Effect of acute L-Dopa pretreatment on apomorphine-induced rotational behavior in a rat model of Parkinson's disease.

Currently, reduction of apomorphine-induced rotational behavior in the 6-hydroxydopamine (6-OHDA) lesioned rat is the most utilized drug-induced paradigm for assessing functional efficacy in a rat model of Parkinson's disease (PD). Any clinically predictive animal model of PD should include a positive response to l-dopa, the standard pharmacotherapy for PD. However, the acute interaction between L-dopa and apomorphine has never been studied to determine if L-dopa pretreatment could reduce apomorphine-induced rotational behavior in a 6-OHDA lesioned rat. The present study was designed to explore whether, indeed, pretreatment with subrotational doses of L-dopa could inhibit apomorphine-induced rotations. The data indicate that L-dopa significantly reduced apomorphine-induced rotational behavior only at one dose (5.0 mg/kg) for 12 min. Based on these and other data, it is concluded that although the apomorphine-induced rotational paradigm may continue to be utilized as one additional indicator of efficacy in the 6-OHDA rat model of PD, it is not in itself a completely valid functional assay.