Finding novel compounds that affect neuronal or muscular function is of great interest, as they can serve as potential pharmacological agents for a variety of neurological disorders. For instance, conopeptides have been developed into powerful drugs like the painkiller PrialtTM. Most conopeptides, however, have yet to be characterized, revealing the need for a rapid and straightforward screening method. We have designed a novel bioassay, which allows for unbiased screening of biological activity of compounds in vivo against numerous molecular targets on a wide variety of neurons and muscles in a rapid and straightforward manner. For this, we paired nanoinjection of compounds with electrophysiological recordings from the Giant Fiber System of Drosophila melanogaster, which mediates the escape response of the fly. / by Monica Mejia. / Thesis (Ph.D.)--Florida Atlantic University, 2013. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Vita. / Includes bibliographies. / by Binseng Wang. / Sc.D.

Fast excitatory neurotransmission is critical for learning and memory, and its dysregulation is linked to numerous neurological diseases. These include developmental diseases such as fragile X syndrome, psychiatric disorders like schizophrenia, and chronic neurodegenerative disorders such as Parkinson’s and Alzheimer’s diseases. Throughout the central nervous system, AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid)-subtype ionotropic glutamate receptors (AMPARs) mediate the fastest excitatory neurotransmission. In response to the neurotransmitter glutamate, AMPARs open their ion channels and allow cation flux through the post-synaptic membrane. This initiates rapid depolarization and signaling in the post-synaptic neuron. Nearly all AMPARs exist as complexes with auxiliary subunits, which are regulatory proteins that modulate receptor assembly, trafficking, pharmacology and function. These auxiliary subunits determine brain region-specific AMPAR signaling, and aberrancies in complex formation or function lead to neuropathologies. Despite their importance for CNS signaling and implication in neurologic disorders, the structural bases underlying the function of AMPARs and AMPAR complexes remain ambiguous, representing a critical barrier to our understanding of excitatory neurotransmission. As a consequence, structure-based design of neuro-therapeutics is largely undeveloped: there is only a single FDA-approved drug targeting AMPARs. To address these problems, I wanted to dedicate my thesis work to study AMPAR synaptic complexes across an array of functional states and provide a new foundation for our structural understanding of AMPAR signaling. First, I designed a covalent-fusion construct approach to guarantee assembly and expression of AMPAR synaptic complexes in heterologous cells (HEK293). Then, I developed purification protocols allowing me to obtain chemically homogenous and pure complex protein. Since synaptic signaling is highly dynamic, complexes of AMPARs with auxiliary subunits are conformationally heterogeneous and are not amenable to X-ray crystallography. Cryo-electron microscopy (cryo-EM) enabled me to approach these complexes structurally, where I could collect data and parse out heterogeneity through image classification. With cryo-EM, I solved the structure of an AMPAR bound to the auxiliary subunit stargazin, which promotes AMPAR activation. This work provided the first structural information on how AMPARs form complexes with regulatory subunits. In a following study, I solved the structure of an AMPAR in complex with a functionally distinct auxiliary subunit, GSG1L. In contrast to stargazin, GSG1L promotes inactivation and desensitization of AMPARs, thus having a neuroprotective effect. To further characterize the function of these auxiliary subunits, I designed chimeras between stargazin and GSG1L and examined their function electrophysiologically. This experiment revealed that AMPAR auxiliary subunits have a modular design, where variable extracellular domain regions, supported by a conserved transmembrane α-helical bundle, distinctly regulate function of the core AMPAR. This study provided the first evidence of how brain region-specific expression patterns of similarly-structured auxiliary subunits may contribute to unique AMPAR functions. More recently, I’ve taken advantage of the modulatory effects of stargazin on AMPARs and I applied cryo-EM to an AMPAR-stargazin complex. This study determined how AMPARs are activated by the neurotransmitter glutamate, and revealed a novel mechanism by which glutamate binding induces opening of AMPAR ion channels. Our data show that two-fold symmetric kinking of ion channel helices allows cation flux into neurons, which triggers neurotransmission. Importantly, this study also provides insights into how mRNA editing and patient-derived disease mutations in the transmembrane (i.e., resulting in aberrantly firing of receptors during epilepsy) reshape AMPAR function and excitatory neurotransmission. Collectively, the findings from my thesis work provide a new paradigm for the molecular-level understanding of glutamatergic neurotransmission throughout the CNS. These studies lay the groundwork for new directions in precision-medicine design of therapeutics targeting brain region-specific AMPAR synaptic complexes in neurological diseases.

Chen Lei. / "February 2004." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (p. 124-161). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

No description available.

Thesis (Ph.D.)--University of Alberta, 2009. / A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy, Centre for Neuroscience. Title from pdf file main screen (viewed on October 31, 2009). Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin, 1951. / Typescript (carbon copy). eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves [82]-86).

Thesis (M. SC.)--Carleton University, 2001. / Includes bibliographical references (p. 35-53). Also available in electronic format on the Internet.

by Zsolt Laszlo Kovacs. / Bibliography: p. 175-184. / Originally presented as the author's thesis, (Ph.D.) in the M.I.T. Dept. of Electrical Engineering and Computer Science, 1977. Partial support provided by the Funda? de Amparo a Pesquisa do Estado de S?Paulo, Brazil and by the National Science Foundation Grant no. NSF/ENG-7705200.

My thesis has accomplished 3 significant contributions to neuroscience. Firstly, I have discovered a novel example of vertebrate deep-brain photoreception. Spontaneously generated fictive locomotion from the isolated nervous system of pro-metamorphic Xenopus tadpoles is sensitive to the ambient light conditions, despite input from the classical photoreceptive tissues of the retina and pineal complex being absent. The photosensitivity is found to be tuned to short wavelength UV light and is localised to a small region of the caudal diencephalon. Within this region, I have discovered a population of neurons immuno-positive for a UV-specific opsin protein, suggesting they are the means of phototransduction. This may be a hitherto overlooked mechanism linking environmental luminance to motor behaviour. Secondly, I have advanced the collective knowledge of how both nitric oxide and dopamine contribute to neuromodulation within motor control systems. Nitric oxide is shown to have an excitatory effect on the occurrence of spontaneous locomotor activity, representing a switch in its role from earlier in Xenopus development. Moreover, this excitatory effect is found to be mediated in the brainstem despite nitric oxide being shown to depolarise spinal neurons. Thirdly, I have developed a new preparation for patch-clamp recording in pro-metamorphic Xenopus tadpoles. My data suggest there are several changes to the cellular properties of neurons in the older animals compared with the embryonic tadpole; there appears to be an addition of Ih and K[sub](Ca) channels and the presence of tonically active and intrinsically rhythmogenic neurons. In addition, I have shown that at low doses dopamine acts via D2-like to hyperpolarise the membrane potential of spinal neurons, while at higher doses dopamine depolarises spinal neurons. These initial data corroborate previously reported evidence that dopamine has opposing effects on motor output via differential activation of dopamine receptor subtypes in Xenopus tadpoles.