Daza-Losada M, Rodríguez-Arias M, Aguilar M A, Miñarro J
Unidad de Investigación Psicobiología de las Drogodependencias, Departamento de Psicobiología, Facultad de Psicología, Universitat de Valencia, Avda. Blasco Ibáñez 21, 46010 Valencia, Spain.
Prog Neuropsychopharmacol Biol Psychiatry. 2008 Apr 1;32(3):701-9. doi: 10.1016/j.pnpbp.2007.11.017. Epub 2007 Nov 23.
It is well known that an elevated percentage of ecstasy users also consume cocaine. Recently, it has been reported that a high frequency of heroin smokers first consumed heroin under the effects of ecstasy with the hope of reducing the stimulant effects of the latter drug. The aim of the present study was to evaluate the effect of exposure to MDMA and cocaine during adolescence on morphine-induced conditioned place preference (CPP) and reinstatement in adulthood. In the first experiment, adolescent mice were exposed to six injections of MDMA and three weeks later their response to the reinforcing properties of 40 mg/kg of morphine was evaluated using the CPP paradigm. All the treatment groups developed the same magnitude of morphine-induced preference and, after CPP was extinguished, it was restored in all the groups with a priming dose of 10 mg/kg of morphine. Only mice that had been treated with 10 or 20 mg/kg of MDMA had their morphine-induced preference reinstated after receiving only 5 mg/kg of morphine. In the second experiment, adolescent mice were similarly treated with six administrations of cocaine (25 mg/kg) or cocaine plus MDMA (5, 10 or 20 mg/kg), and their response to morphine-induce CPP was evaluated three weeks later. Similarly to the first experiment, all the groups developed a preference for the morphine-paired compartment, but this preference was not reinstated with a priming dose of 10 mg/kg of morphine following extinction, as was the case among the control animals. These results lead us to hypothesize that periadolescent MDMA exposure alters responsiveness to the rewarding properties of morphine, highlighting MDMA as a gateway drug whose use may increase the likelihood of dependence on other drugs.
众所周知，摇头丸使用者中同时吸食可卡因的比例较高。最近有报道称，相当一部分海洛因吸食者最初是在摇头丸的影响下首次吸食海洛因的，希望借此减轻后者的兴奋作用。本研究的目的是评估青春期接触摇头丸和可卡因对成年后吗啡诱导的条件性位置偏爱（CPP）及复吸的影响。在第一个实验中，给青春期小鼠注射六次摇头丸，三周后使用CPP范式评估它们对40mg/kg吗啡强化特性的反应。所有治疗组产生的吗啡诱导偏爱程度相同，在CPP消退后，所有组用10mg/kg的吗啡启动剂量均可使其恢复。只有接受10或20mg/kg摇头丸治疗的小鼠在仅接受5mg/kg吗啡后，其吗啡诱导的偏爱得以恢复。在第二个实验中，给青春期小鼠同样注射六次可卡因（25mg/kg）或可卡因加摇头丸（5、10或20mg/kg），三周后评估它们对吗啡诱导CPP的反应。与第一个实验类似，所有组都对与吗啡配对的隔室产生了偏爱，但在消退后，用10mg/kg的吗啡启动剂量并不能使其恢复偏爱，而对照组动物则可以。这些结果使我们推测，青春期前后接触摇头丸会改变对吗啡奖赏特性的反应性，突出了摇头丸作为一种先导药物，其使用可能会增加对其他药物产生依赖的可能性。
