Animal Models Of Craving: A Roundtable Discussion - Panel Discussion

Alcohol Research & Health, Fall, 1999 by Barbara Breen Vann, Lori A. Wolfgang

Five experts respected for their work in the development of animal models of alcohol craving offer their, perspectives in a roundtable discussion format. The panel members discuss the various definitions and theories of alcohol craving and the benefits and limitations of using animal models to study alcohol craving in humans. Animal models have helped further the understanding of craving by providing information about behavior associated with craving. Animal models do have limitations, however. The fact that animals cannot "talk" about their feelings poses difficulties for researchers seeking to map an animal analog of craving onto the human experience. KEY WORDS: AOD (alcohol and other drug) craving; animal model; animal behavior; AOD use behavior; theory of AODU (alcohol and other drug use); operant conditioning; motivation; alcohol cue; AODD (alcohol and other drug dependence) relapse; AOD withdrawal syndrome; disorder definition; laboratory study; interview

The use of animals to model humans has long been an integral part of medical and scientific research into human functions and conditions. Research using animals has led to many important medical discoveries in the past century, from the use of depancreatized dogs in 1921 to study the effects of insulin to the recent mapping and sequencing of rat, mouse, and fruit fly genomes to better understand human genetic makeup.

Likewise, the field of alcohol research has benefited from a number of discoveries that were first identified using animal models. The development of animal models for alcoholism began in the 1 1940s. Since that time, rats and monkeys have been used to model different drinking behaviors and to study how alcohol damages different bodily organs. Animal models also have helped scientists to analyze the changes in brain chemistry that occur when alcohol is consumed. Perhaps most promising, genetically altered animal models are proving to be valuable in the search for genes that may be involved in the development of alcoholism.

Whereas the use of animal models to study the physiological effects of alcohol on tissue and organs has been fairly straightforward, using animal models to assess psychological effects raises questions. How do scientists measure "craving," the uncontrollable desire for alcohol that is associated with alcohol dependence?

Alcohol Research & Health (AR&H) asked several renowned scientists currently working in the field to share their views on animal models of human alcohol craving. Our panel of experts includes the following:

* George F. Koob, Ph.D.--professor in the Department of Neuropharmacology at The Scripps Research Institute, La Jolla, California

* Friedbert Weiss, Ph.D.--associate professor in the Department of Neuropharmacology at The Scripps Research Institute, La Jolla, California

* Stephen T Tiffany Ph.D.--professor in the Department of Psychological Sciences at Purdue University, West Lafayette, Indiana

* Walter Zieglgansberger, Ph.D.--Head of Clinical Neuropharmacology at the Max Planck Institute of Psychiatry, Munich, Germany

* Rainer Spanagel, Ph.D.--Head of Drug Abuse Research at the Max Planck Institute of Psychiatry, Munich, Germany

AR&H: What would you say is the greatest advantage to using animal models to study alcohol craving?

Tiffany: Without question, animal studies have taught us and can continue to teach us a great deal about craving. Most importantly, animal research offers a rich source of ideas regarding the fundamental nature of drug craving. Indeed, almost all of the major conceptualizations of craving developed over the past 50 years originated in the animal laboratory.

The link between animal research and craving is obvious when you consider major craving theories like Abraham Wikler's conditioned-withdrawal model, Shepherd Siegel's compensatory-response model, or Jane Stewart's incentive-motivational model. Wikier's model proposed that situations paired with drug withdrawal (e.g., being in an alcohol detoxification ward in a treatment clinic) become conditioned stimuli that trigger conditioned withdrawal reactions. These reactions might include sweating, racing heart, and nausea. The theory proposed that in humans, these conditioned reactions would trigger craving, which would trigger drug use. Siegel's model is very similar to Wikler's. The major difference is that Siegel proposed that situations paired with drug use (e.g., being with other drug users), rather than drug withdrawal, could produce conditioned withdrawal reactions and craving. The craving model developed by Stewart and colleagues emphasized the reinforcing effects of substance use in the generation of cravi ng. In this model, situations associated with substance use (e.g., the sight and smell of alcohol) become conditioned reinforcers. These reinforcers activate positive motivational states that produce craving and drug-seeking behaviors. Less obvious, but equally important, is the influence of concepts borrowed from animal learning theory in the development of social-cognitive models of craving. For example, G. Alan Marlatt has hypothesized that alcohol craving represents a person's expectations about the positive effects of alcohol. The idea that expectancies about outcomes strongly influence behavior was taken directly from animal models of learning.