RESUMEN
<p><b>AIM</b>To ascertain the bioactivity and to analyse quantificationally the denervating action of botulinum toxin A (BTXA) in gel.</p><p><b>METHODS</b>36 Sprague-Dawley rats were randomized into four groups. In group A - D, the gastrocnemius muscle of one leg was randomly selected to receive injection of BTXA solution 5U in 0.1 ml, BTXA gel 12.5U in 0.1 ml, BTXA gel 5U in 0.1 ml and BTXA gel 2U in 0.1 ml respectively, while the gastrocnemius muscle of other leg was injected with 0.1 ml of saline solution in group A and 0.1 ml of gel in group B to group D as control. Compound muscle action potential (CMAP) of both gastrocnemius muscles were measured and the amplitudes were recorded before injections, and 5 days, 2 weeks, 3 weeks, 1 month, 2 months and 3 months after the injections respectively.</p><p><b>RESULTS</b>The reduction of CMAP amplitude was significantly different at various time (P < 0.01), and CMAP amplitude decreased significantly after the treatment of BTXA (P < 0.01). The reduction of CMAP amplitude was significantly dif ferent in group A to I) (P < 0.01), and more reduction was found in group A and B (P < 0.01), and the reduction was higher in group C than in group D (P < 0.05). However, there were no significant differences in the reduction of CMAP amplitude between group A and group B.</p><p><b>CONCLUSION</b>Bioactivity of BTXA in gel was showed and the denervating action of BTXA in gel was demonstrated in a dosage and time dependent manner.</p>