Neuromedin N is a neurotensin-like hexapeptide that is synthesized from the same precursor as neurotensin. It is highly expressed in the brain but is also expressed in the gastrointestinal system and adrenal glands. It competitively inhibits neurotensin binding to rat brain synaptic membranes and has increased potency in the presence of the peptidase inhibitor bestatin (IC50s = 16.7 and 3 nM, respectively). Neuromedin N (10 pM) increases the phagocytic function of isolated murine peritoneal macrophages and increases chemotaxis two-fold compared with control, an effect that is blocked by the calcium-channel blocker ryanodine. It induces hypotension in rats and contraction of isolated guinea pig ileum. Neuromedin N (0.05 - 5 μg, i.c.v.) also elicits hypothermia in rats in a dose- and time-dependent manner, which is potentiated by bestatin . Neuromedin N is more potent than neurotensin in stimulating spontaneous motor activity and increasing dopamine metabolism in several brain regions following injection into the rat ventral tegmental area but is less potent than neurotensin when injected into the nucleus accumbens.