Dr. Rene Hen of Columbia University, who also collaborated with Rocha, made mice lacking one of the receptors for serotonin. These mutant mice are more aggressive than normal mice. When the mice were allowed to give themselves cocaine, they frantically self-administered the drug, much more so than normal animals. The Columbia researchers studied the brains of mice missing the serotonin receptor and discovered their brains resembled those of mice accustomed to receiving large amounts of cocaine. In a sense, they are born addicted.
People say the dopamine system drives addiction.
I think we've shown it is more complicated than that. All the momentum in drug therapies is geared toward the dopamine system, especially the transporter. But a combined therapy that targets both the serotonin and dopamine systems may be worth pursuing. The research was funded in part by grants from the National Institutes of Health and by unrestricted grants from Bristol Myers Squibb and Zeneca Pharmaceuticals.