Drug Addiction as a Psychobiological Process
The emphasis is on biological
mechanisms underlying addiction, although some other factors influencing
drug addiction will also be discussed. The presentation is limited primarily to
psychomotor stimulants (e.g., amphetamine, cocaine) and opiates (e.g.,
heroin, morphine) for two reasons. First, considerable knowledge has been
gained during the past 15 years regarding the neurobiological mechanisms
mediating their addictive properties. Second, these two pharmacological
classes represent the best examples of potent addictive drugs, and the
elucidation of their addiction potential can provide a framework for
understanding abuse and addiction to other psychotropic agents. Some
psychologists and sociologists assert that animal studies do not model the
important psychological variables governing drug addiction. They suggest that
psychological processes critical in the etiology of addiction cannot be studied
in animal models and/or that environmental influences important in producing
an addiction cannot be duplicated in animal studies. This position is generally
untenable, and animal models have been developed that accurately represent
the primary processes involved in drug addiction. Support for the validity of
these animal models will emanate from an understanding of the characteristics
and the neural basis of drug addiction summarize...
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...endence (i.e., the periaqueductal gray
region; see Figure 2) are not rewarding (Bozarth and Wise 1984). This
neuroanatomical dissociation of reward and physical dependence shows that
opiates can be rewarding without the development of physical dependence.
The interpretation of research identifying the neural basis of opiate reward has
been somewhat controversial, but considerable data suggest that opiates can
activate the same brain reward system as that mediating reward from
psychomotor stimulants. Direct support for this hypothesis comes from a
study showing that ventral tegmental morphine injections can partially
substitute for intravenous cocaine injections (Bozarth and Wise 1986).