Treatment with the 5HT1A receptor agonist buspirone almost completely resolved their dyskinesia, providing suggestive evidence that even in the absence of levodopa treatment, by an unclarified mechanism, a high ratio of 5HT to DA in the striatum may induce dyskinesia (Politis et al. 2010; 2011). This evidence concerns the gene HTR1A and drug-induced dyskinesia.