A biological switch in the brain that might some day be used to turn off drug addicts' craving for cocaine has been found in laboratory rats by Yale University researchers.
In a study in the journal Science, researchers report that they isolated a receptor on brain cells that could be manipulated by drugs to suppress the desire for cocaine."We haven't found a drug to substitute for cocaine, but we have found a receptor in the brain that may be the target of such a drug," said David W. Self, a researcher at Yale School of Medicine.
In the study, Self and his colleagues addicted laboratory rats to injectable cocaine and then allowed the animals to self-administer the drug by pressing a lever.
Saline was then substituted for the cocaine and the animals gradually lost interest in the self-administer lever.
The rats then were dosed with compounds that are known to act on brain cell receptors that normally absorb dopamine, a natural neurotransmitter in the brain. One set of compounds attached to the D1 receptor and another set to the D2 receptor.
The researchers found that the compounds that attached to the D2 receptor caused the rats to exhibit "a cocaine-seeking behavior," said Self. Drugs that linked with the D1 receptor caused the rats to show no interest in seeking more cocaine.
In a second test, some of the rats were later "primed" with doses of cocaine, an exposure that can renew addiction. The rats that had received the D2 receptor drugs quickly again exhibited addictive behavior, but those who got the D1 receptor drugs did not, said Self.