Do Dopamine Agonists Spark Gambling Compulsion?

Nonetheless, she and her colleagues suspect that dopamine agonists triggered the pathological gambling in the cases they reported and hypothesized why this may have occurred.

For example, they were able to follow up eight of the 11 individuals they cited, and once these individuals tapered or stopped taking a dopamine agonist, their urge to engage in pathological gambling ceased as well.

Also, after taking dopamine agonists, six of the patients felt a strong desire not just to gamble but also to engage to excess in other behaviors such as eating, drinking alcohol, having sex, and making purchases. And once these patients stopped taking the drug or took less, their urges in all of these domains declined dramatically. One of these patients was George. He stopped taking his dopamine agonist abruptly. Two days later, he felt his longings to engage in such behaviors rapidly resolve. It was “like a light switch being turned off,” he said.

Two pathological gambling authorities—Suck Won Kim, M.D., a professor of psychiatry at the University of Minnesota, and Jon Grant, M.D., an associate professor of psychiatry there—told Psychiatric News that they have little doubt that dopamine agonists can trigger an impulse to gamble. Indeed, Grant said, “Those of us who treat pathological gamblers have also seen many movement-disordered patients who report pathological gambling onset secondary to starting dopamine agonists.”

And the reason why dopamine agonists might trigger pathological gambling, Kim explained, is that they exert their pharmacological actions not only in the basal ganglia that govern Parkinson's symptoms, but in the nucleus accumbens. The nucleus accumbens is known to give rise to craving and pleasure, which in turn are mediated by dopamine. Thus, if a dopamine agonist overly excites dopamine receptors in the nucleus accumbens, it might well“ trigger cravings to gamble and excitement when winning,” Kim speculated.

But if dopamine agonists can truly ignite the urge to gamble, then why do they awaken it in only a few patients who take them? Dodd suspects that the answer may lie in which genetic version of dopamine receptors one has inherited.

In other words, one version of the receptors might be more receptive to dopamine stimulation than another. In fact, Dodd said, she and her colleagues may be “doing a genetic study looking for possible polymorphisms in the gene that codes for the dopamine D₃ receptors that may be contributing to the way this small population of patients is responding to the dopamine agonists.”

Grant believes that in addition to genetic research, functional brain imaging could help answer an even more intriguing question: Why did the patients who only gambled secondary to taking dopamine agonists not also develop problems with sex, alcohol, or eating?

“Pathological Gambling Caused by Drugs Used to Treat Parkinson Disease” can be accessed at<http://archneur.amaassn.org> by searching on the study title. ▪