage-clamp recordings before P10, burst conductance of all three neuronal populations was dominated by the NMDA receptor-mediated conductance, and therefore synapses were “silent”. In cortex and RTN, after P10, bursts were associated with strong AMPA/kainate receptor-mediated conductances, and synapses had become “functional”; silent synapses persisted in a large proportion of VP cells after P10.

Before P9, the NMDA receptor antagonist APV or the non-NMDA receptor antagonist CNQX blocked the prolonged bursts. After P9, CNQX continued to block the prolonged bursts, but APV merely shortened their duration.

Thus, NMDA receptor-based silent synapses are essential for paroxysmal corticothalamic activity during early postnatal development, and connections between layer VI neurons are sufficient for horizontal cortical synchronization.
Calcitonin Gene-Related Peptide Rapidly Downregulates Nicotinic Receptor Function and Slowly Raises Intracellular Ca2+in Rat Chromaffin CellsIn Vitro
Authors: Giniatullin R. , Di Angelantonio Silvia , Marchetti Cristina , Sokolova Elena , Khiroug L. , Nistri A.
Published: April 2018

Although calcitonin gene-related peptide (CGRP) modulates muscle-type nicotinic acetylcholine receptors (nAChRs) via intracellular second messenger-mediated phosphorylation, the action of this peptide on neuronal-type nAChRs remains unknown. Using neuronal nAChRs of rat chromaffin cellsin vitrowe studied the effect of CGRP, which is physiologically present in adrenal medulla, on membrane currents and [Ca2+]itransients elicited by nicotine. Our main novel observation was that CGRP (either bath-applied or focally applied for a few seconds or even co-applied with nicotine for a few milliseconds) selectively and rapidly blocked nAChRs (a phenomenon unlikely caused by intracellular messengers in view of its speed) without affecting GABA receptors. The inhibitory effect of CGRP was independent of [Ca2+]ior membrane potential and not accompanied by baseline current changes. Like the competitive antagonistN,N,N-trimethyl-1-(4-trans-stilbenoxy)-2-propilammonium, CGRP induced a rightward, parallel shift of the nicotine dose–response curve; during co-application of these blockers the nicotine dose–ratio value was the sum of the values obtained with each antagonist alone. The block by CGRP was insensitive to the receptor antagonist hCGRP8–37but mimicked by CGRP1–7. Persistent application of CGRP slowly increased [Ca2+]i, a phenomenon independent from external Ca2+, thus implying Ca2+release from internal stores, and suppressed by hCGRP8–37. CGRP1–7had no significant effect on [Ca2+]i. We propose that the 1–7 amino acid sequence of CGRP was responsible for the direct, rapid block of nAChRs, whereas the full-length peptide molecule was necessary for the delayed rise in internal Ca2+potentially able to trigger phosphorylation-dependent modulation of nicotinic receptor function.
Overexpression of α-Internexin Causes Abnormal Neurofilamentous Accumulations and Motor Coordination Deficits in Transgenic Mice
Authors: Ching Gee Y. , Chien Chung-Liang , Flores Roberto , Liem Ronald K. H.
Published: April 2018

α-Internexin is the first neuronal intermediate filament (IF) protein expressed in postmitotic neurons of the developing nervous system. In the adult, its expression is restricted to mature neurons in the CNS. To study the potential role of α-internexin in neurodegeneration, we have generated transgenic mice that overexpress rat α-internexin. The total levels of α-internexin expressed in the hemizygous and homozygous transgenic mice were ∼2 and ∼3 times the normal level, respectively. Overexpression of α-internexin resulted in the formation of cerebellar torpedoes as early as 1 month of age. These torpedoes are abnormal swellings of Purkinje cell axons that are usually seen in neurodegenerative diseases involving the cerebellum. EM studies showed accumulations of high levels of IFs and abnormal organelles in the torpedoes and soma of Purkinje cells, as well as in the large pyramidal neurons of the neocortex and in the ventral anterior and posteromedial nuclei of the thalamus. Behavioral tests demonstrate that these mice have a deficit in motor coordination as early as 3 months of age, consistent with the morphological neuronal changes. Our data further demonstrate that the neurofilamentous inclusions also lead to progressive loss of neurons in the aged transgenic mice. The motor coordination deficit and the loss of neurons are transgene dosage-dependent. These data yield direct evidence that high levels of misaccumulated neuronal IFs lead to neuronal dysfunction, progressive neurodegeneration, and ultimate loss of neurons. Moreover, the degrees of neuronal dysfunction and degeneration are proportional to the levels of misaccumulated neuronal IFs.
Glutamate Receptor Expression Regulates Quantal Size and Quantal Content at theDrosophilaNeuromuscular Junction
Authors: DiAntonio Aaron , Petersen Sophie A. , Heckmann Manfred , Goodman Corey S.
Published: April 2018

At theDrosophilaglutamatergic neuromuscular junction, the postsynaptic cell can regulate synaptic strength by both changing its sensitivity to neurotransmitter and generating a retrograde signal that regulates presynaptic transmitter release. To investigate the molecular mechanisms underlying these forms of plasticity, we have undertaken a genetic analysis of two postsynaptic glutamate receptors that are expressed at this synapse. Deletion of both genes results in embryonic lethality that can be rescued by transgenic expression of either receptor. Although these receptors are redundant for viability, they have important differences. By transgenically rescuing the double mutant, we have investigated the relationship of receptor gene dosage and composition to synaptic function. We find that the receptor subunit composition regulates quantal size, Argiotoxin sensitivity, and receptor desensitization kinetics. Finally, we show that the activity of the receptor can regulate the retrograde signal functioning at this synapse. Thus, the diversity of receptors expressed at this synapse provides the cell with mechanisms for generating synaptic plasticity.
Differential c-Fos Expression in Cholinergic, Monoaminergic, and GABAergic Cell Groups of the Pontomesencephalic Tegmentum after Paradoxical Sleep Deprivation and Recovery
Authors: Maloney Karen J. , Mainville Lynda , Jones Barbara E.
Published: April 2018

Multiple lines of evidence indicate that neurons within the pontomesencephalic tegmentum are critically involved in the generation of paradoxical sleep (PS). From single-unit recording studies, evidence suggests that unidentified but “possibly” cholinergic tegmental neurons discharge at higher rates during PS than during slow wave sleep or even waking and would thus play an active role, whereas “presumed” monoaminergic neurons cease firing during PS and would thus play a permissive role in PS generation. In the present study performed on rats, c-Fos immunostaining was used as a reflection of neuronal activity and combined with immunostaining for choline acetyltransferase (ChAT), serotonin (Ser), tyrosine hydroxylase (TH), or glutamic acid decarboxylase (GAD) for immunohistochemical identification of active neurons during PS recovery (∼28% of recording time) as compared with PS deprivation (0%) and PS control (∼15%) conditions. With PS recovery, there was a significant increase in ChAT+/c-Fos+ cells, a significant decrease in Ser+/c-Fos+ and TH+/c-Fos+ cells, and a significant increase in GAD+/c-Fos+ cells. Across conditions, the percent PS was correlated positively with tegmental cholinergic c-Fos+ cells, negatively with raphe serotonergic and locus coeruleus noradrenergic c-Fos+ cells, and positively with codistributed and neighboring GABAergic c-Fos+ cells. These results support the hypothesis that cholinergic neurons are active, whereas monoaminergic neurons are inactive during PS. They moreover indicate that GABAergic neurons are active during PS and could thus be responsible for inhibiting neighboring monoaminergic neurons that may be essential in the generation of PS.
A Theory of Geometric Constraints on Neural Activity for Natural Three-Dimensional Movement
Authors: Zhang Kechen , Sejnowski Terrence J.
Published: April 2018

Although the orientation of an arm in space or the static view of an object may be represented by a population of neurons in complex ways, how these variables change with movement often follows simple linear rules, reflecting the underlying geometric constraints in the physical world. A theoretical analysis is presented for how such constraints affect the average firing rates of sensory and motor neurons during natural movements with low degrees of freedom, such as a limb movement and rigid object motion. When applied to nonrigid reaching arm movements, the linear theory accounts for cosine directional tuning with linear speed modulation, predicts a curl-free spatial distribution of preferred directions, and also explains why the instantaneous motion of the hand can be recovered from the neural population activity. For three-dimensional motion of a rigid object, the theory predicts that, to a first approximation, the response of a sensory neuron should have a preferred translational direction and a preferred rotation axis in space, both with cosine tuning functions modulated multiplicatively by speed and angular speed, respectively. Some known tuning properties of motion-sensitive neurons follow as special cases. Acceleration tuning and nonlinear speed modulation are considered in an extension of the linear theory. This general approach provides a principled method to derive mechanism-insensitive neuronal properties by exploiting the inherently low dimensionality of natural movements.
Sympathetic Neuronal Oscillators are Capable of Dynamic Synchronization
Authors: Chang Hong-Shiu , Staras Kevin , Smith Julia E. , Gilbey Michael P.
Published: April 2018

In this paper we show that the discharges of sympathetic neurons innervating an identified peripheral target are driven by multiple oscillators that undergo dynamic synchronization when an entraining force, central respiratory drive (CRD), is increased. Activity was recorded from postganglionic sympathetic neurons (PGNs) innervating the caudal ventral artery of the rat tail: (1) at the population level from the ventral collector nerve (VCN); and (2) from pairs of single PGNs recorded simultaneously using a focal recording technique. Autospectral analysis of VCN activity revealed a more prominent rhythmical component in the presence of CRD than in its absence, suggesting that (1) multiple oscillators drive the discharges of PGNs and (2) these oscillators can be entrained and therefore synchronized by CRD. This interpretation was supported by analysis of the firing behavior of PGN pairs. Autocorrelation and cross-correlation analysis showed that pairs were not synchronized in the absence of CRD but showed significant synchronization when CRD was enhanced. Time-evolving spectral analysis and raster plots demonstrated that the temporal stability of PGN-to-PGN and CRD-to-PGN interactions at a given level of CRD were also dynamic in nature, with stable constant phase relationships predominating as CRD was increased. This is the first reported example of dynamic synchronization in populations of single postganglionic sympathetic neurons, and we suggest that, as in sensory processing and motor control, temporal pattern coding may also be an important feature of neuronal discharges in sympathetic pathways.
Key Role of 5-HT1BReceptors in the Regulation of Paradoxical Sleep as Evidenced in 5-HT1BKnock-Out Mice
Authors: Boutrel Benjamin , Franc Bernard , Hen René , Hamon Michel , Adrien Joëlle
Published: April 2018

The involvement of 5-HT1Breceptors in the regulation of vigilance states was assessed by investigating the spontaneous sleep–waking cycles and the effects of 5-HT receptor ligands on sleep in knock-out (5-HT1B−/−) mice that do not express this receptor type. Both 5-HT1B−/− and wild-type 129/Sv mice exhibited a clear-cut diurnal sleep–wakefulness rhythm, but knock-out animals were characterized by higher amounts of paradoxical sleep and lower amounts of slow-wave sleep during the light phase and by a lack of paradoxical sleep rebound after deprivation. In wild-type mice, the 5-HT1Bagonists CP 94253 (1–10 mg/kg, i.p.) and RU 24969 (0.25–2.0 mg/kg, i.p.) induced a dose-dependent reduction of paradoxical sleep during the 2–6 hr after injection, whereas the 5-HT1B/1Dantagonist GR 127935 (0.1–1.0 mg/kg, i.p.) enhanced paradoxical sleep. In addition, pretreatment with GR 127935, but not with the 5-HT1Aantagonist WAY 100635, prevented the effects of both 5-HT1Bagonists. In contrast, none of the 5-HT1Breceptor ligands, at the same doses as those used in wild-type mice, had any effect on sleep in 5-HT1B−/− mutants. Finally, the 5-HT1Aagonist 8-OH-DPAT (0.2–1.2 mg/kg, s.c.) induced in both strains a reduction in the amount of paradoxical sleep. Altogether, these data indicate that 5-HT1Breceptors participate in the regulation of paradoxical sleep in the mouse.
Brain-Derived Neurotrophic Factor Mediates the Anti-Apoptotic Effect of NMDA in Cerebellar Granule Neurons: Signal Transduction Cascades and Site of Ethanol Action
Authors: Bhave Sanjiv V. , Ghoda Lucy , Hoffman Paula L.
Published: April 2018

Cerebellar granule neurons cultured in medium containing a physiological concentration of KCl (5 mm) undergo apoptosis. The cells can be rescued by thein vitroaddition of NMDA. The protective effect of NMDA is thought to reflect thein vivoinnervation of developing cerebellar granule neurons by glutamatergic afferents. In the current work, we investigated the mechanism of the anti-apoptotic (protective) effect of NMDA. NMDA treatment reduced caspase-3-like activity in cerebellar granule neurons, and the time course and concentration dependence of the protective effect of NMDA mirrored the ability of NMDA to induce brain-derived neurotrophic factor (BDNF) expression. Furthermore, a Trk receptor antagonist, K252a, as well as a blocking antibody to BDNF, attenuated the protective effects of both NMDA and BDNF. These results suggest that NMDA-induced BDNF expression mediates the anti-apoptotic effect of NMDA. The protective effects of NMDA and BDNF were reduced by inhibitors of the phosphatidylinositol 3′-OH kinase (PI 3-kinase) signal transduction cascade (wortmannin and LY29004) but not by a MAP kinase kinase (MEK) inhibitor (PD98059) or a protein kinase A inhibitor (Rp-cAMPS). BDNF increased phosphorylation of Akt, a target of PI 3-kinase, and NMDA also induced Akt phosphorylation, but only after an exposure that was long enough to induce BDNF expression. Furthermore, ethanol, which interferes with NMDA receptor function, inhibited the NMDA-induced increase in BDNF levels but did not block the protective effect of BDNF. These findings further support the role of BDNF in the anti-apoptotic effect of NMDA in cerebellar granule neurons and suggest that the NMDA–BDNF interaction may play a key role inin vivocerebellar granule neuron development, as well as in the deleterious effects of ethanol on the developing cerebellum.
Granule Cells in Aging Rats Are Sexually Dimorphic in Their Response to Estradiol
Authors: Miranda Phillippa , Williams Christina L. , Einstein Gillian
Published: April 2018

Normal aging comprises cognitive decline, including deterioration of memory. It has been suggested that this decline in memory is sexually dimorphic because of the cessation in gonadal steroid secretion that occurs during reproductive aging in female, but not male, mammals. We wondered whether neurons in brain regions associated with learning and memory underwent morphological changes that were dimorphic as well and whether cessation of the secretion of gonadal steroids influenced these morphological changes. To explore these questions, we deprived and restored estrogens to young and old gonadectomized females and males and studied the morphology of dentate granule cells by intracellular dye filling in a lightly fixed slice preparation. We found the following: (1) Aged female dentate granule cells deprived of gonadal steroids long-term have a paucity of dendritic spines compared with young females deprived short-term; however, aged male dentate granule cells deprived of gonadal steroids long-term have no decrease in dendritic spines compared with young males deprived short-term. (2) Aged female dentate granule cells with long-term estrogen replacement at either high or low levels still had a decline in spine density. (3) Aged female dentate granule cells with short-term estradiol replacement had spine density increased to levels normally observed in young adults, whereas aged males with short-term estradiol replacement had decreased spine density. These data suggest that the response of rat dentate granule cells to aging and estradiol is sexually dimorphic and that, in females, the responsiveness of granule cells depends on the temporal pattern of estradiol replacement.
Tonic Dopamine Inhibition of L-Type Ca2+Channel Activity Reduces α1DCa2+Channel Gene Expression
Authors: Fass Daniel M. , Takimoto Koichi , Mains Richard E. , Levitan Edwin S.
Published: April 2018

Hormones and neurotransmitters have both short-term and long-term modulatory effects on the activity of voltage-gated Ca2+channels. Although much is known about the signal transduction underlying short-term modulation, there is far less information on mechanisms that produce long-term effects. Here, the molecular basis of long-lasting suppression of Ca2+channel current in pituitary melanotropes by chronic dopamine exposure is examined. Experiments involvingin vivoandin vitrotreatments with the dopaminergic drugs haloperidol, bromocriptine, and quinpirole show that D2 receptors persistently decrease α1DL-type Ca2+channel mRNA and L-type Ca2+channel current without altering channel gating properties. In contrast, another L-channel (α1C) mRNA and P/Q-channel (α1A) mRNA are unaffected. The downregulation of α1DmRNA does not require decreases in cAMP levels or P/Q-channel activity. However, it is mimicked and occluded by inhibition of L-type channels. Thus, interruption of the positive feedback between L-type Ca2+channel activity and α1Dgene expression can account for the long-lasting regulation of L-current produced by chronic activation of D2 dopamine receptors.
Ca2+-Permeable P2X Receptor Channels in Cultured Rat Retinal Ganglion Cells
Authors: Taschenberger H. , Jüttner R. , Grantyn R.
Published: April 2018

ATP has been identified as an excitatory neurotransmitter in both the CNS and peripheral nervous system; however, little is known about the functional properties of ATP-gated channels in central neurons. Here we used a culture preparation of the postnatal rat retina to test the responsiveness of identified retinal ganglion cells (RGCs) and putative amacrines to exogenous ATP and other purinoceptor agonists. Rapidly activating ATP-induced currents (IATP) were exclusively generated in a subpopulation (∼65%) of RGCs. The latter were identified by Thy1.1 immunostaining, repetitive firing patterns, and activation of glutamatergic autaptic currents. None of the putative amacrine cells was ATP-sensitive.IATPcould be induced with ATP, ADP, and α,β-mATP but not with adenosine. It was antagonized by suramin. The current–voltage relationship ofIATPshowed marked inward rectification. Dose–response analysis yielded an EC50of 14.5 μm, with a Hill coefficient of 0.9. Noise analysis ofIATPsuggested a mean single channel conductance of 2.3 pS. Retinal P2X purinoceptor channels exhibited a high permeability for Ca2+. PCa/PCsobtained from reversal potentials ofIATPunder bi-ionic conditions amounted to 2.2 ± 0.7. In the majority of cells, the decay ofIATPwas biphasic. The degree of current inactivation during the first 2 sec of agonist application was highly variable. Heterogeneity was also found with respect to the sensitivity to ADP and α,β-mATP and the blocking action of suramin, suggesting expression of multiple P2X receptor subtypes. Our results indicate that activation of P2X receptor channels represents an important pathway for Ca2+influx in postnatal RGCs.
Regulation of Calcitonin Gene-Related Peptide Secretion by a Serotonergic Antimigraine Drug
Authors: Durham Paul L. , Russo Andrew F.
Published: April 2018

We have investigated the regulation of calcitonin gene-related peptide (CGRP) release from trigeminal neurons by the serotonergic antimigraine drug sumatriptan. Serum levels of the neuropeptide CGRP are elevated during migraine. Treatment with the drug sumatriptan returns CGRP levels to normal coincident with the alleviation of headache. However, despite this clinical efficacy, the cellular target and mechanism of sumatriptan action are not well understood beyond the pharmacology of its recognition of the 5-HT1class of serotonin receptors. We have used cultured trigeminal neurons to demonstrate that sumatriptan can directly repress CGRP secretion from sensory neurons. The stimulated secretion in response to depolarization or inflammatory agents was inhibited, but not the basal secretion rate. Unexpectedly, sumatriptan did not lower cAMP levels, in contrast to the classical role ascribed to the 5-HT1receptors. Instead, activation of 5-HT1receptors caused a slow and remarkably prolonged increase in intracellular calcium. The inhibition of CGRP secretion is attenuated by the phosphatase inhibitor okadaic acid, suggesting that sumatriptan action is mediated by calcium-recruited phosphatases. These results suggest that 5-HT1agonists may block a deleterious feedback loop in migraine at the trigeminal neurons and provide a general mechanism by which this class of drugs can attenuate stimulated neuropeptide release.
Afferent–Target Cell Interactions in the Cerebellum: Negative Effect of Granule Cells on Purkinje Cell Development in Lurcher Mice
Authors: Doughty Martin L. , Lohof Ann , Selimi Fekrije , Delhaye-Bouchaud Nicole , Mariani Jean
Published: April 2018

Lurcher (Lc) is a gain-of-function mutation in the δ2 glutamate receptor gene that results in a large, constitutive inward current in the cerebellar Purkinje cells of +/Lcmice. +/LcPurkinje cells fail to differentiate fully and die during postnatal development. In normal mice, interactions with granule cells promote Purkinje cell dendritic differentiation. Partial destruction of the granule cell population in young +/Lcmice by x irradiation resulted in a significant increase in Purkinje cell dendritic growth and improved cytoplasmic structure but did not prevent Purkinje cell death. These results indicate two components to Purkinje cell abnormalities in +/Lcmice: a retardation/blockade of dendritic development that is mediated by interactions with granule cells and the death of the cell. Thus, the normal trophic effects of granule cell interaction on Purkinje cell development are absent in the +/Lccerebellum, suggesting that granule cells are powerful regulators of Purkinje cell differentiation.