Dopamine regulates spine density in striatal projection neurons in a concentration-dependent manner.

Dopaminergic afferents innervate spiny projection neurons (SPNs) in the striatum, maintaining basal ganglia activity. The loss of striatal innervation is the hallmark of Parkinson's disease (PD), which is characterized by dopaminergic denervation. A lack of dopamine in the dorsal striatum induces plasticity changes in SPNs.