[etrautmann]

Careful there - the compensatory decrease in number of receptors is NOT the same thing as a reduction in the number of neurons. Each neuron will have a lower response to the same amount of dopamine, but the neurons will still be there and will be healthy.

In Parkinson's, a specific group of neurons in the Substantia Nigra (which do happen to be dopaminergic neurons), selectively die off. They no longer release dopamine to their downstream targets, causing the motor and other affects characteristic of PD.

The compensatory mechanism you described is unlikely to cause those specific neurons to die, unless something far more complicated is going on, which you can almost never rule out but doesn't tell us much.

edit for clarity

[Retric]

causes parkinson's symptoms != causes Parkinson's.

However, if you combine fewer neurons and fewer receptors there is presumably going to be a faster apparent disease progression.