bluuebunny/crossref_metadata_2025 huggingface dataset:
Cloning and Functional Characterization of Roaz, a Zinc Finger Protein that Interacts with O/E-1 to Regulate Gene Expression: Implications for Olfactory Neuronal Development
Authors: Tsai Robert Y. L. , Reed Randall R.
Published: April 2018

We have identified a protein, Rat O/E-1-associated zinc finger protein (Roaz), that plays a role in regulating the temporal and spatial pattern of olfactory neuronal-specific gene expression. This protein functions by interacting with the olfactory factor O/E-1 and modulating its transcriptional activity. Roaz, isolated via a yeast two-hybrid screen, encoded a protein containing 29 C2H2zinc fingers of the TFIIIA type. The Roaz mRNA was found in brain, eye, olfactory epithelium, spleen, and heart.In situhybridization data indicated that Roaz was expressed in the basal layer, consisting of neural precursor cells and immature sensory neurons of the olfactory epithelium, but not in the mature receptor cells. We showed that the Roaz protein bound specifically to O/E-1 by using the yeast two-hybrid system. The two proteins formed a stable complex in coimmunoprecipitation andin vitrobinding assays. Introduction of Roaz and O/E-1 into cells containing an olfactory promoter-driven luciferase reporter demonstrated that Roaz abolished O/E-1-mediated transcriptional activation. We propose that the function of Roaz is to modulate negatively the transactivational activity of O/E-1 and to act as a switch protein in the coordination of olfactory sensory neuron differentiation.
Tissue Inhibitor of Metalloproteinases-1 (TIMP-1) Is Differentially Induced in Neurons and Astrocytes after Seizures: Evidence for Developmental, Immediate Early Gene, and Lesion Response
Authors: Rivera Santiago , Tremblay Evelyne , Timsit Serge , Canals Oriol , Ben-Ari Yezekiel , Khrestchatisky Michel
Published: April 2018

We investigatedin vivothe expression of the tissue inhibitor of metalloproteinases-1 (TIMP-1) in the rat CNS after kainate (KA)-induced excitotoxic seizures.In situhybridization revealed that TIMP-1 mRNA is induced rapidly and massively in most regions of the adult forebrain after KA treatment. Neuronal activity seems to be necessary but not sufficient to trigger TIMP-1 induction, because it is not observed in seizing 10-d-old pups, unlike what is observed in 21- and 35-d-old animals after seizures. The rapid induction of TIMP-1 is not prevented by the inhibitor of protein synthesis cycloheximide, suggesting that, after seizures, TIMP-1 is induced in neurons as an immediate early gene (IEG). The initial neuronal upregulation is followed by enhanced expression in astrocytes, as assessed by double-labeling experiments. In the hippocampus rapid increases in mRNA are followed by relatively delayed (8 hr after KA) increases in TIMP-1 immunoreactivity in the perisomatic and dendro–axonic areas, suggesting secretion of the protein. At 3 d after KA treatment, strong immunoreactivity is found in astrocytes and in the cell bodies and dendro–axonic projections of resistant neurons such as the dentate granule cells. Taken together, the results suggest that TIMP-1 may be instrumental for neurons and astrocytes in coupling early cellular events triggered by seizures with the regulation of long-lasting changes involved in tissue reorganization and/or neuroprotection.
A New Form of Inherited Red-Blindness Identified in Zebrafish
Authors: Brockerhoff Susan E. , Hurley James B. , Niemi Gregory A. , Dowling John E.
Published: April 2018

A red-blind zebrafish mutant,partial optokinetic response b (pob), has been isolated by measuring eye movements of larvae in a three-generation screen for recessive mutations affecting the visual system.poblarvae exhibit eye movements in response to rotating black and white stripes illuminated with white light, but they do not move their eyes when the stripes are illuminated with red light. Physiological, immunohistochemical, andin situhybridization analyses ofpobretinas showed a selective loss of red-sensitive cones at 5 days postfertilization (dpf). At 3 dpf, cells expressing red opsin are present, suggesting that red-sensitive cones form initially but then disappear rapidly, whereas other photoreceptors remain. Linkage analysis indicated that the mutation identified in thepobmutant is not at the red opsin locus. Because red opsin is the only known molecule unique to red cones, these data suggest that a novel gene is required for the maintenance or function of red cones.
Neurotrophin-3 Promotes the Differentiation of Muscle Spindle Afferents in the Absence of Peripheral Targets
Authors: Oakley Robert A. , Lefcort Frances B. , Clary Douglas O. , Reichardt Louis F. , Prevette David , Oppenheim Ronald W. , Frank Eric
Published: April 2018

The neurons of the dorsal root ganglia (DRG) that supply muscle spindles require target-derived factors for survival. One necessary factor for these neurons is neurotrophin-3 (NT3). To determine whether NT3 can promote the survival of these neurons in the absence of other target-derived factors, we analyzed the effects of exogenous NT3 after early limb bud deletion in the chick. In control embryos, limb bud deletion eliminated ∼90% of the trkC-positive (trkC+) neurons in lumbar DRG on the deleted side. In addition, the deletion led to a dramatic loss of collateral sensory projections to motoneurons. Exogenous NT3 restored a normal population of trkC+ neurons in lumbar DRG on the deleted side and increased the number of trkC+ neurons in DRG with normal targets (contralateral lumbar and thoracic). The effect was highly selective; NT3 increased the number of trkC+ neurons without significantly changing the number of either trkA+ or trkB+ neurons. The effect of NT3 was attributable to the rescue of DRG neurons from cell death, because exogenous NT3 reduced the number of pyknotic nuclei without significantly altering proliferation. Analysis of spinal projections showed further that many of the trkC+ neurons rescued by NT3 projected to the ventral spinal cord. These neurons thus had central projections characteristic of muscle spindle afferents. Together, our results indicate that NT3 signaling is both necessary and sufficient for the development of the proprioceptive phenotype, even in the absence of other signals from limb muscle.
Temperature Dependency of Basal and Evoked Release of Amino Acids and Calcitonin Gene-Related Peptide from Rat Dorsal Spinal Cord
Authors: Dirig David M. , Hua Xiao-Ying , Yaksh Tony L.
Published: April 2018

Moderate hypothermia significantly diminishes consequences of spinal and cerebral anoxia. One component of this neuroprotection has been hypothesized to be suppression of excitotoxic transmitter release. Whether this suppression is attributable to reduced hypoxic injury that induces release or an alteration of the release process itself is unclear. We sought to characterize the temperature sensitivity (Q10) of basal and evoked calcitonin gene-related peptide (CGRP) and amino acid release from dorsal horn slices of rat spinal cord over a range of temperatures from 40 to 8°C. At 40°C, potassium (60 mm) and capsaicin (10 μm) evoked a 21- and 32-fold increase in basal CGRP concentrations, respectively. Capsaicin had no effect on glutamate release, but potassium evoked a 2.7-fold increase. Release evoked by either potassium or capsaicin was reduced in a biphasic fashion with declining temperature. Over the range of 40 to 34°C, theQ10values for evoked release for CGRP were 11.3 (potassium) and 39.7 (capsaicin) and for glutamate, 5.5 (potassium). Over the range of 34 to 8°C,Q10values were near unity for all evoked release (0.8 and 1.3 for CGRP and 1.2 for glutamate). Although serine, glycine, glutamine, taurine, and citrulline showed no evoked release, basal levels were reduced at temperatures below 34°C. The pronounced temperature dependency of evoked transmitter release between 40 and 34°C is consistent with the profound cerebral protection observed with mild hypothermia in which metabolic activity is only slightly depressed.
Synaptic Enhancement and Enhanced Excitability in Presynaptic and Postsynaptic Neurons in the Conditioned Stimulus Pathway ofHermissenda
Authors: Frysztak R. J. , Crow T.
Published: April 2018

Identified type A photoreceptors ofHermissendaexpress differential effects of classical conditioning. Lateral type A photoreceptors exhibit an increase in excitability to both the conditioned stimulus (CS; light) and extrinsic current. In contrast, medial type A photoreceptors do not express enhanced excitability, but do show enhancement of the medial B to medial A synaptic connection. Therefore, both enhanced excitability and changes in synaptic strength may contribute to long-term plasticity underlying classical conditioning. The activation of protein kinase C (PKC) is involved in the induction of enhanced excitability of identified type B photoreceptors produced by one-trial conditioning and the expression of enhanced excitability in B photoreceptors after multitrial classical conditioning. We have examined a possible role for persistent kinase activity in the expression of enhanced excitability in lateral type A photoreceptors and enhancement of the medial B to medial type A synaptic connection after classical conditioning. Injection of the PKC inhibitor peptide PKC(19–36) into medial type B photoreceptors of conditioned animals did not significantly change the amplitude of medial A IPSPs elicited by single spikes in the medial B photoreceptor. Injections of PKC(19–36) into medial B photoreceptors of pseudorandom controls also did not significantly change the amplitude of IPSPs recorded from the medial A photoreceptor. In contrast, spikes elicited by extrinsic current in lateral type A photoreceptors of conditioned animals were significantly reduced in frequency after intracellular injection of PKC(19–36) as compared with pseudorandom controls. Injection of the noninhibitory analog peptide [glu27]PKC(19–36) did not affect excitability. Thus, enhanced excitability in the lateral A photoreceptor of conditioned animals seems to be influenced, in part, by a constitutively active kinase or a persistent kinase activator, whereas synaptic enhancement of the connection between the medial B and medial A photoreceptors of conditioned animals may involve a different mechanism.
A Novel Allosteric Potentiator of AMPA Receptors: 4-[2-(Phenylsulfonylamino)ethylthio]-2,6-Difluoro-Phenoxyacetamide
Authors: Sekiguchi Masayuki , Fleck Mark W. , Mayer Mark L. , Takeo Jiro , Chiba Yoshiyuki , Yamashita Shinya , Wada Keiji
Published: April 2018

We report that a novel sulfonylamino compound, 4-[2-(phenylsulfonylamino)ethylthio]-2,6-difluoro-phenoxyacetamide (PEPA), selectively potentiates glutamate receptors of the AMPA subtype. PEPA (1–200 μm) dose dependently potentiated glutamate-evoked currents inXenopusoocytes expressing AMPA (GluRA–GluRD), but not kainate (GluR6 and GluR6+KA2) or NMDA (ζ1 + ε1–ε4), receptor subunits. PEPA was effective at micromolar concentrations and, in contrast to the action of cyclothiazide, preferentially modulated AMPA receptor flop isoforms. At 200 μm, PEPA potentiated glutamate responses by 50-fold in oocytes expressing GluRCflop(EC50∼50 μm) versus only threefold for GluRCflip; a similar preference for flop isoforms was observed for other AMPA receptor subunits. Dose–response analysis for GluRCfloprevealed that 100 μmPEPA produced a sevenfold increase in AMPA receptor affinity for glutamate. PEPA produced considerably weaker potentiation of kainate-evoked than glutamate-evoked currents, suggesting modulation of the process of receptor desensitization. In human embryonic kidney 293 cells transfected with AMPA receptor subunits, PEPA either abolished or markedly slowed the rate of onset of desensitization and potentiated steady-state equilibrium currents evoked by glutamate with subunit (GluRC ≥ GluRD > GluRA) and splice-variant (flop > flip) selectivity similar to that observed in oocytes. Our results show that PEPA is a novel, flop-preferring allosteric modulator of AMPA receptor desensitization at least 100 times more potent than aniracetam.
Muscle Response to Changing Neuronal Input in the Lobster (Panulirus interruptus) Stomatogastric System: Spike Number- versus Spike Frequency-Dependent Domains
Authors: Morris Lee G. , Hooper Scott L.
Published: April 2018

We aimed to determine the neuronal parameters controlling the contraction of slowly contracting, non-twitch (“tonic”) muscles driven by rhythmic neuronal activity. These muscles are almost completely absent in mammals but are common in lower vertebrates and invertebrates. Slow muscles are often believed to function primarily in tonic motor patterns. However, previous research and data presented here indicate that slow muscles are also driven by rhythmic neuronal inputs.

In rapidly contracting “twitch” muscles, motor unit force is believed to be primarily determined by motor neuron spike frequency. What determines slow muscle output is less well understood. We present a simple model that suggests that when motor neuron burst duration is brief compared with muscle summation time, spike number, not spike frequency, determines slow muscle contraction amplitude.

We present analyses that distinguish between spike number and spike frequency dependence in two slow muscles in the lobster stomatogastric system. Our analysis shows that, functionally, one muscle is spike number dependent, whereas the other is primarily spike frequency dependent. Thus, both of these parameters can determine slow muscle output. To predict the movements elicited by neuronal activity in preparations in which slow muscles are common, it may be necessary to determine spike number versus spike frequency dependence for each muscle.

Spike number dependence couples motor neuron burst duration and spike frequency in that changing either parameter alone alters spike number (and hence muscle contraction amplitude). Neural networks innervating spike number-dependent muscles may therefore have specific properties to compensate for the complexity intrinsic to spike number coding.
rGβ1: A Psychostimulant-Regulated Gene Essential for Establishing Cocaine Sensitization
Authors: Wang Xiao-Bing , Funada Masahiko , Imai Yasuo , Revay Randal S. , Ujike Hiroshi , Vandenbergh David J. , Uhl George R.
Published: April 2018

Repeated doses of cocaine or amphetamine lead to long-lasting behavioral manifestations that include enhanced responses termed sensitization. Although biochemical mechanisms that underlie these manifestations currently remain largely unknown, new protein synthesis has been implicated in several of these neuroadaptive processes. To seek candidate biochemical mechanisms for these drug-induced neuroplastic behavioral responses, we have used an approach termed subtracted differential display (SDD) to identify genes whose expression is regulated by these psychostimulants. rGβ1is one of the SDD products that encodes a rat G-protein β subunit. rGβ1expression is upregulated by cocaine or amphetamine treatments in neurons of the nucleus accumbens shell region, a major center for psychostimulant effects in locomotor control and behavioral reward. Antisense oligonucleotide treatments that attenuate rGβ1expression in regions including the nucleus accumbens abolish the development of behavioral sensitization when they are administrated during the repeated cocaine exposures that establish sensitization. These treatments fail to alter acute behavioral responses to cocaine, and they do not block the expression of cocaine sensitization when it is established before oligonucleotide administrations. Full, regulated rGβ1expression is a biochemical component essential to the establishment of a key consequence of repeated cocaine administrations, sensitization.
Recovery from Desensitization of Neuronal Nicotinic Acetylcholine Receptors of Rat Chromaffin Cells Is Modulated by Intracellular Calcium through Distinct Second Messengers
Authors: Khiroug L. , Sokolova Elena , Giniatullin R. , Afzalov R. , Nistri A.
Published: April 2018

The mechanisms through which changes in intracellular Ca2+concentration ([Ca2+]i) might influence desensitization of neuronal nicotinic receptors (nAChRs) of rat chromaffin cells were investigated by simultaneous patch-clamp recording of membrane currents and confocal microscopy imaging of [Ca2+]iinduced by nicotine. Increases in [Ca2+]ithat were induced by membrane depolarization or occurred spontaneously did not influence inward currents elicited by focally applied test pulses (10 msec) of nicotine, indicating that raised [Ca2+]iper se did not trigger desensitization of nAChRs. Desensitization of nAChRs, evoked by 2 sec focal application of nicotine, which largely raised [Ca2+]i, was not affected by intracellular application of agents that activate or depress protein kinase C (PKC) or A (PKA) or inhibit phosphatase 1, 2 A and B. Conversely, recovery from desensitization was facilitated by the phorbol ester phorbol 12-myristate 13-acetate (PMA) or the phosphatase 2 B inhibiting complex of cyclosporin A–cyclophilin A, whereas it was impaired by the broad spectrum kinase inhibitor staurosporine. The effects of PMA or staurosporine were prevented by the intracellularly applied Ca2+chelator BAPTA. The adenylate cyclase activator forskolin accelerated recovery, whereas the selective PKA antagonist Rp-cAMPS had an opposite effect. The action of staurosporine and Rp-cAMPS on recovery from desensitization was additive. It is proposed that when nAChRs are desensitized, they become susceptible to modulation by [Ca2+]ivia intracellular second messengers such as serine/threonine kinases and calcineurin. Thus, the phosphorylation state of neuronal nAChRs appears to regulate their rate of recovery from desensitization.
Obesity on a High-Fat Diet: Role of Hypothalamic Galanin in Neurons of the Anterior Paraventricular Nucleus Projecting to the Median Eminence
Authors: Leibowitz Sarah F. , Akabayashi Akira , Wang Jian
Published: April 2018

Previous studies have suggested that the peptide galanin (GAL) in the hypothalamus is related to the preference of an animal for dietary fat. The present report investigates this relationship further to identify the specific GAL-synthesizing cell groups involved and to characterize their association to circulating glucose or hormones and their possible contribution to body fat deposition. Male albino Sprague Dawley rats were tested in different feeding paradigms with diets containing the macronutrients, fat, carbohydrate, or protein. These studies, using multiple techniques, identify a cell group in the hypothalamus that expresses GAL and that shows a shift in peptide activity in close relation to dietary fat, circulating glucose, and body fat. In all paradigms, a rise in fat intake, from 10 to 30%, is associated with reduced levels of insulin and corticosterone and normal glucose levels, whereas a further increase in fat ingestion (>30%) leads to hyperglycemia along with greater adiposity. In the hypothalamus, GAL gene expression, peptide production, and peptide release rise significantly (by 40%) in association with fat ingestion, showing no relation to either carbohydrate or protein ingestion. This change is highly site specific, evident predominantly in GAL-synthesizing neurons in the anterior parvocellular region of the paraventricular nucleus (aPVN) and in GAL-containing terminals in the external zone of the median eminence (ME). Positive correlations detected between mRNA abundance in the aPVN and GAL peptide in the ME support the existence of an aPVN–ME projection system related to fat intake and fat deposition. When activated by dietary fat, the contribution of this projection to body fat is suggested by consistent positive correlations between aPVN–ME GAL and either dietary fat, circulating glucose, or body fat and by significantly higher GAL levels (+30%) in obesity-prone compared with obesity-resistant rats. This evidence supports a role for this hypothalamic GAL projection system in the development of obesity produced by the overconsumption of fat.
A Scorpion α-Like Toxin That Is Active on Insects and Mammals Reveals an Unexpected Specificity and Distribution of Sodium Channel Subtypes in Rat Brain Neurons
Authors: Gilles Nicolas , Blanchet Christophe , Shichor Iris , Zaninetti Marc , Lotan Ilana , Bertrand Daniel , Gordon Dalia
Published: April 2018

Several scorpion toxins have been shown to exert their neurotoxic effects by a direct interaction with voltage-dependent sodium channels. Both classical scorpion α-toxins such as Lqh II fromLeiurus quiquestratus hebraeusand α-like toxins as toxin III from the same scorpion (Lqh III) competitively interact for binding on receptor site 3 of insect sodium channels. Conversely, Lqh III, which is highly toxic in mammalian brain, reveals no specific binding to sodium channels of rat brain synaptosomes and displaces the binding of Lqh II only at high concentration. The contrast between the low-affinity interaction and the high toxicity of Lqh III indicates that Lqh III binding sites distinct from those present in synaptosomes must exist in the brain. In agreement, electrophysiological experiments performed on acute rat hippocampal slices revealed that Lqh III strongly affects the inactivation of voltage-gated sodium channels recorded either in current or voltage clamp, whereas Lqh II had weak, or no, effects. In contrast, Lqh III had no effect on cultured embryonic chick central neurons and on sodium channels from rat brain IIA and β1 subunits reconstituted inXenopusoocytes, whereas sea anemone toxin ATXII and Lqh II were very active. These data indicate that the α-like toxin Lqh III displays a surprising subtype specificity, reveals the presence of a new, distinct sodium channel insensitive to Lqh II, and highlights the differences in distribution of channel expression in the CNS. This toxin may constitute a valuable tool for the investigation of mammalian brain function.
Role of Cell Cycle Regulatory Proteins in Cerebellar Granule Neuron Apoptosis
Authors: Padmanabhan Jaya , Park David S. , Greene Lloyd A. , Shelanski Michael L.
Published: April 2018

Cerebellar granule neurons (CGNs) undergo apoptosis when deprived of depolarizing concentrations of KCl, but the underlying molecular mechanisms are not yet clear. Although caspases have been postulated to be involved in CGN cell death, inhibitors of caspases failed to prevent apoptosis under our culture conditions, suggesting an involvement of other molecules and pathways. We find that inhibitors of cyclin-dependent kinases—flavopiridol, olomoucine, and roscovitine—protect CGNs from KCl withdrawal-induced apoptosis, suggesting that cell cycle components play a significant role in the death of these neurons. Analysis of the different cell cycle regulatory elements in this model revealed that apoptosis is preceded by an increase in the level of cyclin E protein, with elevated nuclear levels of cyclin D1 and with enhanced activity of the cyclin D1- and E- associated kinases. In addition, there was a significant decrease in the level of the cyclin-dependent kinase (cdk) inhibitor p27. In agreement with these changes, analysis of a major substrate of cyclin-activated cdks, retinoblastoma protein (Rb), showed an increase in the level of phosphorylated forms within 1 hr of KCl withdrawal. Moreover, the overall levels of Rb protein were significantly reduced within 6–12 hr of KCl withdrawal and did so by a caspase-independent mechanism. All of these responses were blocked by cdk inhibitors. These findings indicate that cdks act at an early step in the pathway by which KCl withdrawal induces apoptotic death of cerebellar granule cells and suggest that additional elements of the cell cycle machinery participate in this mechanism.
Generation and Analysis of GluR5(Q636R) Kainate Receptor Mutant Mice
Authors: Sailer Andreas , Swanson Geoffrey T. , Pérez-Otaño Isabel , O’Leary Lora , Malkmus Shelle A. , Dyck Richard H. , Dickinson-Anson Heather , Schiffer Hans H. , Maron Cornelia , Yaksh Tony L. , Gage Fred H. , O’Gorman Stephen , Heinemann Stephen F.
Published: April 2018

The physiological significance of RNA editing of transcripts that code for kainate-preferring glutamate receptor subunits is unknown, despite the fact that the functional consequences of this molecular modification have been well characterized in cloned receptor subunits. RNA editing of the codon that encodes the glutamine/arginine (Q/R) site in the second membrane domain (MD2) of glutamate receptor 5 (GluR5) and GluR6 kainate receptor subunits produces receptors with reduced calcium permeabilities and single-channel conductances. Approximately 50% of the GluR5 subunit transcripts from adult rat brain are edited at the Q/R site in MD2. To address the role of glutamate receptor mRNA editing in the brain, we have made two strains of mice with mutations at amino acid 636, the Q/R-editing site in GluR5, using embryonic stem cell–mediated transgenesis. GluR5(RloxP/RloxP) mice encode an arginine at the Q/R site of the GluR5 subunit, whereas GluR5(wtloxP/wtloxP) mice encode a glutamine at this site, similar to wild-type mice. Mutant animals do not exhibit developmental abnormalities, nor do they show deficits in the behavioral paradigms tested in this study. Kainate receptor current densities were reduced by a factor of six in acutely isolated sensory neurons of dorsal root ganglia from GluR5(RloxP/RloxP) mice compared with neurons from wild-type mice. However, the editing mutant mice did not exhibit altered responses to thermal and chemical pain stimuli. Our investigations with the GluR5-editing mutant mice have therefore defined a set of physiological processes in which editing of the GluR5 subunit is unlikely to play an important role.
Choosing between Small, Likely Rewards and Large, Unlikely Rewards Activates Inferior and Orbital Prefrontal Cortex
Authors: Rogers Robert D. , Owen Adrian M. , Middleton Hugh C. , Williams Emma J. , Pickard John D. , Sahakian Barbara J. , Robbins Trevor W.
Published: April 2018

Patients sustaining lesions of the orbital prefrontal cortex (PFC) exhibit marked impairments in the performance of laboratory-based gambling, or risk-taking, tasks, suggesting that this part of the human PFC contributes to decision-making cognition. However, to date, little is known about the particular regions of the orbital cortex that participate in this function. In the present study, eight healthy volunteers were scanned, using H2150 PET technology, while performing a novel computerized risk-taking task. The task involved predicting which of two mutually exclusive outcomes would occur, but critically, the larger reward (and penalty) was associated with choice of the least likely outcome, whereas the smallest reward (and penalty) was associated with choice of the most likely outcome. Resolving these “conflicting” decisions was associated with three distinct foci of regional cerebral blood flow increase within the right inferior and orbital PFC: laterally, in the anterior part of the middle frontal gyrus [Brodmann area 10 (BA 10)], medially, in the orbital gyrus (BA 11), and posteriorly, in the anterior portion of the inferior frontal gyrus (BA 47). By contrast, increases in the degree of conflict inherent in these decisions was associated with only limited changes in activity within orbital PFC and the anterior cingulate cortex. These results suggest that decision making recruits neural activity from multiple regions of the inferior PFC that receive information from a diverse set of cortical and limbic inputs, and that the contribution of the orbitofrontal regions may involve processing changes in reward-related information.
Ventromedial Thalamic Neurons Convey Nociceptive Signals from the Whole Body Surface to the Dorsolateral Neocortex
Authors: Monconduit Lénaı̈c , Bourgeais Laurence , Bernard Jean-François , Le Bars Daniel , Villanueva Luis
Published: April 2018

The somatosensory properties of ventromedial (VM) thalamic neurons were investigated in anesthetized rats by examining their responses to calibrated cutaneous stimuli. A population of neurons within the lateral part of the ventromedial thalamus (VMl) showed two peaks of activation after percutaneous electrical stimuli, regardless of which part of the body was stimulated. The early and late peaks were elicited by Aδ- and C-fiber activities with mean conduction velocities of 12.9 ± 0.9 and 1 ± 0.2 m/sec, respectively. These responses were strongly depressed or blocked after microinjections within the medullary subnucleus reticularis dorsalis of xylocaine or the NMDA antagonist MK-801. None of the VMlneurons responded to innocuous cutaneous or proprioceptive stimuli. In contrast, all these neurons responded to noxious mechanical and thermal stimulation of the limbs and showed monotonic increases in their discharges to increasingly strong noxious cutaneous stimuli. In addition, some VMlneurons were antidromically activated by stimulation in layer I of the dorsolateral frontal cortex. These findings suggest that the rat VMlconveys and encodes cutaneous nociceptive inputs from any part of the body surface to layer I of the dorsolateral neocortex. This reticulo-thalamo-cortical network may allow any signal of pain to gain access to widespread areas of the neocortex and thus help prime the cortex for attentional reactions and/or the coordination of motor responses.
The Spectral Main Sequence of Human Saccades
Authors: Harwood Mark R. , Mezey Laura E. , Harris Christopher M.
Published: April 2018

Despite the many models of saccadic eye movements, little attention has been paid to the shape of saccade trajectories. Some investigators have argued that saccades are driven by a rectangular “bang-bang” neural control signal, whereas others have emphasized the similarity to fast arm movement trajectories, such as the “minimum jerk” profile. However, models have not been tested rigorously against empirical trajectories. We examined the Fourier transforms of saccades and compared them with theoretical models. Horizontal saccades were recorded from 10 healthy subjects. The Fourier transform of each saccade was accurately computed using a padded fast Fourier transform (FFT), and the frequencies of the first three minima (M1, M2, M3) in each energy spectrum were measured to a precision of 0.12 Hz. Each subject showed near-linear trends in the relationships among M1, M2, and M3 and the reciprocal of duration (1/T), which we call the “spectral main sequence.” Extrapolation of plots did not pass through the origin, indicating a subtle departure from self-similarity. Bivariate confidence regions were established to allow for slope-intercept variability. The nonharmonic relationships seen cannot arise from a rectangular saccadic pulse driving a linear ocular plant. The relationships are also incompatible with minimum acceleration, minimum jerk, or higher-order minimum square derivative trajectories. The best fits were made by trajectories that minimize postmovement variance with signal-dependent noise (Harris and Wolpert, 1998). It is concluded that the spectral main sequence is exquisitely sensitive to the saccade trajectory and should be used to test objectively all present and future models of saccades.
Two-Stage, Input-Specific Synaptic Maturation in a Nucleus Essential for Vocal Production in the Zebra Finch
Authors: Stark Laura L. , Perkel David J.
Published: April 2018

In most songbirds, vocal learning occurs through two experience-dependent phases, culminating in a reduction of behavioral plasticity called song crystallization. At ends of developmentally plastic periods in other systems, synaptic properties change in a fashion appropriate to limit plasticity. Maturation of glutamatergic synapses often involves a reduction in duration of NMDA receptor (NMDAR)-mediated synaptic responses and a coincident reduction in the contribution of NMDARs to synaptic transmission. We hypothesized that similar changes in the zebra finch song system help limit behavioral plasticity during song development. Nucleus robustus archistriatalis (RA) is a key nucleus in the forebrain song motor pathway and receives glutamatergic input from the motor nucleus HVc. RA also receives glutamatergic input, mediated primarily by NMDARs, from the lateral magnocellular nucleus of the anterior neostriatum, which is part of a circuit essential for learning but not song production. We examined whether synaptic maturation occurs in either input to RA by recording synaptic currents in brain slices prepared from zebra finches of different ages. We find the motor input from HVc to RA uses both AMPA receptors (AMPARs) and NMDARs, and synaptic maturation occurs in two phases: an early reduction in duration of NMDAR-mediated synaptic currents in both inputs, and a later reduction in the NMDAR contribution to synaptic responses in the motor pathway. Although NMDAR kinetics change too early to account for crystallization, the reduction of the relative NMDAR contribution to synaptic transmission could contribute to the onset of crystallization. Thus, synaptic maturation events can be temporally distinct and input-specific and may play different roles in behavioral plasticity.
Tyrosine Phosphorylation Regulates Rapid Endocytosis in Adrenal Chromaffin Cells
Authors: Nucifora Paolo G. P. , Fox Aaron P.
Published: April 2018

Secretion of neurotransmitter at the synapse and in secretory cells depends on the availability of vesicles for exocytosis. Rapid endocytosis is responsible for initiating local vesicle recycling and is essential during sustained neurotransmission. Although exocytosis is triggered by Ca2+influx and modulated by serine/threonine kinases, relatively little is known about the regulation of rapid endocytosis. Our data suggest that rapid endocytosis is controlled by tyrosine phosphorylation. Treatment of bovine adrenal chromaffin cells with tyrphostin 23, a protein tyrosine kinase inhibitor, dramatically slowed the time course of rapid endocytosis. In contrast, there was no effect on either the amount or rate of exocytosis. Application of orthovanadate, Zn2+, or poly(Glu, Tyr) (4:1), each of which is a tyrosine phosphatase inhibitor, reversed the effect of tyrphostin 23 on rapid endocytosis. Thus rapid endocytosis, like exocytosis, is subject to regulation by intracellular signaling pathways.
Block of an ether-a-go-go-Like K+Channel by Imipramine Rescuesegl-2Excitation Defects inCaenorhabditis elegans
Authors: Weinshenker David , Wei Aguan , Salkoff Lawrence , Thomas James H.
Published: April 2018

K+channels are key regulators of cellular excitability. Mutations that activate K+channels can lower cellular excitability, whereas those that inhibit K+channels may increase excitability. We show that theCaenorhabditis elegansegl-2gene encodes an eag K+channel and that a gain-of-function mutation inegl-2blocks excitation in neurons and muscles by causing the channel to open at inappropriately negative voltages. Tricyclic antidepressants reverseegl-2(gf)mutant phenotypes, suggesting that EGL-2 is a tricyclic target. We verified this by showing that EGL-2 currents are inhibited by imipramine. Similar inhibition is observed with the mouse homolog MEAG, suggesting that inhibition of EAG-like channels may mediate some clinical side effects of this class of antidepressants.
Functional Properties of Channels Formed by the Neuronal Gap Junction Protein Connexin36
Authors: Srinivas Midituru , Rozental Renato , Kojima Takashi , Dermietzel Rolf , Mehler Mark , Condorelli Daniele F. , Kessler John A. , Spray David C.
Published: April 2018

The expression and functional properties of connexin36 (Cx36) were examined in two communication-deficient cell lines (N2A-neuroblastoma and PC-12 cells) transfected with Cx36 and in hippocampal neurons that express the connexin endogenously. Transfected cells expressed the expected 2.9 kb Cx36 transcript and Cx36 immunoreactivity, whereas nontransfected cells were devoid of Cx36. The relationship between steady-state junctional conductance (gj) and transjunctional voltage was well described by a two-state Boltzmann equation. The half-inactivation voltage (V0), the ratio of minimal to maximalgj(gmin/gmax), and the equivalent gating charge were ± 75 mV, 0.55, and 1.75, respectively, indicating that Cx36 exhibits very low voltage sensitivity. Conductance of single Cx36 channels measured with patch pipettes containing 130 mmCsCl was 10–15 pS (n= 15 cell pairs); despite this low unitary conductance, Cx36 channels were permeable to the dye Lucifer yellow. Hippocampal neurons expressed Cx36 bothin vivoand in culture. The electrophysiological properties of channels in cultured hippocampal neurons were similar to those of the channels expressed by the transfected cell lines, and the neuronal channels were similarly permeable to Lucifer yellow. The unique combination of weak voltage sensitivity, small unitary conductance, and permeation by anions as large as second messenger molecules endows Cx36 gap junction channels with properties well suited for mediating flexible electrical and biochemical interactions between neurons.
C Terminus of Presenilin Is Required for Overproduction of Amyloidogenic Aβ42 through Stabilization and Endoproteolysis of Presenilin
Authors: Tomita Taisuke , Takikawa Rie , Koyama Akihiko , Morohashi Yuichi , Takasugi Nobumasa , Saido Takaomi C. , Maruyama Kei , Iwatsubo Takeshi
Published: April 2018

Mutations in presenilin (PS) genes cause early onset familial Alzheimer's disease (FAD) by increasing production of the amyloidogenic form of amyloid β peptides ending at residue 42 (Aβ42). To identify a PS subdomain responsible for overproduction of Aβ42, we analyzed neuro2a cell lines expressing modified forms of PS2 that harbor an N141I FAD mutation. Deletion or addition of amino acids at the C terminus and Ile448 substitution in PS2 with the N141I FAD mutation abrogated the increase in Aβ42 secretion, and Aβ42 overproduction was dependent on the stabilization and endoproteolysis of PS2. The same C-terminal modifications in PS1 produced similar effects. Hence, we suggest that the C terminus of PS plays a crucial role in the overproduction of Aβ42 through stabilization of endoproteolytic PS derivatives and that these derivatives may be the pathologically active species of PS that cause FAD.
Similarities and Differences between the Responses of Rat Sensory Neurons to Noxious Heat and Capsaicin
Authors: Nagy Istvan , Rang Humphrey P.
Published: April 2018

We have compared the membrane response of rat primary sensory neurons to capsaicin and noxious heat, using electrophysiological and ion flux measurements. Our aim was to determine whether, as recently proposed, the same molecular entity accounts for excitation by both types of stimulus.

The properties of the ion channels activated by heat and capsaicin show many similarities but also important differences. The calcium permeability of heat-activated channels is lower than that of capsaicin-activated channels. Distinct single channels respond to heat or capsaicin, and only a few show dual sensitivity. At the whole-cell level, individual cells invariably show dual sensitivity, but the amplitudes of the responses show little correlation.

We conclude that distinct molecular entities, which are both likely to be derived from the VR1 gene product, account for the membrane responses to heat and capsaicin.
Differences in Expression of Acetylcholinesterase and Collagen Q Control the Distribution and Oligomerization of the Collagen-Tailed Forms in Fast and Slow Muscles
Authors: Krejci Eric , Legay Claire , Thomine Sébastien , Sketelj Janez , Massoulié Jean
Published: April 2018

The collagen-tailed forms of acetylcholinesterase (AChE) are accumulated at mammalian neuromuscular junctions. The A4, A8, and A12forms are expressed differently in the rat fast and slow muscles; the sternomastoid muscle contains essentially the A12form at end plates, whereas the soleus muscle also contains extrajunctional A4and A8forms. We show that collagen Q (ColQ) transcripts become exclusively junctional in the adult sternomastoid but remain uniformly expressed in the soleus. By coinjectingXenopusoocytes with AChETand ColQ mRNAs, we reproduced the muscle patterns of collagen-tailed forms. The soleus contains transcripts ColQ1 and ColQ1a, whereas the sternomastoid only contains ColQ1a. Collagen-tailed AChE represents the first evidence that synaptic components involved in cholinergic transmission may be differently regulated in fast and slow muscles.
A Kv1.5 to Kv1.3 Switch in Endogenous Hippocampal Microglia and a Role in Proliferation
Authors: Kotecha Suhas A. , Schlichter Lyanne C.
Published: April 2018

The proliferation of microglia is a normal process in CNS development and in the defense against pathological insults, although, paradoxically, it contributes to several brain diseases. We have examined the types of voltage-activated K+currents (Kv) and their roles in microglial proliferation. Microglia were tissue-printed directly from the hippocampal region using brain slices from 5- to 14-d-old rats. Immediately after tissue prints were prepared, unipolar and bipolar microglia expressed a large Kv current, and the cells were not proliferating. Surprisingly, this current was biophysically and pharmacologically distinct from Kv1.3, which has been found in dissociated, cultured microglia, but it was very similar to Kv1.5. After several days in culture the microglia became highly proliferative, and although the Kv prevalence and current density decreased, many cells exhibited a prominent Kv that was indistinguishable from Kv1.3. The Kv1.5-like current was present in nonproliferating cells, whereas proliferating cells expressed the Kv1.3-like current. Immunocytochemical staining showed a dramatic shift in expression and localization of Kv1.3 and Kv1.5 proteins in microglia: Kv1.5 moving away from the surface and Kv1.3 moving to the surface as the cells were cultured. K+channel blockers inhibited proliferation, and the pharmacology of this inhibition correlated with the type of Kv current expressed. Our study, which introduces a method for the physiological examination of microglia from identified brain regions, demonstrates the differential expression of two functional Kv subunits and shows that a functional delayed rectifier current is necessary for microglia proliferation.
The Organization of the Golgi Complex and Microtubules in Skeletal Muscle Is Fiber Type-Dependent
Authors: Ralston Evelyn , Lu Zhuomei , Ploug Thorkil
Published: April 2018

Skeletal muscle has a nonconventional Golgi complex (GC), the organization of which has been a subject of controversy in the past. We have now examined the distribution of the GC by immunofluorescence and immunogold electron microscopy in whole fibers from different rat muscles, both innervated and experimentally denervated. The total number of GC elements, small polarized stacks of cisternae, is quite similar in all fibers, but their intracellular distribution is fiber type-dependent. Thus, in slow-twitch, type I fibers, ∼75% of all GC elements are located within 1 μm from the plasma membrane, and each nucleus is surrounded by a belt of GC elements. In contrast, in the fast-twitch type IIB fibers, most GC elements are in the fiber core, and most nuclei only have GC elements at their poles. Intermediate, type IIA fibers also have an intermediate distribution of GC elements. Interestingly, the distribution of microtubules, with which GC elements colocalize, is fiber type-dependent as well. At the neuromuscular junction, the distribution of GC elements and microtubules is independent of fiber type, and junctional nuclei are surrounded by GC elements in all fibers. After denervation of the hindlimb muscles, GC elements as well as microtubules converge toward a common pattern, that of the slow-twitch fibers, in all fibers. Our data suggest that innervation regulates the distribution of microtubules, which in turn organize the Golgi complex according to muscle fiber type.
Blue- and Green-Absorbing Visual Pigments ofDrosophila: Ectopic Expression and Physiological Characterization of the R8 Photoreceptor Cell-Specific Rh5 and Rh6 Rhodopsins
Authors: Salcedo Ernesto , Huber Armin , Henrich Stefan , Chadwell Linda V. , Chou Wen-Hai , Paulsen Reinhard , Britt Steven G.
Published: April 2018

Color discrimination requires the input of different photoreceptor cells that are sensitive to different wavelengths of light. TheDrosophilavisual system contains multiple classes of photoreceptor cells that differ in anatomical location, synaptic connections, and spectral sensitivity. The Rh5 and Rh6 opsins are expressed in nonoverlapping sets of R8 cells and are the onlyDrosophilavisual pigments that remain uncharacterized. In this study, we ectopically expressed Rh5 and Rh6 in the major class of photoreceptor cells (R1–R6) and show them to be biologically active in their new environment. The expression of either Rh5 or Rh6 in “blind”ninaE17mutant flies, which lack the gene encoding the visual pigment of the R1–R6 cells, fully rescues the light response. Electrophysiological analysis showed that the maximal spectral sensitivity of the R1–R6 cells is shifted to 437 or 508 nm when Rh5 or Rh6, respectively, is expressed in these cells. These spectral sensitivities are in excellent agreement with intracellular recordings of the R8p and R8y cells measured inCalliphoraandMusca. Spectrophotometric analyses of Rh5 and Rh6in vivoby microspectrophotometry, and of detergent-extracted pigmentsin vitro, showed that Rh5 is reversibly photoconverted to a stable metarhodopsin (λmax= 494 nm), whereas Rh6 appears to be photoconverted to a metarhodopsin (λmax= 468 nm) that is less thermally stable. Phylogenetically, Rh5 belongs to a group of short-wavelength-absorbing invertebrate visual pigments, whereas Rh6 is related to a group of long-wavelength-absorbing pigments and is the first member of this class to be functionally characterized.
Control of Action Potential Timing by Intrinsic Subthreshold Oscillations in Olfactory Bulb Output Neurons
Authors: Desmaisons David , Vincent Jean-Didier , Lledo Pierre-Marie
Published: April 2018

Rhythmic patterns of neuronal activity have been found at multiple levels of various sensory systems. In the olfactory bulb or the antennal lobe, oscillatory activity exhibits a broad range of frequencies and has been proposed to encode sensory information. However, the neural mechanisms underlying these oscillations are unknown. Bulbar oscillations might be an emergent network property arising from neuronal interactions and/or resulting from intrinsic oscillations in individual neurons. Here we show that mitral cells (output neurons of the olfactory bulb) display subthreshold oscillations of their membrane potential. These oscillations are mediated by tetrodotoxin-sensitive sodium currents and range in frequency from 10 to 50 Hz as a function of resting membrane potential. Because the voltage dependency of oscillation frequency was found to be similar to that for action potential generation, we studied how subthreshold oscillations could influence the timing of action potentials elicited by synaptic inputs. Indeed, we found that subthreshold oscillatory activity can trigger the precise occurrence of action potentials generated in response to EPSPs. Furthermore, IPSPs were found to set the phase of subthreshold oscillations and can lead to “rebound” spikes with a constant latency.

Because intrinsic oscillations of membrane potential enable very precise temporal control of neuronal firing, we propose that these oscillations provide an effective means to synchronize mitral cell subpopulations during the processing of olfactory information.