Meth & The Brain

Like pretty much all psychoactive drugs, meth "works" by interfering with the normal workings of the brain’s neurotransmitters. These are the chemicals that pass messages between neurons in the brain and work together to perform many tasks, including creation of the sensation of pleasure.

All neurotransmitters come from amino acids. L-Tryptophan is the amino acid precursor (forerunner) for serotonin, and tyrosine is the precursor for dopamine and norepinephrine. The neurotransmitter systems that we'll be talking about are dopamine, norepinephrine, epinephrine, and serotonin. These transmitters all play a role in the effect meth has on the brain, and their functioning can be impaired on a short and long-term basis even after fairly minimal exposure to methamphetamine.

That's in part because methamphetamine's chemical structure closely resembles, or "mimics" these neurotransmitters. So meth affects these real neurotransmitters, either by increasing chemical release, or by interfering with the breakdown and "re-uptake" (absorption) of these neurochemicals.

As a chemical messenger, dopamine is similar to adrenaline. Dopamine affects brain processes that control movement, emotional response, and ability to experience pleasure and pain. Regulation of dopamine plays a crucial role in our mental and physical health. Neurons containing the neurotransmitter dopamine are clustered in the midbrain in an area called the "substantia nigra." (There's a term you'll use everyday!)

As a stress hormone, norepinephrine is released from the adrenal medulla and affects parts of the human brain where attention and responding actions are controlled. Along with epinephrine, norepinephrine underlies the fight-or-flight response, directly increasing heart rate, triggering the release of glucose from energy stores, and increasing skeletal muscle readiness. "Nor" stands for the German abbreviation "Nitrogenium Ohne Rest" meaning "Nitrogen without rest" referring to the absence of a methyl group at the N-atom present in epinephrine/adrenaline.

As mentioned above, in tandem with norepinephrine, epinephrine also underlies the "fight or flight" hormone which is released from the adrenal glands when danger threatens. When secreted by the area of the brain called the adrenal medulla into the bloodstream, it rapidly prepares the body for action in emergency situations. The hormone boosts the supply of oxygen and energy-giving glucose to the brain and muscles; and some bodily processes not vital to the response are suppressed.

And when we say the epinephrine is released "when danger threatens," once all the systems are damaged because of the introduction of a powerful stimulant like meth into the system, "danger" can be interpreted by the system as something as subtle as a loud noise or bright light.

When released into the bloodstream, epinephrine binds to multiple receptors and has numerous effects throughout the body. In addition to increases increases in heart rate and stroke volume, it also dilates the pupils, and constricts arterioles in the skin and gut while dilating arterioles in leg muscles. It elevates the blood sugar level by increasing catalysis of glycogen to glucose in the liver, and at the same time begins the breakdown of lipids in fat cells. Like some other stress hormones, epinephrine has a suppressive effect on the immune system.

In the central nervous system, serotonin is believed to play an important role in the regulation of anger, aggression, body temperature, mood, sleep, vomiting, sexuality, and appetite. Low levels of serotonin may be associated with several disorders, namely increase in aggressive and angry behaviors, clinical depression, obsessive-compulsive disorder (OCD), migraine, irritable bowel syndrome, tinnitus, fibromyalgia, bipolar disorder, anxiety disorders.

Serotonin taken orally does not pass into the serotonergic pathways of the central nervous system because it does not cross the blood-brain barrier. (BBB) However, tryptophan and its metabolite 5-Hydroxytryptophan (5-HTP), from which serotonin is synthesized, can and does cross the blood-brain barrier. These agents are available as dietary supplements and may be effective serotonergic agents. (Activated by, or capable of liberating serotonin, especially in transmitting nerve impulses.)

On the next page, we'll take all this scientific stuff and try and construct an analogy that will help you make sense of it.