Effects of odor cue on morphine-induced dependence and craving in mice

The olfactory system may play a pivotal role in drug addiction. To clarify the issues, we investigated the morphine dependence and psychological craving in morphine addicted mice using the conditioned place preference (CPP) paradigm by taking an only odor cue as the conditioned stimulus (CS). The results showed that by pairing morphine with odor, the CPP could be induced in mice. When the morphine addicted mice were exposed to a novel environment during morphine withdrawal, they spent significantly longer time in the chamber with morphine-paired odor than in the control chamber. The effects of odor cue on the morphine CPP were blocked by the administration of dopamine D1 or D2 antagonists. The studies indicated that olfactory system plays an important role in drug addiction.