HTR1A and Parkinson disease: There is currently a placebo-controlled, double-blind, pilot study of buspirone in 27 participants with PD and anxiety underway to test the tolerability of buspirone, a 5HT1A receptor partial agonist with weak dopamine D2 and 5HT2 receptor activity,79 which has been shown to be effective for the treatment of GAD.80–82 It has been shown to be beneficial in PD in two small trials, but through its effects on the dopaminergic system and weak affinity for D2 receptors could potentially be associated with worsening of PD motor function.