An experiment on controlled release levodopa/benserazide-loaded microspheres in treatment of levodopa-induced dyskinesia of rats with Parkinson' s disease / 中华神经科杂志

ABSTRACT

Objective To investigate the effects of levodopa/benserazide-loaded poly-lactide-coglycolide (PLGA) microspheres on motor deficits and levodopa-induced dyskinesia in a rat model of Parkinson' s disease (PD) and to explore the mechanisms underlying this effects.Methods The content of levodopa/benserazide released from the microspheres was determined by high-performance liquid chromatography.The rat model of PD was induced by 6-OHDA injections.Then the valid PD rats were treated with levodopa ( 12 mg/kg,s.c.)/benserazide ( 15 mg/kg,s.c.) or microspheres.Forepaw adjusting steps were measured on 1,4,7,10 and 14 days after treatment.After 2 weeks of treatment,the abnormal involuntary movements (AIM) were measured.Phosphorylated dopamine,cAMP-regulated phosphoprotein of 32 kDa (DARPP-32) at threonine 34 levels were determined by immunohistochemistry and Western blot respectively.In addition,the levels of △FosB were measured by Western blot.Results In vivo release test showed that 76.2％ of levodopa and 83.6％ benserazide were released from the microspheres on day 7.Forepaw adjusting steps showed that the scores of forepaw adjusting steps in microspheres-treated PD rats were ( 5.8 ± 1.6 ) and ( 5.2 ± 1.5 ) respectively on 10 and 14 days of treatment,which were increased compared to levodopa-treaded PD rats (2.4 ± 1.1 and 1.2 ± 0.5 ; t =4.12,5.43,all P ＜0.01 ).The AIM scores of microspheres-treated rats ( 16.0 ±2.1 ) were decreased significantly compared to levodopa-treated rats ( 26.0 ± 3.2 ) on day 14 ( t =6.59,P ＜ 0.01 ).Immunohistochemistry indicated that the phosphorylated levels of DARPP-32 in microspheres-treated rats ( (3.7 ± 1.3 ) × 104 )were decreased significantly compared to levodopa-treated rats ( (7.9 ± 2.2) × 104 ; t =2.95,P ＜ 0.05 ).In addition,Western blot showed that the levels of phosphorylated DARPP-32 and △FosB were 119.4％ ± 11.3％ and 149.3％ ± 12.3％ respectively,which were decreased significantly compared to levodopatreated rats ( 184.8％ ± 13.7％ and 300.4％ ± 14.2％ ; t =4.12,2.91,all P ＜ 0.05 ).Conclusions Microspheres can be used to improve the motor deficits and reduce the expression of dyskinesia in PD rats.This may be due to the continuous release of levodopa/beserazide from the microspheres,which leads to continuous stimulation of PD rats and reduces the levels of phosphorylated DARPP-32 and △FosB in the striata of these rats.