"In summary, repeated administration of drugs of abuse and alcohol induces a common pattern of changes in gene expression and protein levels selectively in the VTA [ventral tegmental area]. A subset of these changes is reversed by intra-VTA GDNF [glial cell line-derived neurotrophic factor], as are some of the drug-induced behavioral effects. Endogenous GDNF systems appear to inhibit drug related behaviors, while repeated drug administration appears to inhibit GDIVF signaling itself. Based on these studies, we propose that GDNF is an endogenous anti-addiction agent. This possibility is directly supported by the finding that the activity of the anti-addiction drug, ibogaine, on alcohol consumption is mediated via increased expression of GDNF in the midbrain and the subsequent activation of the GDNF pathway."
Ron, Dorit, and Janak, Patricia H., "GDNF and addiction," Reviews in the Neurosciences, Vol. 16, No. 4, 2005, p. 281.