Behavioral performance at early (4 weeks) and later (6 months) stages in rats with unilateral medial forebrain bundle and striatal 6-hydroxydopamine lesions.

Our previous studies showed differences in striatal D(2) receptor functional activity between two different rat parkinsonian models, with lesions induced by 6-hydroxydopamine injection in the striatum and in the medial forebrain bundle (MFB) at both early (4 weeks) and later (6 months) stages after lesioning. The present study compared behavioral changes, including rotational movements induced by methamphetamine and bromocriptine, and the stepping test, in both models at both stages. No differences in behavioral performance were observed between the early and later stages in both striatal and MFB lesion models, whereas simultaneous D(2) receptor study showed dynamic change in D(2) receptors in MFB lesion rats. Behavioral characteristics might be controlled by comprehensive effects of the whole dopaminergic system, instead of variation in a few parameters of the dopaminergic system. More behavioral tests of different mechanisms with simultaneous molecular studies are needed for evaluation of parkinsonian animal models and the efficacy of treatments.