Effect of picrotoxin and nipecotic acid on inhibitory response of dopaminergic neurons in the ventral tegmental area to stimulation of the nucleus accumbens.

Electrical stimulation of nucleus accumbens inhibited the activity of neurons in the ventral tegmental area (VTA). Inhibition was potentiated by nipecotic acid, a GABA uptake inhibitor, and was attenuated by picrotoxin, a GABA antagonist. Four units inhibited by nucleus accumbens stimulation were also antidromically activated. These observations suggest that neurons in the VTA, including specifically those projecting to the nucleus accumbens, receive a descending GABAergic input from that area.