No description available.

It has been estimated that approximately 300,000 Canadians are afflicted with schizophrenia (SCZ). Due to the severity of symptoms as well as critical age of onset, the quality of life among SCZ patients can be poor; thus, further therapeutic research is of great interest. In addition to the more-common rodent models of SCZ (amphetamine sensitization, PCP sensitization, etc.), our lab has proposed the medial prefrontal cortex (mPFC) synapsin-II knockdown (KD) model. Prior to this study, the cognitive effects of mPFC synapsin-II KD had yet to be reported. Using a 14-day continuous infusion of antisense (AS) deoxyoligonucleotides for synapsin-II to the mPFC, the results of the KD model have been recreated for further study. The 5-choice-serial-reaction-time-task was utilized to determine the effects of mPFC synapsin-II KD on attention and vigilance. In addition to reductions in both PPI (p<0.05) and social interaction (p<0.05), as well as hyper-locomotion (p<0.05); rats treated with synapsin II AS performed significantly worse on the 5-CSRTT than did control (mismatch/aCSF) animals. The AS animals were significantly less likely to make correct responses (p<0.001), and significantly more likely to commit omissions (p<0.0001) and perseverative responses (p<0.05) than were control animals. Additionally, an [18F]FDG tracer and PET/CT scans were used to determine differences in brain metabolism due to synapsin-II KD. Results revealed significant reductions in [18F]FDG among AS treated rats (p<0.05) when compared to control animals. This reduction appeared to be a global result, however it followed 13-days of treatment which may account for the widespread effect. The mPFC synapsin-II KD model of SCZ has showcased cognitive and metabolic effects similar to that of SCZ. These findings, in conjunction with past research, provide evidence for the synapsin-II KD model as a viable rodent model of SCZ. Further research utilizing this model will provide valuable insight into the pathogenesis of SCZ and potential therapeutics. / Thesis / Master of Health Sciences (MSc)

The present thesis examined the relative contribution of dopamine (DA) receptors in the brain and periphery in the control of sucrose intake. Intraperitoneal (ip) administration of pimozide, an antagonist at peripheral and brain DA receptors, suppressed both sham and real sucrose intake in a dose-related manner. In contrast, ip injections of the peripheral DA antagonist domperidone affected neither sham nor real sucrose intake. The inability of domperidone to influence sucrose intake did not result from a lack of biological activity because doses of domperidone that did not alter sucrose intake significantly inhibited gastric acid secretion. The results indicate that central, but not peripheral DA receptors are involved in the control of feeding of sucrose solutions and that sham sucrose intake appears to be more sensitive to disruption of DA activity than real sucrose intake. / Thesis / Master of Science (MSc)

Yes / Background: Presently, there is limited guidance on the maximal dosing of psychosis drugs that is based on effectiveness rather than safety or toxicity. Current maximum dosing recommendations may far exceed the necessary degree of dopamine D2 receptor blockade required to treat psychosis. This may lead to excess harm through cognitive impairment and side effects. Aims: This analysis aimed to establish guidance for prescribers by optimally dosing drugs for psychosis based on efficacy and benefit. Methods: We used data from two dose–response meta-analyses and reviewed seven of the most prescribed drugs for psychosis in the UK. Where data were not available, we used appropriate comparison techniques based on D2 receptor occupancy to extrapolate our recommendations. Results: We found that the likely threshold dose for achieving remission of psychotic symptoms was often significantly below the currently licensed dose for these drugs. We therefore recommend that clinicians are cautious about exceeding our recommended doses. Individual factors, however, should be accounted for. We outline potentially relevant factors including age, ethnicity, sex, smoking status and pharmacogenetics. Additionally, we recommend therapeutic drug monitoring as a tool to determine individual pharmacokinetic variation. Conclusions: In summary, we propose a new set of maximum target doses for psychosis drugs based on efficacy. Further research through randomised controlled trials should be undertaken to evaluate the effect of reducing doses from current licensing maximums or from doses that are above our recommendations. However, dose reductions should be implemented in a manner that accounts for and reduces the effects of drug withdrawal.

Dans le cadre de la production de nouvelles espèces aquacoles, le sandre, Sander lucioperca, est devenu, depuis plusieurs années, une espèce d’intérêt piscicole en raison de sa valeur économique potentielle. Pour développer et pérenniser sa production aquacole, il est nécessaire de comprendre et maîtriser son cycle de reproduction ainsi que les mécanismes physiologiques mis en jeu afin d’obtenir des œufs et des juvéniles viables tout au long de l’année. Dans cet optique d’optimisation du contrôle du cycle, la dopamine apparaît, chez de nombreux téléostéens dont certains perciformes, comme un inhibiteur de l’axe gonadotrope, via les récepteurs de la famille D2, en bloquant le pulse ovulatoire de LH et l’ovulation. Chez le sandre, le rôle de la dopamine et de ses récepteurs, notamment les récepteurs de la famille D1, est inconnu. L’objet de cette thèse est de déterminer le rôle du système dopaminergique lors des phases finales de l’ovogénèse chez le sandre à travers trois axes principaux : (1) déterminer l’effet du blocage des récepteurs de la dopamine, D1 ou D2, sur la régulation de l’axe gonadotrope et l’induction de l’ovulation en absence et en présence d’une molécule de sGnRHa, (2) définir le répertoire et le profil d’expression des récepteurs dopaminergiques par l’étude du transcriptome cérébral du sandre en période pré-ovulatoire et (3) établir le rôle de la dopamine et de ses différents récepteurs (familles D1 et D2) dans la régulation directe et locale de l’axe gonadotrope aux niveaux cérébral et ovarien. La première partie de ce travail a permis pour la première fois, par l’utilisation d’antagonistes spécifiques des familles de récepteurs D1 et D2, de mettre en évidence un rôle potentiel de la dopamine sur la sécrétion de certains stéroïdes sexuels en période pré-ovulatoire chez le sandre par l’intermédiaire des récepteurs de la famille D1. L’identification de l’ensemble des récepteurs de la dopamine existant chez le sandre nous a permis de confirmer leur expression à tous les niveaux de l’axe gonadotrope (cerveau, hypophyse et ovaires) étayant l’hypothèse d’un rôle de la dopamine dans la reproduction du sandre. Enfin, la dernière partie de ce projet a permis de montrer un rôle régulateur du système dopaminergique, directement au niveau ovarien, sur la production de testostérone par l’intermédiaire des deux familles de récepteurs de la dopamine. L’implication des deux familles de récepteurs a également été mise en évidence dans la production ovarienne de la 17β-estradiol. Au niveau cérébral, seule la famille des récepteurs D2 a été montrée impliquée dans la régulation de l’expression du gène de la GnRH-3. De façon générale, cette étude a permis de mettre en évidence l’implication des récepteurs de la dopamine dans la régulation de l’axe gonadotrope lors des phases finales de l’ovogenèse. Toutefois, des travaux ultérieurs devront être menés pour approfondir les mécanismes physiologiques mis en jeu. D’un point de vue aquacole, les traitements hormonaux à base d’antagonistes des récepteurs de la dopamine ont été inefficaces pour améliorer les performances de reproduction du sandre ce qui n’est pas en faveur de leur utilisation future pour induire l’ovulation chez cette espèce. Ainsi, la mise au point d’autres méthodes d’optimisation sera nécessaire pour continuer à développer la production aquacole du sandre / Pikeperch, Sander lucioperca, is a potential valuable economic fish, making it a species of interest for aquaculture diversification. In the domestication process, controlling and understanding the reproductive cycle is a crucial step in order to produce viable offspring in a synchronous and predictable way. In many teleosts including some perciforms, dopamine inhibits the ovulatory pulse of LH and the ovulation step through D2 dopamine receptors family. In pikeperch, the roles of dopamine and its receptors, especially those belonging to the D1 receptors family, are unknown. For the purpose of the optimization of pikeperch reproduction, we investigated the role of the dopaminergic system during the final stages of oogenesis in this species: (1) by determining the effects of D1 or D2 receptor antagonists alone or in association with sGnRHa on the regulation of the reproductive axis and on the induction of ovulation, (2) by determining the repertoire and the expression profile of the dopamine receptors using a brain transcriptome analysis during the pre-ovulatory period and (3) by evaluating the role of dopamine and its receptors (D1 and D2 families) in the direct and local regulation of the gonadotropic axis at the brain and ovarian levels. For the first time, we showed that the dopamine/D1 receptors complex regulates the sex-steroids release during the pre-ovulatory period, suggesting that dopamine is involved in pikeperch reproduction. Also, we support its involvement thanks to the identification of the dopamine receptors gene expression at the brain, pituitary and ovarian levels. Finally, we showed that the dopaminergic system directly regulates the ovarian testosterone production, through both D1 and D2 receptor families. The involvement of both dopamine receptor families was also highlighted on ovarian 17β-estradiol production. Only the D2 receptor family was shown to be involved on the brain GnRH-3 gene expression. In conclusion, we point out a dopamine receptors implication on the gonadotropic axis regulation during the final stages of oogenesis in pikeperch. However, further studies should be performed to pinpoint the physiological mechanisms behind this phenomenon. From an aquaculture point of view, hormonal treatments with dopamine receptor antagonists appear to be ineffective to improve pikeperch reproductive performances. Therefore, their use to induce pikeperch ovulation should be put into question and the development of alternative methods is necessary to further promote pikeperch production

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 138-142).

No description available.

Previous reports have indicated that prenatal, but not postnatal, haloperidol impairs the ontogenic development of striatal dopamine D-2 receptors. In the present study a specific D-2 receptor antagonist, spiroperidol (1.0 mg/kg i.p.) and/or a specific D-1 receptor antagonist, SCH 23390 (0.30 mg/kg i.p.), was administered to rats for 32 successive days from birth. Postnatal spiroperidol and SCH 23390 treaments markedly impaired the development of striatal dopamine D-2 and D-1 receptors, respectively, at 12 weeks after birth. Spiroperidol did not affect D-1 receptor development and did not modify the effect of SCH 23390 treatment. Also, SCH 23390 did not affect D-2 receptor development and did not modify the effect of spiroperidol treatment. When rats with impaired development of striatal D-2 receptors were challenged at 12 weeks with spiroperidol (1.0 mg/kg per day i.p. × 17 days) D-2 receptors did not up-regulate. However, when rats with impaired development of striatal D-1 receptors were challenged at 12 weeks with SCH 23390 (0.30 mg/kg per day i.p. × 17 days) D-1 receptors did up-regulate. These findings demonstrate that postnatal treatment with D-1 and D-2 receptor antagonists can permanently impair the development of striatal D-1 and D-2 receptors. Moreover, the ability of developmentally impaired striatal D-1 receptors to up-regulate in adulthood appears to be greater than that for the developmentally impaired striatal D-2 receptors.

No description available.

The mesoaccumbens dopamine system has been implicated in many basic psychological processes (e.g. "wanting" and "liking") and illnesses (e.g. addiction, depression, schizophrenia). However, the precise computational functions of nucleus accumbens and dopamine neurons within the system remain unknown. In this thesis, we test some of the current hypotheses regarding the function of this system using a behavioural neurophysiology approach in the rat. The first question we wanted to answer was whether nucleus accumbens neurons process reward-predictive stimuli (e.g. conditioned reinforcers) and reward delivery differently, since previous studies report equivocal findings. To do so, we trained thirsty rats to bar-press on a second-order schedule of saccharin reinforcement, within which the temporal pattern of rats' bar-pressing was reinforced by presentations of a conditioned reinforcer and primary reinforcer (reward). We found that nucleus accumbens neurons typically responded to these conditioned and primary reinforcers with opposite sign, which suggests they were processed differently. We were not sure whether responses to conditioned reinforcers encoded reward-prediction or facilitated a behavioural switch in the rat's behaviour. Indeed, since studies using a variety of experimental techniques have implicated the mesoaccumbens dopamine system in both reward prediction and behavioural switching, we sought to test whether neurons in the nucleus accumbens and dopamine-rich areas of the midbrain respond to outcome-associated stimuli to predict reward or switch behaviour. We found both sets of neurons predominantly did the former. Finally, to understand more about reward consummatory responses from both sets of neurons, we developed a rat behavioural task providing measures of reward "wanting" and "liking". In conclusion, on the basis of our data, the most parsimonious explanation for the function of the mesoaccumbens dopamine system is that it acts to modulate goal-seeking behaviour. Further research is required to identify the function of the interactions between nucleus accumbens and dopamine neurons during goal-seeking and goal consumption.