Parkinson's Disease and Tourette's Syndrome Essay

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Parkinson's Disease and Tourette's Syndrome

Parkinson's Disease is a literally crippling neurodegenerative disorder, manifested in about 1% of the aged population. People who have Parkinson's Disease gradually lose control of their movements; specific symptoms include, "tremor, slowness of movement, stiffness, difficulty in walking, and loss of balance." (1) Evidence strongly suggests that Parkinson's Disease is the result of severe cell loss in the substantia nigra. This brain structure is principally involved in the production of dopamine. (2) Dopamine, among other functions, is the neurotransmitter involved in initiation of movement. Hence, the link between dopaminergic cell loss and cessation of voluntary movement, as manifested
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where movement is planned or motor behavior is organized. Surely enough, research done on the basal ganglia, namely the striatum and the caudate nucleus, has revealed that dopamine indeed impacts on these areas more prominently in Tourette's patients than in unaffected controls. (5,6) The increased dopamine effect in Tourette's patients may be due to two mechanism. One, the patients may produce more dopamine, hence, their receptors are over-stimulated, leading to excessive neuronal firing, in turn leading to involuntary movements. However, this theory seems to not hold, as presumably neurons would activate compensatory mechanism to deal with the increase in neurotransmitter concentration. If really dopamine was present in excess, one would expect receptor sites to down-regulate. One can assume that dopamine is not present in excess in Tourette's patients. A second mechanism has been proposed. According to this, the dopamine levels in Tourette's patients are equivalent to non-patients, but their receptor sites are supersensitive. This theory seems to hold true and has been successfully confirmed in the laboratory. Research surrounding dopamine binding in implicated structures of the brain yielded, "that binding to D2 dopamine receptors in the caudate nucleus was higher in the sibling

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