3 L5 Stimulants Flashcards
(13 cards)
Define tolerance
Decrease in potency of a drug after repeated use- More drug is required for same response
2 mechanisms of tolerance
Change in receptor expression - Internalisation of receptors
How can change in receptor expression lead to tolerance
Fewer receptors are present on neurons
How can receptor internalisation lead to tolerance
Prolonged exposure to agonists will cause receptors to be internalised into cell
How does tolerance impact neurotransmission
Receptor down regulation- Fewer Rs available on PS neurons - NT release results in less receptor activation - Decreased intracellular signalling - If fewer D1 GPCRs are present, less cAMP will be produced inside cell
Where is dopamine released from
VTA (Ventral Tegmental Area)
Where are dopamine receptors found
In the nucleus accumbens
Is phasic or tonic firing of dopamine receptors more likely to increase drug dependence
Phasic or “fast burst” firing is more likely to increase drug dependence
What is the role of dopamine in drug dependence
Most drugs increase dopamine levels in brain
NDRAs examples and mechanism of action
Amphetamine and Methamphetamine enter vesicles and push dopamine and NA into synapse- These high levels of NT bind to their receptors
Does methamphetamine or amphetamine enter the brain more rapidly- Explain
Methamphetamine enters more rapidly- exhibits increased dependence risk compared to amphetamine
SRAs example and method of action
MDMA released serotonin- less dependence than methamphetamine
Compare D1 and D2 receptors in terms of speed of administration
D2- High dopamine affinity - Active at low dopamine levels - Involved in tonic functions
D1- Low dopamine affinity - Requires high dopamine levels - Needs phasic firing to activate
