Schizophrenia is a serious psychiatric disorder that affects 1% of the population. Current theories implicate NMDA receptor hypofunction as a contributor to the symptomology and pathological alterations in schizophrenia. Cognitive impairments are increasingly recognized as not only fundamental to schizophrenia, but the strongest predictor of patient functional outcomes. Current antipsychotics do not improve the cognitive symptoms of the disorder; however, recent efforts have resulted in the identification of novel drug targets. One target is metabotropic glutamate receptors as they interact with and modulate NMDA receptors. Another approach focuses on dopamine, the neurotransmitter system targeted by traditional antipsychotics. Tetrahydroprotoberberines, such as D- and L-govadine, are synthetic compounds derived from traditional medicine that have demonstrated efficacy in treating schizophrenic symptoms. The present study assessed the effects of CDPPB (a metabotropic glutamate receptor 5 positive allosteric modulator), D- and L-govadine, and the typical antipsychotic haloperidol on the Paired Associates Learning (PAL) task in rats. The PAL task is impaired in patients with schizophrenia, has been adapted for use with rodents using touchscreen-equipped operant chambers, and has been promoted by MATRICS as a promising behavioural task with the potential to further translational health research in schizophrenia. The objectives of this study were: 1) examine the effects of acute NMDA receptor antagonism with MK-801 as a model for schizophrenia on performance of the PAL task; 2) test the effects of the putative antipsychotics, CDPPB and D- and L-govadine on reversing the effects of NMDA receptor antagonism on the task; and 3) to compare these novel therapeutics to a classic antipsychotic. Two squads of male Long-Evans rats were trained to perform the PAL task in touchscreen-equipped operant chambers. After the rats reached criterion the following treatment schedules were divided between the two squads: 1) vehicle (10% cyclodextrin; i.p.), and CDPPB (1.0, 3.0, and 10.0 mg/kg, i.p.); or 2) vehicle (10% cyclodextrin; i.p.), CDPPB (3.0 mg/kg, i.p.), the NMDA receptor antagonist MK-801 (0.15 mg/kg, i.p.), and CDPPB with MK-801; or 3) vehicle (50% DMSO; s.c.), MK-801, D-govadine (1.0 mg/kg; s.c.), L-govadine (1.0 mg/kg; s.c.) and MK-801 with each isomer of govadine; or 4) vehicle (sodium acetate and acetic acid, pH 5.0, s.c.), and haloperidol (0.05 and 0.1 mg/kg, s.c.). Acute MK-801 significantly reduced the number of trials completed, impaired accuracy, and increased the number of errors in the PAL task. CDPPB had no effect on the PAL task and did not improve the MK-801 induced impairments. Administration of L-govadine, but not D-govadine, prior to MK-801 improved accuracy and reduced errors compared to MK-801 alone. L-govadine alone, but not D-govadine, reduced total responding compared to vehicle. Haloperidol caused a dose-dependent decrease in all activity in the task confounding interpretation of the results in regard to cognition. These data establish disruptive effects of acute MK-801 treatment on PAL task performance and demonstrate that L-govadine is capable of cognitive enhancement in a rodent model of schizophrenia.

Deficits in working memory are typical symptoms in schizophrenia. The gene for the Dopamine Receptor 1 (DRD1) is one of the candidate genes for schizophrenia, and it is critical for memory function. Magnetic Resonance Imaging (fMRI) was used to detect neurocircuitries engaged during a behavioral task of subjects with chronic schizophrenia and healthy people. Multivariate analysis in particular Partial Least Squares, was adopted to quantitatively capture diagnosis-specific patterns. The brain-behavior analyses identified diagnosis-specific circuitries that included many cortical areas. Furthermore, we compared two groups of schizophrenics with different DRD1 genotype. The imaging-genetics analysis showed that covariance patterns of different areas (including the dorsolateral prefrontal cortex and the inferior parietal lobule) were inversely related between the two genotypes. Therefore, it appears that the speed in subjects' response may be indicative of diagnostic-specific networks, and that DRD1 genotype may suggest differential use of neural networks.

No description available.

M5 muscarinic receptors are associated with dopamine neurons of the ventral tegmental area (VTA) and substantia nigra, and provide an important excitatory input to the mesolimbic dopamine system. Here, I studied locomotion induced by systemic morphine (3, 10, 30 mg/kg, i.p.) in M5 knockout mice of the C57Bl/6 (B6) and CD1 x 129SvJ (129) background strains. M5 knockout mice of both strains showed reduced locomotion in response to 30 mg/kg morphine, while only B6 M5 knockout mice showed reduced locomotion in response to 10 mg/kg morphine. In B6 wild-type mice VTA pre-treatment with the non subtype-selective muscarinic receptor antagonist atropine (3 mg per side), but not the non subtype-selective nicotinic receptor antagonist mecamylamine (5 mg per side), reduced locomotion in response to 30 mg/kg (i.p.) morphine to a similar extent as systemic M5 knockout, suggesting that the reduced morphine-induced locomotion in M5 knockout mice was due to the loss of M5 receptors on VTA dopamine neurons. By contrast, in M5 knockout mice, either intra-VTA atropine or mecamylamine alone increased locomotion by almost 3 times relative to saline, and potentiated morphine-induced locomotion. Therefore, in M5 knockout mice, more clearly than in wild-type mice, blockade of either VTA muscarinic or nicotinic receptors activated locomotion. Infusions of morphine (50 ng) into the VTA increased nucleus accumbens dopamine efflux in urethane-anesthetized wild-type mice. Either M5 knockout or pre-treatment with VTA scopolamine (50 ug) in wild-type mice blocked accumbal dopamine efflux in response to VTA morphine. Therefore, M5 receptors are critical for excitation of dopamine neurons by intra-VTA morphine, suggesting that the reduced locomotion produced by systemic morphine in M5 knockout mice was, in part, due to loss of M5-mediated excitation of VTA dopamine neurons by opiates. The locomotion data also show that in the absence of M5 receptors, cholinergic afferents to mesolimbic dopamine neurons are inhibitory. This supports and extends the conclusions from many studies that non-M5 muscarinic receptors inhibit, and M5 receptors excite, dopamine neurons. Loss of M5-mediated excitation results in reduced acute effects of opiates.

Dopamine D3 receptors (DRD3) are implicated in relapse to drugs. The current study investigated the role of DRD3 in cue-induced reinstatement of nicotine-seeking in rats. Rats were trained to lever-press for intravenous infusions of nicotine, associated with the illumination of a cue-light, under a fixed-ratio schedule of reinforcement. Following extinction of the behaviour, where lever pressing had no consequences, reinstatement testing was performed by reintroduction of the cues after systemic or local administration (into discrete brain areas) of the DRD3 selective antagonist SB277011-A. Systemic antagonism of DRD3 significantly attenuated cue-induced reinstatement of nicotine-seeking. The same effect was observed upon infusions of SB277011-A into the basolateral amygdala or the lateral habenula, but not the nucleus accumbens. The current findings implicate DRD3 in cue-induced reinstatement of nicotine, delineate some of the neural substrates underlying this role and support a potential for using selective DRD3 antagonists for the prevention of relapse to smoking.

M5 muscarinic receptors are associated with dopamine neurons of the ventral tegmental area (VTA) and substantia nigra, and provide an important excitatory input to the mesolimbic dopamine system. Here, I studied locomotion induced by systemic morphine (3, 10, 30 mg/kg, i.p.) in M5 knockout mice of the C57Bl/6 (B6) and CD1 x 129SvJ (129) background strains. M5 knockout mice of both strains showed reduced locomotion in response to 30 mg/kg morphine, while only B6 M5 knockout mice showed reduced locomotion in response to 10 mg/kg morphine. In B6 wild-type mice VTA pre-treatment with the non subtype-selective muscarinic receptor antagonist atropine (3 mg per side), but not the non subtype-selective nicotinic receptor antagonist mecamylamine (5 mg per side), reduced locomotion in response to 30 mg/kg (i.p.) morphine to a similar extent as systemic M5 knockout, suggesting that the reduced morphine-induced locomotion in M5 knockout mice was due to the loss of M5 receptors on VTA dopamine neurons. By contrast, in M5 knockout mice, either intra-VTA atropine or mecamylamine alone increased locomotion by almost 3 times relative to saline, and potentiated morphine-induced locomotion. Therefore, in M5 knockout mice, more clearly than in wild-type mice, blockade of either VTA muscarinic or nicotinic receptors activated locomotion. Infusions of morphine (50 ng) into the VTA increased nucleus accumbens dopamine efflux in urethane-anesthetized wild-type mice. Either M5 knockout or pre-treatment with VTA scopolamine (50 ug) in wild-type mice blocked accumbal dopamine efflux in response to VTA morphine. Therefore, M5 receptors are critical for excitation of dopamine neurons by intra-VTA morphine, suggesting that the reduced locomotion produced by systemic morphine in M5 knockout mice was, in part, due to loss of M5-mediated excitation of VTA dopamine neurons by opiates. The locomotion data also show that in the absence of M5 receptors, cholinergic afferents to mesolimbic dopamine neurons are inhibitory. This supports and extends the conclusions from many studies that non-M5 muscarinic receptors inhibit, and M5 receptors excite, dopamine neurons. Loss of M5-mediated excitation results in reduced acute effects of opiates.

Dopamine D3 receptors (DRD3) are implicated in relapse to drugs. The current study investigated the role of DRD3 in cue-induced reinstatement of nicotine-seeking in rats. Rats were trained to lever-press for intravenous infusions of nicotine, associated with the illumination of a cue-light, under a fixed-ratio schedule of reinforcement. Following extinction of the behaviour, where lever pressing had no consequences, reinstatement testing was performed by reintroduction of the cues after systemic or local administration (into discrete brain areas) of the DRD3 selective antagonist SB277011-A. Systemic antagonism of DRD3 significantly attenuated cue-induced reinstatement of nicotine-seeking. The same effect was observed upon infusions of SB277011-A into the basolateral amygdala or the lateral habenula, but not the nucleus accumbens. The current findings implicate DRD3 in cue-induced reinstatement of nicotine, delineate some of the neural substrates underlying this role and support a potential for using selective DRD3 antagonists for the prevention of relapse to smoking.

Parkinson’s disease is a common neurodegenerative disorder caused by nigrostriatal dopamine loss, with motor deficiencies as the primary outcome. To increase the striatal dopamine content, patients are treated with 3,4-dihydroxyphenyl-l-alanine (l-DOPA). Beneficial relief of the motor symptoms is achieved initially, although the efficacy is lost with time and severe side effects, referred to as l-DOPA-induced dyskinesia, manifest in the majority of patients. Biological mechanisms responsible for the dopaminergic degeneration and the upcoming of dyskinesia are still unclear, and thus knowledge regarding critical factors for maintenance of the nigrostriatal system as well as neurochemical changes upon chronic l-DOPA is urgent. The present work aims at studying the importance of glial cell line-derived neurotrophic factor (GDNF) for nigrostriatal preservation, and the involvement of the dopaminergic, serotonergic, and glutamatergic systems in l-DOPA-induced dyskinesia. Effects from different levels of GDNF expression were evaluated on fetal mouse nigrostriatal tissue in a grafting study. In GDNF gene-deleted grafts, degeneration of the entire nigrostriatal system was evident at 6 months. In grafts with partial GDNF expression, significant loss of dopamine neurons was observed at later time points, although deviant findings in the dopamine integrity such as reduced innervation capacity and presence of intracellular inclusions-like structures were already present at earlier stages. The results emphasize GDNF as a crucial factor for long-term maintenance of the nigrostriatal system. Furthermore, striatal neurochemical alterations upon chronic l-DOPA treatment were studied in hemiparkinsonian rats using in vivo voltametry. The findings demonstrated impaired dopamine as well as glutamate releases in dyskinetic subjects, with no effects from acute l-DOPA administration. Conversely, in l-DOPA naïve dopamine-lesioned animals, dopamine release was increased and glutamate release attenuated upon a l-DOPA challenge. Moreover, l-DOPA-derived dopamine release was demonstrated to originate from serotonergic nerve fibers in the dopamine-lesioned striatum, an event that contributes significantly to dopamine levels also in intact striatum, and thus, is not a consequence from dopamine depletion. Assessment of serotonergic nerve fibers in l-DOPA treated animals and in a grafting study concluded that nerve fiber density was not affected by chronic l-DOPA treatment, nevertheless, dysfunction of this system can be suspected in dyskinetic animals since dopamine release was impaired and regulation of glutamate release by serotonergic 5-HT1A receptor activation was achieved in normal but not in dyskinetic animals. Furthermore, the selective serotonin reuptake inhibitor, fluoxetine, attenuated l-DOPA-induced dyskientic behavior, an effect that was demonstrated to be mediated via 5-HT1A receptors. In conclusion, dysmodulation of multiple transmitter systems is evident in LID.

While studies have examined risk factors and consequences of child maltreatment in general, relatively few have focused specifically on neglect, especially maternally perpetrated child neglect. This is despite evidence that neglect is the most common and most rapidly increasing form of maltreatment, with some of the most serious long-term effects on child development. Maternal neglect constitutes a substantial disturbance in the mother-child relationship. For this reason, after establishing the epidemiology of neglect at a population level, this thesis examines the neurobiology of patterns of mother-infant attachment using functional MRI. Disturbance in mother-infant attachment, in conjunction with family, social and societal risk and protective factors, constitutes the likely pathway to maternal neglect. Specific objectives were: 1) to describe the magnitude of the problem of maternal neglect in Australia, using longitudinal population-based studies; 2) to identify risk and protective factors associated with neglect, both in a high risk population of extremely low birth weight (ELBW) infants and a representative birth cohort; 3) to specifically explore whether breastfeeding was protective against maternally perpetrated neglect; 4) to examine the consequences of child neglect on infant cognitive development and head growth; and 5) to determine how maternal brain and endocrine responses differ according to patterns of adult attachment security. In Part A, two cohort studies examined the epidemiology of child abuse and neglect among mothers and their infants born at the Mater Mothers’ Hospital in Brisbane, Australia. Cohort databases were confidentially linked with official notifications of child abuse and neglect. The first cohort included 353 ELBW infants who were assessed at birth and at 1, 2 and 4 years of age. The second cohort included 7223 children whose mothers were enrolled prenatally into the Mater-University of Queensland Study of Pregnancy (MUSP), where data were collected at birth, 6 months, and 5 and 14 years. The initial ELBW study examined all reported notifications of neglect, while the MUSP study focused particularly on substantiated maternally perpetrated neglect and the protective effect of breastfeeding. These studies examined a broad range of social and biological predictors. Outcome variables for child neglect were examined in the ELBW cohort using cognitive z-scores and growth parameters. Analytic techniques included multivariate modelling. In Part B, the neurobiology of mother-infant attachment was examined by monitoring a cohort of 61 first-time mothers from Houston, Texas, over 4 study visits. The mothers’ attachment classifications were determined during pregnancy using the Adult Attachment Interview. At 6 months, mother-infant pairs were videotaped, and serum oxytocin measures collected before, during and after interaction. At 10 months, the mothers viewed pictures of their own and unknown infants during functional MRI scanning. The first report examined the brain responses of 28 mothers to happy, neutral and sad infant face cues. The next compared brain responses of 15 mothers with “secure” attachment patterns to 15 “insecure/dismissing” mothers, and also examined differences in peripheral oxytocin response to mother-infant interaction. Data were analysed using a general linear model and repeated measures ANOVA. Overall, more than 1 in 10 children were reported for suspected child maltreatment, 3-5% as a result of substantiated neglect and 3% with maternally perpetrated neglect, with higher rates seen in the ELBW cohort. Duration of breastfeeding was inversely associated with the odds of maternal neglect, with non-breastfeeding mothers almost 4 times more likely to neglect their child compared to mothers who breastfed for 4 or more months, after adjusting for covariates. Other significant risk factors for substantiated maternal neglect included low education, young maternal age, and race, which were also significant univariate predictors in the ELBW population. ELBW children exposed to neglect showed a progressive decline in cognitive functioning over the first 4 years of life, as well as a significantly reduced head circumference at 2 and 4 years. When mothers viewed their own infant’s faces, compared with an unknown infant, key dopamine-associated reward processing regions of the brain were activated, including the midbrain’s ventral tegmental area/substantia nigra, striatum and prefrontal cortex. Mothers with an insecure/dismissing type of attachment showed significantly less activation of these reward regions in response to both happy and sad own-infant faces. On viewing their own infant’s crying faces, these mothers showed activation of the anterior insula, a region involved in feelings of unfairness, pain and disgust. “Secure” mothers showed greater peripheral oxytocin responses during mother-infant interaction, which were correlated with activation of the pituitary/hypothalamic region of the brain, where oxytocin is produced and secreted. These findings confirm the magnitude of neglect as a public health concern, with identifiable consequences and specific risk and protective factors. The neurobiological studies identify neuroendocrine systems associated with mother-infant responses and patterns of adult attachment. Together, these studies theoretically link secure mother-infant attachment with brain reward activation and oxytocin response, breastfeeding success, and a reduced risk for maternal neglect. Implications for prevention and intervention, and future research plans, are discussed.

Typescript. / Thesis (PhD)--Macquarie University (Division of Environmental & Life Sciences, Dept. of Chemistry & Biomolecular Sciences), 2005. / Includes bibliographical references. / Microelectrode voltammetry -- Experimental -- Microelectrode fabrication -- Characterisation of the carbon film surface: Surface stability - X-ray photoelectron spectroscopy - Raman spectroscopy - Capacitance - Edge plane concentration - Potential window - Surface concentration of alkenes and alkynes - Outer sphere electron transfer using hexaamineruthenium (III) chloride - Reduction of potassium hexacyanoferrate (III) - Anodic oxidation: diol to dione; dopamine and ascorbic acid - Surface oxidation - Ferrocene in a non aqueous solvent -- Selectivity: Formation of carboxylic acid groups on a carbon film surface by ferrous II sulfate complex oxidation - Ethanol modified carbon film surface - Modification of carbon film microelectrode surface using aromatic amines - Modification of carbon film surfaces to form a dual functional ascorbic acid barrier -- In vivo anti fouling properties of surface modified carbon film microelectrodes -- Conclusion. / In this thesis a procedure is presented for the fabrication of a microelectrode to monitor the neurotransmitter dopamine in vivo. The microelectrodes are fabricated by in situ pyrolysis of acetylene under a nitrogen blanket onto a quartz capillary. The carbon film was then anodically oxidised in the presence of 2,4-dinitroaniline. These microelectrodes are stable, provide the physical strength to penetrate brain tissue, have a low capacitance, are resistant to fouling in vivo and selectively suppress the endogenous ascorbic acid which oxidises at the same potential as dopamine. With such properties the carbon film microelectrode appears ideally suited for fast scanning cyclic voltammetric studies of cationic neurotransmitters such as dopamine in vivo. / xxviii, 323 p. ill