What are opioids, and how do they work in the brain?
A poppy plant, a pharmacist in 1804 and a lab bench in 1973 explain why one family of molecules can ease pain and also stop breathing.
Opioids are a family of drugs that come from the opium poppy or imitate its chemistry. They work by fitting onto opioid receptors, which are docking points on nerve cells in the brain, the spinal cord and the gut. Once they dock, they turn down pain signals, and they also bring drowsiness, a feeling of calm or , and slower breathing.
The story starts with a pharmacist. In 1804 Friedrich Sertürner isolated morphine from opium, probably the first time anyone pulled a medicinal ingredient out of a plant in pure form. He named it after Morpheus, the Greek god of dreams, because it made people sleepy. Doctors have used morphine and its relatives ever since, mainly to relieve severe pain, including during surgery. They are also used to calm a cough or diarrhoea and, in carefully supervised treatment, to help people with opioid addiction.
Why do poppy chemicals fit into our nerves at all? Because our own bodies make opioid molecules, such as endorphins, that dock on the same receptors. In 1973 Candace Pert and Solomon Snyder published the first detailed evidence of a of this kind, now called the mu opioid receptor. A drug like morphine is a borrowed key that happens to fit our own lock.
Step 1: Opioid molecule
From the opium poppy, or a lookalike made in a lab
Step 2: Fits a
Docks on a mu opioid on a nerve cell
Step 3: Pain signals dampen
The same lock the body's own endorphins use
Step 4: Other effects follow
Pleasure, drowsiness and slower breathing
That is also the catch. The same receptors that dampen pain also sit in a brain area called the pleasure centre, and activating them slows breathing. With repeated use the body adapts: it needs bigger amounts for the same effect (), and stopping suddenly causes unpleasant . Because opioids are addictive and can cause a fatal overdose, most are controlled substances.
Try it
What tolerance does to the curve
y = 1 / (1 + e^(−1(x − 3)))
Challenge · Tolerance pushes the curve to the right. Move the midpoint from 3 to 6: how many times more drug now gives the same half effect?
Quiz me
0/3
Recap
Opioids work by fitting the body's own opioid receptors, so one drug can relieve pain, bring euphoria and slow breathing.
💡 A trick to remember it · A borrowed key in the body's own lock: it opens pain relief, but the same lock sits next to the breathing switch.
Surprising fact · Morphine, isolated in 1804, was named after Morpheus, the Greek god of dreams.
Connects to
- 🫁 Why does an opioid overdose stop your breathing?
- 😴 Why did surgeons race against the clock until a dentist put a patient to sleep in 1846?
- ⚓ Was the Opium War really about opium, or about something bigger?
- 🔑 How does a drug find the right cells in a whole body?
- 🏃 Does the 'runner's high' really come from endorphins?
Sources (5)
No source, no claim. Every fact in this lesson (13 claims) cites at least one of these.