The impact of fluorine in medicinal chemistry is reviewed in the first chapter of this work and the fluorine gauche effect, which has not been fully exploited in medicinal chemistry, is also discussed. GABAA and GABAB receptors are then presented and the synthesis of neurosteroid antagonists acting at GABAA receptors is reported. The synthesis of such compounds was motivated to explore the mode of action of neurosteroids at GABA receptors. The observation that the C-F bond has a strong preference to align gauche to the C-N+ bond in protonated β-fluoroamines stimulated the enantioselective synthesis of 3-fluoro-GABA enantiomers. This was achieved from L- and D- phenylalanine in six steps and in an overall yield of 31%. The preferred conformations of 3-fluoro-GABA in solution are then explored by NMR analysis and ab initio calculations. The biological evaluation of 3-fluoro-GABA enantiomers on GABA aminotransferase was then investigated and showed that the (R)-enantiomer undergoes HF elimination ten times more rapidly than the (S)-enantiomer, suggesting a preferred binding conformation of GABA on GABA aminotransferase. This study demonstrates that the C-F bond can be used as a chemical probe to reveal the binding conformation of a bioactive amine and this offers exciting prospects for future research. The synthesis of 3-fluoro-GABA from phenylalanine indicated that amino acids are practical starting materials for the preparation of β-fluoroamines. This methodology is applied to L-lysine to generate (2R)-fluorohexane-1,6-diamine. The formation of a diamine of potential interest for catalysis is also observed in this synthesis.

Neuropathic pain is a significant and frequent outcome of spinal cord injury (SCI), and is often refractory to treatment. A better understanding of the pathological processes following injury that contribute to the development of neuropathic pain will aid the search for novel therapeutics. In the second chapter of this thesis a murine model of post-SCI below-lesion neuropathic pain was utilized to investigate changes in GABAergic tone. The gad1:GFP transgenic mouse line allowed the study of a subpopulation of GFPlabeled GABAergic neurons under control of the GABA synthesizing glutamate decarboxylase enzyme. SCI was observed to result in a loss of GABAergic neurons, and secondary markers of GABAergic tone supported this observation. This finding suggests that GABAergic interneuron cell death accounts for the decreased GABAergic tone previously reported post-SCI. In the third chapter of this thesis it was attempted to prevent the death of GABAergic neurons post-SCI using a transgenic mouse line expressing increased levels of the X-linked inhibitor of apoptosis (XIAP) under the ubiquitin C promoter. No differences were observed between ubXIAP and wildtype mice, indicating that increased expression of XIAP is not sufficient to prevent the development of neuropathic pain post- SCI. The fourth chapter of this thesis attempted to prevent the development of neuropathic pain through a novel treatment schedule of the drug pregabalin. Pregabalin administered shortly after SCI prevented the development of neuropathic pain. Pregabalin initiated 1 week post-SCI had no effect. Early pregabalin treatment did not appear to dramatically alter glial activation, or expression of the pregabalin receptor, but we observed changes in markers associated with synaptic plasticity. My findings build upon our knowledge of the mechanisms underlying post-SCI below-lesion neuropathic pain, and suggest new avenues of research, such as the uses of preemptive treatment with pregabalin, that offer promise for translation to clinical use.

γ-Hydroxybutyrate (GHB) is an intermediate of γ-aminobutyrate (GABA) catabolism in plants subjected to abiotic stress and its formation is catalyzed by two NADPH-dependent glyoxylate/succinic semialdehyde reductases (GLYRs). GABA and/or GHB accumulation in ‘Honeycrisp’ and ‘Empire’ apple fruit stored under controlled atmosphere (CA) conditions (i.e., low temperature, low O2, elevated CO2) in the presence or absence of the ethylene-antagonist 1-methylcyclopropene, coincided with the onset of physiological injury, suggesting an association with cellular disruption. Salinity and chilling stresses differentially influenced the expression of GABA pathway genes and the levels of GHB among various GABA pathway mutants of Arabidopsis. Furthermore, the occurrence of GHB in glyr1/glyr2 double knockout mutants indicates the presence of an additional pathway for GHB production. Evidence for GHB oxidation was not detectable in cell-free leaf extracts, suggesting the existence of a novel enzyme for GHB turnover. / NSERC Alexander Graham Bell Canada Graduate Scholarship (CGS-M), Ontario Graduate Scholarship (OGS), NSERC, Ontario Apple Growers, Rohm & Haas, MITACS

Transcriptional fusion mutants and Tn5-B20 transposon mutants were isolated where the only genes affected are believed to either be involved in the hypothetical GABA shunt or code for subunits of the alpha-ketoglutarate dehydrogenase enzyme complex of Sinorhizobium meliloti. The growth phenotypes of Rm30222 (gabT) and eight mutants in gabD1, 2, 3, and 4 on minimal media were comparable to that of the wild-type. Compared to wild-type, Rm30222 (gabT) lacked alpha-ketoglutarate-dependent gamma-aminobutyrate transaminase activity showed high induction of gabT on GABA but produced green plants indicative of being Fix+. Mutants in gabD alleles maintained wild-type levels of succinic semialdehyde dehydrogenase activity and could fix nitrogen as well as the wild-type in symbiosis. / Mutation of sucB encoding a subunit of a-ketoglutarate dehydrogenase produced a mutant, Rm30230, that initially had difficulty growing on minimal media supplemented with either arabinose or glutamate. In symbiosis with alfalfa, Rm30230 had a fix- phenotype and was also devoid of alpha-ketoglutarate dehydrogenase activity. The ability of Rm30230 to grow on arabinose or glutamate, without alpha-ketoglutarate dehydrogenase activity, strengthens the hypothesis that S. meliloti has a functional GABA shunt allowing it to circumvent the forward-direction TCA cycle from alpha-ketoglutarate to succinate. Mutation of the second potential dihydrolipoamide succinyltransferase component (E2) of alpha-ketoglutarate dehydrogenase yielded Rm30267 (SMb20019) with wild-type growth on minimal media and a Fix+ phenotype in plants. The introduction or a sucB mutation into the SMb20019 mutant background (Rm30275) was comparable to the sole sucB mutation. This finding shows that the locus SMb20019 cannot be substituted for sucB in the alpha-ketoglutarate dehydrogenase enzyme complex.

The goal of this project is to synthesize and purify a library of novel 4-alkyl-3,5-diamino-1-(2,6-dichloro-4-trifluoromethylphenyl)pyrazoles. These molecules are similar to other fiproles, which have been shown by Sammelson et al. to have pesticidal activities at the GABA receptor.' Fiproles are analogues of Fipronil, a very important pesticide. Replacing the cyano group normally located at the 3-position of the pyrazole ring with an amino group will change the binding potency of the phenylpyrazoles. Changes in binding produced by the changes introduced in molecular structure can create more information about the GABA receptor.Synthesis of our target compounds starts with production of monosubstituted malononitriles. Conventionally a two-step process, our research developed a new, efficient one-step process using borohydride as the only reagent. We utilized this method in the synthesis of desired monosubstituted malononitriles. These were converted to unsymmetrical disubstituted malononitriles, and to our target fiprole compounds, through a 4-alkyl-3,5-diaminopyrazole intermediate. / Department of Chemistry

In this thesis, I examined the inhibitory control of REM sleep motor activity using both a pharmacological rat model and a genetic mouse model. I characterized the role for GABA and glycine in mediating the REM-specific suppression of muscle activity as well as their involvement in regulating the phasic muscle twitches that punctuate this atonia. Based on four specific research objectives, the following conclusions were drawn: 1. REM atonia is not directly mediated by glycinergic or GABAA-mediated inhibition. These data refute the prevailing hypothesis that REM atonia is caused by glycinergic inhibition. These receptors are, however, important in the regulation of phasic muscle twitch activity. 2. GABAB receptors can modulate REM atonia but only when acting in concert with GABAA and glycine receptors. Blockade of all three receptor types results in a partial reversal of REM atonia, suggesting a functional interaction is occurring between these receptors during REM sleep. 3. The phasic glycinergic/GABAA-mediated inhibitory drive present in REM sleep regulates the temporal pattern of phasic twitch activity that is seen across this state. I hypothesize that this progressively decreasing inhibitory input counteracts a gradually increasing excitatory input to shape the temporal distribution of muscle twitches across REM sleep. 4. A loss of normal inhibitory function may play a causal role in the pathology of REM sleep behaviour disorder (RBD), the sleep disorder characterized by excessive motor activity in REM sleep.

Diss. (sammanfattning) Umeå : Univ., 2006. / Härtill 4 uppsatser.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 72-87). Also available via the Internet.

Thesis (Ph. D.)--West Virginia University, 1998. / Title from document title page. "September 1998." Document formatted into pages; contains x, 184 p. : ill. (some col.) Includes abstract. Includes bibliographical references (p. 161-184).

Thesis (Ph. D.)--University of Virginia, 1997. / Spine title: Brain microvascular regulation. Includes bibliographical references (99-122). Also available online through Digital Dissertations.