SLC18A2 and Parkinson disease: Our second aim was to assess if the vmat2 mutant larvae are a suitable model for drug discovery of novel PD therapeutics by administering selected dopamine precursor and agonists (L-Dopa and pramipexole, which also has a low affinity to serotonin [28]), as well as glial cell line-derived neural growth factor (GDNF), a putative neurorestorative agent [29].