Dynamic changes of striatal dopamine D2 receptor binding at later stages after unilateral lesions of the medial forebrain bundle in Parkinsonian rat models

Abstract

Our previous study regarding the changes of D2 receptor in nigrostriatal dopamine system at an early stage (4 weeks after lesion) indicated a different functional activity of striatal D2 receptor between two different rat parkinsonian models, lesioning with 6-hydroxydopamine in the striatum and in the medial forebrain bundle (MFB). In the present study, we further examined binding of D2 receptor as well as pre-synaptic dopamine transporter (DAT) at later stages (6 months after lesion) both in the striatal and MFB lesion models. The D2 receptor binding in MFB model at 6 months after lesion was significantly lower than that at 4 weeks after lesion, albeit it was still higher than the normal side. The D2 receptor binding in striatal model was decreased to the same extent at both 4 weeks and 6 months after lesion. DAT binding decreased at 6 months after lesion, more profound in MFB model, and the degree of reduction was not different from that at 4 weeks after lesion. These findings indicated different dynamic processes of the D2 receptor and DAT during a longer time observation in the striatal and MFB lesion models. The dynamic changes of D2 receptor activity after lesion should be considered when selecting 6-hydroxydopamine-induced rat parkinsonian models.