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Psychoactive Drugs and What Makes Them So Hazardous
Psychoactive drugs are chemicals which alter the normal functioning of the brain by suppressing or stimulating the Central Nervous System. These are known to cause temporary changes in behavior, mood and consciousness. While these drugs can be used therapeutically to treat both physical and psychological disorders, they have become notorious for their recreational use; especially since perpetual use of these drugs is known to cause drug dependence i.e. addiction to the particular drug. Psychoactive drugs successfully alter the emotional state of the mind because of their chemical and morphological resemblance to natural biomolecules involved in neuronal pathways. The nature of drug dependence can be analyzed under two different aspects, normally psychological dependence and physiological dependence.
Despite having varying effects on the Central Nervous System, all psychoactive drugs essentially follow the same mechanism, i.e. stimulation of the self reward system of the brain. The brain recognizes actions which enhance the survival of an individual and perpetuates these actions by coupling them to a reward system. This is hypothesized to have developed during the course of human evolution. Stimulation of brain reward systems produces changes in affect ranging from slight mood elevation to a deep sense of well being and euphoria. For example, the addition of various ingredients in food (e.g. sugars, fats) activates taste receptors which in turn activate the brain reward pathways. Psychoactive drugs activate the brain reward system directly or indirectly.
The brain reward pathway functions through the neurotransmitter dopamine. Dopamine is associated with feelings ranging from motivation, desire and hypnotism. A study performed on animals showed that rats depleted of dopamine by 99% showed resistance even to the most basic life sustaining activities such as feeding. Thus dopamine dependent neuronal pathways are to a large extent responsible for maintaining the emotional well being of the concerned organism. Normally, dopamine pathways function at a slow rate, i.e. small quantities of dopamine are periodically released into the synaptic cleft or inter neuronal space. The levels of dopamine produced when cells are active at this low rate may be accountable for maintaining the ‘normal’ mood and tone. Psychoactive drugs step up this neuronal pathways to varying degrees. For example, heroin increases the action potential and consequently the concentration of dopamine in synaptic clefts. Cocaine on the other hand inhibits the reuptake of dopamine from the synaptic cleft. Such an increase in dopamine concentration brings about feelings of jubilation, relief and contentment.
However these effects are not long lasting and their perpetual functioning is hindered because of the negative feedback mechanism of the mesolimbic system. The cells respond to the increased concentration of dopamine by slowing down its synthesis; moreover, continuous release of dopamine into the blood results in the up regulation of the molecule,
adenylate cyclase which is an inhibitor of self reward response and dopamine. Together,
these adaptations cause a decrease in the magnitude of the drug response, an effect
known
as tolerance. In simpler words, tolerance implies that the nerve cells have to a certain extent, become resistant to the administered drug. This explains the need for higher doses to get the same degree of euphoric response once the user becomes well accustomed to the drug. When the nerve cells are pushed to a highly tolerant state, the levels of dopamine in blood, in the absence of the drug touch an extreme low. This is a direct consequence of the negative feedback mechanism which acts against dopamine pathways. This means that under such conditions the user may feel depressed, lifeless and empty. In regular users, this state is realized as soon as the effect of the drug diminishes, and to escape this situation the user is compelled to administer the drug again. In extreme cases addicts need drugs merely to feel normal. This leads to psychological dependence, a more common term for which is called ‘drug craving’.
While all drugs produce psychological dependence to various extents, they may or may not have a tendency to cause physiological dependence. Where emotional well beings is the primary motive for repeated and intense administration of a drug, certain drugs when taken in sufficient dose and frequency, are capable of producing physiological changes which encourage their continued use. Once the user abstains from such a drug, severe physical illness follows. It is the desire to escape withdrawal sickness that ultimately causes physical dependence. The withdrawal symptoms range from stomach cramps, insomnia, body chill to severe pain and convulsions.
Various psychoactive drugs, depending on their mechanism, are characterized as narcotics, depressants, stimulants and hallucinogens. Stimulants are a class of psychoactive drug that tend to increase brain activity. These drugs can temporarily elevate alertness, mood and awareness. Drugs that are classed as stimulants include caffeine, nicotine, cocaine and amphetamines. Excessive use of caffeine products (e.g. tea, coffee) can lead to low degrees of psychological dependence, although withdrawal symptoms mainly include anxiety and mild stress. Depressants are drugs which inhibit the function of the central nervous system and are among the most widely used drugs in the world. Drugs which are classed as depressants include alcohol, barbiturates, equanil and valium. Equanil and valium are also used as medicinal drugs and in low doses they act as tranquilizers and analgesics. Most people overlook the fact that alcohol or ethyl alcohol is ultimately a drug. Its major behavioral effects are derived from its depressant action on the central nervous system, where it acts to suppress the control of thought processes like judgment, memory, concentration and also muscle coordination.
Hallucinogens are psychoactive drugs that affect thinking, alter moods and distort perceptions. The most commonly used hallucinogen is marijuana; others include LSD (Lysergic Acid Diethylamide) and phencyclidine. The term narcotic is derived from the Greek word ‘narkotikos’, which implies a state of lethargy or sluggishness. Pharmacologists classically narcotic drugs as substances that give relief from pain and induce sleep. Narcotics are perhaps the most dangerous drugs and cause high degree of dependence in its users; examples include heroin, morphine, methadone and codeine. There are many instances where drug ‘overdose’ proves to be fatal. This mostly happens when a mixture of cocaine and heroin are consumed together. Since heroin and cocaine work on different parts of the mesolimbic dopamine neurons, they can be combined to produce even more intense dopamine activation. The heroin increases the cell action potential and dopamine release, while the cocaine keeps the released dopamine in the synaptic cleft longer thereby intensifying and prolonging its effects. This combination of drugs is extremely dangerous, and users show very rapid psychological and physiological deterioration and in extreme cases this mixture can prove to be fatal.
Drug abuse over the years has grown from a problem generally associated with members of the lower end of the socio­economic ladder to one that cuts across all social classes of society. Today twenty three million people in the United States alone are users of illicit drugs. The number is increasing at alarming rates especially among adolescents. Experts treat drug addiction as a disease without a definite cure. In this case prevention is the best cure which can be implemented only through mass awareness. References:
T.L Lemke and D.A Williams, Medicinal Chemistry. Campbell and Reece, Biology, 7th edition.
Sadava, Heller, Purves, Hillis and Oriams, Life, 8th edition.
R. Saferstein, Criminalistics, 6th edition.
J.A. Siegel, Forensic Science, 3rd edition.