Neurokinin B is a tachykinin peptide. Tachykinin peptides are one of the largest family of neuropeptides, found from amphibians to mammals. The tachykinin family is characterized by a common C-terminal sequence, Phe-X-Gly-Leu-Met-NH2, where X is either an Aromatic or an Aliphatic amino acid. The most notable tachykinin is Substance P.

There are three known mammalian tachykinin receptors termed NK1, NK2 and NK3. All are members of the 7 transmembrane g protein-coupled family of receptors and induce the activation of phospholipase C, producing inositol triphosphate. NK1, NK2 and NK3 selectively bind to substance P, neurokinin A and neurokinin B, respectively. Whilst the receptors are not specific to any individual tachykinin, they do have differing affinity for the tachykinins: NK1: SP>NKA>NKB; NK2: NKA>NKB>SP; NK3: NKB>NKA>SP.

Antagonists of neurokinin-1 (NK(1)) receptors (NK1 receptor antagonists), through which substance P acts, have been proposed to belong to a new class of antidepressants.