Rat Park

I'm continuing to find both fascinating and horrible things as I do my research on unusual types of rat cages.

Here is a Wikipedia entry on Rat Park, a study done in the 1970's by Dr. Bruce K. Alexander who believes that narcotics are not addictive and that what appears to be addiction is a result of poor living conditions. (This dovetails nicely with what we know about rabbits, incidentally because if rabbits are in a crowded or filthy warren the does will not breed and in fact if they become pregnant their bodies will absorb the young.)

Alexander's hypothesis was that drugs do not cause addiction, and that the apparent addiction to morphine commonly observed in laboratory rats exposed to it is attributable to their living conditions, and not to any addictive property of the drug itself. ^[1] He told the Canadian Senate in 2001 that experiments in which laboratory rats are kept isolated in cramped metal cages, tethered to self-injection apparatus, show only that "severely distressed animals, like severely distressed people, will relieve their distress pharmacologically if they can." ^[2]

To test his hypothesis, Alexander built Rat Park, a 200-square-foot (18.6 m²) housing colony, 200 times the square footage of a standard laboratory cage. There were 16–20 rats of both sexes in residence, an abundance of food, balls and wheels for play, and private places for mating and giving birth. ^[3] The results of the experiment appeared to support his hypothesis. Rats who had been forced to consume morphine hydrochloride for 57 consecutive days were brought to Rat Park and given a choice between plain tap water and water laced with morphine. For the most part, they chose the plain water. "Nothing that we tried," Alexander wrote, "... produced anything that looked like addiction in rats that were housed in a reasonably normal environment." ^[1]

Another quote from further in the article:

In Rat Park, Alexander built a short tunnel large enough to accommodate one rat at a time. At the far end of the tunnel, the rats could drink a fluid from one of two drop dispensers, which automatically recorded how much each rat drank. One dispenser contained a morphine solution and the other plain tap water.

Alexander designed a number of experiments to test the rats' willingness to consume the morphine. Rats have a sweet tooth, so in an experiment called "The Seduction," the researchers exploited the rats' apparent sweet tooth to test whether they could be enticed to consume morphine if the water was sweet enough. Morphine in solution has a bitter taste for humans, and appears to have the same effect on rats, Alexander writes, since they shake their heads and reject it as they do with bitter quinine solutions. The Seduction involved four groups of rats. Group CC was isolated in laboratory cages when they were weaned at 22 days of age, and lived there until the experiment ended at 80 days of age; Group PP was housed in Rat Park for the same period; Group CP was moved from laboratory cages to Rat Park at 65 days of age; and Group PC was moved out of Rat Park and into cages at 65 days of age.

The caged rats (Groups CC and PC) took to the morphine instantly, even with virtually no sweetener, with the caged males drinking 19 times more morphine than the Rat Park males. But no matter how sweet the morphine became, the rats in Rat Park resisted it. They would try it occasionally — with the females trying it more often than the males — but invariably they showed a preference for the plain water. It was, writes Alexander, "a statistically significant finding." ^[1] He writes that the most interesting group was Group CP, the rats who were brought up in cages but moved to Rat Park before the experiment began. These animals rejected the morphine solution when it was stronger, but as it became sweeter and more dilute, they began to drink almost as much as the rats that had lived in cages throughout the experiment. They wanted the sweet water, he concluded, so long as it did not disrupt their normal social behavior. ^[1] Even more significant, he writes, was that when he added a drug called Naloxone, which negates the effects of opioids, to the morphine-laced water, the Rat Park rats began to drink it.

In another experiment, he forced rats in ordinary lab cages to consume morphine for 57 days on end, giving them no liquid to drink other than the morphine-laced solution, then moved them into Rat Park, where he allowed them to choose between the morphine solution and plain water. They drank the plain water. He writes that they did show some signs of dependence, but no sign of addiction. There were "some minor withdrawal signs, twitching, what have you, but there were none of the mythic seizures and sweats you so often hear about ..." ^[10]

Alexander believes his experiments show that animal self-administration studies provide no empirical support for the theory of drug-induced addiction, and that the theory has no other basis in empirical science, although it has not been disproven. "The intense appetite of isolated experimental animals for heroin and cocaine in self-injection experiments tells us nothing about the responsiveness of normal animals and people to these drugs. Normal people can ignore heroin ... even when it is plentiful in their environment, and they can use these drugs with little likelihood of addiction ... Rats from Rat Park seem to be no less discriminating." ^[1]

You should definitely read the entire piece. It's fascinating. http://en.wikipedia.org/wiki/Rat_Park