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Domoic acid (DomA) is a marine neurotoxin and an analogue to the excitatory neurotransmitter glutamate. At high doses, it acts as an agonist of the glutamate system in exposed marine wildlife and humans. Acute, high-dose exposure to DomA is well documented and known to cause severe neurological damage and, in some cases, death. The neurological effects of chronic asymptomatic doses, however, are not well understood, which is alarming since chronic low-dose exposure is likely far more common than symptomatic acute exposure. The objective of this research is to examine whether chronic low-dose DomA exposure results in altered regulation of certain glutamaterelated proteins. Immunohistochemical staining will be used to examine AMPA receptors, glial glutamate transporters, and neuronal nuclei in organotypic brain slice cultures from mice. This will allow quantification of protein expression levels and cellular location in DomA-exposed tissues compared to control samples. The expectation is to find a downregulation of AMPA receptors after prolonged low-level exposure to DomA based on reports from a study of DomA-exposed zebrafish. It is also expected that there will be no measurable change in the total number of neurons present in the DomA-treated samples compared to controls; this will confirm that the dosage was appropriately asymptomatic and did not damage the tissue.
IS GONADOTROPIN-RELEASING HORMONE-II HYPOPHYSIOTROPIC IN BIRDSCydni Baker, Darcy Ernst, George Bentley.
University of California, Berkeley, Berkeley, CA.
Gonadotropin releasing hormone II (GnRH-II) is a neuropeptide located in the midbrain and involved in the sexual behavior of vertebrates. Neuropeptides synthesized and stored in the hypothalamus influence hormone release from the anterior pituitary gland via the median eminence and hypothalamo-hypophyseal portal system. Since GnRHII cell bodies are located outside of the hypothalamus, it is unknown whether GnRH-II acts on the pituitary gland to cause gonadotropin release. GnRH-II can cause release of gonadotropins from pituitary cultures, but whether this occurs in vivo has not been determined. There is some immunocytochemical evidence for the presence of GnRH-II in the median eminence of quail, but these data are controversial. To determine if GnRH-II neurons are truly hypophysiotropic in a songbird (zebra finch), we made use of the retrograde fluorescent tracer Fluoro-Gold.
After peripheral injection, Fluoro-Gold circulates through the blood and enters the brain via axons that project to the hypophyseal portal system in the median eminence. In theory, any hypophysiotropic neuropeptide neurons should be labeled as a result. In order to visualize cell bodies that had taken up Fluoro-Gold, immunocytochemistry was performed using Fluoro-Gold primary antibody. All neurons containing Fluoro-Gold were immunolabeled, and a second primary antibody specific to GnRH-I and II was used to identify GnRH-II cells. Finally, the routes of these neural projections will be traced. Data are still being analyzed. If it is determined that these neurons contact the median eminence, it will provide unequivocal evidence that midbrain GnRH-II could act on the pituitary directly to control avian reproduction.
LOCALIZATION OF SIRT3 IN THE ENTERIC NERVOUS SYSTEM IN HEALTH AND DISEASEWilmarie Morales Soto1, Brian Gulbransen2.
University of Puerto Rico at Cayey, Cayey, PR, 2Michigan State University, East Lansing, MI.
1 Oxidative stress is a contributing factor in the development of inflammatory bowel disease (IBD). Increased production of reactive oxygen species and decreased antioxidant defenses contribute to disease pathology in both humans and animal models of IBD. Oxidative stress promotes the death of enteric neurons, leading to permanent gut dysfunction.
The mechanisms that render enteric neurons susceptible to oxidative stress are unknown. Sirtuin3 is a mitochondrial protein that plays a role in antioxidant defenses. Given that Sirtuin3 expression is high in nervous tissue and
136 UNDERGRADUATE POSTER ABSTRACTS
Biological Sciences visceral organs, we hypothesized that Sirtuin3 is expressed by enteric neurons and that altered Sirtuin3 expression is associated with IBD. We tested our hypothesis using immunohistochemistry to localize Sirtuin3 in the enteric nervous system of healthy and diseased (DNBS-colitis) mice. We performed dual-labeling with Sirtuin3 and the panenteric neuron marker Hu or enteric neuron subtype markers neuronal nitric oxide synthase (nNOS) and calretinin to determine the extent of Sirtuin3 expression in the enteric nervous system. We find that Sirtuin3 is expressed in 86% of all myenteric neurons: 58% of Sirtuin3 positive neurons colocalize with nNOS and 41% colocalize with calretin.
Overall, the percentage of Sirtuin3–expressing neurons declined by 21% following DNBS-colitis. Losses of both nNOS and calretinin neurons contributed to the loss of SIRT3-expressing neurons as the percentage of Sirtuin3 neurons expressing calretnin declined by 11% and those expressing nNOS declined by 9%. Our results indicate that Sirtuin3 is expressed in a subset of enteric neurons and that it may contribute to neuron susceptibility in inflammatory bowel disease.
THE ROLE OF THE MAUTHNER NEURON DEPENDENT ESCAPE RESPONSE IN LONG DURATION RAMP
WAVE AUDITORY PULSESUlysses Savage1, Cindy Martinez2, Adam Roberts2, David Glanzman2.
Center for Neural Repair, University of California, San Diego, San Diego, CA, 2University of California, Los Angeles, 1 Los Angeles, CA.
The use of zebrafish as a model organism is advantageous due to their rapid reproduction rate, the transparency of its larvae and its simple neural circuitry. Their neural circuitry can be easily studied in experiments focusing on understanding the underlying mechanisms of learning and memory. Zebrafish larvae exhibit a rapid escape (C-start) reflex when presented with an auditory stimulus that triggers Mauthner cell (M-cell) circuitry. The C-start reflex can be easily habituated through repeated auditory stimulation. Previous experiments have used short tone bursts to elicit the C-start response, however, these short duration tones most likely fail to activate the zebrafish feedforward inhibitory circuit. This problem can be remedied by creating longer duration ramp waves. Using laser ablation of M-cells, we will determine if C-start escapes elicited by long duration auditory pulses requires the M-cell. This project will expand on research pertaining to inhibitory plasticity models and potentially open new avenues to molecular and mechanistic understanding of short-term and long-term memory.
ANALYZING THE ADDICTION CIRCUIT IN THE BRAIN USING BACTRAPCheryl Fonteh1, Erika Andrade2.
University of California San Diego, San Diego, CA, 2Rockefeller University, New York, NY.
1 Drug addiction is characterized by 3 main stages: compulsion to seek/take the drug, loss of control limiting intake, and emergence of a negative emotional state. Various studies have shown distinct circuits mediate each stage of addiction. Our goal is to target distinct neuronal subpopulations within these regions to more specifically understand the microcircuit responsible for each stage. By using bacterial artificial chromosome (BAC) transgenic mice that can express GFP-tagged ribosomal protein L10a (GFP-L10a) in a defined cell population, a methodology was developed for affinity purification of polysomal mRNAs (bacTRAP) from genetically defined cell populations. Using adeno-associated viral-mediated delivery, neurons projecting to the ventral tegmental area, an area well studied for its role in addictive behavior, are examined through tracing studies. Follow-up experiments using this information for bacTRAP analysis following exposure to cocaine provides information on the neurons that make up the microcircuit.
Expression of c-Fos by neurons is a useful marker of cell activation and staining these proteins is a useful technique for mapping of the addiction circuit in the brain. Expression of GFP-L10a using the c-fos promoter will allow more relevant characterization of the neurons involved in cocaine exposure. To test this, the lab generated transgenic mice by replacing the coding region of the target gene in the BAC with the transgene cre recombinase upstream of the start codon by homologous recombination in bacteria. Introduction of cre-dependent GFP-L10a using adeno-associated virus under the control of the c-fos promoter provides a way of examining the activated neurons in cocaine addiction.
PREFERENTIAL SELECTION OF HIPPOCAMPAL CA1 PYRAMIDAL CELLS BY PARVALBUMIN BASKET CELLSMichelle Oberoi1, Ivan Marchionni2, Sanghun Lee2, Ivan Soltesz2.
University of California, Irvine, Irvine, CA, 2School of Medicine, University of California, Irvine, Irvine, CA.
1 The hippocampus is a brain structure known to play key roles in memory, spatial navigation, and neurological disorders. Its major output station is the CA1 region where neurotransmission occurs between interneurons and pyramidal cells (PC). Studies have attempted to classify CA1 PCs despite their reputation for being homogenous.
So far, PCs have been grouped as superficial PC (SPC) or deep PC(DPC) based on their somatic positioning from the border of the stratum radiatum and the stratum pyramidale sublayers: SPCs lie within 50 μm from the border while DPC lie beyond 50 μm to 150 μm. Also found in the stratum pyramidale are GABAergic interneurons, like the parvalbumin basket cell (PVBC), which make synaptic contacts on the soma and proximal dendrites of PCs.
Differential, layer-based inhibition from PVBCs to both types of CA1 PCs remains unexplored. Preferential selection of PVBCs to CA1 PCs via GABAergic neurotransmission would suggest that heterogeneity is critical for the modulation.
We hypothesize that differential GABAergic inhibitory regulation of CA1 PCs could be layer specific. In this study, we focus our attention on the number of synaptic contacts from biocytin-filled PVBCs to CA1 PCs across the stratum pyramidale. We tested this hypothesis by visually counting synaptic contacts between PVBCs’ axon and S/DPCs’ perisomatic area, which averaged to 4.8 for 5 SPCs and 9.35 for 6 DPCs. This indicates that PVBCs preferentially target DPCs, suggesting differential innervation between DPCs and SPCs. This could play a crucial role in regulation of CA1 PC output, suggesting differential inhibition of PVBCs to SPCs and to DPCs.
DETERMINATION OF A GENETIC ETIOLOGY OF CEREBRAL SINOVENOUS THROMBOSIS THROUGH EXOME
GENOTYPE ANALYSISAlex Kivimaki1, Matthew Grantz2. Jennifer Majersik2.
University of Wisconsin, Madison, WI, 2University of Utah, Salt Lake City, UT.
1 Cerebral sinovenous thrombosis (CSVT) is a rare form of cerebrovascular disease which accounts for approximately 1% of all strokes with mortality around 10% to 13%. The disease remains a major diagnostic and therapeutic challenge given the diversity of symptomatic presentation and variety of etiological factors. Genetic predisposition to clotting is suspected but only proven in a small proportion of cases. To date, there is no well-characterized DNA repository for CSVT cases and unaffected controls. Our study identifies patients through retrospective chart review of patients hospitalized for CSVT and spousal controls or controls from clinic without CSVT. Case patients include any CSVT patient over the age of 3 months. Control patients are 18 years of age or older, with no history of clotting issues. First, identified patients’ consent for permission for a blood draw is needed. Then DNA is extracted from the blood and is sent to collaborators in the United Kingdom for an exome genotype analysis to find associations between genotype and case/control status. Initial data results show 188 total CSVT cases, 115 female and 73 male, admitted to the University of Utah Hospital between 2000 and 2012. Of the 188 total patients, 174 survived. Ages ranged from 16 to 81 years of age. Comprehensive investigation into the genetics of CSVT holds the potential to identify at-risk groups, determine prognosis, and support development of novel therapeutic interventions.
SEX DIFFERENCES IN THE CLINICAL EXPRESSION AND RESTING STATE BRAIN CONNECTIVITY IN
BIPOLAR DISORDERSara Kimmich, Lisa Eyler.
University of California San Diego, La Jolla, CA.
The course and expression of bipolar disorder (BD) clearly differs between women and men. Previous studies have observed sex effects in connectivity of the default mode network (DMN) of healthy individuals, but more research is needed to see whether a similar effects holds among BD patients. This study investigates how sex differences in DMN activity among BD I patients compared to individuals without BD and how sex differences may relate to clinical or cognitive differences in BD. We compared 21 euthymic patients with bipolar I disorder to 29 age and gender comparable healthy participants using functional magnetic resonance image during a period of eyes-open rest.
Averaged functional activity between the nodes of the DMN (medial prefrontal cortex, posterior cingulate, and bilateral angular gyrus) revealed that BD females tend to have greater connectivity within the default mode network than male BDs, contrasted with the pattern of greater connectivity among male healthy participants compared to females (p =.08). This interaction was significant for the connections between the right angular gyrus and other nodes in the
EFFECTS OF DIET ON DRUG REWARD IN FEMALE RATSCarolina Gonzalez, Sari Izenwasser.
University of Miami, Miami, FL.