Complex sentence: Many drugs have been developed to counter the effects of PD by increasing the levels of dopamine in the brain by working as agonist on dopamine receptors Zhang A, Neumeyer J, Baldessarini R (2007).
Split into simpler sentences: Many drugs have been developed to counter the effects of PD by increasing the levels of dopamine in the brain. These drugs primarily act as agonists on dopamine receptors Zhang A, Neumeyer J, Baldessarini R (2007).