Essay on Parkinson’s Disease and Action of Drugs on Movement

520 Words 3 Pages
Parkinson’s Disease and Action of Drugs on Movement

Introduction:

Parkinson’s disease is a neurological disorder that seriously impairs motor function, with people afflicted with this condition exhibiting akinesia, muscle rigidity and having a tremor at rest. It is accepted that the loss of motor function is brought upon by the progressive degeneration of nigrostriatal dopamine neurons, which leads to a corresponding loss of dopamine in the caudate/putamen part of the basal ganglia, which is accepted as the main receiving area in motor circuits. Information coming to it from the cortex and thalamus is processed and channeled to the pallidum and to the substantia nigra reticular. There are two
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Aside from functioning as a neurotransmitter, dopamine is also the precursor to noradrenaline in all central and peripheral noradrenergic neurons. Dopamine is made from the precursor Tyrosine which is converted to DOPA by the enzyme tyrosine hydroxylase, and DOPA is then converted to dopamine by the enzyme dopa decarboxylase. This enzyme has a much higher activity in comparison to tyrosine hydroxylase so under normal conditions there is little or no endogenous DOPA found in most cells.

The first line of treatment for a patient is to replenish their dopamine stores, which have diminished due to loss of dopaminergic neurones. As dopamine cannot cross the blood-brain barrier it is of no use to simply administer dopamine, instead its precursor L-DOPA is given. This is able to cross the blood-brain barrier upon which it is then converted to dopamine by aromatic amino acid decarboxylase. However L-DOPA can also be converted to dopamine in the periphery, which can cause unwanted effects and so to prevent this a decarboxylase inhibitor is given. Not only does this reduce adverse effects but also lowers the effective dose.

Dopamine is rapidly taken up into storage vesicles by an energy-dependent transporter-mediated process, achieving high local concentrations within the storage vesicles by complexing with

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