Figure 3. Effect of botulinum toxin E on the activation of TG-evoked Ca²⁺ entry in human platelets.

A, resting fura-2-loaded platelets (top and bottom panels) or platelets incubated for 1 h at 37°C (middle panel) were stimulated with TG (1 μm; top panel) or the vehicle (HBS; middle and bottom panels), as indicated, in a Ca²⁺-free medium (200 μm EGTA was added). CaCl₂ (final concentration 300 μm) was added to the medium 3 min later. Elevations in [Ca²⁺]_i were monitored using the 340/380 nm ratio and traces were calibrated in terms of [Ca²⁺]_i. B, platelets were incubated for 1 h with several concentrations of BoNT E (30–300 nm) at 37°C and then stimulated with TG (1 μm) in a Ca²⁺-free medium (200 μm EGTA was added). CaCl₂ (final concentration 300 μm) was added to the medium 3 min later to initiate Ca²⁺ entry. Data are presented as mean values of 4–12 experiments. Inset: bar graph showing the Ca²⁺ entry under different experimental conditions expressed as the percentage of control. Values are mean ±s.e.m. of 4–12 experiments performed using six different donors. *P < 0.01 compared to control.