K;k;K

Painkiller Analogues81the brain that use the neurotransmitter dopamine. Circuits inthe brain that use dopamine are primarily involved in thecontrol of motor skills such as movements of the arms, legs,and face. This MPTP-laced heroin explained why this youngman showed signs of Parkinson’s disease.In 1982, many more cases of drug addicts becoming“frozen” after injecting themselves with (what they thought tobe) heroin were reported by various emergency rooms inthe San Francisco Bay area. Neurologists, psychiatrists, andmimic the action of dopamine, or are converted to dopamineonce taken, such as L-dopa, are currently used to treatParkinson’s disease, but with limited success.When heroin laced with toxic MPTP enters the body, itis metabolized to form MPP+, which is very toxic to neuronscontaining dopamine, such as those in the substantia nigra. Inaddition, it is a relatively selective toxin, so it does not destroyneurons containing other types of neurotransmitters. Whenheroin addicts injected that bad batch of heroin containingthe meperidine analogue MPTP, it was converted to MPP+and destroyed many neurons in their substantia nigra, resultingin a dopamine shortage in their striatum and subsequentlycausing symptoms resembling Parkinson’s disease.Despite the misfortunes of these addicts, MPTP hasproved an invaluable tool for studying the biology of Parkinson’sdisease. When MPTP is injected into experimental rats,mice, or monkeys, neurons in the substantia nigra ofthese animals start to die, and the animals develop motorproblems that closely resemble the symptoms of Parkinson’sdisease. Researchers hope to use MPTP in animals tounravel the mystery of what causes Parkinson’s disease inhumans, in the hope that they can develop a cure for thisdevastating disease.