FOUR LEVERS

Where a drug can act

Almost every drug that acts on neurotransmission works at one of a few places.

Learn the four levers and you can read most mechanisms.

REAL EXAMPLES

Each lever, with a drug

Agonist Nicotine activates nicotinic receptors, and pramipexole activates dopamine D2 and D3 receptors

Antagonist Haloperidol blocks D2 receptors, and curare blocks nicotinic receptors at muscle

Reuptake blocker Fluoxetine blocks SERT, and cocaine and methylphenidate block the dopamine transporter

Enzyme inhibitor Donepezil inhibits acetylcholinesterase, and selegiline inhibits MAO-B

The mechanism often hides in the drug's name or class.

SUPPLY AND RELEASE

More, or release more

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Precursors

L-DOPA is converted to dopamine, so it increases supply

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Releasers

Amphetamine pushes dopamine out of terminals by reversing the transporter

A drug can add transmitter, not just stop its removal.

A SUBTLER LEVER

Allosteric modulators

Benzodiazepines bind to a separate site on the GABA-A receptor. They do not open it themselves, but they make GABA's own effect stronger. This is called positive allosteric modulation.

A drug can turn up the volume without being the signal.

THE CATCH

Drugs are rarely perfectly selective

A drug may touch several receptors or transporters, so it can have side effects. It also has to reach the brain, which means crossing the blood-brain barrier. Both problems are why researchers want better models and sensors.

A drug has to be effective, selective, and able to get there.

UNIT 12 STUDY COMPLETE

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Ready for the Fab Challenge?

You've matched real drugs to the four levers they pull at a synapse.