Different roles of dopamine receptor subtypes in footshock stress-induced enhancement of morphine conditioned place preference

The present study investigated the involvement of dopamine mechanism in the effect of intermittent footshock stress on the morphine-induced place preference. A single intermittent footshock session significantly enhanced the place preference induced by 3.0 mg/kg morphine. This enhancing effect was inhibited by selective D1 receptor antagonist SCH23390 and selective D2 receptor antagonist sulpiride pretreatment 20 min before footshock session, suggesting dopamine D1 and D2 receptors are required for the development of intermittent footshock stress-induced enhancement of morphine-associated place preference. However, different from D1 and D2 receptors this enhancing effect was blocked by stimulation of dopamine D3 receptor with selective D3 receptor agonist 7-OH-DPAT pretreatment 20 min before footshock session which suggest dopamine D3 receptor play a negative mediation effect on the intermittent footshock stress-induced this enhancement. These results indicate that dopamine D1, D2, and D3 receptor subtypes play different roles in footshock stress-induced enhancement of morphine conditioned place preference.