Effect of nicotine on L-dopa-induced dyskinesia in animal models of Parkinson's disease: a systematic review and meta-analysis.

L-dopa-induced dyskinesias (LIDs) are abnormal involuntary movements (AIM) that develop with long-term L-dopa therapy for Parkinson's disease (PD). In this study, we used these tools to describe the efficacy of nicotine reduced LID in animal models of PD. Studies were identified by electronic searching of six online databases up to September of 2013 to identify preclinical trials involving nicotine for LID in animal model. Data were extracted for AIM compared with LID animals. Pre-specified subgroup analysis was carried out according to method of model, gender, anesthetic used, and species. Combined standardized mean difference (SMD) estimates and 95 % confidence intervals (CIs) were calculated using a random-effects model. Eleven studies involving 181 animals which described the effect of nicotine on LID were included in the meta-analysis. Nicotine was efficacious in reducing total AIM compared with control group (SMD -3.77, 95 % CI -5.30 to -2.23, P < 0.00001). Meanwhile, four studies showed certain effects of nicotine for improving the axial AIM (SMD -2.21, 95 % CI -4.17 to -0.24, P = 0.03); oral AIM and forelimb AIM were obvious improved in six studies in the nicotine group (SMD -3.00, 95 % CI -4.55 to -1.44, P = 0.0002; SMD -2.52, 95 % CI -3.52 to -1.53, P < 0.00001, respectively). We conclude that nicotine appears to have efficacy in animal models of LID. Large randomized clinical trials testing the effect of nicotine in PD patients with LID are warranted.