This dual mechanism may explain why a CB1 antagonist (SR 141716) could not improve the severity of motor symptoms and levodopa-induced dyskinesia (LID) measured with UPDRS III and IV in an exploratory randomized, double-blind, placebo-controlled (RCT) study on 24 patients with PD (Mesnage et al., 2004). Here, CNR1 is linked to Parkinson disease.