Tachykinins are peptides sharing a common C-terminal amino acid sequence: Phe-X-Gly-Leu-Met-NH2. This neuropeptide family is composed of substance P, neurokinin A, and neurokinin B, which are widely distributed in mammalian central and peripheral nervous systems. These three molecules serve as both neurotransmitters and neuromodulators. Their actions are mediated by binding with three distinct receptors, namely NK1, NK2, and NK3. NK3 receptors show affinity for neurokinin B. They are predominantly expressed in both the peripheral and central nervous systems. NK3 receptors appear to modulate monoaminergic and amino acid neurotransmission. Studies show that manipulating modulation of NK3 receptor activity may have therapeutic utility in psychiatric diseases such as schizophrenia and affective disorders.