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Shriners Hospital, Sacramento, CA, 2University of California, Davis, Davis, CA, 3Shriners Hospital for Children, 1 Sacramento, CA, 4University of California, School of Medicine, Sacramento, CA Multiple sclerosis (MS) is a neuroinflammatory disorder, characterized by multifocal inflammation, demyelination and axonal damage within the central nervous system (CNS). MS manifests a broad range of physical and cognitive disabilities and may include balance and coordination impairments, which are linked to poor prognosis. Little is known about the pathogenesis of these deficits. Experimental autoimmune encephalomyelitis (EAE) is a commonly used animal model for MS. Wild-type (WT) mice with EAE develop ascending paralysis associated with lesions in the spinal cord. EAE induction in mice lacking interferon gamma (IFNg) results in development of balance and coordination defects. Although these atypical deficits were previously associated with inflammatory foci within the cerebellum/ brainstem, we showed that the onset is not dependent upon the extent, composition, or areas of inflammatory foci formation in the CNS. Instead, we showed that atypical deficits are linked to the absence of IFNgR/STAT1 in the CNS cells. We hypothesize that IFNg signaling in the CNS promotes anti-inflammatory/neuroprotective events in EAE.
Results from this study will be instrumental in understanding the disease process that contributes to balance and coordination deficits in multiple sclerosis.
THE REGULATION OF PH IN AN IN VITRO BRAINSTEM PREPARATION OF THE BULLFROG TADPOLE,
LITHOBATES CATESBEIANUS, BY CENTRAL RESPIRATORY CHEMORECEPTORS DURING INDUCED
ALTERATIONS IN MEMBRANE POTENTIALElma Frias1, Matthew Gdovin2.
University of California, Riverside, Riverside, CA, 2University of Texas, San Antonio, San Antonio, TX.
1 Sudden infant death syndrome (SIDS) is the spontaneous and unexpected death of an infant who is less than 1 year of age. Even though the incidence of SIDS has declined by more than 50% since 1990, SIDS represents the third leading cause of infant fatalities in the United States. Although risk factors associated with an increased incidence of SIDS have been described, the cause of death and documented health disparity basis of SIDS remain unexplained.
Dysfunctions of brainstem regions responsible for central carbon dioxide chemoreception have been proposed as an underlying pathophysiology of SIDS. Our experiments will test the hypothesis that an inverse relationship exists between intracellular pH (pHi) regulation by the central respiratory chemoreceptors and the neuron’s membrane potential. Simultaneous recordings of both variables will be done using an in vitro brainstem preparation of the bullfrog tadpole, Lithobates catesbeianus, because of its synaptic connectivity to respiratory rhythm generators, central respiratory chemoreceptors, and motor neurons. Moreover, the ratiometric fluorescent dyes to be used are di-8-ANEPPS, which responds to membrane potential variances, and BCECF, which responds to changes in pHi.
Using electrophysiology and ratiometric fluorescence, preliminary data demonstrate we can employ flash photolysis to induce decreases in pHi within physiological limits and it is possible to record and optically quantify, pH regulation during extracellular pH (pHe) and pHi modifications. The definitive aim is to understand if impairments in brainstem regions responsible for central carbon dioxide chemoreception are possible mechanisms of SIDS.
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EFFECTS ON BEHAVIORAL IMPAIRMENT OF BLOCKING ADENOSINE IN THE DORSAL STRIATUMBrandy Briones, Thomas Minor, Traci Plumb.
University of California, Los Angeles, Los Angeles, CA.
Stress-anxiety disorders are the most common mental health disorders among the human population, affecting about 40 million Americans. Adenosine A2A receptors play an important role in the development of behavioral depression in a rat model of post-traumatic stress disorder (PTSD). Adenosine is a neuroprotectant released to inhibit neural activity, preventing further cell damage. Binding adenosine at the striatal A2A receptor has been shown to decrease dopamine binding at D2 receptors. This antagonistic relationship disrupts dopamine-signaled motivation, preventing adaptive stress coping, thus resulting in behavioral depression. Blockade of A2A receptors in the ventral striatum (nucleus accumbens) following traumatic stress prevents behavioral impairment in rats. However, it is unknown if A2A receptor blockade in the dorsal medial striatum (DMS) will have the same effect. Rats were implanted with bilateral cannulae into the DMS (bregma: AP +1.2, ML +1.5, DV -5.5) during stereotaxic surgery. Following recovery from surgery, rats were exposed to traumatic, inescapable shock or simple restraint. Rats were tested for their ability to learn to escape administered shocks in a shuttle-escape apparatus 24 hours after traumatic stress. Ten minutes prior, rats’ cannulae were infused with adenosine A2A receptor antagonist CSC (8-(3-chloro-styrl) caffeine) or vehicle. Brains were extracted to confirm cannula placement using crystal violet stain. Shuttle-escape testing revealed that blockade of A2A receptors in the DMS had no effect on escape deficits, indicating that A2A receptors in the nucleus accumbens are strictly involved in learned helplessness. These findings may be significant in treating stress-anxiety disorders such as PTSD with comorbid depression.
SELECTIVE PRESYNAPTIC GENE MODULATION BY IN VIVO ELECTROPORATION IN THE CALYX OF HELD IN
NEONATE MICERigina Gallagher, Xuelin Lou.
University of Wisconsin-Madison, Madison, WI.
The Calyx of Held is a glutamatergic nerve terminal that innervates a small but vital group of auditory inhibiting neurons and originates from globular bushy cells in the ventral cochlear nucleus in mice. The Calyx is the largest, most reliable synapse in the mouse brain, making it an excellent model system for studying neuron circuit organization, vesicle mediated exocytosis, and synaptic development. Many of the molecular mechanisms underlying these fundamental processes remain unknown. Gene-knockout mice and viral-vector mediated gene expression techniques used to study these mechanisms are costly and time consuming. A faster, efficient, and more adaptable technique is needed to augment understanding of vital synaptic processes by using the Calyx of Held as a powerful model synapse in the brain. In this study, we refine a cutting-edge gene expression technique comprised of targeted microinjection followed by electroporation to reproducibly deliver and express desired genes into the Calyx of Held.
By establishing precise timing for hypothermia, injection coordinates, postinjection recovery time, and implementing a novel stereotaxic set up, we can reliably inject plasmids into the 0.2 to 0.9 mm VCN region with relatively high mouse survival rate and achieve EGFP gene expression. Developing the targeted microinjection- electroporation technique in the Calyx of Held region opens a new avenue to efficient molecular manipulation in this often-elusive structure in vivo. Further studies can implement this fast-acting, virus-free method to study the vesicle-formation and calciumdependent signaling mechanisms at the Calyx and other central synapses, which are the underlying mechanisms in synaptic development, Alzheimer’s disease, and autism.
USING CHANGE BLINDNESS TO STUDY THE EFFECT OF VISUAL ATTENTION ON NEURAL ACTIVITY INVISUAL AREA V4 Daniel Foster, James Bisley.
University of California Los Angeles, Los Angeles, CA.
Visual attention is necessary to perceive and react to our world; when we do not attend to something, we are often completely unaware of it. This lack of perception is exemplified in change blindness tasks in which we are unable to detect a difference between 2 scenes of objects separated by a blank screen even though the change may be huge. Past studies have suggested that any behavioral effects of attention, including change blindness, are due to a change in neural activity in visual area V4. The current study seeks to test this hypothesis. Subjects were trained in a simplified change blindness task comprised of 1, 2, 4, or 8 objects on a screen. Subjects had to pay attention
PROTEASOME AND IMMUNOPROTEASOME DISTRIBUTION IN CEREBELLAR CELLS OF EXPERIMENTAL
AUTOIMMUNE ENCEPHALOMYELITISClaudia Espinoza, Oscar Bizzozero.
University of New Mexico, Albuquerque, NM.
Multiple sclerosis (MS) is a severe neuroinflammatory disorder characterized by the loss of myelin around the axons of the central nervous system. Experimental autoimmune encephalomyelitis (EAE) is a commonly used animal model of MS that recapitulates the various stages of the disease. Our laboratory has recently discovered that oxidized proteins accumulate in the cerebellum of mice with chronic EAE, and this seems to be the result of diminished levels of proteasomes, the proteolytic machinery responsible for their degradation. The build-up of oxidized proteins is toxic to cells and thought to play a role in the pathophysiology of MS and EAE. We have recently found that the reduction in the standard proteasome levels, as measured by the catalytic b5 subunit, and immunoproteasomes, as measured by the catalytic ib5 subunit, is not a generalized phenomenon, but occurs in particular cell types. Specifically, ib5 and b5 levels are reduced in neurons and oligodendrocytes in the EAE cerebellum during the chronic phase of the disease.
This supports insights into the relationship between proteasomal dysfunction and tissue damage in this disease.
(Work supported by IMSD and R01 NS057755 from NIH.) SAT-592
SCREENING CHEMICALS FOR HCN CHANNEL INHIBITIONGaurang Limachia1, Ye Han2.
DePaul University, Chicago, IL, 2Northwestern University, Chicago, IL.
1 Depression impacts many people and the drugs currently on the market primarily target serotonin, norepinephrine, or other neurotransmitters. Though these drugs are effective antidepressants, large populations of people still suffer from depression. Therefore, alternative drugs that target different neural channels are being considered for treatment.
An example of ion channels being considered is HCN1 and its auxiliary subunit Trip8b. The interaction between the two has been studied in previous research. Trip8b is necessary for proper trafficking of HCN channels’ selectivity to dendrites. Mouse models where Trip8b was knocked out displayed anti-depressed phenotypes. Therefore, the inhibition of Trip8b binding to HCN is the topic of interest for this study. The process of screening chemicals will be conducted through pull down assays which tell us about protein-protein interaction. Through the screening process, different HCN derivatives will be paired with different chemicals (drugs) to see whether there is an inhibition of Trip8b.
Consequently, an inhibition of HCN channels by the chemical will provide an understanding of how HCN channels are blocked. As a result, this inhibition by the chemicals will later be used to develop a drug that combats depression.
Thus, this screening process represents the first steps in developing a drug that provides an alternative form of antidepressant medication that works on HCN channels.
NEURODEVELOPMENTAL TRAJECTORY OF SIMPLE ARITHMETIC IN BILINGUAL CHILDRENAndres Ruiz, Nicole Wicha.
University of Texas at San Antonio, San Antonio, TX.
It has been established that adult bilinguals retrieve arithmetic facts from memory more efficiently in the language in which a concept was learned (LA+) than in their second language (LA-). There is a developmental transition for learning simple arithmetic that begins with calculating (i.e., the procedural method) and develops toward the retrieval of arithmetic facts from memory. In bilingual children, the transition in arithmetic strategy may occur at a time when they are taught arithmetic using a language that may not be their first language (L1). To examine the impact of the second language on arithmetic and investigate the neurodevelopmental trajectory of simple arithmetic, electrophysiological activity will be measured in English/Spanish bilingual children in 3rd grade (novice multipliers)
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and 5th grade (experienced multipliers) while they complete a simple arithmetic judgment task. English monolinguals at each grade level will act as controls. As in previous studies, an N400 component along with a late positive component is expected when presented with erroneous solutions to multiplication problems. The distribution of the N400 is predicted to change as the transition from procedural to memory extraction occurs, with the N400 being more prominent in the frontal lobe for the 5th grade population as facts are extracted using a verbal memory strategy. In addition, the N400 component is expected to be more negative-going among the monolingual population compared to their bilingual counterparts, as they are predicted to be more attuned to recognizing incongruent solutions in their L1.
TREATMENT OF A MOUSE MODEL OF MULTIPLE SCLEROSIS WITH HIGHLY SPECIFIC ESTROGENRECEPTOR-Β LIGANDS, WAY200070 AND WAY200041 Ervin Herrera, Timothy Yoo, Spencer Moore, Anna Khalaj, Seema Tiwari-Woodruff.
University of California, Los Angeles, Los Angeles, CA.