BDNF and schizophrenia: The trkB−TK− mRNA levels were significantly increased in the DLPFC in schizophrenia, thereby significantly altering the ratio of trkB−TK+ to trkB−TK− mRNA and protein levels.20 The truncated trkB form is capable of binding to BDNF; however, it is not able to mediate the classic neurotrophic response via tyrosine signaling.