Changes of Ultrastructure of Muscle in Rats with Spastic Palsy after Injected with Botulinum Toxin / 实用儿科临床杂志

ABSTRACT

Objective To observe the ultrastructural changes of end-plate and gastrocnemius muscle of rats with spastic palsy after injected with botulinum toxin type A in order to provide scientific base of histomorphology for clinical use of botulinum toxin type A.Methods Wistar rats′ pyramidal tracts in experiment group were injured by electric current 2.5 mA for 30 s,twice,but 36 normal control rats were only drilled hole in skull(control group).Seventy-two rats were successful in building spastic palsy model.Botulinum toxin type A (6 U/kg) were injected into right gastrocnemius muscles of 36 spastic palsy rats (group B),and physiological saline were injected into the same muscles in 36 spastic palsy rats as control(group A).Control group were not injected.The rats of group A,group B were sacrificed on 3,7,15,30,60 and 90 days after botulinum toxin therapy,and right gastrocnemius muscles was separated for histological analysis.Results Under the electron microscope,the structure of muscle fiber in group B had changed(Z line rupture,disorder and abolition,myofilament lysis,triad tract diso-rder,vacuolar degeneration) and these changes in group B occurred earlier and were severer than those in group A.There was compensatory hypertrophy of muscle fiber at later stages in group B.During the first 15 days after botulinum toxin type A injection,there were many synaptic vesicle without pre-synaptic membranes near terminal portion of nonmedullated nerve fibers.Following this,between 15 to 30 days,there were many folds similar to postsynaptic membranes in the cellular membranes and there were many grains in it.But there was no synaptic vesicle and pre-synaptic membranes near them.Compensatory hypertrophy and atrophy of muscle fiber coexist at 90 days after injection in group B.Conclusions Injection of botulinum toxin type A maybe induce the sprout of nerve and degeneration of the partial postsynaptic where there are many grains.It also accelerates muscle atrophy,but it induces compensatory hypertrophy of muscle fiber at later stage.It implies that injection of botulinum toxin type A can improve spasm symptom of the gastrocnemius muscles and this is good for muscle fiber repairing.