The Effects of Dilution Volume and Muscle Activity on the Paralysis of Gastrocnemius Muscle of Rabbit after Botulinum Toxin A Injection

ABSTRACT

OBJECTIVE: To evaluate the effects of botulinum toxin A (BT) dilution volume and post- injection exercise with electrical stimulation on muscle paralysis. METHOD: Eighteen New Zealand white rabbits are randomly assigned to 0.1 ml dilution group, 0.5 ml dilution group or control group. Control group did not receive any injection and 10 units of BT was diluted with 0.1 ml (B1) or 0.5 ml (B5) normal saline and injected to the both gastrocnemius muscles. The right lower limbs of experimental groups did not have any treatment after botulinum toxin A injection (B1C, B5C) and left lower limbs had stretching exercise after injection (B1S, B5S) for 2 hours using the pneumatic kicking machine. Electrical stimulation was also applied to the gastrocnemius muscle with the intensity of 20 mA to 30 mA to evoke plantar flexion of ankle joint. Muscle paralysis effect of BT was evaluated with compound muscle action potential (CMAP) amplitude of gastrocnemius muscle with the sciatic nerve stimulation before and 1 week after injection. RESULTS: There were significant CMAP amplitude decreases in all animals after BT injection. There were significant decreases of CMAP amplitudes in B5 group compared with that of B1 group (p<0.001). Left limbs with stretching exercise and electrical stimulation showed lower CMAP amplitude (p=0.01) compared with right limbs which did not have any treatment after BT injection. CONCLUSION: To maximize muscle paralysis effect of the botulinum toxin A, increasing dilution volume and performing post-injection stretching exercise with electrical stimulation are considered a good strategy.