expresses expresses medium spiny neuron indirect pathway medium spiny neuron Despite the direct and indirect circuits are often described not only as functionally opposing but also as anatomically segregated there are several anatomical and functional studies that have challenged this notion of pure segregation based on extensive collateral projections between pathways, dual-projection neurons, simultaneous co-activation during behavior. A GABAergic medium spiny neuron located in the striatum that gives rise to the indirect basal ganglia pathway. It projects to the GPe, where its axon typically ramifies in two regions but does not extend beyond this nucleus (Gerfen et al., 2022). It selectively expresses the D2 dopamine receptor (DRD2), which couples to inhibitory G-proteins (Gi/o) to decrease cAMP and suppress PKA-mediated signaling (Gerfen et al., 2022). Morphologically, this cell displays fewer and shorter dendrites than the MSN-D1 and receives fewer glutamatergic inputs, yet it exhibits significantly higher intrinsic excitability (Gertler et al., 2022). Functionally, activation of this cell suppresses competing or alternative motor actions by inhibiting GPe neurons, leading through STN and other GPe circuits to increased GPi/SNr output and stronger inhibition of thalamic and brainstem targets (Mink, 1996; Tecuapetla et al., 2016). dopamine 2 medium spiny neuron D(2) dopamine receptor