The researchers conducted a series of experiments with male rats that were trained to self-administer METH by pressing a lever. In a group of rats that consistently self-administered METH, the researchers exchanged METH with lobeline to determine whether lobeline would serve as a substitute for METH. When METH was exchanged with lobeline, the number of times the rats pressed the lever decreased daily over the course of the experiment, indicating that lobeline did not serve as substitute for METH.
In a different experiment, the researchers investigated whether lobeline would cause rats to resume drug-seeking behavior after a period of abstinence or if it alters METH-induced reinstatement of drug-seeking behavior. They found that lobeline did not restore drug-seeking behavior nor did it alter METH-induced reinstatement. These findings indicate that lobeline appears to alter the mechanisms mediating METH reward, but not the mechanisms mediating the reinstatement of drug-seeking behavior.
In another experiment, the effects of lobeline on dopamine levels in the brains of rats were examined. It was found that lobeline had no effect on dopamine levels, the brain chemical that regulates feelings of pleasure. This finding indicates that lobeline does not induce the same feelings of reward as METH and that lobeline did not act as a substitute reinforcer. This finding would indicate that lobeline, unlike some other pharmacological agents used to treat addiction, does not itself pose a risk for abuse.
WHAT IT MEANS: The ability of lobeline to decrease METH self-administration without inducing reward itself suggests that lobeline may be a useful pharmacological treatment without risk of abuse.
Dr. Steven Harrod and colleagues published the study in the February 23 issue of the journal Psychopharmacology.
Journal
Psychopharmacology