Neuropeptide
A peptide that acts as a signalling molecule in the nervous system, functioning as a neurotransmitter or neuromodulator. Neuropeptides influence pain perception, mood, appetite, and sleep. Examples include oxytocin, vasopressin, substance P, and the endorphins.
Technical Context
Neuropeptides are produced and released by neurons and typically act on G-protein coupled receptors. They differ from classical neurotransmitters (dopamine, serotonin, glutamate) in several ways: they are larger molecules (3-40+ amino acids vs single amino acids or small molecules), synthesised in the cell body and transported to nerve terminals (rather than synthesised locally), stored in large dense-core vesicles, and typically produce slower-onset but longer-lasting effects. Over 100 neuropeptides have been identified. Relevant examples include oxytocin, vasopressin, substance P (pain), neuropeptide Y (appetite), endorphins (pain/reward), and CGRP (migraine). Several research compounds target neuropeptide systems for cognitive or neuroprotective applications.