Animals 2 Cocaine 2 D2 2 Discrimination (Psychology) 2 Dopamine 2 Dopamine Antagonists 2 Dopamine Uptake Inhibitors 2 Dose-Response Relationship, Drug 2 Drug discrimination 2 Female 2 Genotype 2 Knockout 2 Locomotor activity 2 Male 2 Mice 2 Mice, Knockout 2 Motor Activity 2 Raclopride 2 Receptors, Dopamine D2 2 animal experiment 2 article 2 cocaine 2 controlled study 2 discriminative stimulus 2 dopamine 2 receptor 2 dopaminergic system 2 dose response 2 drug discrimination 2 drug effect 2 drug receptor binding 2