In vivo injection of α‐bungarotoxin to improve the efficiency of motor endplate labeling

INTRODUCTION Motor endplates are composed of a motor neuron terminal and muscle fiber and are distributed in skeletal muscle, causing muscle contraction. However, traditional motor endplate staining methods are limited to the observation of partial skeletal muscle. The procedure was time-consuming due to strict incubation conditions, and usually provided unsatisfactory results. We explored a novel method to label motor endplate rapidly by in vivo injection of fluorescent α-bungarotoxin. METHODS Fifty-two mice were randomly divided into two groups, an experiment group (n = 50), and a contrast group (n = 2). In experiment group, α-bungarotoxin was injected via the caudal vein. The injection dosages were designated as 0.1, 0.2, 0.3, 0.4, and 0.5 μg/g. The experimental mice were divided into five subgroups of ten mice per group. The contrast group was only injected with 200 μL normal saline solution. Bilateral gastrocnemius were acquired for microscope analysis and optical clearing to seek specific fluorescent signal. RESULTS A dose of 0.3 μg/g of α-bungarotoxin with 1 h conjugation time could display the number and structure of motor endplate in plane view. Compared with the traditional procedure, this method was rapid, convenient, and time-saving. Combined with the optical clearing technique, spatial distribution could also be seen, helping to better understand the stereoscopic view of motor endplate position in skeletal muscle. CONCLUSIONS In vivo injection of α-bungarotoxin proved effective for studying motor endplate in skeletal muscle.