neuropeptide

A neuropeptide is a small chain of amino acids that nerve cells use as a chemical message. Compared with classic fast neurotransmitters, neuropeptides are like longer, more detailed memos: released in smaller amounts, acting more slowly, and often modulating a circuit's mood rather than flipping a single switch. The brain uses dozens of them to fine-tune appetite, pain, social behavior, and stress.

Neuropeptides are made the way other peptide hormones are, cut from larger precursor proteins and packaged in granules, then released from nerve terminals. The same molecule may act locally on neighboring neurons, like a neurotransmitter, or be released into the blood to act far away, like a neurohormone. Familiar examples include CRH, oxytocin, vasopressin, the appetite peptides NPY and AgRP, and the endorphins.

Because neuropeptides act through G protein-coupled receptors and tend to shape the overall tone of neural and endocrine systems, they are central to neuroendocrinology and are major drug targets, including the GLP-1 based therapies that grew out of gut peptide biology.