Thesis (Ph.D. in Human Medical Genetics) -- University of Colorado at Denver and Health Sciences Center, 2005. / Typescript. Includes bibliographical references (leaves 166-195).

Ketamine and phencyclidine (PCP) are noncompetitive antagonists of the N-methyl-D-aspartate (NMDA) type of ligand-gated glutamate receptors. Both agents have high abuse liability, and may produce dependence. Tolerance to the reinforcing effects of drugs of abuse is widely regarded as a key component of the dependence process. Therefore, the present study was conducted to examine whether tolerance develops to the reinforcing effects of ketamine, and whether PCP and dizocilpine, a noncompetitive NMDA antagonist with negligible abuse liability, produce cross-tolerance to the reinforcing effects of ketamine. Further, identification of the neural mechanisms that underlie tolerance to the reinforcing effects of drugs may yield information regarding drug dependence.

Les antagonistes du récepteur N-méthyl-D-aspartate (NMDA) comme la kétamine, le dextrométhorphane et la mémantine sont utilisés pour la prise en charge de la douleur neuropathique. La kétamine est très efficace contre les douleurs neuropathiques réfractaires aux traitements conventionnels. Cependant, son utilisation est limitée du fait de nombreux effets indésirables. Un relais antalgique est alors proposé. Ce travail de thèse s’insère dans un programme de recherche dédié aux antagonistes du récepteur NMDA dans la prise en charge de la douleur neuropathique. Le premier objectif était d’évaluer dans une étude clinique randomisée, en simple insu, en groupes parallèles, contrôlée versus placebo, les effets antalgiques du dextrométhorphane et de la mémantine, administrés en relais de la kétamine chez 60 patients souffrant de douleurs neuropathiques d’origine périphérique. L’impact de ces traitements sur le statut cognitivo-émotionnel des patients et leur qualité de vie a également été examiné, ainsi que la modulation des effets de ces médicaments par le polymorphisme génétique impliqué dans le métabolisme (CYP2D6, CYP3A4,5), la biodisponibilité et l’élimination (NR1I2) de ces deux molécules. En parallèle une étude mécanistique centrée sur le dextrométhorphane a été réalisée chez vingt volontaires sains (étude randomisée, en double aveugle, en groupes croisés). L’objectif était d’étudier dans un modèle d’hyperalgie induite par le froid « Freeze injury » les caractéristiques pharmacologiques et mécanistiques déterminant les effets anti-nociceptifs, centraux et cognitifs du dextrométhorphane ainsi que le polymorphisme génétique impliqué dans leur modulation. Chez les patients, les effets antalgiques immédiats de la kétamine ont été confirmés et s’accompagnaient de l’amélioration des scores d’anxiété et de dépression, des aspects cognitifs et affectifs et du sommeil. Toutefois, par rapport au placebo, la mémantine et le dextrométhorphane n’ont pas permis de renforcer significativement l’antalgie induite par la kétamine. Chez les volontaires sains, le dextrométhorphane a révélé des effets anti-hyperalgiques suite à une sensibilisation périphérique et centrale. Cependant, aucun effet analgésique sur la douleur thermique aiguë n’a été observé. Ces deux approches clinique et mécanistique concernant l’effet curatif des antagonistes du récepteur NMDA ont permis d’une part de montrer : 1 - chez le patient, l’effet curatif prolongé de la kétamine et l’intérêt du dextrométhorphane et de la mémantine dans la prise en charge du retentissement négatif de la douleur neuropathique sur le statut cognitivo-émotionnel et la qualité de vie des patients; 2 - chez le volontaire sain, l’efficacité anti-hyperalgique du dextrométhorphane sur les phénomènes de sensibilisation périphérique et centrale ainsi que ses répercussions sédatives et cognitives. En complément de ces deux études et dans le but de confirmer en clinique les effets curatifs du dextrométhorphane sur le triptyque douleur-cognition-émotion, une étude clinique randomisée, en double aveugle, en groupes parallèles, contrôlée versus placebo est en cours de réalisation chez 40 patientes souffrant de douleur neuropathique chimio-induite subséquente au traitement du cancer du sein. En conclusion de ce travail de thèse, l’étude des effets du dextrométhorphane dans deux populations différentes souligne l’intérêt de la recherche translationnelle. Chez le sujet volontaire sain, le dextrométhorphane exerce un effet anti-hyperalgique marqué et provoque des effets centraux délétères. Chez le patient présentant une douleur neuropathique d’origine périphérique et étant répondeur à la kétamine, seule une tendance est observée en faveur de l’effet anti-nociceptif du dextrométhorphane donné en relais de la kétamine. En revanche l’administration de dextrométhorphane s’accompagne d’un certain bénéfice au niveau cognitif et sur la qualité de vie des patients. / N-methyl-D-aspartate (NMDA) receptor antagonists such as ketamine, dextromethorphan and memantine have gained an increasing interest in the management of neuropathic pain. In Pain Clinics, ketamine is widely used in the relief of neuropathic pain. However, its use in clinical practice is limited due to its numerous side effects. It is therefore necessary to propose to patients a drug relay with other NMDA receptor antagonists. This work is part of an academic program research dedicated to NMDA receptor antagonists in the management of neuropathic pain. Its first objective was to evaluate the antalgic effects of dextromethorphan and memantine. This randomized, single-blind, parallel-group, placebo-controlled study in 60 ketamine responder patients aimed also to assess the cognitive-emotional status of patients and their quality life. In parallel, a mechanistic study focusing on dextromethorphan was performed in 20 healthy volunteers in a randomized, double-blind, cross-over, placebo-controlled study. The objective was to investigate in a freeze-injury model the pharmacokinetic and mechanistic characteristics of the anti-nociceptive, central and cognitive effects of dextromethorphan as well as the genetic polymorphism involved in its response variability.In patients, the immediate analgesic effects of ketamine were confirmed with improved anxiety and depression scores, cognitive and affective aspects of pain, and different sleep parameters. However, memantine and dextromethorphan, compared to placebo, did not significantly increase the ketamine-induced analgesia. The analysis of the genetic polymorphism did not reveal any variability in the analgesic efficacy of these treatments. In healthy volunteers, dextromethorphan revealed anti-hyperalgesic effects following peripheral and central sensitization but no analgesic effect on acute heat pain. Moreover, the variability of the anti-nociceptive activity of dextromethorphan described in the literature seems to be more related to the genetic polymorphism of the CYP2D6 gene than to that of the CYP3A4,5 and ABCB1 genes. Finally, dextrorphan, the main active metabolite of dextromethorphan, appears to be responsible for the deleterious sedative and cognitive effects of the drug. These two clinical and mechanistic approaches concerning the curative effect of the NMDA receptor antagonists showed : 1 - in patients, the prolonged curative effect of ketamine and the interest of dextromethorphan and memantine in the management of the neuropathic pain-related cognitive-emotional and quality of life impairment; 2 - in healthy volunteers, the anti-hyperalgesic efficacy of dextromethorphan on peripheral and central sensitization and its sedative and cognitive side effects. In addition to these two studies, a randomized, double-blind, parallel-group, placebo-controlled clinical study is ongoing in 40 patients with chemotherapy-induced peripheral neuropathic pain subsequently to the treatment of breast cancer. In conclusion the assessment of the effects of dextromethorphan in two different populations led to discordant results. In the healthy volunteer, dextromethorphan exerts a marked anti-hyperalgesic effect and causes deleterious central effects. In the patient with peripheral neuropathic pain, only a trend is observed in favor of the anti-nociceptive effect of dextromethorphan given in ketamine responder patients. More studies with larger population are needed to determine the importance of the CYP2D6, CYP3A4,5 and ABCB1 genetic polymorphisms on the anti-nociceptive activity of dextromethorphan. The translational approach of this thesis does not allow a firm conclusion on the clinical use of dextromethorphan in the curative treatment of chronic peripheral neuropathic pain. The use of dextromethorphan as a preventive agent via other administration routes (i.e. local) or in combination with other drugs, all require further exploration in order to improve the benefit/risk ratio of this molecule.

The induction of synaptic plasticity at CA1 synapses requires NMDAR activation. Modulation of NMDAR function by various GPCRs can shift the thresholds for LTP and LTD induction and contribute to metaplasticity. Here we showed that the activity of GluN2A- and GluN2B-containing NMDARs is differentially regulated by Gαi/o-coupled, Gαq- and Gαs-coupled receptors. Furthermore, enhancing the relative function of GluN2A-to-GluNB NMDAR activity by GPCRs can alter the balance of LTP and LTD induction and contribute to metaplasticity. In CA1 neurons, activation of the Gαs-coupled D1/D5R selectively recruited Fyn kinase and enhanced GluN2B-mediated NMDAR currents. Biochemical experiments confirmed that D1/D5R stimulation activates Fyn kinase and enhances the tyrosine phosphorylation of GluN2B subunits. In contrast, activation of the Gαq-coupled PAC1R selectively recruited Src kinase to enhance the function of GluN2A-containing NMDARs. Enhancing the functional ratio of GluN2A-to-GluN2B subunits by PAC1R activation lowered the threshold for LTP induction whereas enhancing the functional ratio of GluN2B-to-GluN2A subunits by D1/D5R activation increased the threshold for LTP induction. Unexpectedly, activation of the Gαi/o-coupled mGluR2/3 enhanced NMDAR-mediated function via a previously unidentified mechanism. Inhibition of the cAMP-PKA pathway via mGluR2/3 activation resulted in activation of Src via decreased phosphorylation of its C-terminal Tyr527 by Csk. Stimulation of mGluR2/3 selectively potentiated the function of GluN2A-containing NMDARs but whether it shifted the modification threshold θm to the left requires further investigation.

The induction of synaptic plasticity at CA1 synapses requires NMDAR activation. Modulation of NMDAR function by various GPCRs can shift the thresholds for LTP and LTD induction and contribute to metaplasticity. Here we showed that the activity of GluN2A- and GluN2B-containing NMDARs is differentially regulated by Gαi/o-coupled, Gαq- and Gαs-coupled receptors. Furthermore, enhancing the relative function of GluN2A-to-GluNB NMDAR activity by GPCRs can alter the balance of LTP and LTD induction and contribute to metaplasticity. In CA1 neurons, activation of the Gαs-coupled D1/D5R selectively recruited Fyn kinase and enhanced GluN2B-mediated NMDAR currents. Biochemical experiments confirmed that D1/D5R stimulation activates Fyn kinase and enhances the tyrosine phosphorylation of GluN2B subunits. In contrast, activation of the Gαq-coupled PAC1R selectively recruited Src kinase to enhance the function of GluN2A-containing NMDARs. Enhancing the functional ratio of GluN2A-to-GluN2B subunits by PAC1R activation lowered the threshold for LTP induction whereas enhancing the functional ratio of GluN2B-to-GluN2A subunits by D1/D5R activation increased the threshold for LTP induction. Unexpectedly, activation of the Gαi/o-coupled mGluR2/3 enhanced NMDAR-mediated function via a previously unidentified mechanism. Inhibition of the cAMP-PKA pathway via mGluR2/3 activation resulted in activation of Src via decreased phosphorylation of its C-terminal Tyr527 by Csk. Stimulation of mGluR2/3 selectively potentiated the function of GluN2A-containing NMDARs but whether it shifted the modification threshold θm to the left requires further investigation.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 5 uppsatser.

Thesis (Ph.D. in Neuroscience) -- University of Colorado Denver, 2007. / Typescript. Includes bibliographical references (leaves 200-233). Free to UCD affiliates. Online version available via ProQuest Digital Dissertations;

Doctor Pharmaceuticae - Dpharm / Among neurological disorders, many of the most devastating disorders are neurodegenerative. Modern research associates excitotoxicity to a variety of neuropathological conditions, suggesting that the neurodegenerative diseases with distinct etiologies may have excitotoxicity as a common pathway. Excitotoxicity occurs through over-stimulation of receptors for excitatory neurotransmitters like the N-methyl-D-aspartate (NMDA) receptors. Due to the relevance of NMDA receptors and excitotoxic processes, the antagonism or modulation of NMDA receptors is used as a therapeutic tool against neurodegenerative diseases. NMDA receptor activity can be modulated by S-nitrosylation and this modulation of NMDA receptor activity can be utilised in the development of neuroprotective drugs.

Orientadores: Elenice Aparecida de Moraes Ferrari, Luiz Roberto Giorgetti Britto / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-06T11:20:23Z (GMT). No. of bitstreams: 1 Sperandeo_MariaLuizaAntunes_M.pdf: 1329953 bytes, checksum: 9e4252fe270a020cdc4182cde457725e (MD5) Previous issue date: 2005 / Resumo: O presente estudo investigou os efeitos do antagonista do receptor NMDA, MK-801 na expressão do produto do zenk no hipocampo (Hp) de pombos, submetidos ao condicionamento clássico aversivo. Antes do treino, administrou-se MK-801, i.p, para o grupo condicionado MK (GCMK, n=6), salina para o grupo condicionado salina (GCS, n=6) e nenhum tratamento para os grupos-controle: randômico (GCR, n=6), contexto (GCC=7) e manipulação (GM=4). GCMK e GCS receberam três associações de som (1000-Hz, 83 dB,1 s) e choque (10 mA, 35ms) numa sessão de 20 min. Para GCR os estímulos foram aleatórios e o GCC não recebeu estímulos. O teste de re-exposição ao contexto ocorreu 24 h após o treino. A análise de freezing no treino mostrou maior ocorrência para o GCS em comparação ao GCC (p<0,05), com aumento gradual na sessão (p<0,01). No teste, GCS expressou maior ocorrência de freezing em comparação a todos os grupos (p<0,001). A expressão de zenk foi avaliada por imuno-histoquímica. O GCS teve maior número de núcleos ZENK-positivos no Hp ventral, especificamente no Hp ventro-medial, comparativamente aos outros grupos (p<0,01). A baixa ocorrência de freezing ao contexto no GCMK evidencia o efeito amnésico do MK-801. A análise da marcação de núcleos ZENK-positivos no Hp sugeriu sua ativação regionalizada na evocação de memória contextual aversiva em pombos. O presente estudo indica o envolvimento de receptores de glutamato do tipo NMDA em mecanismos sinápticos de plasticidade neural durante a evocação de memória aversiva ao contexto. Palavras-chave: condicionamento clássico aversivo, hipocampo, MK-801, antagonista dos receptores NMDA, recuperação da memória aversiva, zenk / Abstract: The present study investigated the effects of the antagonist of the glutamate NMDA receptor, MK- 801, in the activation of zenk in the hippocampus of pigeons (Hp) submitted to the classical aversive conditioning. Two groups of pigeons received MK-801 (MKG, n=6) or saline (SG, n=6) 30 min before training with tone-shock associations. The control groups received unpaired stimulation (RCG, n=6), exposure to the context (CCG=7) or manipulation alone (MG=4). During the 20 min training session MKG and SG received three sound (1000-Hz, 83 dB, 1 s) and shock associations (10 mA, 35ms). The test to the context occurred 24 hours after the training. During the training session SG animals showed more freezing as compared with CCG (p<0,05). During the test, SG expressed higher freezing than all the other groups (p<0,001). ZENK analysis was conducted with imunohistochemistry. The density of ZENK-positive nuclei in the ventral hippocampus, specifically in the ventromedial hippocampus, was higher for SG as compared to the other groups (p<0,01). The fact that the animals from the MKG expressed lower freezing to the context may be considered as indicative of an amnesic effect of the MK-801. The density of ZENK-positive nuclei in the hippocampus suggests a regional activation that may be related to the retrieval of contextual aversive memory. The present study indicates that synaptic mechanisms mediated by NMDA glutamate receptors participate in the neural plasticity related to the retrieval of contextual aversive memory / Mestrado / Fisiologia / Mestre em Biologia Funcional e Molecular

>Magister Scientiae - MSc / This study focused on the synthesis of a series of novel tricycloundecane derivatives and evaluation of these compounds for neuroprotection using the fluorescent ratiometric calcium assay that indicates the ability of the test compounds to inhibit NMDA receptors and VGCC. The cycloaddition reaction between p-benzoquinone and monomerised dicyclopentadiene yielded tricycloundeca- 4,9-diene-3,6-dione which was used as the base structure and further derivatised. These derivatives were conjugated with benzylamine to form a series of imines and amines. A total of 10 compounds were synthesised for evaluation of inhibition of calcium influx through NMDA receptor channels and voltage-gated calcium channels. The structures were confirmed using NMR, IR and MS. On the proton NMR, the characteristic AB-quartet system was observed in the region of 1-2 ppm for all the compounds and the aromatic moiety was observed between 6.5-7.5 ppm for the novel polycyclic amines. These, with other functional groups, were used to confirm the individual structures