Pharmacology - Just curious about Requip (ropinerole)

[StarryEyedNoOne]

This drug is used to treat Parkinson's and restless leg syndrome (swim has found it works well for this, although it may just be because it seems to completely knock her out!). Since it is a dopamine agonist, swim is curious as to why it has no pleasant effects, however. She read on wiki and a few other sites that it binds primarily to the D3 receptor, but is having a hard time determining what the different dopamine receptors effect exactly. Does anyone have expertise on this subject that could satisfy swim's curiosity?