Amphetamines are psychostimulants. That is, they stimulate the central nervous system and basically speed us up.
All psychostimulants cause these effects by increasing the presence of three chemicals known as neurotransmitters. These three neurotransmitters are
- Serotonin (also referred to as 5-hydroxytryptamine or 5-HT)
- Norepinephrine (also referred to as Noradrenaline)
Although they affect all three neurotransmitters, amphetamines predominately work on dopamine.
What are neurotransmitters?
Neurotransmitters are the brain chemicals that communicate information throughout our brain and body. They relay signals between nerve cells, called “neurons.” The brain uses neurotransmitters to tell your heart to beat, your lungs to breathe, and your stomach to digest. It is believed that the brain contains several hundred different types of neurotransmitters. Different neurotransmitters serve different functions.
Videos courtesy, Laboratory of Neuro Imaging, UCLA and modified by Bluebelly with permission.
Dopamine plays a critical role in the function of the central nervous system, including roles in behaviour, cognition, voluntary movement, sleep, mood, attention, and learning.
Dopamine is also linked with the brain's complex system of motivation and reward. The release of dopamine into the brain elicits a sense of reward and pleasure. Instances where dopamine release would normally occur include during sex, when hugging your child, or consuming a nice meal.
Serotonin is associated with levels of arousal, thermoregulation, mood, appetite, sleep and pain regulatory systems. Normally an increase in serotonin levels will cause a diminishing of appetite, sexual behaviour, aggressiveness and pain perception, and an increase in empathy for those around you.
(MDMA has a far greater impact on serotonin release and uptake compared with amphetamines or cocaine).
Norepinephrine is associated with the body’s fight or flight response, increasing heart rate, triggering the release of glucose from energy stores, and moving blood flow away from the digestive system and towards the skeletal muscles.
Amphetamines and the brain
*Please note: Accurate knowledge about psychostimulants and their actions on the brain is the topic of much current research. Theories are emerging, but a lot of research has been conducted on animals and using greater than recreational doses. Below is the current best guess on what happens in humans but this may change as we learn more
When we take amphetamines they travel to the brain and enter our nerve cells. Within these brain nerve cells it is thought that amphetamines increase dopamine levels in three ways:
- They invade the nerve cell preceding the synapse (or gap) and push out extra dopamine into the synapse
- They then plug the transporter molecules to prevent the re-uptake of dopamine, artificially holding the dopamine at high levels
- It is possible that while amphetamines are bound to transporters they actually cause the transporters to work in reverse, pumping even more dopamine out into the synapse
What does this mean?
Dopamine is normally released into the synapse as a result of a pleasurable activity such as eating good food and then is recycled by transporters back into the nerve cell and the good feeling is over.
Amphetamines cause an increased release of dopamine into the synapse and then prevent it from being recycled, making the feeling more intense and lasting longer.
Depending on a range of variables, including the type of drug, dopamine levels can remain high and we feel the effects of amphetamines for 4 to 24 hours.
Although dopamine is the major neurotransmitter released, we need to remember that amphetamines also cause an increase in serotonin and a resulting depletion, as well as noradrenaline leading to a fight-or-flight response.