Motor System
Different types of drugs have been used to study the effects of dopamine activity in the striatum:
- apomorphine--dopamine agonist that binds to dopamine receptors
- amphetamine--drug that stimulates release of dopamine from nerve terminals in the striatum; secondarily, then the released dopamine will bind to dopamine receptors
- haloperidol--dopamine receptor antagonist that acts by blocking dopamine receptors (blocks the ability of dopamine to bind to its receptor)
The administration of apomorphine or amphetamine increases dopamine activity within the brain (including the striatum); two main motoric effects are produced:
- first, there is an increase in locomotion and exploratory behavior
- second, there is an increase in the display of stereotyped behaviors--repetitive movements of head, whiskers and forelimbs; these repetitive movements can include: chewing movements, excessive sniffing, up/down movements of the head, and so on