Neuromedin N

NMN binds NTR1 and NTR3 (also known as sortilin), with lower affinity than neurotensin for NTR1 but comparable interaction with NTR3. NTR1 is a Gq-coupled GPCR that activates phospholipase C, increases intracellular calcium, and activates PKC. NTR3/sortilin mediates endocytosis and intracellular sorting of bound peptide. NMN also inhibits dopamine signaling in mesolimbic pathways.

NMN is co-released with neurotensin from neurons in the intestinal mucosa and central nervous system. This co-transmission may allow NMN to modulate or extend neurotensin signaling, particularly at NTR3 which has high affinity for NMN. The distinct receptor binding profiles of neurotensin and NMN suggest complementary roles in neural circuit modulation.

Like neurotensin, NMN produces analgesia in rodent pain models following central administration. The analgesic effect is opioid-independent, mediated through NTR1 activation in the periaqueductal gray and spinal cord. NMN is of interest as a template for non-opioid analgesic development.

NMN reduces amphetamine-induced locomotor activity and conditioned avoidance responses in rodent models, behavioral correlates of antipsychotic activity. These effects are consistent with NMN inhibiting dopaminergic transmission in the nucleus accumbens and prefrontal cortex, suggesting relevance to schizophrenia research.