Parkinsons -question

[usmleprep88]

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Hey everyone,

I'm very much confused about the pathophysiology behind parkinsons. Is it due to a loss in the balance b/w striatonigral (ACh) & nigrostriatal? From my understanding... striatum release ACh on substantia nigra, whereas substantia nigra releases dopamine on striatum. P.152 of kaplan pharm lecture notes shows a pic which shows a Dopaminergic neuron & a Cholinergic neuron both acting on a GABA-nergic neuron in striatum...but should not the cholinergic neuron be acting on substantia nigra..?

Any help would be appreciated. Thanks.

 

[seminoma]

Imbalance between DA and ACh. Loss of DA from the pars compacta results in loss of stimulation of the indirect pathway (inhibitory pathway) and loss of stimulation of the direct pathway (activating pathway).

 

[Mr. Mojo Risin]

Imbalance between DA and ACh. Loss of DA from the pars compacta results in loss of stimulation of the indirect pathway (inhibitory pathway) and loss of stimulation of the direct pathway (activating pathway).

Close, but dopamine loss associated with Parkinson's disease leads to underinhibition of the indirect pathway and understimulation of the direct pathway. Dopamine normally serves to stimulate the direct pathway and inhibit the indirect pathway.