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 3.0mg/kg morphine. This enhancing effect was inhibited by selective D(1) receptor antagonist SCH23390 and selective D(2) receptor antagonist sulpiride pretreatment 20min before footshock session, suggesting dopamine D(1) and D(2) receptors are required for the development of intermittent footshock stress-induced enhancement of morphine-associated place preference. However, different from D(1) and D(2) receptors this enhancing effect was blocked by stimulation of dopamine D(3) receptor with selective D(3) receptor agonist 7-OH-DPAT pretreatment 20min before footshock session which suggest dopamine D(3) receptor play a negative mediation effect on the intermittent footshock stress-induced this enhancement. These results indicate that dopamine D(1), D(2), and D(3) receptor subtypes play different roles in footshock stress-induced enhancement of morphine conditioned place preference.