Function of Acetylcholine do in the Direct Pathway, of the Basal Ganglia?

[Gooner007]

I posted this in the Step 1 discussion forum, but no answers so far. I'm not sure if this is too detailed or picky for the Step 1 exam, but its in the FA, and I'm just stuck on this 1 concept.

As far as I remember, Ach has the Opposite effect of Dopamine, in the Striatum.

Dopamine excites the direct pathway. And inhibits the indirect pathway. Both leading to movement.

So you'd think that Ach inhibits the direct pathway, and excites the indirect pathway.

In FA, Ach is shown to excite the indirect pathway. But its also illustrated (in 2010 FA), that it EXCITES THE DIRECT PATHWAY TOO, which doesn't make sense to me.

This has been bugging me for sometime now. Am I overlooking something here?

---

Members don't see this ad.

 

[sab3156]

Bump.

What is the effect of ACh from the intrastriatal pathway on the direct and indirect basal ganglia pathways?

And what about the effect of the corticostriate pathway on the direct and indirect basal ganglia pathways?

 

[deathmerchant]

ACh has a very small role. I don't think it modulates much and is mostly a connecting neurotransmitter. So current knowledge is that Ach is inhibitory from Striatum to BOTH Gpi and Gpe( direct and indirect respect.) Although, both muscarinic and nicotinic cholinergic receptors are found in the striatum. Some research says muscarinic receptors on glutamatergic terminals are thought to inhibit release of the excitatory transmitter, acting as a modulator of glutamatergic stimulation of striatal neurons, whereas nicotinic receptor activation enhances transmitter release.

Similarly, Corticostriate pathways is always excitatory to striatum.
Most modulations happen at and after Globus pallidus. I am not very uptodate on this though.