Cocaine and amphetamine-regulated transcript (CART) peptides are neurotransmitters with important roles in drug abuse. The increase of CART expression in the brain induced by psychostimulants is associated with changes of behavior in addicted animals. We expressed and purified the single-chain variable fragments antibody (scFv) against CART55-102, and observed the effect of CART scFv on the expression of cocaine-induced behavior sensitization in mice. Results showed that the titer of CART scFv was 1.6 μg/ml. Single administration of CART scFv (intraperitoneal 0.04, 0.2, and 1 mg/kg) reduced the increasing locomotor activity induced by chronic cocaine intake in mice (P<0.05-0.01), but failed to affect the locomotor activity of naive mice. These results suggested that CART scFv may be a potential therapeutic tool to treat drug abuse.

Objective:To study the effect of cocaine-and amphetamine-regulated transcript(CART)protein vaccine on morphine analgesia and tolerance.Methods:The expression plasmid pGEX-4T3-CART was constructed by gene cloning.The CART protein was purified by glutathione s-transferase(GST)-affinity chromatography.The experiment included 6 groups: blank control,normal saline(NS),GST+Freund's adjuvant,and CART protein vaccine(5μg,10μg and 20μg)groups.After immunization for twice,all groups were tested in hot plate.Morphine analgesia effect was evaluated through s.c.injection with 6 mg/kg morphine solution,calculated by MPE%.Then morphine tolerance model was established,and the tolerance to morphine was tested by s.c.injection with 6 mg/kg morphine 12 h after the last injection.Results:CART vaccine itself had no pronounced effect on the pain threshold(P0.05).CART vaccine at 10μg significantly depressed the analgesic effect of morphine analgesia (P0.05).Compared with NS group,vaccine groups showed a potential antagonizing tolerance effect,especially in the 10μg group,with the MPE% significantly increased(P0.05).Conclusion..CART vaccine itself has no influence on the pain re- sponse;however,it can impair the analgesia effect of morphine and can antagonize the analgesia tolerance to morphine.