neuropeptide
Meaning of neuropeptide: Short protein-like messengers used by nerve cells for slower, longer-lasting signals than ordinary neurotransmitters send.
Definition of neuropeptide
A neuropeptide is a short chain of amino acids used by nerve cells as a chemical message. Neuropeptides are made in the cell body from a larger precursor, packaged into vesicles and carried down the nerve fiber before release. They act more slowly than classical neurotransmitters, spread further from where they are released, and their effects last far longer.
How do they differ from ordinary neurotransmitters?
Both are released by nerve cells, but almost everything else about them differs.
| Classical neurotransmitter | Neuropeptide | |
|---|---|---|
| Size | Single small molecule | Chain of amino acids |
| Where made | At the nerve ending | In the cell body |
| Speed of effect | Milliseconds | Seconds to minutes |
| Range | Across one synapse | Diffuses to nearby cells |
| After release | Recycled or broken down locally | Broken down, must be made again |
How are they made?
Production starts with a gene, so the process is slower and less flexible than making a small transmitter on the spot. The cell builds a long precursor protein, then cuts it into pieces with enzymes. One precursor can yield several different active peptides, which is why related messengers often arrive together. The finished peptides are stored in dense vesicles and transported along the nerve fiber to the ending. Because supply depends on manufacture in the cell body, heavy firing can deplete the store faster than it is replaced.
What do they actually do?
They act as fine control rather than as the main signal. Substance P carries pain information from the periphery inward. Endorphins and enkephalins damp that same signaling down, and opioid drugs work by imitating them. Oxytocin and vasopressin are made in the brain but released into the blood as hormones, so the same molecule can be a neuropeptide in one place and a hormone in another. Neuropeptide Y is among the strongest known drivers of appetite. Each is built from an amino acid chain, and small differences in that chain decide which receptor it fits.
Used in a sentence
Immunostaining demonstrated neuropeptide expression within the nerve fibers of the specimen.
Good to know
Neuropeptides are made in the cell body rather than at the nerve ending, so they cannot be replaced quickly after release and sustained firing depletes them.
Word origin
Where “neuropeptide” comes from
Joins the Greek neuron, meaning sinew or nerve, with peptide, from peptos, meaning digested.