Levodopa-induced dyskinesia and rotational behavior in hemiparkinsonian rats: Independent features or components of the same phenomenon?

Chronic daily administration of 6.25 mg/kg of levodopa in unilaterally 6-OHDA lesioned rats did not induce any observable behavioral effects for the first 12.5 ± 2.5 days. Thereafter, levodopa administration induced abnormal involuntary movements (AIMs), involving the contralateral limb, head, neck and trunk, along with the development of contralateral rotations. AIMs and rotations followed a progressively worsening, highly correlated, parallel course. We suggest that rotational behavior does not represent a pure antiparkinsonian response, but along with levodopa-induced dyskinesia is part of the levodopa-induced motor response complications syndrome.