Thesis (M.S.)--University of Nevada, Reno, 2008. / "August, 2008." Includes bibliographical references (leaves 20-23). Online version available on the World Wide Web.

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 98-115).

Thesis (Ph. D.)--Florida State University, 2005. / Advisor: Dr. Marc E. Freeman, Florida State University, Program in Neuroscience. Title and description from dissertation home page (viewed June 8, 2005). Document formatted into pages; contains xi, 172 pages. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (PhD) - Swinburne University of Technology, Faculty of Life and Social Sciences, Brain Sciences Institute, 2008. / A thesis for Doctorate of Philosophy, Brain Sciences Institute, Faculty of Life and Social Sciences, Swinburne University of Technology - 2008. Typescript. Includes bibliographical references (p. 193-250).

Thesis (Ph. D.)--Illinois State University, 2001. / Title from title page screen, viewed April 13, 2006. Dissertation Committee: Paul A. Garris (chair), John E. Baur, Hou T. Cheung, Maarten E.A. Reith, David L. Williams. Includes bibliographical references (leaves 170-186) and abstract. Also available in print.

The striatum is the major input structure of the basal ganglia, and is composed of two major populations of spiny projection neurons (MSNs), which give rise to the socalled direct and indirect pathways, and several types of interneuron. Dopaminergic inputs to striatum are critical for its proper function. Indeed, loss of dopaminergic neurons in Parkinsonism leads to motor disturbances, grossly disturbs striatal activity, and is associated with the emergence of excessively-synchronized network oscillations at beta frequencies (15-30 Hz) throughout the basal ganglia. How the distinct structural, neurochemical and other properties of striatal neurons are reflected in their firing rates and patterns in vivo is poorly defined, as are their possible cell-type-selective contributions to the aberrant oscillations arising in the Parkinsonian brain. To address these issues, I first used multi-electrode arrays to record the spontaneous firing of ensembles of neurons in dorsal striatum in both anaesthetised dopamine-intact and Parkinsonian (6-hydroxydopamine-lesioned) rats during two well-defined brain states, slow-wave activity (SWA) and spontaneous activation. The chronic loss of dopamine led to an overall increase in the average firing rates of striatal neurons, irrespective of brain state. However, many neurons in the Parkinsonian striatum still exhibited the low firing rates and irregular firing patterns typical of neurons in the dopamine-intact striatum. During SWA in Parkinsonian rats, the firing of striatal neurons was more strongly synchronized at low frequencies, in time with cortical slow (~1 Hz) oscillations. During spontaneous cortical activation in Parkinsonian rats, more striatal neurons engaged in synchronized firing in time with cortical beta oscillations. Under the same experimental conditions, I then recorded the spontaneous firing of individual striatal neurons and juxtacellularly labelled the same neurons to verify their cell types, and locations; indirect pathway and direct pathway MSNs were distinguished by the expression (and lack of expression respectively), of the neuropeptide precursor preproenkephalin (PPE). After chronic dopamine loss, and on average, only indirect pathway (PPE+) MSNs significantly increased their firing rates during both brain states, and engaged in widespread, synchronized firing in the beta-frequency range. This did not hold true for all PPE+ MSNs; the Parkinsonian striatum contained many MSNs that were virtually quiescent, which were just as likely to belong to the indirect pathway as the direct pathway. Direct pathway (PPE-) MSNs increased their firing only during SWA after chronic dopamine loss and rarely engaged in aberrant beta oscillations. Taken together, these data suggest that (1) the firing patterns, as well as the firing rates of many striatal neurons are grossly disturbed by chronic loss of dopamine and (2) that the pathological synchronization of the rhythmic firing of a subpopulation of indirect pathway MSNs could contribute to the propagation of aberrant beta-frequency oscillations to downstream basal ganglia nuclei in Parkinsonism.

In the case of Parkinson’s disease, a common neurodegenerative disorder, the loss of motor function results from the selective degeneration of dopaminergic neurons (DNs) in the brain. Current treatments focus on pharmacological approaches that lose effectiveness over time and produce unwanted side effects. A more complete concept of rehabilitation to improve on current treatments requires the production of DNs to replace those that have been lost. Although pluripotent stem cells (PSCs) are a promising candidate for the source of these replacement neurons, current protocols for the terminal differentiation of DNs require a complicated cocktail of factors. Recently, a naturally occurring steroid called guggulsterone has been shown to be an effective terminal differentiator of DNs and can simplify the method for the production of such neurons. I therefore investigated the potential of long-term guggulsterone release from drug delivery particles in order to provide a proof of concept for producing DNs in a more economical and effective way. Throughout my study I was able to successfully encapsulate guggulsterone in Poly-ε-caprolactone (PCL)-based microspheres and I showed that the drug was capable of being released over 44 days in vitro. These guggulsterone-releasing microspheres were also successfully incorporated in human induced pluripotent stem cell (hiPSC)-derived neural aggregates (NAs), providing the foundation to continue investigating their effectiveness in producing functional and mature DNs. Together, these data suggest that guggulsterone delivery from microspheres may be a promising approach for improving the production of implantable DNs from hiPSCs. / Graduate

Dopamine exerts an important role in the regulation of motor activity in humans. During the progression of Parkinson’s disease, patients are faced with the progressive neurodegeneration of nigro-striatal dopamine neurons resulting in an array of pathological symptoms characteristic of the disease. Current treatment relies on targeting symptomatic aspects of the disease but currently Parkinson’s disease is incurable. Targeting the regeneration of DA neurons in PD patients could offer an alternative therapeutic approach that could stall and perhaps even revert the progression of the disease and improve the quality of life for patients. Here, I describe the generation of a transgenic zebrafish line for the non-invasive, conditional and specific ablation of dopaminergic neurons in both larval and adult zebrafish. Understanding the endogenous regenerative ability of the zebrafish may in the future contribute to the development of novel therapeutic approaches targeting DA neuron regeneration in humans. The Tg(dat:CFP-NTR) line efficiently labels and ablates most clusters of DA neurons in both the larval and the adult zebrafish brain. Neuronal ablation is followed by a locomotor and tail bend phenotype as well as by an increase in exploratory behavior. Using double transgenic larvae, we showed through live imaging that loss of DA neurons induces an increase in nestin expression; in addition we show an increase in the number of proliferating cells and an up regulation of genes involved in neurogenesis and tissue repair. Adult zebrafish were able to fully recover their DA neuronal population in the olfactory bulb within 45 days post ablation. Overall the Tg(dat:CFP-NTR) zebrafish offers a novel tool for the study of the molecular and cellular mechanisms driving the regeneration of DA neurons in the zebrafish brain and will be a useful tool for the field of regenerative medicine.

After unilateral lesions of the mesotelencephalic dopamine (DA) system, the administration of DA receptor agonists results in circling. This response is believed to reflect an asymmetry in mesotelencephalic DA activity. Moreover, drug-induced circling is thought to be directed away from the projection of higher dopaminergic activity. Recently, it has been reported that circling can be established and maintained using operant procedures in surgically intact and drug naive rats. The phenomenon of conditioned circling has been associated with an asymmetrical change in DA metabolism within the striatum and nucleus accumbens. The present series of experiments was designed to characterize further the involvement of mesotelencephalic DA in conditioned circling. Rats trained to circle for water according to a continuous schedule of reinforcement did not exhibit increased DA metabolism within either the striatum or the nucleus accumbens (Experiment I). However, a bilateral augmentation was observed when rates of responding were increased by implementing an intermittent schedule of reinforcement (Experiment II). Concurrent increases in the biosynthesis of DA, as estimated by accumulation of DOPA following the administration of a DOPA decarboxylase inhibitor, were not observed (Experiment III). Experiments IVa and IVb examined the extent to which inherent directional biases, which play a role in determining the magnitude and direction of drug-induced circling, influenced the acquisition and performance of the conditioned circling response. No effects were evident. Moreover, a symmetrical, bilateral enhancement in DA metabolism was observed in the striatum, irrespective of directional preferences. While conditioned circling can be established and maintained by reinforcing the response with food, food itself influenced DA metabolism and therefore precluded the detection of changes in DA metabolism specific to the circling response. Specifically, striatal and accumbens DA metabolism was augmented to a similar extent in animals given matched amounts of non-contingently presented food (Experiment V). Concentrations of DA, DOPAC and homovanillic acid (HVA) were found to be differentially distributed throughout the striatum (Experiment Via), suggesting a possible chemical basis for the heterogeneity of striatal DAergic functions. Changes in striatal DA metabolism associated with conditioned circling were observed only within localized regions of the anterior striatum (Experiment VIb). All changes noted were, however, bilateral in nature. Finally, unilateral lesions of the mesotelencephalic DA projection, following the establishment of the conditioned circling response, disrupted responding, irrespective of the relative locus of the lesion (i.e. ipsilateral or contralateral to the direction of turning) (Experiment VII). However, the extent of the behavioral deficit was more severe following contralaterally placed lesions. It is concluded that circling, established and maintained by positive reinforcement, is subserved by a bilateral augmentation in DA metabolism within the nucleus accumbens and discrete regions of the striatum. However, lesion studies indicate an asymmetrical involvement of the ipsilateral and contralateral projections in this response. / Medicine, Faculty of / Graduate