Effects of different doses of L-dopa on rotational behavior and amounts of cells expressing D2 receptors in hemiparkinsonian rats

AIM：To observe the effects of different doses of L-dopa on the rotational behavior and amounts of cells expressing D₂ receptors in striatum in hemiparkinsonian rats.METHODS：A hemiparkinsonian model was established in rats by pretreatment with 6-hydroxydopamine.The D₂ receptor expression were detected by immunohistochemical staining.The numbers of rotations induced by apomorphine was counted within 30 min before and after L-dopa (10 mg·kg^-1·d^-1,50 mg·kg^-1·d-^-1 or 100 mg·kg^-1·d^-1,ip) was introduced to Parkinson’s disease (PD) model rats for 15 days.RESULTS：In successful PD model rats,the increased percentage of D₂ receptor in lesioned side compared with intact side was associated linearly with the numbers of rotations within 30 min (r=0.927,P<0.01).After high dose of L-dopa intervention to PD model,the numbers of rotations decreased significantly (P<0.05),the amounts of cells expressing D₂ receptor at the lesioned side striatum decreased significantly (P<0.01).CONCLUSION：After high dose of L-dopa intervention,rotation behavior of PD rats improves,and D₂ receptor is down-regulated significantly.