Activation of dopamine D2 receptors in the shell of nucleus accumbens triggers conditioned avoidance responses in rats

Conditioned avoidance responses (CAR) behavior is a classical instrumental response paradigm, which is widely used to study aversive conditioning and defensive motivation behavior. Previous studies have shown that dopamine D₁ and D₂ receptors are involved in CAR behavior; however, it is unclear in which brain regions that dopamine evokes CAR behavior. The aim of the study is to investigate whether dopamine triggers CAR behavior via activating dopamine D₁ or D₂ receptors in the shell of nucleus accumbens or dorsolateral striatum. The present study found that infusion of the dopamine D₂ receptor agonist quinpirole, but not D₁ receptor agonist SKF38393, into the shell of nucleus accumbens evoked CAR behavior in reserpine-treated rats. Whereas, infusion of neither SKF38393 nor quinpirole into the dorsolateral striatum evoked CAR behavior. In addition, infusion of quinpirole into the shell of nucleus accumbens enhanced CAR behavior in the unsuccessful trained rats without affecting the motor function in the balance beam and locomotor tests. In conclusion, activation of dopamine D₂, but not D₁ receptors in the shell of nucleus accumbens evokes CAR behavior. However, activation of dopamine D₁ and D₂ receptors in the dorsolateral striatum does not evoke CAR behavior. It is suggested that the shell of nucleus accumbens is the critical brain region for dopamine to invoke CAR behavior, and activation of dopamine D₂ receptors in the shell of nucleus accumbens is sufficient and necessary to evoke CAR behavior.