- Also called affinity 
- The attraction between a drug/ligand to a receptor 
- Drugs can have a high or low binding affinity for receptors

Binding Affinity 

- Also called efficacy 
- The extent of a drug/ligand to activate a response after binding to a receptor 
- Agonists have high intrinsic activity 
- Antagonists have low intrinsic activity 
- Partial agonists have a middle response 

Intrinsic Activity

- Greater drug doses tend to produce greater effects
- This relationship is shown in dose-response curves

Dose Response Relationship 

- Binding affinity (where it binds to) and intrinsic activity (what it does) determines the action of a drug
- Drugs may bind strongly or weakly to receptors or not bind to any receptors at all 
- Drug molecules that affects more than one kind of receptor have more than one action in the body 
- Drugs exhibit dose response relationships 

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- Medicine used in the treatment of a disease 
- Examples include psychoactive drugs which alter functions of the brain and affect conscious experiences

Drug 

Breedlove, S. & Watson, N. (2017). Behavioral neuroscience, eighth edition. Oxford University Press.

Behavioral Neuroscience 8th Edition

- Drug molecules spread throughout the body 
- When drug molecules contact a receptor with the same shape, the two molecules bind together and create a chain of events 
- Lock (receptor) and key (drug molecules) action 
- Binding is usually temporary 
- When the drug leaves the receptor, the receptor returns to its unbound shape and normal functioning 

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