BDNF and peripheral nerve injury: Other studies applied various chemicals, including ζ-pseudosubstrate inhibitory peptide (ZIP; Li et al., 2010), IEM1460 (Liu et al., 2015) and clonidine (Zuo et al., 2015), to the ACC locally, and unmasking effects on the aversion induced by peripheral nerve injury were observed, whereas lesion (Qu et al., 2011) or injection of brain-derived neurotrophic factor (BDNF)–tropomyosin receptor kinase B (TrkB) antagonist into the rostral ACC completely blocked the CPP induced by clonidine (Zhang et al., 2016), suggesting that the ACC is necessary for the regulation of spontaneous pain.