In contrast, in PD patients, while buspirone, a partial 5-HT1A agonist, ameliorates dyskinesia (Kleedorfer et al., 1991; Bonifati et al., 1994), sarizotan, another 5-HT1A receptor agonist, failed to improve it compared with placebo (Goetz et al., 2008) and significantly increased off time (Goetz et al., 2007). This evidence concerns the gene HTR1A and drug-induced dyskinesia.