Psychoactive drugs can affect the Central Nervous System via:
- Selective inhibition of the production of a particular neurotransmitter
- Speeding the metabolism of a particular neurotransmitter
- Mimicking a neurotransmitter at a particular receptor site
- Increasing the production of a neurotransmitter
- Inhibiting the re-uptake of a neurotransmitter thereby creating an artificial build up
Types of neurotransmitters
Dopamine is well known as the neurotransmitter responsible for feelings of pleasure and is present in several different parts of the brain. Dopamine is also associated with the coordination of movement, logical thinking, emotion, cognition and motivation.
Recreational psychoactive drugs have their first effect on dopamine. The pleasurable feeling of euphoria, relief or excitement that is so intensely satisfying and rewarding is caused by the drug dumping large amounts of dopamine into synapses, or preventing its re-uptake. This is “the rush”.
Dopamine is also linked to survival areas in the brain and when it stimulates these areas, creates a response of “Aaaah, that feels great, do it again”. The effects of dopamine explain why some people use drugs more than once – because most people like to repeat experiences that are pleasurable or ones that reduce suffering (Denning et al, 2004:75/76).
Norepinephrine: One of the brain’s natural stimulants is norephinephrine, responsible for increasing alertness and mental focus. Norepinephrine is also responsible for the human stress response or “fight or flight” response. When there is a threat of danger, a series of chemical responses prepares us to deal with it by pumping adrenaline into our bodies to allow us to think fast and move even faster. (Adrenaline is called epinephrine and is a very similar chemical to norephineprine in the brain). Stress hormones are released by this output of energy which can, over time, weaken the immune system and cause greater susceptibility to illnesses (Denning et al, 2004).
Serotonin has several complicated roles in the brain including affecting or controlling mood and is associated with depression. Low levels of serotonin are also linked to aggression, irritability and premenstrual syndrome.
Serotonin helps to regulate sleep, sexual functioning and appetite. Some serotonin cells are responsible for hallucinations. The actions of other neurotransmitters may also be regulated by serotonin. Low levels of serotonin may also result in the dysregulation of neurotransmitters that affect other conditions such as anxiety, panic and pain sensitivity (Denning et al, 2004).
GABA (gamma-aminobutyric acid) acts to relax the brain and is often called “the brain’s Valium”. Certain kinds of brain activity, hyperactivity or overexcitement are suppressed by GABA, whilst higher cognitive processes remain unaffected. Thus the release of GABA produces feelings of calm but the individual can remain alert. Not enough GABA produces anxiety and worry. There is also a risk of seizures which are the result of excessive electrical activity in the brain. This electrical activity is calmed by GABA (Denning et al, 2004).
Endorphins: Several different types of chemicals that are all related to pain perception and pain control are called endorphins. Pain can take many forms including physical and emotional and relief from emotional pain may be part of this neurotransmitter’s role. A release of endorphins not only decreases pain but also induces a sense of well-being and happiness (Denning et al, 2004)
Anandamide is found in the hippocampus of the brain where memory formation and retrieval is contained. Anandamide may be associated with forgetfulness, whether this is related to ageing, disease or psychological conditions (Denning et al, 2004).
Glutamate is considered to be the major mediator of excitatory signals in the central nervous system and is involved in most aspects of normal brain function including cognition, memory and learning. Glutamate receptors are implicated in a number of neurological conditions including many neurodegenerative diseases and several other conditions have been further linked to glutamate receptor gene mutations or receptor autoantigen/antibody activity.
Acetylcholine helps with memory formation. It also works across several different areas of the brain and body transmitting orders from the brain to the muscular system (Denning et al, 2004).