Does neurotropin-3 have a therapeutic implication in major depression?

Although several classes of antidepressants are used to treat major depression, there is an unmet need in real clinical practice because not all patients treated with an antidepressant fully recover from their functional impairment. Hence, the development of new antidepressants based on a novel therapeutic mechanism may help in the development of more effective and ideal antidepressive agents. There is emerging evidence suggesting that the etiopathogenesis of depression involves transmitters other than the major neurotransmitters such as serotonin, norepinephrine, and dopamine. Therefore, it has consistently been suggested that an alteration in neuroprotection and synaptic plasticity is associated with the pathogenesis and therapeutic mechanism of depression. Neurotropin-3 (NT3) is an interesting protein that regulates neuronal survival, synaptic plasticity, and neurotransmission. It is widely expressed in the hippocampus and facilitates hippocampal plasticity by regulating neurogenesis. It has been also reported that an infusion of NT3 increases the level of brain-derived neurotrophic factor (BDNF) mRNA expression in the cerebral cortex and produces BDNF-like effects that induce cortical tyrosine kinase B phosphorylation. BDNF has been consistently implicated in the pathogenesis of depression and the therapeutic mechanism of antidepressants. It has also been implicated in the treatment effect of mood stabilizers such as lithium. NT3 has demonstrated its possible antidepressant effect in a learned helpless animal model. Animal studies have shown that it also modulates the neurotransmitters, serotonin and noradrenaline, which are essential in the development and treatment of depression. Therefore, further studies on the therapeutic implications of NT3 for depression are warranted and are expected for the development of newer, effective antidepressants.