Mechanisms of addiction in stimulants, depressants, and opioids

¶ … biological aspects of drug addiction. In order to do this we provide a detailed analysis of two main categories of drugs. These categories include stimulants and depressants. We then compare their mechanisms of addiction and then finally conclude with the possible therapies that can be administered to counter these addictions.

The addiction to drugs a condition also referred to as drug dependence is one of the most serious health problems (Nutt,1996).It causes a massive amount of direct health costs that results due to psychiatric and physical financial burden associated with the condition. The other costs that are associated with this health problem are crime, loss of productivity and earnings as well as social damage. The drugs of our primary concern are stimulants (cocaine and amphetamines), opioids and depressants such as alcohol. The other one which we are not going to focus on is nicotine addiction (smoking), another major cause of health concern. One of the major goals of medicine is to come up with a way of reducing the extent of drug addiction.

The addiction mechanisms in the brain

The process of drug addiction involves the alteration of certain functions of the brain since the abused drugs are neuroactive substances that are involved in a process of altering the brain transmitter functions.There is a lot of research which is currently being undertaken in order to provide further insight into the exact neurochemical as well as the molecular actions of drug use and abuse. This is with the intention of determining the reasons as to why humans misuse drugs and how to rehabilitate the users. There are various interesting new development into the study of the mechanism of drug addiction in the brain. One of these is neuroimaging that entails:

PET (position emission tomography)

SPELT (single photon emission computed tomography),technologies that have been hailed as being the very first to be used in the testing for the mechanisms of drug addiction in humans by means of data derived from various preclinical studies.

The specific processes in the brain that have been noted to be responsible for alcoholism and its various manifestations have been documented to involve the functions of attention, learning, emotion as well as cognition. A normal human brain must first of all orchestrate most of these functions at the same time in order to perceive a given environment. They then access the significance of the environment in relations to survival. This is then followed with an initiation of the behavioral reactions. These processes and activities require a very efficient communication mechanism between the different regions of a person's brain. There is also a multilevel communication within these brain regions. In order to illustrate the mechanism of addiction in the brain of a human being, we consider the case of alcohol addiction. In this paper we presents this process by means of a three level process of communication within the brain of a human being. These are:

1. The synaptic level-involves the transfer of information between the individual neurons

2. The system level that represents the integrated activities of the different regions of the brain

3. The intracellular level-comprises of the various signaling processes that takes place within the neurons.

Information is then effectively transferred by the various chemical messengers (neurotransmitters) which gets released by a neuron then bound effectively by a specialized protein type called receptors. These receptors are embedded in the membrane (outer one) of another neuron. There exists a tiny gap between these communicating neurons. It is referred to as a synapse.

Several neurotransmitters are active during the process of addiction. Each of these transmitters does bind to a certain specific receptor. It is however worth pointing out that a specific receptor may be in existence in multiple subtypes. Each of these subtypes may produce unique responses to the same transmitter. This is what accounts for the multiple effects of a certain neurotransmitter in different parts of the same neuron as pointed out by Weiner et al. (1997).It is worth noting that a given neuron's response to a certain information that is received from other neurons depends largely on the complex interactions that exists between potentially conflicting messages that do arrive simultaneously as indicated by Charness (1990).

One of the most dominant effects of alcohol is the reduction of the pace at which the brain activity takes place through;

1. The reduction of the excitatory mechanisms of glutamate, a neurotransmitter at the NMDA subtype of the glutamate receptor.

The boosting of the various inhibitory actions of a transmitter referred to as gamma-aminobutyric acid (GABA) .This occurs at the GABAA receptor as pointed out by Diamond and Gordon (1997).These actions are just among the reasons as to why alcohol is considered a depressant.

The actions of the NMDA and GABAA re c e p t o r s are effectively linked via ionic channels. These do function through the opening of a special pore at the surface of the membrane that allows for the specific ion (atoms that are electrically charged ) to go into the cell hence affecting the cell's electrolytic balance as postulated by Harris (1999).The other neurotransmitters that affect the process of alcohol addiction are dopamine, opioptides and serotonin (5-HT).These neurotransmitters do interact in specific ways with the various receptors in order to modulate the various activities of the specific neurons in which the reside. The role of dopamine in the encouragement of motivational behavior has been noted. This happens through a complex process of pursing of a certain rewarding stimuli. The administration of alcohol causes the release of dopamine in the brain of an individual. This region is called the nucleus accumbens and is a key member of a special group of structures that are linked and associated with the process of development of addiction to drugs (Rassnick et al. 1992; Bro'd I e and Pesold 1999).

The Opioid peptides are yet another class of neurotransmitters that are active in the production of physiological effects that are very similar to those of heroin and morphine. In the body of a human being however, the opioid peptides do interact with certain other neurotransmitters in order to influence a particularly broad spectrum of physiological functions that include the control of pain in humans.

A very high level of certain types of opioid peptides does have an effect in the encouragement of euphoria. The consumption of alcohol does affect the activity of the opioid peptide transmitter which responds by increasing the effects of alcohol as pointed out by Roberts et al. (2000).There is a medication referred to as naloxone which is active in the inhibition of the various functions of the receptors, opiod peptides. It blocks the release of the receptor dopamine which resides in the nucleus accumbens which has also been noted to suppress the consumption of alcohol through a laboratory test carried on animals as indicated by the work of Benjamin et al. (1993).Serotonin is also actively involved in the process of regulating mood, appetite, body temperature and a host of other humanly physiological functions. There have been certain experiments involving the mice that involved the genetic altering of the mice to lack serotonin receptor subtypes. These have suggested that there is role of serotonin in the regulation of the drinking levels.

It is worth pointing out that alcohol can lead to induced activation of certain specific serotonin receptor subtypes can lead to a stimulation of the dopaminergic activity in an individual's nucleus accumbens.This potentially contributes to the rewarding effects of alcohol. There are however other serotonin receptors have been shown to have effects and roles in the process of drug intoxication and withdrawal (Venezula,1997).

Symptomology

Addiction to depressants such as alcohols leads the user to exhibit the following symptoms of addiction:

Craving -- the user experiences a very strong desire and compulsion to drink

Physical dependence: the user experiences withdrawal symptoms whenever they stop drinking after an extended period of drinking. These include anxiety, nausea and shaking

Tolerance: The person undergoes a continuous need to take more and more quantities of alcohol in order to get drunk

Loss of control: The user experiences the inability to limit their drinking over a period of time

Alcohol's neuronal circuit

The 1980s discovery that alcohol at certain concentration can cause or rather produce intoxication in human beings which can inhibit the various excitatory effects of the special NMDA receptor thereby enhancing the inhibitory functions of the other special GABA receptor. A lot of research on alcohol has been dedicated towards the identification of the specific ions channels and receptors that get affected by alcohol. Alcohol has a unique characteristic that is absent in the other illicit drugs since it does not have a specific and special transmitter bind site in an individual's brain. It is worth noting that there is a complex behavior that is associated with the use of alcohol. These behaviors cannot be attributed to a certain limited number of special chemical interactions. This form of realization has given rise to an intimate look at the various effects of alcohol on the neuronal communication which can effectively integrate the various activities of a many brain regions.

Demographics

All factors remaining constant, studies shows that the overuse of alcohol is most common among young individuals. A survey revealed that 15.9 million American are classified as "heavy" drinkers and another 27.4% of the 2009 high school classes were reported to have drunk at least one a month. The survey was annual (DINF,2010)

The addiction process of stimulants

The addiction mechanism of stimulants such as cocaine has been a subject of late scientific research. New studies such as have shown that there is a more detail regarding the way stimulants acts in the body of the users. In order to illustrate the process of cocaine addiction, we use the latest model advanced by scientists (NIH,2010).

Researchers have demonstrated how the pleasurable effects of cocaine are achieved and whuy it is so addictive. They have proven that it affects certain areas of the brain. They have shown that cocaine affects a region in the midbrain referred to as ventral tegmental area (VTA).The various nerve fibres tha originate in the VTA do extend to another region referred to as the nucleus acumens.An increased level of dopamine, a neurotransmitter increases brain activity in the brain's nucleus accumbens. During the normal process of communication, dopamine gets released by a neuron into a small gap that exists between two neutrons (synapse).This then binds to a specialized group of proteins referred to as dopamine receptors which resides on the nearby neutron and then sends the signal to the next one. The use of stimulants such as cocaine interferes with the normal process of communication. Scientists have found that cocaine works by blocking the process of removing dopamine from the synapse. This results in an accumulation of dopamine at the synapse and hence an amplification of the signal being transmitted. This causes the initial euphoria which is often reported b cocaine abusers (NIDA,2010).

Symptomology of stimulant addiction

Insomenia

Restlessness

Loss of appetite

High energy level and euphoria

Sudden depression

Anxiety

Paranoia

Loss of energy

Weight loss

Pupil dilation

Involuntary muscle twitches

Psychosis

Convulsion

Fever

Coma

Demographics

The use of cocaine has sharply fallen since 1080's when it was highest. The year 2008 saw the number of Americans who admitted to using cocaine stand at 1,855,000.A figure which was just a third of the earlier 5,686,000 who were reported to be users in 1985.This figure is also about 25% below the totals for 2006 (DINF,2010)

Comparison and contrasting of the mechanism

It is clear that the process of addiction by stimulants and depressants are quite different in terms of the overall mechanisms and processes.The similarity comes in the fact that certain receptors such as dopamine are present in both processes as well as regions of the brain such as nucleus accumbens

Conclusion

A knowledge of the mechanisms of addiction is integral in the process of coming up with treatment of drug addiction. It is therefore crucial to come up with the best ways of treatment that is derived from the existing research work.