• 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 Release: Studies in an Animal Model. Arch Neurol. 1989;46(10):1070–1075. doi:https://doi.org/10.1001/archneur.1989.00520460046012
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