PARKINSON’S DISEASE AND ITS TREATMENT

This is a disorder associated to dopamine oversecretion. Dopamie, a neurotransmitter
is involved in signal transduction in dopaminergic neurons. Basic symptoms include tremor, bradykinesia, reluctance to movement, and disturbed gait.




The cause of Parkinson’s disease is idiopathic.However,some clues were offered with the discovery of a selective dopamine toxicity produced by the synthetic compound 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine(MPTP).MPTP was synthesized by illicit drug dealers in an attempt to produce MPPP, a synthetic heroin.When injected,MPTP produces neurological symptoms remarkably similar to Parkinson’s disease. The toxic effects of MPTP can be blocked by pargyline, an inhibitor of MAO-B which is normally distributed in serotonin containing neurons. Serotonin terminals are found in the substantia nigra.




The dopaminergic neurons of the substantia nigra project to the striatum,and their degeneration in Parkinson’s disease is associated with a reduction in the striated dopamine content. Parkinson’s disease has been linked to genetic disposition, viral infection, drugs such as resorpine deplete dopamine stores and doesnot inhibit the vessicularisation of dopamine stores. In the prevalence of Parkinson’s disease,1% of people of age 50years and above are affected. Beyond 25years,13% of such cells are lost per decade. β-N-methylaminoalanine,a plant product can also contribute to the incidence of Parkinson’s disease.




Treatment of Parkinson’s disease can be achieved via the use of the following; anticholinergic drugs, dopamine precursors, and dopamine receptor agonists such as bromocryptine. Parkinson’s disease has been treated successfully with the dopamine precursor 3,4-dihydroxyphenylalanine(L-DOPA),which unlike dopamine, is able to cross the blood-brain barrier. Inorder to prevent the rapid decarboxylation of L-DOPA in the bloodstream, decarboxylase inhibitors such as carbidopa are often given to increase the circulating levels of L-DOPA and decrease the side effects. Tolcapone is a selective inhibitor of catechol-o-methyltransferase is useful in the treatment of Parkinson’s disease. Catechol-o-methyltransferase converts L-DOPA to an inactive form, which contributes to the limited effects of L-DOPA treatment.