A distinct D1-MSN subpopulation down-regulates dopamine to promote negative emotional state

Dopamine (DA) level inthe nucleus accumbens (NAc) is critical for reward and aversion encoding.DA released from the ventral mesencephalon (VM) DAergic neurons increases the excitability of VM-projecting D1-dopamine receptor-expressing medium spiny neurons (D1-MSNs) in the NAc to enhance DA release and augment rewards.However,how such a DA positive feedback loop is regulated to maintain DA homeostasis and reward-averSion balance remains elusive.Here we report that the ventral pallidum (VP)projection of NAc D1-MSNs (D1NAc-VP) is inhibited by rewarding st muli and activated by averslVe stimuli.In contrast to the VM projection of D1-MSN (D1NAc-VM),activation ofD1 NAc-VP projection induces aversion,but not reward.D1NAc-VP MSNs are distinct from the D1NAc-VM MSNs,which exhibit conventional functions of D1-MSNs.Activation of D1NAc-VP projection stimulates VM GABAergic transmission,inhibits VM DAergic neurons,and reduces DA release into the NAc.Thus,D1NAc-VP and D1NAc-VM MSNs cooperatively control NAc dopamine balance and reward-aversion states.