Known ligands of TrkB induce platelet aggregation. Example trace (A) and quantification (B) of platelet aggregation in response to 370 nM BDNF, 370 nM NT4, 10 µg/ml TrkB-activating antibody (n = 7), and 370 nM β-NGF (n = 3). IgG₁ was used as an isotype control (10 µg/mL). Repeated-measures ANOVA, P = .005; compared with vehicle, BDNF 370 nM P < .0001, NT4 370 nM P < .0001 and TrkB-activating antibody, P = .037. Arrowheads indicate the time point at which the agonist was added. Data are presented as median and IQR.