Will rats really keep taking cocaine til they die?
||I was told in highschool in the 1980's and by the media and government that cocaine is so addictive that rats will keep pressing a lever to get it til they die, but someone told me that wasn't true. What's right? |
||The "drug education" of the 1980's about cocaine included some really awful lies and intentional misrepresentations by "well meaning" and confused "experts". One of the often repeated myths was that cocaine was so addictive that if given a choice between food and cocaine, rats would keep pushing a lever for cocaine until they starved to death. As with most of the counter-intuitive anti-fun-drug propaganda, this isn't true.|
What is true, however, is that cocaine is a very compelling stimulant for many people and animals. Many people (and animals) find the effects pleasureable and fun and will choose to use it given the chance to, once they are trained to its effects.
Beyond that, it gets somewhat murkier. There is a great introduction to cocaine animal self-administration by John P. Morgan and Lynn Zimmer in the book Crack in America: Demon Drugs and Social Justice. The chapter can be found at Druglibrary.org, search down to "Animal Self-Administration".
What the research has shown is that rats who are tethered, alone in a small plastic box with nothing else to do, raised in isolation from other rats, trained to inject cocaine, and hooked to a constant feed of cocaine through a permanent IV in some experimental designs will fatally self-administer cocaine. If rats are given acess to sweetened water, adequate food, raised in families and given activity options, they do not fatally administer the cocaine, their daily dosages are much lower, and they tend to remain healthier.
This is the excerpt from the Morgan & Zimmer chapter:
"Laboratory scientists sometimes joke that the definition of a drug is any substance that, when injected into a rat, produces a journal article. Hundreds of studies have proven that laboratory animals can be taught to self-administer cocaine, even to the point of causing their own death. The earliest such studies, conducted in the late 1960s (Deneau et al., 1969; Pickens and Thompson, 1968) are important because they show that even drugs that do not produce physical dependence and withdrawal can be highly "reinforcing"; that is, after being administered the drug, lab animals can be made to self-administer more of it. Deneau et al., for example, demonstrated that monkeys would push a lever for cocaine over twelve thousand times-nearly as many times as physically dependent monkeys push it for heroin. By the late 1980s, over five hundred articles describing the reinforcing properties of cocaine had been published (Johanson and Fischman, 1989).
The assumption on which animal research is justified-and repeatedly funded-is that much can be learned about human cocaine use from studying cocaine self-administration in caged animals (Bozarth, 1988; Brady and Griffiths, 1976; Fischman, 1988; Washton, 1989). However, to provoke animals to self-administer cocaine (and most other drugs), they must be "trained" to do so. In order to maximize the dose and frequency of use, researchers tether animals to the cage and surgically implant a permanent injection apparatus in their backs. This unreachable catheter injects cocaine intravenously following operant behavior (such as depressing a lever).
Many researchers starve the rats before training begins because this increases the likelihood that animals will repeatedly inject cocaine. But just as humans are typically distracted from drug use by other pleasures and life commitments, so are animals. Simply giving a cocaine-injecting rat a solution of water sweetened with glucose and saccharin decreases the injection rate (Carroll et al., 1989); so does maintaining rats on an adequate diet (Carroll et al., 1979). In addition, if instead of unlimited access, animals are given cocaine (or heroin) under conditions of limited access, they tend to arrive at a controlled daily dose and do not "choose drugs over life." In fact, in these settings, if the concentration of the drug is increased, the animals tend to administer fewer injections, holding constant their total daily doses (e.g., Wilson et al., 1971). When animals are allowed to interact socially, their drug consumption also tends to decrease. In one series of studies, rats were trained to drink a morphine solution but then permitted access to an open area populated with other rats and scattered with objects for inspection and play. These opportunities for exercise, play, and socializing markedly decreased their consumption of morphine (Alexander et al., 1981). Environmental factors also affect the trainability of rats for cocaine injection-for example Schenk et al. (1987) found that rats reared in groups were less likely to self-administer cocaine than were rats reared in isolation Studies of drug self-administration by rodents, dogs, and even primates have garnered much attention but have not contributed much to understanding cocaine use in humans.
This is true because the conditions used in most animal studies are so extreme, so unlike the conditions of ordinary human life. In fact, experimental conditions are expressly designed to maximize animals' self-injection of cocaine. For example, test animals are raised in isolation or removed from social interaction with others of their kind. They are outfitted for solitary life and implanted with an IV injection apparatus. They are often starved to prepare them for their lives as cocaine "addicts" and almost always denied all opposing reinforcers-even sweetened water. And experimenters make unlimited supplies of cocaine constantly available. Thus, it is not surprising that researchers can train "nine out of ten laboratory rats" to inject themselves with lethal doses of cocaine (Bozarth and Wise, 1985). Such studies are then cited as scientific "proof" of cocaine's extreme addictiveness-implying that what is true for rats is also true for humans. This is the clear message in the Partnership for a Drug-Free America's "Dead Rat" video, which has been shown frequently on television.
The National Institute on Drug Abuse has paid for much of this animal research and continues to do so-now defining as a prime objective the discovery of a cocaine "antagonist" that will block or counter cocaine's effects and be useful for "treating" cocaine and crack addiction in humans (Leary, 1993; McNeil, 1992). This effort is premised on the idea that current "cocaine addicts" cannot stop using the drug-an idea that is continuously reinforced by the animal self-administration studies. However, the accumulated data on human cocaine use show that most users do not become addicted to the drug, and, of those who do, most eventually stop or greatly reduce their use."
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