tokens: Levodopa and the DA D2 - like receptor agonist , LY - 171555 ( [ 4aR - trans ] - 4 , 4a , 5 , 6 , 7 , 8 , 8a , 9 - o - dihydro - 5n - propyl - 2H - pyrazo lo - 3 - 4 - quinoline hydrochloride ) were also used for comparison .