Figure 3.

Progressive changes in D₃-receptor binding and levodopa-induced rotations and neuropeptide mRNAs in CdPu of unilaterally 6-OHDA-lesioned rats following repeated treatment with levodopa and withdrawal. Rats received levodopa (50 mg/kg i.p.) twice daily for up to 15 days (horizontal bar) and were challenged with a single same dose of levodopa at the indicated time during this chronic treatment or after withdrawal. Animals were killed 4 h after the challenge, D₃ receptor autoradiography using [³H]7-OH-DPAT or in situ hybridization with probes for prodynorphin (DYN) or preprotachykinin (SP) mRNAs. Note that rotations were not measured in all groups of animals. No significant changes were observed in D₃ receptor binding or in situ hybridization signals in the control side. Means ± SEM of values from 4–9 animals. ∗, P < 0.05; ∗∗, P < 0.01 as compared with the control side by the paired Student’s t test; §, P < 0.05; §§, P < 0.01 compared with values obtained following the first levodopa injection by the Mann–Whitney U test.