Biology, Behavior, and the Brain: Methamphetamine Addiction

Methamphetamine is a powerful drug, roaring through our reservations at an alarming rate of "speed.”  Maybe you've seen a movie that depicts some of the paranoid behaviors of a meth addict, or maybe there's someone from your own life experience who has used crystal meth.  I know that has been true in my life.  Though we may have seen the outward effects of crank use, most of us have no idea how this deadly, persuasive menace affects us at a biochemical level.

Classified by the scientific community as a psychomotor stimulant, methamphetamine acts as a chemical messenger in the sympathetic nervous system. This is the system responsible for “fight or flight” and other similar behaviors. For this reason scientists call methamphetamines, cocaine, and other central stimulants sympathomimetics, meaning they act upon the sympathetic nervous system.

Chemical Characteristics of Methamphetamines

Chemical messengers, or neurotransmitters, communicate information at specific receptor sites. Methamphetamine is a compound that mimics a neurotransmitter at serotonin (5-HT) and dopamine (DA) receptor sites, which means that it relays information as though it were that specific neurotransmitter.  The relationship between receptor and receptor site is similar to that of a lock and its key; the receptor site (lock) is prepared to receive only information that the specific neurotransmitter (key) recognizes as its chemical counterpart.

 Methamphetamine increases the release and blocks the uptake of dopamine.  These monoamines,  along with norepinephrine, (NE), and epinephrine (E), play a critical role in understanding the way in which methamphetamines act upon neurotransmitters in the sympathetic nervous system and act on the behavior of the organism.    

Behavioral Effects of Methamphetamine

The dopamine and serotonin systems influence aggressive, defensive, social and sexual behaviors.  Users of methamphetamines exhibit exaggerations in these behaviors.  Bipolar (manic-depressive) people might also behave this way.  People using speed also exhibit behaviors similar to a schizophrenic. 

             In animal studies, methamphetamine consumption stimulates locomotor activity, and produces stereotypic behaviors.  These have been related to the norepinephrine, dopamine and serotonin systems.

 

Drug-related stereotypy is term referring to repetitive behaviors.  In rats, stereotypic behaviors may include head sways, hyperactivity, avoidance behaviors, and automutilation (self-mutilation). 

 E.Rylander, a researcher in the 1960’s, studied several Danish methamphetamine users.  He was the first to note a behavior known as Punding.  Punding is performing a useless task compulsively again and again.   This seems to be the human equivalent of drug-related stereotypy.

Interestingly, these Danish users reported being aware of their Punding behavior, but were unable to cease performing it.  The behavior could be assembling, disassembling, and reassembling an apparatus after a compulsive fashion.  Punding is known colloquially as “tweaker habits,” and could include coloring, writing, playing cards, or taking apart items in a prolonged and bizarre manner.

            Amphetamine psychosis is another prominent aspect of methamphetamine use, and is nearly identical to full-blown schizophrenia.   There is a direct relationship between this psychosis and the alterations in the DA system.  Other similarities include hallucinations, aggression, and increased excitability. 

Biology, Behavior, and the Brain

  Animal studies have cast a fascinating light into drug studies at a cellular level.  The basic assumption behind all drug use is that it does not take place repeatedly in the absence of some kind of reinforcement or reward.   One contemporary model used as a framework for the biological basis of addiction is called the "Brain Reward System.”  This model studies the psychological and chemical aspects of drug addiction, proposing that an organism engages in a drug-seeking behavior because it is somehow rewarding for them to do so.  Experiments show that an animal will work to obtain electrical stimulation to the lateral hypothalamic brain region.  Drugs such as methamphetamine lower the threshold for this rewarding brain stimulation. 

For psychologists, these are important activities to investigate, because it is essential to understand what the "hook" is for people who get "hooked."  (The trouble with drugs is that people who use 'em just keep on using!)  The answer to the question, "WHY "is a bit involved, however. 

Biopsychology and Addiction

Biopsychology is the study of behavior from a biological perspective.  Researchers have established that central stimulants, including methamphetamine, have very specific actions on certain brain structures.   These structures, including the brain's pleasure centers, are stimulated, which creates a pleasurable effect on the organism.  Studies also show that when an animal receives a stimulant, its reward threshold (minimum level at which an organism becomes sensitive to a pleasurable stimulus) is reduced, an immediate response to a small amount of drug.  This electrochemical stimulation is what produces sensations of euphoria. 

The sensation of euphoria encourages the organism to repeat the pleasure-producing behavior, but a tricky thing happens after the user experiences the initial enjoyment: It quits being as enjoyable.  The reward threshold increases again, meaning that while these drugs may be pleasurable at first, the sensitivity to the drug quickly goes down, and the drug fails to yield the same euphoric results. 

This phenomenon is called  "Chasing the Ghost" by drug users.  There could be an internal mechanism that serves to protect the system from toxification (poisoning), yet the insanity of addiction drives the creature to pursue the pleasurable sensation again and again.

The destructive action of this drug is compelling and profound.  Though it is unlikely that drugs will affect every being identically, this overview of the biopsychology of methamphetamine use paints a dark image for anyone who considers using meth.

One might wonder how an understanding of neurotransmitters and Brain Reward Systems can have any impact on the monstrous problem of drug addiction.  Some argue that it is a problem only experienced by people of weak moral constitutions or defective characters. In reality, methamphetamine abuse and addiction is an affliction of many people in many cultures.  "Fathers, soldiers, sons," anyone can join the ranks of methamphetamine addicts.  It remains a leveling influence, a great "respecter of no one." 

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