l-DOPA activation of ERK2 in the dopamine-depleted striatum is not significantly reduced in DARPP-32 knock-out mice. Western immunoblot data from wild-type (n = 7) and DARPP-32 knock-out (n = 5) animals with unilateral 6-OHDA lesions of the nigrostriatal dopamine pathway treated for 10 d with l-DOPA (20 mg/kg with 12 mg/kg benserazide). Animals were killed 30 min after the last injection and the dissected striatum were processed by Western blotting to determine levels of immunoreactivity for DARPP-32, TH, and phosphorylated ERK2 (pERK2). There is robust activation of pERK2 in the dopamine-depleted compared with the intact striatum of both wild-type and DARPP32 KO animals (*p < 0.05). However, there is no significant difference in the activation of pERK2 in the dopamine-lesioned striatum comparing wild-type and DARPP-32 KO animals (percentage above intact control: wild type, 406%; KO, 371%; p > 0.05).