DRD2 and Parkinson disease: Furthermore, the expression of D2R, A2AR and mGluR5 heteromers, and therefore the interaction between these receptors, within the dendritic spines of dorsal and ventral striato-pallidal GABAergic neurons involved in PD, may suggest an involvement of these receptors in the pathogenesis of PD (Fuxe et al., 2003).