Monkey Study: Environmental Enrichment Can Reduce Cocaine Use
SAN DIEGO, California, April 6, 2008 (ENS) – In a study that scientists say can be applied directly to human behavior, simple environmental enrichment can affect the level of individual cocaine use in monkeys,
With more living space, monkeys self-administered cocaine less frequently, according to new research by Michael Nader, PhD at the Wake Forest University School of Medicine presented today at the Experimental Biology 2008 scientific meeting in San Diego.
The presentation was part of the scientific program of the American Society for Pharmacology and Experimental Therapeutics.
Nader and colleagues worked with a group of 24 cynomolgus macaques who were already self-categorized socially from the most dominant to the most subordinate. For additional enrichment, the monkeys were placed in larger-than-normal cages for three days.
Once exposed to cocaine and taught to self-administer the drug, the more subordinate animals are far more inclined to engage in the human equivalent of serious drug abuse than are the dominant animals, previous research has shown.
Nader’s monkeys were given their usual choice of an intravenous cocaine mixture or food pellets. The enrichment reduced the drug response of all the animals.
“This is very significant for at least two reasons,” said Nader, professor of physiology and pharmacology and of radiology. “First, it is a result that could be directly applied to the human situation. It suggests that a better environment could alleviate at least some of the risk that individuals will turn to drugs.
“Secondly,” Nader said, “we are talking about very rudimentary enrichment here – just a slightly improved living condition. Imagine what the effect could be with higher quality but easily achievable enrichment, such as interesting activities.”
Previous research has shown that social rank – whether animals are dominant or subordinate within their social groups – can affect the amount of cocaine that monkeys will self-administer.
Researcher have measured the differences in certain neurochemicals in the brains of the animals, both as predictors and results of the social ranking, and therefore as predictors of drug abuse.
Nader and his team also tested the monkeys for drug reponse during increased stress.
For increased stress, the 24 macaques were placed next to another social group for 15 minutes, acting as an intruder to that group.
Nader says the detrimental affect of the stress – more drug intake, less food – was more prominent in the subordinate monkeys.
