Figure 4. Effect of botulinum toxin E on the activation of thrombin-induced Ca²⁺ entry in human platelets.

Fura-2-loaded human platelets were incubated for 1 h in the presence of 300 nm BoNT E at 37°C and then stimulated with thrombin (1 U ml⁻¹), as indicated, in a Ca²⁺-free medium (200 μm EGTA was added). CaCl₂ (final concentration 300 μm) was added to the medium at the time indicated to initiate Ca²⁺ entry. Elevations in [Ca²⁺]_i were monitored using the 340/380 nm ratio and traces were calibrated in terms of [Ca²⁺]_i. Data are presented as mean ±s.e.m. of five experiments performed using five different donors.