The Addicted Brain Read Online Free PDF Page B

a cue, which was typically a light and/or a tone. Drug self-administration was stable at about 140 responses (on the vertical axis), except for the first day when the animals were learning. In the second phase of the experiment (right half of figure), animals underwent “extinction training” during which no drug was administered in response to lever presses (E1–E14), and the rate of lever pressing dropped nearly to zero. At the end of this second phase, animals were presented with the cue that had accompanied each drug infusion during self-administration, a mild stressor (typically foot shock), or the drug itself. Each of these stimuli reliably overcame extinction training and the animals pressed the lever, even though no drug was delivered. This reinstatement or reoccurrence of lever pressing is considered to be a bout of drug seeking or relapse. Although this is a complicated experiment, it is clear evidence that stress or a single injection of a drug can stimulate drug seeking in an animal with previous drug-taking experience. This animal model can be used to study relapse. (Adapted from PW Kalivas, Jamie Peters, and Lori Knackstedt. “Animal Models and Brain Circuits in Drug Addiction.”
Mol Interv.
December 2006: 6:339–344.)

    In this animal model, it is possible to ask a variety of questions about relapse, and we can begin to consider which medications are best for treating or preventing relapse.
Other Animal Models
    Other models allow us to study additional properties of the brain and of drugs. These models, such as “conditioned place preference” and “drug discrimination,” are technical and sometimes complex but quite useful. These are mentioned only to inform you that the experimental repertoire in drug addiction research is quite rich. In the next chapter, we explore “electrical self-stimulation” and why it is important for this discussion.
A Transformation in Thinking
    The realization that addiction is not only a human vulnerability but is shared by animals is important. Drug abusers were and sometimes still are considered disgusting, moral failures, hardly worthy of help, much less research programs. Their out-of-control drug seeking with its associated crimes and degradations leaves them stigmatized and sometimes abandoned. The drug abusers themselves feel helpless and hopeless. But realizing that addiction is a brain disorder, maybe like a migraine headache or a seizure, is transformative. Now we think that if we can learn enough about the brain, we can more effectively treat addicts, and this is becoming true. The drug users themselves realize that a new realm of treatment possibilities has been opened to them. These include medications and behavioral therapies directed at the brain and how it functions. This is not to say that older, existing programs are not effective. On the contrary, many are effective. However, we are now adding to the options for treatment. One of the most important functions of research is not only to make discoveries, but also to provide hope for the future and hope for treatments that are now lacking.
Summary
    Animals take drugs in the same way that humans do and are considered as models for human drug use. Because studies of drugs and thebrain are essential, and because many types of studies on humans are not possible, animal models have been used and have been successful.
Endnotes
    1 Under certain, strict conditions, it is possible to carry out research with human drug abusers. The conditions of the experiments must minimize any risk to the human subject. The subjects must be physically fit and offered treatment even if they refuse it. Of course, they must be medically monitored to avoid any unsuspected and damaging effects of drugs. For example, certain doses of certain drugs that can sometimes be toxic must be avoided. Finally, every human experiment must be described in detail in writing in advance, and the description must be studied by an expert committee that