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OVER 98% PASS RATE FOR THE NCS, PCS, OCS, AND GCS EXAMS forums NCS Advantage How the Indirect Pathway is impacted by PD

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    • #490165

      Hi everyone!

      I was wondering if someone could help me better understand how PD impacts the neurotransmitters and parts of the brain. I understand when the Substantia Nigra is acting normal it behaves as follows…
      > The motor cortex sends glutamate (+++) to the Striatum and the Substantia Nigra releases dopamine to the D2 receptors (which are inhibitory) the Striatum (thus inhibiting it in a way)
      > Therefore the striatum sends less GABA (-) to the GPE (so it is less inhibited)
      > So the GPE releases more GABA (—) to the subthalamic nucleus (inhibiting it)
      > Then the subthalamic nucleus releases less glutamate (+) to the GPI
      > Since the GPI is not as stimulated it releases less GABA (-) to the Thalamus
      > As the Thalamus is less inhibited it releases more Glutamate (++++) to the Motor cortex resulting in more movement

      Here is where I get stuck with this system when PD gets involved…
      > 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 ?

      I would greatly appreciate it if anyone can help. I have rewatched the lecture and watched multiple videos on YouTube and I am still confused.

    • #490176

      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.

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