The pathophysiology, etiology, and treatment of schizophrenia remain elusive, but research is closing the gap. Schizophrenia globally affects less than 1% of the population and presents with positive, negative, and cognitive symptoms. As treatment for schizophrenia is not completely and meaningfully effective at treating all of the symptoms, without eliciting side effects, the current thesis aimed to evaluate a new drug candidate. PAOPA is a novel allosteric modulator that increases dopamine binding to the dopamine D2 receptor. It has previously shown positive findings in preventing and reversing behaviours proposed to model phenotypes of schizophrenia. However, it has not yet been tested to improve cognitive deficits in animal models, nor has its effects on other animals models been investigated. Lastly, its mechanism of action has not yet been comprehensively answered. In three separate studies, PAOPA was tested on ameliorating attentional deficits using the 5-choice serial reaction time task in an amphetamine model, deficits in novel objection recognition memory, sensorimotor gating, social interaction, and locomotor activity using a PCP model, and its effects on proteins regulating G protein-coupled receptors (GRK2 and arrestin-3), downstream signalling (ERK1 and ERK2), and synaptic vesicular control (synapsin II) were investigated. Although the sample sizes were too small to draw valid interpretations, the results suggested that PAOPA partially attenuated deficits in attention, novel object recognition memory, social interaction, sensorimotor gating, but not locomotor. Furthermore PAOPA increased the protein expression of GRK2, arrestin-3, ERK1 and 2, and synapsin IIa in the medial prefrontal cortex, striatum, and the nucleus accumbens. The results suggest that PAOPA influences the dopaminergic system in the striatum to change behaviour via receptor internalization and possibly downstream signalling. The present studies illuminate new insights, and point to future explorations for the potential development of PAOPA as a therapeutic for schizophrenia. / Thesis / Master of Science (MSc)

NMDA glutamate receptor is a ligand-gated ion channel that mediates a major component of excitatory neurotransmission in the central nervous system (CNS). NMDA receptors are activated by simultaneous binding of two different agonists, glutamate and glycine/ D-serine1. With aging, glutamate concentration gets altered, giving rise to glutamate toxicity that contributes to age-related pathologies like Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis, and dementia88,95. Some treatments for these conditions include NMDA receptor blockers like memantine130. However, when completely blocking the receptors, there is a restriction of the receptor's normal physiological function59. A different approach to regulate NMDAR receptors is thorough allosteric modulators that could allow cell type or circuit-specific modulation, due to widely distributed GluN2 expression, without global NMDAR overactivation59,65,122. In one study, we hypothesized that the compound CNS4 selectively modulates NMDA diheteromeric receptors (GluN2A, GluN2B, GuN2C, and GluN2C) based on (three) different glutamate concentrations. Electrophysiological recordings carried out on recombinant NMDA receptors expressed in xenopus oocytes revealed that 30μM and 100μM of CNS4 potentiated ionic currents for the GluN2C and GluN2D subunits with 0.3μM Glu/100μM Gly. However, when using 300μM Glu/100μM Gly, CNS4 inhibited the relative response in the GluN2D subunit and had no effect on the remaining subunits. CNS4 reduced the response to glutamate alone for GluN2A but increased it for GluN2B and did not appear to replace glutamate. Another set of electrophysiological recordings measuring current-voltage relationship was made in order to understand ion flow across the channel in the presence of CNS4. 100μM CNS4 numerically increased the ionic inward current through the channel pore with more positive membrane potential, reflected by a significant difference in reversal potential values, in the GluN2C and GluN2D subunits. CNS4 also exhibited a non-voltage dependent activity and it did not appear to compete with magnesium which naturally blocks the receptor. Finally, the effect of CNS4 on calcium uptake and cellular viability was study in neurons from primary rat brain culture. Cortial and striatal neurons were given excessive doses of synthetic agonist NMDA in order to hyperactivate native NMDAR. In the calcium assay, 100µM of CNS4 significantly increased calcium upatake when given with 300µM NMDA compared with NMDA alone in cortex and when given with 100µM and 300µM NMDA in striatum. In the MTS assay, CNS4 did not alter neuronal viability in either cortical or striatal neurons compared with NMDA alone. Also, when CNS4 was used in non treated neurons it did not alter neuronal viability. Findings from the primary brain culture let us conclude that CNS4 could facilitate calcium influx and possibly be non toxic for neurons. / Master of Science / NMDA ionotropic glutamate receptors are predominately expressed in the central nervous system (CNS). These receptors are activated by glutamate and glycine/ D-serine1. With aging, glutamate concentration in the synapse gets altered giving rise to toxic environments for neurons that can contribute to age-related pathologies like Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis, and dementia88,95. Some treatments of these conditions include the receptor blockers like memantine130. However, when completely blocking the receptors, there is a restriction of the receptor's normal physiological function59. A different approach to regulate NMDAR is through allosteric modulators that are compounds that modulate the receptor function without competing with endogenous agonists59,65,122. In this study, we hypothesized that the compound CNS4 selectively modulates NMDAR based on glutamate concentration. Electrophysiological recordings on stage four xenopus oocytes helped us to identify the dose-dependent activity of CNS4 and we found that 30 and 100μM of CNS4 selectively potentiates ionic currents for GluN2C and GluN2D subunits with 0.3μM Glu/100μM Gly but inhibited currents for only GluN2D with 300μM Glu/100μM Gly. Following this, a current-voltage plot was made to examine the channel activity of CNS4. We found a numerical increase of ionic inward current through the channel pore with more positive membrane potential values in the GluN2C and GluN2D subunits. Also, the effect of CNS4 on the ion current activity changed based on glutamate concentration, and CNS4 did not exhibit a voltage-dependent activity, which is a positive feature for compounds that target the receptor133. Finally, to better understand the effect of the compound CNS4 in primary neurons in a toxic environment, a rat brain neuronal culture was made. Increasing doses of NMDA with constant 100µM CNS4 increased cellular Ca2+ influx in a dose-dependent manner. Particularly, 100µM CNS4 with 300µM NMDA exhibited a significant increase in Ca2+ influx in both cortical and striatal neurons compared with 300µM NMDA alone. However, when used alone, 100µM CNS4 did not have an effect on the amount of Ca2+ influx. In addition, CNS4 plus NMDA did not increase viability compared to NMDA alone, and CNS4 alone did not proportionally reduce neuronal viability.

Intracellular polymerization of deoxygenated sickle hemoglobin (Hb S) remains the principal cause of the pathophysiology associated with sickle cell disease (SCD). Naturally occurring and synthetic allosteric effectors of hemoglobin (AEH) have been investigated as potential therapeutic agents for the treatment of SCD. Several aromatic aldehydes, including vanillin, have been studied previously as AEHs for their antisickling activities. Specifically, these compounds form Schiff- base adduct with Hb to stabilize the oxygenated (R) state, increase Hb affinity for O2 and concomitantly prevent the hypoxia-induced primary pathophysiology of Hb S polymerization and RBC sickling, in turn, ameliorating several of the cascading secondary adverse effects. These compounds, however, undergo significant metabolism leading to suboptimal pharmacokinetic properties, e.g. short duration of pharmacologic action and low bioavailability. These drawbacks have severely hampered the use of aromatic aldehydes as AEHs to treat SCD. To counter these challenges, we designed and synthesized 14 novel compounds (PP- compounds) based on previously studied pyridyl derivative of vanillin. These modifications were expected to increase binding interactions with the protein and thus stabilize the Schiff-base adduct, as well as lead to perturbation of the surface-located F-helix that would stereospecifically destabilize polymer contacts. We investigated the in vitro pharmacokinetic/pharmacodynamic properties of these newly synthesized compounds to ascertain sustained binding and modification of normal human Hb. Subsequently, we conducted in vitro screening assays to test for inhibition of sickling, modification of Hb to the high-affinity form, as well as for a direct left-shift in oxygen equilibrium curves (OEC). Three selected compounds, PP6, PP10, and PP14, that demonstrated not only high antisickling activity but also showed sustained pharmacologic action were chosen for preliminary in vivo studies. Our results showed maximal levels of Hb modification, which were sustained for the entire 24 h experimental period. In contrast, TD-7 after reaching maximum effect at 1 h gradually decreased in potency and at 24 h has lost 45% of its activity, consistent with the low bioavailability of this compound. These findings suggested that our modifications appeared to successfully limit drug metabolism in red blood cells. Most of these compounds showed almost complete inhibition of sickling at 2 mM concentration; with significant modification of Hb to a higher affinity Hb as well as an increase in O2 affinity of Hb. Interestingly, while TD-7 demonstrated a clear linear correlation between its ability to increase Hb-O2 affinity and antisickling activity, PP2, PP3, PP6, PP9, PP10, and PP14, showed a weak correlation between these parameters. In fact, these compounds demonstrated high antisickling effect despite only marginally increasing Hb affinity for O2. This observation indicated that these compounds possibly exhibit the dual mechanism of antisickling activity. We hypothesize that their secondary mechanism of action is due to interactions with the surface located αF-helix that would lead to direct or stereospecific inhibition of polymer formation. To establish the mode of interaction with Hb, we further conducted x-ray crystallography studies and co-crystallized PP2, PP6, PP9 and PP11 with CO-liganded Hb. Our studies showed that these compounds bind in symmetry-related fashion at the α-cleft of Hb to form Schiff-base adducts with the N-terminal Val1 and showed direct interactions with the F-helix which overall enhanced interactions with Hb. PP6, PP10, and PP14 demonstrated significant in vivo modification of intracellular Hb in mice after IP administration, with increasing levels from 1 h to the 6 h experimental period. They also showed corresponding changes in O2 affinity observed at 3 h and 6 h, compared to 0 h pre-treatment samples in vivo. Thus, our results establish these compounds as a novel, promising group of potent anti-sickling agents, demonstrate their proposed mechanism of action and provide proof-of-concept justifications for our structure-based approach to developing potent therapeutics for SCD.

The small- and intermediate-conductance Ca2+ activated K + (SK/IK) channels play a fundamental role in the regulation of neurons in the central nervous system. In animal models, SK/IK channel positive modulators have been shown to be effective in reducing the symptoms of neurological diseases such as ataxia. Ataxia is a lethal neurological rare disease characterized by lack of balance and incoordination of muscle movements, often as a result of cerebellar or spinocerebellar neurodegeneration. SK/IK channel modulators have been developed over the past few decades. Currently available modulators are often weak in potency. Lack of knowledge about the binding site for the compounds is the main reason hindering the development of more potent and effective therapeutics targeting SK channels. Dr. Zhang and his colleagues recently discovered the binding pocket for these positive modulators of SK/IK channels. This pocket is located at the interface between the channel and calmodulin. Dr. Zhang and his colleagues performed screening of a large number of compounds in silico, to find those fitting into the binding pocket. I performed electrophysiological recordings to evaluate the efficacy and the potency of these modulators on SK2 channels. We discovered a correlation between the total binding energy values calculated from the structures and the potencies determined from electrophysiological recording.

京都大学 / 0048 / 新制・論文博士 / 博士(農学) / 乙第13146号 / 論農博第2852号 / 新制||農||1056(附属図書館) / 学位論文||H30||N5093(農学部図書室) / (主査)教授 植田 和光, 教授 加納 健司, 教授 三芳 秀人 / 学位規則第4条第2項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

No description available.

The adhesion G protein–coupled receptor (aGPCR) GPR126/ADGRG6 plays an important role in several physiological functions, such as myelination or peripheral nerve repair. This renders the receptor an attractive pharmacological target. GPR126 is a mechano-sensor that translates the binding of extracellular matrix (ECM) molecules to its N terminus into a metabotropic intracellular signal. To date, the structural requirements and the character of the forces needed for this ECM-mediated receptor activation are largely unknown. In this study, we provide this information by combining classic second-messenger detection with single-cell atomic force microscopy. We established a monoclonal antibody targeting the N terminus to stimulate GPR126 and compared it to the activation through its known ECM ligands, collagen IV and laminin 211. As each ligand uses a distinct mode of action, the N terminus can be regarded as an allosteric module that can fine-tune receptor activation in a context-specific manner.

Les récepteurs métabotropiques du glutamate (mGluRs) sont des récepteurs couplés aux protéines G (RCPGs) modulant la transmission synaptique au sein du système nerveux central. D'un point de vue structural, ils ont la particularité de posséder un large domaine extracellulaire, le Venus Flytrap (VFT), où se lie leur ligand endogène, le glutamate. Leur domaine transmembranaire à 7 hélices, commun à tous les RCPGs, est connu pour être la cible d'une nouvelle classe de molécules à visée thérapeutique, les modulateurs allostériques. Au contraire, le VFT est le siège du développement de ligands compétitifs du glutamate et peu de choses sont connues quant à l'existence de modulateurs allostériques du VFT. Des études récentes ont mis en évidence une sensibilité des mGluRs aux ions extracellulaires et en particulier au chlore (Cl-), sans que son site de liaison ne soit identifié. Dans ce contexte, ce travail de thèse explore la possibilité d'une modulation allostérique endogène des mGluRs par les ions Cl-, en identifiant leur(s) site(s) de liaison(s) et leur effet sur la dynamique conformationnelle et la fonction des récepteurs. En combinant une approche pharmacologique, biophysique basée sur la technique de FRET, et la modélisation, nous avons tout d'abord confirmé que le Cl- potentialise l'action du glutamate sur tous les mGluRs et qu'il favorise la conformation active des récepteurs en se liant au niveau du VFT. Les mGluRs présentent également une sensibilité différente au Cl-, mGlu4 étant le plus sensible et mGlu2 le moins. Ceci s'explique notamment par le nombre de sites fonctionnels, tous les mGluRs dont mGlu4 possédant 2 sites par monomère à l'exception de mGlu2 qui n'en possède qu'un, en raison d'une mutation « clé » d'une sérine en aspartate dans le lobe 1 du VFT. D'autre part, le récepteur mGlu3 est apparu comme un cas particulier ayant une sensibilité accrue au Cl-, son domaine VFT cumulant la présence et l'orientation adéquate d'acides aminés formant un « verrou » Cl-, qui favorise de manière drastique la conformation active et une activité basale élevée de ce récepteur. Enfin, la modélisation de la variation de la concentration extracellulaire en Cl- lors d'une activité synaptique GABAergique est compatible avec une modulation des mGluRs les plus sensibles. En conclusion, le Cl- est un modulateur allostérique endogène des mGluRs et l'exploitation de ses sites de liaison au sein du VFT pourrait permettre le développement de nouveaux agents thérapeutiques. / Metabotropic glutamate receptors (mGluRs) are G coupled-protein receptors (GPCRs) playing key roles in synaptic transmission in the central nervous system. They display a large extracellular domain, the Venus Flytrap (VFT) where the endogenous ligand, glutamate, binds. Their 7 transmembrane helices spanning domain, common to all GPCRs, is known to be the target of new therapeutic compounds, called allosteric modulators. In contrast, VFT domain is used to develop glutamate competitive ligands and there are only few data about allosteric modulators targeting the VFT. Recent studies have shown mGluRs are sensitive to extracellular ions, particularly to chloride (Cl-), although its binding site has not been elucidated. This thesis work explores the possibility of an endogenous allosteric modulation of mGluRs by Cl-, aiming to delineate its binding site(s) and its effect on receptor conformational dynamics and function. Using pharmacological, FRET based biophysical approaches and modelling, we have first confirmed that Cl- potentiates glutamate action in all mGluRs and that this ion favors agonist induced active conformation by binding to the VFT. mGluRs are also differently sensitive to Cl-, mGlu4 being the most and mGlu2 the least. This difference is notably explained by the number of Cl- functional sites within the VFT, all mGluRs including mGlu4 displaying 2 sites per monomer whereas mGlu2 has only 1 site due to a serine-aspartate “key” mutation in VFT lobe 1. Besides, mGlu3 receptor appears to be a “special case”, as this receptor is highly sensitive to Cl- because its VFT domain is carrying amino acids creating a “Cl- lock”, which dramatically favors active conformation and a high level of basal activity. Finally, modelling of extracellular Cl- concentration variations in a GABAergic synapse is compatible with a modulation of the most sensitive mGluRs. In conclusion, Cl- is an endogenous allosteric modulator of mGluRs and exploiting its binding sites may yield to the development of innovative therapeutic tools.

Les prostaglandines modulent d’importants rôles physiologiques. Elles sont aussi impliquées dans le développement d’une variété de conditions pathologiques telles l’inflammation, la douleur et le cancer. La prostaglandine PGF2α et son récepteur (récepteur FP) se trouvent impliqué dans la modulation de nombreuses pathologies tels lors de l’accouchement préterme et le cancer colorectal. Récemment, nous avons fait partie d’un groupe de recherche ayant développé des modulateurs allostériques du récepteur FP. Dans une première étude, l’action du PGF2α sur le déclenchement des contractions myométriales a été évaluée, car peu d’information est connue sur la signalisation de cette prostaglandine lors de l’accouchement. Ainsi, nous avons utilisé un peptidomimétique de la deuxième boucle extracellulaire, dénommée PDC113.824. Nos résultats ont démontré que le PDC113.824 permettait de retarder la mise bas chez des souris gestantes, mais agissait de manière différente sur les multiples voies de signalisation de la PGF2α. Ainsi, le PDC113.824 inhibait la voie RhoA-ROCK, dépendante de l’activation de la protéine Gα12 par le. Les protéines RhoA-ROCK sont des acteurs clés dans le remodelage du cytosquelette d’actine et des contractions myométriales lors de l’accouchement. De plus, le PDC113.824 en présence de PGF2α agit comme un modulateur positif sur la voie dépendante de l’activation de la protéine Gαq. Le PDC113.824 serait donc un modulateur allostérique non compétitif possédant des actions à la fois de modulateurs positifs et négatifs sur la signalisation du récepteur FP Dans une seconde étude, des analogues du PDC113.824 ont été conçus et analysés dans un second modèle pathologique, le cancer colorectal. Ce cancer possède de hauts niveaux de récepteur FP. Nous avons donc étudié le rôle du récepteur FP dans le développement et la progression du cancer colorectal et l’effet de modulateurs allostériques. Il est généralement accepté que dans le cancer colorectal, la prostaglandine PGE2 permet la croissance et l’invasion tumorale, ainsi que l’angiogenèse. Toutefois, peu d’informations sont connues sur le rôle du PGF2α dans le cancer colorectal. C’est dans ce contexte que nous avons décidé d’examiner la contribution de ce récepteur dans la progression du cancer colorectal et cherché à déterminer si la modulation des fonctions du récepteur FP a un impact sur la croissance de tumeurs colorectales. Nos recherches ont révélé que l’activation du récepteur FP permet la migration et la prolifération de plusieurs lignées cellulaires humaines et murines d’adénocarcinomes colorectaux. Dans ce contexte, nos expériences ont démontré que la migration des cellules cancéreuses était dépendante de l’activation de la voie Rho. Nos résultats démontrent qu’en effet, l’activation de RhoA, une petite GTPase clé de la voie Gα12, est inhibée de façon sélective par nos composés. De plus, nos molécules allostériques sont également efficaces pour inhiber la voie de signalisation de la ß-caténine, une protéine impliquée dans la genèse du cancer colorectal. In vivo, le traitement de souris avec un des ces modulateurs a permis une inhibition effective de la croissance tumorale. Dans l’ensemble, nos résultats suggèrent donc que les modulateurs allostériques des récepteurs FP pourraient constituer une nouvelle classe de médicaments utilisés pour le traitement du cancer colorectal. / Prostaglandins play many important physiological roles. They are also involved in the development of a variety of pathological conditions such as inflammation, pain and preterm labor. The prostaglandin PGF2α and the FP receptor are implicated in the modulation of many pathological diseases, for example in preterm labor and in colorectal cancer. Our group has recently developed FP receptor allosteric modulators and focused on the role of this receptor and its ligand PGF2α in different models. In a first study, the action of PGF2α on myometrial contraction was evaluated because there is little information about the pathway signalling regulating these contractions. We used a peptidomimectic whose structure is based on the second extracellular loop of the FP receptor and who is an inhibitor of parturition in mice, the PDC113.824. Our results have demonstrated that PDC113.824 is able to delay parturition in mice, affecting multiple pathways activated by the FP receptor and PGF2α. PDC113.824 inhibited the PGF2α mediated activation of the Gα12 dependent activation of the RhoA-ROCK signalling pathway. RhoA and ROCK proteins are keys actors in the remodelling of actin cytosqueleton and in myometrial contractions. Furthermore, PDC113.824 with the presence of PGF2α acted positively by increasing the activation of the Gαq pathway. Our finding suggests that PDC113.824 is an allosteric modulator with dual actions, acting in a positive and negative way on the FP receptor signalling. In a second study, analogues of PDC113.824 were made and analysed in a second pathological model, colorectal cancer development and progression. Colorectal cancer seems to posses high levels of FP receptor but it is generally accepted that PGE2 promotes tumor growth, invasion and angiogenesis. However, little is known about the effect of PGF2α in colorectal cancer and only one report has suggested that this prostaglandin can stimulate motility and invasion. Its in this context, whether modulation of FP receptor function can impact colorectal tumors growth remains to be defined. Using our allosteric modulator, we investigated the contribution of FP receptor in the malignant progression of colorectal cancer. Our findings indicate that activation of FP receptors promote migration and proliferation of different human and murine colorectal cell lines. In this context, we demonstrated that this migration was dependent upon the activation of the Rho signalling pathway. Our results indicate that the activation of RhoA, a key small GTPase of the Gα12/13 pathway, is selectively inhibited by our compounds. We also showed that our allosteric modulator could act negatively on the β-catenin pathway, which is a protein with multiple effects on the progression of colorectal cancer. In vivo, treatment of mice with one this allosteric modulator is effective in inhibiting colorectal tumor growth in a xenograph mouse model. Together these findings suggest that PGF2α and the receptor FP, may play a considerable role in the development and progression of colorectal cancer.

<p>Allosteric modulators are emerging as a new class of therapeutics for the treatment of complex disorders, including psychiatric illnesses such as schizophrenia. The disease is marked by hyperdopaminergic signaling in the striatum, which plays a role in the development of positive symptoms like delusions, hallucinations, and paranoia. Conventional antipsychotic drug therapy typically employs dopamine D2 receptor antagonists that compete with endogenous dopamine at the orthosteric, or dopamine-binding site, in an attempt to normalize these psychotic symptoms. However, they are often associated with adverse motor and metabolic side effects. Furthermore, only some antipsychotic drugs are able to treat the negative symptoms of schizophrenia, which include social withdrawal and anhedonia, and there is currently no treatment for the cognitive impairment associated with the disease.</p> <p>Allosteric modulators are safer alternatives to conventional orthosteric therapeutics as they interact with their receptor at a novel binding site and their mechanism involves modulation of endogenous signaling. Therefore, levels of endogenous ligand limit the activity of an allosteric modulator. Our lab has synthesized and evaluated over 185 compounds for their activity at the dopamine D2 receptor. Of these compounds, PAOPA is the most potent allosteric modulator, and has been shown to be effective in treating the MK-801 induced preclinical animal model of schizophrenia without causing the adverse effects induced by currently prescribed antipsychotic drugs. The objective of this study was to evaluate PAOPA’s ability to treat behavioural abnormalities in an amphetamine-sensitized model of schizophrenia.</p> <p>Four groups (n=10/group) of male Sprague Dawley rats received intraperitoneal injections three days per week on alternate days over three weeks. Group A received saline, group B received D-amphetamine (1mg/kg during week one, 2mg/kg during week two, 3mg/kg during week three), group C received PAOPA (1mg/kg), and group D received the same doses of amphetamine as group B with PAOPA (1mg/kg). Following a three-week withdrawal, each group was tested for prepulse inhibition, social interaction, and locomotor activity. Amphetamine-sensitized rats were subjected to the same tests following PAOPA administration (1mg/kg). To assess whether behavioural changes were associated with changes in brain chemistry, post-mortem dopamine levels were measured in the striatum, nucleus accumbens, and medial prefrontal cortex. Data were analyzed by one-way ANOVA or paired t test where appropriate.</p> <p>Amphetamine sensitization induced schizophrenic-like behavioural abnormalities, including deficits in prepulse inhibition and social interaction, as well as increased locomotor activity and sensitivity to amphetamine challenge. Concurrent amphetamine and PAOPA treatment prevented all amphetamine- induced behavioural abnormalities. Furthermore, amphetamine-induced deficits in prepulse inhibition and social interaction were reversed one hour following PAOPA treatment. PAOPA treatment alone had no effect on behaviour or post-mortem striatal dopamine. Behavioural changes in amphetamine-sensitized rats were accompanied by a reduction in post-mortem striatal dopamine levels. In correlation with behavioural results, PAOPA administration during amphetamine sensitization prevented this biochemical change.</p> <p>These results demonstrate that PAOPA can prevent and reverse behavioural and associated biochemical abnormalities in amphetamine-sensitized rats. PAOPA is a candidate for the development of treatments for schizophrenia.</p> / Master of Science (MSc)