The impact of photobiomodulation in animal models of Parkinson's disease and ageing

The aim of this thesis was to explore whether photobiomodulation improved behaviour and offered neuroprotection in animal models of Parkinson's disease and in ageing. The results are presented as publications following a literature review and ending with a general discussion. For Parkinson's disease, a mouse and monkey MPTP model were used, while for ageing, the twelve month mouse model was used. Photobiomodulation was applied either extracranially in mice or intracranially in monkeys. These applications were used as to ensure that photobiomodulation reached the distressed cells directly, offering the best chance of survival. There were five major sets of results. First, photobiomodulation led to improvements in locomotive behaviour in the mouse and monkey model of Parkinson’s disease, together with a reduction of the "human-like" signs in the monkey model. Second, photobiomodulation was an effective neuroprotective agent for the dopaminergic system in these models. Third, photobiomodulation was associated with clear reductions in gliosis, decreasing both the number and size of the glial cells in the ageing and Parkinson's disease models. Fourth, photobiomodulation prompted the expression of glial derived neurotrophic factor, together with the dopaminergic phenotype, in the striatum of the monkey model of Parkinson's disease. Fifth, there was an extensive encephalopsin network evident across the mouse and monkey striatum. This system was unaffected by either ageing, MPTP insult nor photobiomodulation. In summary, the results have provided evidence that photobiomodulation improved behaviour, was neuroprotective and reduced gliosis in a mouse and monkey model of Parkinson's disease, and reduced gliosis in an ageing mouse model. The results also revealed an extensive light-sensitive opsin network within the striatum, that can potentially impact on aspects of striatal function. Overall, the findings should hopefully serve as a template for translation to the clinic