Does this mean that it creates dopamine, or that it uses what is available? Please explain if you can.

Uprima also affects nitric oxide but is absorbed and transported to the brain. There, like a neurotransmitter, it initiates a chain of reactions in the body that result in increased blood flow and an erection.
Apomorphine has been around for a long time, used through injection to treat tremor-causing Parkinson’s disease. It was found to have the simultaneous result of causing erections, said Dr. Harin Padma-Nathan, director of The Male Clinic in Beverly Hills, Calif., and an investigator in the studies.