BDNF receptor can be described as TrkB and p75 / NGFR. TrkB is a high-affinity receptor while p75 is a low-affinity receptor. When binding to BDNF, BDNF TrkB is induced to dimerize, phosphorylate and activate the intracellular tyrosine kinase domain. These events initiate several complex intracellular signal transduction cascades which subsequently induce biological responses. There are three forms of BDNF TrkB by alternative splicing of trkB mRNA. They are the full-length catalytic receptor (TrkB.FL) and two truncated forms (TrkB.T1 and TrkB.T2). TrkB receptors are highly glycosylated proteins possessing 12 potential N-linked glycosylation sites in the extracellular domain. The truncated forms of BDNF TrkB lack intracellular tyrosine kinase activity and contain different short cytoplasmatic tails. Analysis of the human TrkB gene recently revealed a novel isoform, TrkB-T-Shc, which seems to be expressed predominantly in the human brain. This truncated form contains a Shc-binding site in the juxtamembrane domain similar to TrkB.FL, but it lacks the kinase domain and has a unique truncated C terminus. p75 is a BDNF receptor as a facilitator of Trk-mediated neuronal survival and as a regulator of neuronal cell death. AS a facilitator of Trk, p75 assumes the role of a coreceptor that refines Trk affinity and specificity for BDNF. p75 also influences signaling pathways elicited by Trk activation. For example, p75 can bind Trk adaptor to stimulate its phosphorylation and augment Trk signaling.