(who knows if this little study has clinical significance. If it does, when we know the % of population in which this polymorphism occurs, may be able to determine the true incidence of gambling in PD pts who take L-DOPA meds)

Dopamine Receptor D4 Polymorphism Predicts the Effect of L-DOPA on Gambling Behavior
Biological Psychiatry, 12/07/09

The findings demonstrate that genetic variation in the DRD4 gene determines an individual's gambling behavior in response to a dopaminergic drug challenge. They may have implications for the treatment of Parkinson's disease patients by offering a genotype approach for determining individual susceptibilities for pathological gambling and may also afford insights into the vulnerability mechanisms underlying addictive behavior.

http://www.journals.elsevierhealth.c...11238/abstract

Dopamine Receptor D4 Polymorphism Predicts the Effect of L-DOPA on Gambling Behavior

Christoph Eiseneggera, Daria Knochb, Richard P. Ebsteinc, Lorena R.R. Gianottib, Peter S. Sándord, Ernst Fehrae



Background
There is ample evidence that a subgroup of Parkinson's disease patients who are treated with dopaminergic drugs develop certain behavioral addictions such as pathological gambling. The fact that only a subgroup of these patients develops pathological gambling suggests an interaction between dopaminergic drug treatment and individual susceptibility factors. These are potentially of genetic origin, since research in healthy subjects suggests that vulnerability for pathological gambling may be linked to variation in the dopamine receptor D4 (DRD4) gene. ...
Methods
We administered 300 mg of L-dihydroxyphenylalanine (L-DOPA) or placebo to 200 healthy male subjects who were all genotyped for their DRD4 polymorphism. Subjects played a gambling task 60 minutes after L-DOPA administration.

Results
Without considering genetic information, L-DOPA administration did not lead to an increase in gambling propensity compared with placebo. As expected, however, an individual's DRD4 polymorphism accounted for variation in gambling behavior after the administration of L-DOPA. Subjects who carry at least one copy of the 7-repeat allele showed an increased gambling propensity after dopaminergic stimulation.

Conclusions
These findings demonstrate that genetic variation in the DRD4 gene determines an individual's gambling behavior in response to a dopaminergic drug challenge...