Objective To investigate the effect of insulin-like growth factor 1 antibody (IGF-1Ab) on motor endplate function after injection ofbotulinum toxin A (Btx-A).Methods The total 90 male SD rats were randomly divided into 4 groups:control group,Btx-A group and 2 ug and 20 ug IGF-1Ab groups.In Btx-A and IGF-1Ab groups,a volume of 0.5 U (0.1 mL) Btx-A was intramuscularly injected into a site in the fight gastrocnemius muscle;on day 3,equal volumes (0.1 mL) of IGF-1Ab with a dosage of 2 ug and 20 ug were injected to the 2 ug and 20 ug IGF-1Ab groups respectively at the same site.The gastrocnemius muscle strength and the mean optical density (MOI) value of the positive reaction zone of acetylcholine esterase staining were evaluated at different time points.Results The gastrocnemius muscle strength increased from 12.34±0.16 g before injection to 7.70±0.90 g after injection in the Btx-A group;the gastrocnemius muscle strength decreased in other groups after injection of Btx-A;on day 14,28,42,56 and 70,the muscle strength oflGF-1Ab groups was significantly lower than that of Btx-A group (P＜0.05),and on day 42-70,the value of muscle strength of 20 ug IGF-1Ab group was signficantly lower than that of 2 μg IGF-1Ab group (P＜0.05).The MOI values of the positive reaction zone changed with the same trend.Conclusion IGF-1Ab can suppress the restore of motor endplate function after injection of Btx-A.