Addiction and the Brain
The ponderance that Brain = Behavior and the inherent ramifications of such proves no more fascinating than when addressed in the context of "Addiction and the Brain". Essential to consider is:
-what exactly is an addictive/abusive substance (drugs of abuse)
-what brain center(s)/chemical(s)are involved
-what does it mean to become physiologically dependent
-how should the concept of addiction be addressed
-how might we use animal models
-and what sort of treatment approaches should be pursued.
These questions will be elucidated briefly, while further information remains available at the web sources listed below.
A drug of abuse/addiction would be one which leads to "recurrent and significant adverse consequences related to repeated use of the drug...[involving] compulsive drug use, interference with normal activities and may include tolerance and physical dependence" (2). The tolerance and physical dependence which frequently occurs as a normal physiological adaptation to non-addictive prescription medications must be distinguished from tolerance and physical dependence experienced in the context of addiction, a "chronic, relapsing illness characterized by compulsive drug seeking and use" ( 5).
In general, drugs of abuse tend to provoke a fast and intense change in brain chemistry, resulting in an 'intensely rewarding' euphoric state ( 1). This pleasurable state results from increased levels of the neurotransmitter dopamine (DA), a catecholamine. The elevated concentration, and increased synaptic presence of DA proves significant in the experience of pleasure, decrease of pain, and thus those components critical to the general mechanism of addiction ( 3). Those areas that release relatively large amounts of DA are the ventral tagmental area and the nucleus accumbens, the principle pleasure centers of the brain. All drugs of abuse seem to activate DA release from these two areas although each drug family tends to work via drastically different psychopharmacological mechanisms.
Besides the obvious appeal of the "high" or elation, which occurs subsequent to drug administration, a greater influence leading to an increased dosage and necessitated use, would seem the acquisition of tolerance. There are three subtypes, pharmacokinetic/dispositional tolerance, pharmacodynamic tolerance, and behavioral tolerance which all prove relevant in the drugs of abuse, with the exception of the stimulants (cocaine, methylphenidate, etc). Pharmacokinetic tolerance refers to the changes in substance distribution due to the bodies metabolism of the drug, while pharmacodynamic tolerance addresses the adaptive changes which have taken place within the system thereby reducing the efficacy of the drug. The final, behavioral tolerance, seems perhaps at once the most confusing and most compelling. Behavioral tolerance has to do with the learned tolerance in relation to a specific situation and it's...