BDNF and depressive disorder: Given the increasingly recognized role of neurogenesis and neuronal trophic factors in the depression-related behavior [136, 137], it is interesting to note the novel interaction between A2ARs and Trk-B receptors [95], and neurotrophins, such as brain-derived neurotrophic factor (BDNF) [45, 123], which may provide another potential mechanism for the involvement of A2ARs in anxiety modulation.