The complex heterogeneity of schizophrenia has proved difficult to replicate in preclinical animal models. Of the many molecular targets implicated with schizophrenia, this thesis focuses on synapsin II - a pre-synaptic protein critical for neurotransmission and synaptogenesis; and parvalbumin - a calcium-binding protein found in interneurons of the dorsolateral prefrontal cortex (DLPFC) and the striatum (STR). Patients with schizophrenia display reduced levels of synapsin II mRNA in the DLPFC, while decreased activation of parvalbumin neurons in the same region has resulted in schizophrenia-like cognitive deficits. Knockdown of synapsin II in the medial prefrontal cortex (mPFC) of neonate and adult rats has previously induced schizophrenia-like alterations. However, there are concerns that must be addressed before novel animal models of schizophrenia can be developed using reductions in synapsin II. This thesis was designed to 1) eliminate maternal separation (MS) between post-natal days (PD) 14-23, which correlates with a neurodevelopmental synapsin II model, as a means of inducing schizophrenia-like behaviours; 2) reassess the use of fully and partially phosphorothioated first-generation antisense oligonucleotides to reduce synapsin II levels, and 3) evaluate parvalbumin expression in the STR following synapsin II knockdown. Results from this study indicate 1) a 36 hour MS regimen during PD 14-23 did not cause behavioural changes bearing resemblance to schizophrenia; 2) oligonucleotide sequences stabilized completely with phosphorothioate bonds were insufficient in reducing synapsin II levels and caused localized necrosis, while partially modified sequences induced a slight knockdown effect without cell death; and 3) levels of striatal parvalbumin expression were decreased in rats receiving the partially, but not fully, modified antisense sequences. The findings strengthen the face validity and safety profile of the synapsin II knockdown model. Novel evidence has also been provided for the role of parvalbumin in the striatum and suggests its influence on cognitive dysfunction in schizophrenia. / Thesis / Master of Science (MSc)

Synapsins are primarily neuron-specific proteins critical for neurotransmission, synaptogenesis and synapse maintenance. Synapsin II has been specifically linked with increased susceptibility towards developing schizophrenia. Reduced synapsin II mRNA levels were found in the dorsolateral prefrontal cortex (PFC) of patients with schizophrenia. Moreover, synapsin II knockdown in the medial PFC (mPFC) of the adult rat was previously shown to cause schizophrenia-like behaviour and altered expression levels of vesicular proteins involved in glutamatergic and GABAergic signaling within the mPFC. The study of schizophrenia in recent years has shifted to focus on neurodevelopmental players which influence disease outcome. This study was designed to establish the link between neurodevelopmental dysregulation of synapsin II and schizophrenia. Specific knockdown of synapsin II was performed in the mPFC at postnatal day (PD) 7 and PD 17-23. Schizophrenia-like behavioural abnormalities were assessed at pre-pubertal (PD 32-35) and post-pubertal (PD 65-70) stages. Protein estimation of vesicular transporters involved in glutamate, GABA, and dopamine neurotransmitter systems were also assessed in the mPFC. Results from this study indicate (1) synapsin II knockdown during PD 17-23, but not PD 7, caused lasting schizophrenia-like abnormalities (2) abnormalities exhibited permanence at pre-pubertal and post-pubertal stages, and manifested as a function of brain development, (3) behavioural abnormalities were reminiscent of symptoms in established animal models of schizophrenia (i.e. deficits in prepulse inhibition, social withdrawal, locomotor hyperactivity), (4) neurodevelopmental synapsin II alterations induced hypoactive glutamatergic activity through decreased synapsin IIa expression levels (pre-pubertal) and decreased VGLUT-2 expression levels (post-pubertal), and (5) acute olanzapine treatment effectively attenuated schizophrenia-like abnormalities through normalized synapsin IIa expression levels (pre-pubertal) and increased GAD65/67 expression levels (post-pubertal). Results show the causal link between synapsin II expression during critical neurodevelopmental stages and schizophrenia. Additionally, evidence has been provided for the face, construct, and predictive validities of this newly developed animal model of schizophrenia. / Thesis / Doctor of Philosophy (PhD)

Schizophrenia (SCZ) is a debilitating mental illness that affects roughly 1% of the world's population. Current theories about the etiology of this disease highlight disruptions in dopamine (DA) and glutamine. However, a more recent theory, the 'synaptic hypothesis' proposes that the fundamental pathology of this illness involves disruptions in synaptic transmission. The synapsins are a family of neuron specific phosphoproteins that play an important role in neurotransmitter release, synapse formation and maintaining a reserve pool of synaptic vesicles. Previous research has suggested that synapsin II has a role in the etiology of SCZ. For example, synapsin II mRNA is significantly reduced in the medial prefrontal cortex (MPFC) of patients, and synapsin II knockout mice display a variety of behavioural abnormalities which mimic human SCZ. Considering that SCZ may result from changes in the synapse, we wanted to further elucidate the role of synapsin II by measuring protein expression in post-mortem PFC samples. Overall, our results revealed that synapsin IIa and IIb are not significantly different between patients and controls, however, we hypothesize that synapsin II expression has been normalized in patients due to antipsychotic drug (APD) use. In fact, we discovered that treatment with atypical APDs significantly increases synapsin II in the prefrontal cortex (PFC) of patients, which may underlie the beneficial effects of these drugs. Another objective of our work was to investigate the expression of various presynaptic proteins in post-mortem samples from patients with Parkinson's disease (PD) Parkinson's disease, like SCZ, is an illness which involves dysregulated dopaminergic transmission and synaptic dysfunction. Therefore, we hypothesized that synapsin II might also be disrupted in patients with PD. Our results demonstrated that synapsin IIa and IIb are significantly reduced in the substantia nigra (SN), but not the striatum (STR) or PFC of patients, when compared to controls. Further, no changes were observed in the other synapsins (I or III), or synaptophysin, which suggests that synapsin II dysregulation may be specific to disorders which involve disruptions in dopamine (DA). / Thesis / Master of Science (MS)

Disorders of the central nervous system (CNS) continuously pose problems for current therapeutics. In part, this is due to the uncertainty of underlying pathophysiological changes that give rise to specific disorders. Parkinson’s disease (PD) specifically is a neurodegenerative CNS disorder with unknown origins of dopaminergic degeneration in the substantia nigra. Current therapies are reactive in nature and no existing neuroprotective therapies are available. Two hypotheses have been proposed to contribute to dopaminergic degeneration in PD: endoplasmic reticulum (ER) stress and oxidative stress. This thesis investigates molecular targets involved in each of these responses (mesencephalic astrocyte-derived neurotrophic factor (MANF) and cyclin-dependent 5 (CDK5)/p25 respectively) to support a multi-hit hypothesis in PD neural degeneration. Using behavioural and biochemical analysis, a reduction in MANF was found to participate in the ER stress hypothesis and CDK5/p25 hyperactivation is a viable neuroprotective target related to the oxidative stress hypothesis. Both pathways are evidenced in PD pathology and this thesis proposes specific targets for both pathways in the development of necessary neuroprotective therapies. Subsequently, included in this thesis is a chapter about the unmet pharmacological alleviation of negative and cognitive symptom domains in another CNS disorder of unknown pathophysiology: schizophrenia (SZ). These untreated symptoms are thought to be caused by irregularities in the signalling of multiple neurotransmitter systems. This chapter investigates the role of synapsin II, a protein involved in regulating signalling of multiple neurotransmitters, in manifesting negative and cognitive SZ symptoms and analyzes brain glucose metabolism. Reduced synapsin II levels were consistently implicated in the underlying physiology, and therefore synapsin II is proposed as a potential pharmacological target for these unmedicated symptomologies. Overall this thesis uses interrelated studies to propose novel molecular targets to address unmet therapeutic needs based on evidence of their involvement in the pathophysiology of PD and SZ. / Thesis / Doctor of Philosophy (PhD) / Brain diseases like Parkinson’s disease (PD) and Schizophrenia (SZ) are difficult to treat because their cause has not been discovered. PD shows degeneration of cells in the brain but the cause for degeneration is unknown. This makes developing treatments to protect cells from dying difficult. Two pathways are suggested to cause cell death in PD. This thesis proposes that both pathways are responsible for degeneration through a combined effort. Here, both pathways are shown to lead to cell death resembling PD and specific molecules are suggested as targets for developing protective treatments. Like PD, SZ has symptoms that cannot be treated because the cause is unclear. A protein was investigated for producing SZ-like symptoms and found to have potential for treatment design. This thesis aims to understand molecular changes in the brain leading to PD, with a look at SZ and how they can be used for better treatment design.