This unilateral model of PD has the advantage that each mouse can serve as its own within-subject control as the dopamine sensitized MSNs in the striatum of the 6-OHDA lesioned side respond with intense D1R-mediated signaling to administration of L-DOPA, while the MSNs in the unlesioned side are not affected [15], [19], [20]. The gene discussed is DRD1; the disease is Parkinson disease.