umm... They DON'T block your Dopamine receptors. These are Dopamine AGONISTS. You know what Agonist means? They stimulate dopamine and increase it. Parkinson people have Low dopamine levels, and are given dopamine boosters and reuptakers etccc.
So More Dopamine = Less Prolactin.
Parkinson Meds like Requip, Mirapex, Bromocriptine are notoriously known to cause High Libido, Gambling addiction in some, and i suspect they increase Testosterone levels since they lower prolactin and boost Test.