How do drugs affect the nervous system?

How does the consumption of psychoactive substances influence our nervous system? Let's take a look.

Drug use and abuse is a serious social and health problem worldwide. Substance abuse kills, directly or indirectly, some 11.8 million people annually.

Alcohol and nicotine take the dubious prize in terms of lethality.Alcohol and nicotine take the dubious prize for lethality: because of them, 11.4 million people die earlier than expected each year. According to the WHO, up to half of the people who use tobacco end up dying because of it.

The prevalence of substance use disorders is estimated at 1.5% of the world's population, although in some disadvantaged regions this percentage rises to 5%. However low these figures may seem, don't be fooled: one in five people in the world (20%) use tobacco. The fact that addictive behavior is not reflected in epidemiological data depends solely on whether the person is lucky in not paying for this dependence at the physiological level.

With all these statistics we only want to make it clear that the consumption of addictive substances claims as many lives and causes as many pathologies as many pandemic events caused by viruses and bacteria. With the intention of taking a more biological and anatomical approach to this global problem, here we will review the issue of how drugs affect the nervous system.

The basis of drugs

The World Health Organization (WHO) defines a "drug" as any therapeutic or non-therapeutic substance that, when introduced into the body by any route of administration, produces an alteration, in some way, of the natural functioning of the individual's central nervous system and is also susceptible to creating dependence. It should be noted that the dependence developed may be physiological, psychological or both.

The American Psychological Association (APA) recognizes several types of drugs in use, grouped into 10 categories alcohol, caffeine, cannabis, hallucinogens, inhalants, opioids, sedatives, hypnotics (including anxiolytics), stimulants (cocaine and others) and tobacco. These are the substances that are considered addictive today, but certainly not the only ones.

Among the activities that can generate dependence, only one is currently considered potentially pathological: gambling. Surprisingly, it has been shown that the altered reward circuitry in a patient addicted to gambling responds similarly to the stimulus (winning a cash prize) as a cocaine addict does when receiving a new dose. Other activities that could share mechanisms with drugs, such as video games, compulsive shopping and chronically practiced exercise, are still being evaluated.

Drugs and their effect on the human body's nervous system.

Let's start with the most basic: nicotine. When a person smokes a cigarette, the nicotine passes into the bloodstream, then into the brain and in just 7 seconds it produces excitation in part of the neurons located in the ventral tegmental area (VTA), which send signals to the nucleus of the brain.which send signals to the nucleus accumbens. The latter is responsible for producing dopamine, the neurotransmitter and hormone that makes us feel that "rush" or shock of well-being.

In the case of tobacco, this sensation is very ephemeral, because as soon as the nicotine acts, it stops: the physiological peak of this drug is 7 seconds and its downward range is another 7 seconds, the more the neurons and circuits of the nucleus accumbens are exposed to the substance, the more of it is needed to elicit the desired response. to elicit the desired response. This is how tolerance and long-term dependence are generated.

To find out how drugs affect the nervous system, we can turn to another, rather more aggressive drug: heroin. This drug enters the brain quickly, attaches to the opioid receptors of cells located in different areas and causes changes in the excitability of neurons, stimulating the presynaptic release of gamma-aminobutyric acid (GABA), among other things.

When in contact with this drug at the nervous level, there is a generalized sedative effect and an indescribable well-being (the level of dopamine in the reward system described is increased by 200% in experimental models). All this causes euphoria, drowsiness, a feeling of warmth and gradual loss of consciousness, accompanied by a powerful analgesic effect. People who have taken it are not lying when they say they are "on a cloud". claim to be "on cloud nine" in the in the moments after the injection.

Finally, we can dissect the effects of cocaine on the nervous systemcocaine, the third of the drugs most present in general culture. Once consumed, the effects on the central nervous system are felt within 10 seconds (inhaled) and 3-5 minutes if consumed intranasally. This compound inhibits the action of monoamine transporters, resulting in vasoconstriction in the Blood system, elevated blood pressure, tachycardia and increased cardiac output. All this reports a very characteristic feeling of activation and euphoria.

Chronic cocaine abuse puts the patient at risk of many events, such as suffering a stroke (cerebrovascular accident), subarachnoid hemorrhages, intraparenchymal hemorrhages and many other things. In general, every drug addict is seven times more likely to suffer an ischemic infarction, a value that is multiplied even more in those who use cocaine.

Beyond all these mechanisms, it should be noted that dependence itself also modifies the functioning of the patient's nervous system. When the abstinence syndrome occurs (within 72 hours of cutting off the use of a substance altogether), the person experiences anxiety, restlessness, difficulty concentrating, nervousness, stress and other associated sensations. The addict's brain can only function "normally" with the presence of the chemicals described. When they are withdrawn, the nervous system fails.

Summary

As you have seen, drugs function similarly to the neurotransmitters circulating in the human body: they reach an area, stimulate or inhibit cellular activity, and generate a short-term response.. When their peak activity ceases, the individual physiological state returns to normal, but as dependence is generated, reaching this "normality" is increasingly complex.

In addition, you must keep in mind that we have moved into purely physiological terrain. Addiction to a substance can also have a psychological basis and, therefore, there are people who can manifest addictive mechanisms towards substances that the body does not really need at the moment of crisis. Undoubtedly, we still have a lot of research to do as a society to elucidate the mechanisms of dependence in the human mind.