Figure 1.

Time course of hemidiaphragm paralysis caused by BoNT/A. The amplitude of muscle contraction in mN represents the difference between recorded basal and maximal tensions. All samples were administered at t₀ = 300 s. Addition of 0.1% BSA/PBS lead to spontaneous reduction of only ~35% over a period of 4 h. Upon administration of 500 pg/mL BoNT/A the amplitude remained unchanged for a dose dependent latent period and then decayed in a steep sigmoidale curve down to zero. The time period between application t₀ and the inflection point when the contraction amplitude halved, the so called paralysis time t_1/2, was used for construction of the calibration curves (Figure 2). Whereas 500 pg/mL BoNT/A yielded t_1/2 = 51 min, thermal denaturation or neutralization by serotype-specific antiserum of BoNT/A did not cause paralysis, but only led to spontaneous partial reduction of the contraction amplitude similar to the negative control sample.