Paradoxical kinesia in parkinsonism is not caused by dopamine release. Studies in an animal model
K. A. Keefe, J. D. Salamone, M. J. Zigmond and E. M. Stricker
Department of Behavioral Neuroscience, University of Pittsburgh, PA 15260.
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.
