Caprioli Daniele, Paolone Giovanna, Celentano Michele, Testa Arianna, Nencini Paolo, Badiani Aldo
Department of Human Physiology and Pharmacology, University of Rome Sapienza, 5 Piazzale Aldo Moro, 00185, Rome, Italy.
Psychopharmacology (Berl). 2007 Jun;192(3):397-406. doi: 10.1007/s00213-007-0717-z. Epub 2007 Feb 13.
Previous studies have shown that environmental context can powerfully modulate the induction of psychomotor sensitization to cocaine in the rat. Rats that receive repeated administrations of cocaine in association with environmental novelty exhibit greater psychomotor sensitization than animals that receive the same treatments in their home cages.
The goal of the present study was to investigate whether environmental context can exert its modulatory influence also on cocaine self-administration.
Independent groups of rats with intravenous catheters were given the possibility to self-administer different doses of cocaine (0.0, 0.2, 0.4, and 0.8 mg/kg per infusion) under two environmental conditions. Some animals were housed in the self-administration cages (home groups), whereas other rats were transported to the self-administration cages only for the test sessions (novelty groups).
Environmental "novelty" facilitated the acquisition of cocaine self-administration at the doses of 0.2 and 0.4 mg/kg per infusion. When rats were given access to a higher dose of cocaine (0.8 mg/kg per infusion), there were no significant group differences in drug taking. Environmental context had no effect on the self-administration of the vehicle. Thus, it appears that environmental "novelty" produced a shift to the left in the dose-effect curve for cocaine self-administration. Furthermore, "novelty" enhanced the motivation of the rats to work for cocaine, as indicated by the results of a progressive ratio procedure.
The present findings demonstrate for the first time that the environment surrounding drug taking can alter both the intake of and motivation for cocaine.
先前的研究表明，环境背景能够有力地调节大鼠对可卡因的精神运动性敏感化的诱导。在环境新奇的情况下接受重复可卡因给药的大鼠比在其笼舍中接受相同处理的动物表现出更强的精神运动性敏感化。
本研究的目的是调查环境背景是否也能对可卡因自我给药产生调节作用。
给独立的静脉插管大鼠组提供在两种环境条件下自我给药不同剂量可卡因（每次输注0.0、0.2、0.4和0.8毫克/千克）的机会。一些动物饲养在自我给药笼中（笼舍组），而其他大鼠仅在测试期间被运送到自我给药笼中（新奇组）。
环境“新奇”促进了每次输注0.2和0.4毫克/千克剂量可卡因的自我给药的习得。当给大鼠提供更高剂量的可卡因（每次输注0.8毫克/千克）时，在药物摄取方面没有显著的组间差异。环境背景对赋形剂的自我给药没有影响。因此，似乎环境“新奇”使可卡因自我给药的剂量-效应曲线向左移动。此外，如渐进比率程序的结果所示，“新奇”增强了大鼠为获得可卡因而工作的动机。
本研究结果首次表明，服药时的环境能够改变可卡因的摄入量和动机。
