• Rats become akinetic after large dopamine-depleting brain lesions, yet they show an activation-induced restoration of motor function. In this study, rats were given intraventricular injections of the neurotoxin 6-hydroxydopamine to permanently reduce the dopamine content of the corpus striatum by 98%. Although the rats were akinetic in their home cages, they swam effectively when placed in deep water and escaped from a shallow floating ice bath. These behaviors were not abolished by pretreating the animals with the dopamine antagonists haloperidol and SCH-23390. In contrast, haloperidol completely blocked the brain-damaged animals' behavioral responses to amphetamine. These results suggest that the paradoxical kinesia of dopamine-depleted rats is not a consequence of dopamine release from residual dopaminergic fibers.
Keefe KA, Salamone JD, Zigmond MJ, Stricker EM. Paradoxical Kinesia in Parkinsonism Is Not Caused by Dopamine ReleaseStudies in an Animal Model. Arch Neurol. 1989;46(10):1070–1075. doi:10.1001/archneur.1989.00520460046012