Experimental design. Animals received quinpirole (QNP) injections with consecutive open field (OF) tests twice per week over the course of the whole experiment (syringe symbols), including: (1) phenotype induction phase; (2) intracranial self-stimulation (ICSS) training phase; (3) ICSS test phase. After electrode implantation, animals were trained daily (on injection days and on no-injection days) in the ICSS procedure until stimulation thresholds stabilized. Five ICSS test sessions were carried out in a randomized order on injection days. To demonstrate that the compulsive phenotype was stable over the course of the study, open field data for the 11th and last open field test were assessed.