Persistent decrease of operant ethanol self-administration after intra-VTA GDNF infusion. Long–Evans rats were trained for 2 months to press on a lever to obtain 0.1 ml of a 10% ethanol solution during 1 h sessions. Upon establishing a baseline of ethanol intake, cannulae were implantedinthe VTA, and rats were microinjected with GDNF (10 µg/side) or vehicle (PBS), 12 or 24 h before the beginning of the operant self-administration session. A two-way ANOVA showed a significant effect of treatment (F(1, 10)=12.74, p<0.01), no effect of time (F(1, 10)=0.01, p=0.93), and no interaction between both factors (F(1, 10)= 0.17, p=0.69). n=11. Data are shown as mean±SEM. *p<0.05, **p<0.01.