Kivastik T, Vuorikallas K, Piepponen T P, Zharkovsky A, Ahtee L
University of Helsinki, Department of Pharmacy, Finland.
Pharmacol Biochem Behav. 1996 Jun;54(2):371-5. doi: 10.1016/0091-3057(95)02052-7.
The role of dopamine in opioid reward is unresolved. Furthermore, the issue is somewhat unclear regarding cocaine and the place preference paradigm. In the present study we investigated whether the drugs activating dopamine autoreceptors affect cocaine- and morphine-induced place preference in rats. Neither the dopamine D2/D3 receptor agonist, quinpirole (0.05 mg/kg, SC), nor the partial dopamine autoreceptor agonist, preclamol (2 or 8 mg/kg, SC), induced place conditioning by itself. Quinpirole had no significant influence on the place preference induced either by morphine (3 mg/kg, SC) or cocaine (5 mg/kg, IP). Preclamol, when given at the dose of 8 mg/kg SC, significantly attenuated the effect of cocaine but failed to modify the effect of morphine. Our results suggest that the rewarding properties of morphine involve DA-independent mechanisms whereas in the cocaine-induced reward the role of brain DA is critical. Furthermore, as regards place conditioning, we propose that the activation of DA autoreceptors is not sufficient to reliably modify the rewarding effect of cocaine.
多巴胺在阿片类奖赏中的作用尚未明确。此外，关于可卡因和位置偏爱范式的问题也有些不清晰。在本研究中，我们调查了激活多巴胺自身受体的药物是否会影响大鼠对可卡因和吗啡诱导的位置偏爱。多巴胺D2/D3受体激动剂喹吡罗（0.05毫克/千克，皮下注射）和部分多巴胺自身受体激动剂普拉克莫（2或8毫克/千克，皮下注射）单独使用时均未诱导出位置条件反射。喹吡罗对吗啡（3毫克/千克，皮下注射）或可卡因（5毫克/千克，腹腔注射）诱导的位置偏爱没有显著影响。普拉克莫以8毫克/千克皮下注射给药时，可显著减弱可卡因的作用，但未能改变吗啡的作用。我们的结果表明，吗啡的奖赏特性涉及不依赖多巴胺的机制，而在可卡因诱导的奖赏中，脑多巴胺的作用至关重要。此外，就位置条件反射而言，我们认为激活多巴胺自身受体不足以可靠地改变可卡因的奖赏效应。
