GDNF and Parkinson disease: Moreover, from studies in animal models, it appears that ibogaine and noribogaine may lead to an activation of the GDNF pathway in the VTA of the brain [23] and could be effective in the treatment of Parkinson's disease [83]; similarly, studies have shown that noribogaine led to a reduction in opioid intake and a concomitant increase in GDNF RNA expression in the absence of neurotoxicity [84].