It is more accurate to say the GPe disinhibits the STN, not excites, because it is releasing an inhibitory NT (GABA), not an excitatory one.
Disinhibition - inhibiting an inhibitor
Excitation - activating an inhibitor OR exciter
The GPe normally inhibits the STN. By inhibiting the GPe, the STN is no longer inhibited (i.e., the STN is disinhibited). Excitation of the STN would be if the GPe released glutamate onto the STN. While both result in increased STN activity, the former is due to a lack of inhibition (disinhibition) and the latter is due to activation (excitation).
First Aid 2023: "Indirect (inhibitory) pathway - SNc input stimulates the striatum, releasing GABA that disinhibits STN via GPe inhibition, and STN stimulates GPi to inhibit the thalamus (decreases motion)
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