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Neuropeptides matter because they act alongside the classic neurotransmittersA chemical messenger that nerve cells release to signal to the next cell.Read more → to fine-tune pain, bonding, appetite, and even panic. Several are directly relevant to psychiatric symptoms. A neuropeptide is a small protein-like signalling molecule released by neurons, made by cutting down a larger precursor protein into the active peptide. For example, imagine two patients: one with chronic pain who improves on an opioid-like drug, mimicking endorphins, and one with panic attacks linked to abnormal cholecystokinin (CCK) signalling. In practice, several neuropeptides are co-released alongside a classic neurotransmitter, a process called co-transmission, rather than acting entirely alone.

Endorphins are the body's natural pain-relieving and reward-related neuropeptides, acting on the same opioid receptors that morphine and heroin target. Substance P is a neuropeptide central to pain transmission, and drugs that block its receptor are being studied as pain and mood treatments. Oxytocin and vasopressin are closely related neuropeptides: oxytocin is linked to social bonding, trust, and childbirth, while vasopressin (also called antidiuretic hormone) is linked to water regulation and, separately, to social and aggressive behaviour. Cholecystokinin (CCK) is a neuropeptide involved in satiety (feeling full after eating) and has also been directly implicated in triggering panic attacks. Take a research study that infuses CCK into volunteers: several develop a panic attack, directly demonstrating this neuropeptide's role beyond appetite. In practice, all neuropeptides share a common origin: they are made by cutting a larger precursor protein down to size, unlike classic neurotransmittersA chemical messenger that nerve cells release to signal to the next cell.Read more →, which are synthesised directly from simple building blocks.

• Which property distinguishes neuropeptide handling from that of classical transmitters?
• Which neuropeptide both stimulates appetite and is linked to resilience under stress?
• Beyond water balance, which behaviour is vasopressin most linked to in animal studies?

• Endorphins, act on opioid receptors for pain relief and reward, unlike substance P which signals pain through a separate receptor.
• Oxytocin, linked to social bonding and trust, whereas its close relative vasopressin is linked to water regulation and social behaviour.
• Cholecystokinin, involved in satiety, rather than only pain or bonding, and separately implicated in triggering panic attacks.
• Neuropeptides, made by cutting a larger precursor protein into the active peptide, unlike classic neurotransmittersA chemical messenger that nerve cells release to signal to the next cell.Read more → synthesised directly from simple building blocks.

• They act on neighbouring and distant neurons rather than only on the releasing cell.
• Motor coordination is a cerebellar function rather than a vasopressin one.
• Local synthesis and recycling describe classical small-molecule transmitters.
• They are stored in dense-core vesicles within the neuron.
• Release is calcium-dependent, as for other transmitters.

• Localise the clue to the relevant anatomical level, cell type, pathway or molecular process.
• Map that structure or process to its normal function.
• Predict the deficit or clinical sign produced when it is disrupted.
• Reject options that belong to a neighbouring structure, pathway or level of explanation.