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. 2015 Oct 12;9:273. doi: 10.3389/fnbeh.2015.00273

Figure 1.

Figure 1

Timelines and protocols of methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) intoxication and conditioned place preference (CPP) training. Group I monkeys initially received progressive MPTP injections for 3 to 4 months (0.25 mg/kg, i.m., injections spaced by 2–3 days) until they developed mild PD symptoms. After the progressive intoxication, the group I monkeys were subjected to the CPP procedure. The group I monkeys were tested two times in 12 months. Then these animals received acute injections of MPTP (0.45 mg/kg, i.m., 6–7 daily injections) and developed strong PD symptoms. Then the third CPP test was carried out. The group II monkeys received an acute MPTP intoxication protocol (intracerebroventricular, 5 mg per kg of brain weight, 10–12 daily injections) and developed strong PD symptoms. These animals were tested only once to examine whether they had established a morphine CPP with severe Parkinsonian symptoms. The control group performed the CPP test twice: the first one coincided with CPP training and testing of the group I monkeys; the second test was performed 12 months after the first one.