Hi Kathryn,
Everything you have here is correct.
Just filling in the rest of your PD flow:
> The motor cortex sends glutamate (+++) to the Striatum and the Substantia Nigra releases less dopamine to the D2 receptors (due to PD )to the Striatum (so it is less inhibiting)
> Since the Striatum is less inhibited it should hypothetically release more GABA (++++) to the GPE thereby inhibiting it
>But if the GPE is more inhibited wouldn’t it release less Gaba to the Subthalamic Nucleus ?
Yes.
>The GPe releases less GABA, so the STN is less inhibited.
>The STN then releases relatively more glutamate to excite the GPi.
>The GPi then releases more GABA to inhibit the thalamus.
>The thalamus therefore releases less glutamate to the motor cortex, resulting in less movement.