BDNF and major depressive disorder: It has been reported that the deletion of TrkB in mice caused a significant reduction in behavioural evidence for epileptogenesis (He et al., 2004; Kotloski and McNamara, 2010), and BDNF and TrkB expression increased in the amygdala of rats with epilepsy and depression (Liu et al., 2013; Briz et al., 2015).