Other putative neuroprotective actions of A2A receptor agonists may involve a rather distinct mechanism, namely potentiation of the action of neurotrophic factors, such as glial derived neurotrophic factor (GDNF), on striatal dopaminergic nerve endings [74] and this may prove particularly useful in early stages of neurodegenetive diseases such as Parkinson’s disease, i.e. at stages where it may still be possible to rescue neurones from death through enhancement of trophic support. Here, GDNF is linked to Parkinson disease.