Would love additional resources if you find them.
Do you mind sharing the Dr's name at UT and which city/campus? (I've been told by Drs at UT Southwestern (Dallas) that DAs do NOT contribute to disease severity by reducing receptor sensitivity).
So far have found the following. Indicative, but not scholarly/journal references:
1. http://viartis.net/parkinsons.disease/news.0708.htm (10th July 2008) "Dopamine agonists make use of the different functions of the dopamine receptors by primarily stimulating those dopamine receptors that reduce excessive muscle contraction - usually D2 or D3" ... "Continuous use of dopamine agonists also makes the dopamine receptors progressively less sensitive. Dopamine agonists consequently have progressively less effect, and can also cause naturally produced dopamine to be less effective. In the long term this can make Parkinson's Disease progressively worse."
2. http://www.bazpedia.com/en/p/a/r/Parkinson's_disease.html (Wikipedia) "Dopamine agonists can also eventually contribute to Parkinson's disease symptoms by decreasing the sensitivity of dopamine receptors."
3. http://www.viartis.net/parkinsons.disease/treatments.htm "Besides the side effects they cause, dopamine agonists cause the dopamine receptors to become progressively less sensitive, thereby eventually increasing the symptoms."