It also prevents dyskinesia by functioning as a 5-HT1A receptor agonist.364 The A2A receptor in the basal ganglia is involved in the motor control of PD.365 At present, Istradefylline is the principal adenosine A2A receptor antagonist employed in adult PD patients presenting “off” episodes associated with Levodopa treatment.141. The gene discussed is HTR1A; the disease is Parkinson disease.