A neuropeptide is a small protein-like molecule made of short chains of amino acids (typically 3–40). It functions as a signaling molecule in the nervous system, especially in the brain and spinal cord.
Unlike classic neurotransmitters (like serotonin or dopamine), neuropeptides act more slowly and can have longer-lasting and broader effects on behavior, mood, pain, appetite, and more.
🧠 Where Are Neuropeptides Produced?
Neuropeptides are:
- Synthesized in neurons, especially in the cell body (soma)
- Packaged into vesicles and transported down the axon
- Released from the axon terminal into the synaptic space or bloodstream
They often coexist with neurotransmitters and modulate their actions.
🔬 How Do Neuropeptides Work?
- Released from neurons (often with neurotransmitters)
- Bind to G-protein-coupled receptors (GPCRs) on nearby or distant cells
- Trigger slow, sustained responses that alter:
- Neuronal excitability
- Hormone release
- Behavior patterns (e.g., sleep, hunger, bonding)
Unlike neurotransmitters, neuropeptides aren’t quickly recycled or broken down, so their effects last longer.
🧪 Examples of Neuropeptides & Their Functions:
| Neuropeptide | Function |
|---|---|
| Substance P | Transmits pain signals; involved in inflammation |
| Endorphins | Natural painkillers; promote pleasure and reduce stress |
| Oxytocin | Promotes bonding, social behavior, childbirth, and lactation |
| Vasopressin (ADH) | Regulates water balance and social behavior |
| Neuropeptide Y (NPY) | Stimulates appetite; regulates stress and anxiety |
| Somatostatin | Inhibits growth hormone release and gastrointestinal activity |
| TRH (Thyrotropin-Releasing Hormone) | Stimulates release of TSH and prolactin |
| GnRH (Gonadotropin-Releasing Hormone) | Regulates LH and FSH from the pituitary |
🧠 Major Functions of Neuropeptides:
- 🧩 Pain modulation
- 🍽️ Appetite and metabolism
- 😴 Sleep and circadian rhythms
- 🫀 Heart rate and blood pressure
- 🧠 Mood and emotional regulation
- 🧬 Hormone release from the pituitary
- 👫 Social bonding and behavior
🧪 Neuropeptides vs Neurotransmitters:
| Feature | Neuropeptides | Neurotransmitters |
|---|---|---|
| Size | Larger (3–40 amino acids) | Small molecules (e.g., dopamine, GABA) |
| Speed of action | Slower, long-lasting | Fast, short-lasting |
| Receptors | GPCRs (slow-acting) | Ion channels (fast-acting) |
| Range of effect | Widespread (modulatory) | Local, specific |
| Breakdown | Slow | Rapid (enzymatic reuptake) |
🧠 Summary Table:
| Feature | Neuropeptide |
|---|---|
| Made of | Short amino acid chains (3–40) |
| Produced by | Neurons (and some endocrine cells) |
| Released with | Neurotransmitters (often co-released) |
| Acts on | G-protein-coupled receptors (GPCRs) |
| Functions | Pain, hunger, emotion, bonding, hormone release |
| Duration of effect | Long-lasting |
| Examples | Oxytocin, endorphins, substance P, neuropeptide Y |