Kohut Stephen J, Handler Samantha L, Hertzbach Robin L, Riley Anthony L
Psychopharmacology Laboratory, Department of Psychology, American University, 4400 Massachusetts Avenue, NW, Washington, DC 20016, United States.
Drug Alcohol Depend. 2007 Nov 2;91(1):18-25. doi: 10.1016/j.drugalcdep.2007.04.012. Epub 2007 Jun 4.
Under traditional water-deprived conditions, both LiCl and morphine produce comparable suppression of saccharin consumption after repeated pairings. However, under conditions of spaced food deliveries (i.e., schedule-induced polydipsia; SIP), morphine produces a significantly weaker suppression than LiCl. The differential responses have been attributed to an increase in the rewarding effects of drugs of abuse (such as morphine) that masked the expression of the aversive effects, a masking not evident with LiCl which has no reported rewarding effects. The present study extended this characterization to two additional drugs of abuse; cocaine and ethanol. Following schedule-induced saccharin consumption, female Sprague-Dawley rats were given injections of LiCl, cocaine, ethanol (at doses comparably effective in conditioning taste aversions under water deprivation) or distilled water vehicle. Although cocaine and ethanol both suppressed SIP, only cocaine produced a significantly delayed suppression relative to LiCl. The differential effects of cocaine (and morphine), but not ethanol, may be a function of the different reward profiles of these drugs. Given the differential ability of drugs of abuse to suppress consumption under conditions of spaced feedings, the SIP procedure may be a useful baseline to assess the rewarding effects of such drugs. Further, given the differential results with cocaine and ethanol, the relative rewarding effects of drugs may be differentially indexed in this preparation, as well.
在传统的缺水条件下，重复配对后，氯化锂和吗啡对糖精消耗的抑制作用相当。然而，在间歇性喂食条件下（即定时诱导的多饮；SIP），吗啡产生的抑制作用明显弱于氯化锂。这种差异反应归因于滥用药物（如吗啡）奖赏效应的增加，掩盖了厌恶效应的表现，而氯化锂没有奖赏效应，所以不存在这种掩盖现象。本研究将这种特征扩展到另外两种滥用药物；可卡因和乙醇。在定时诱导糖精消耗后，给雌性斯普拉-道利大鼠注射氯化锂、可卡因、乙醇（剂量在缺水条件下对味觉厌恶条件反射同样有效）或蒸馏水载体。虽然可卡因和乙醇都抑制了SIP，但只有可卡因相对于氯化锂产生了明显延迟的抑制作用。可卡因（和吗啡）的差异效应而非乙醇的差异效应，可能是这些药物不同奖赏特征的作用。鉴于滥用药物在间歇性喂食条件下抑制消耗的能力不同，SIP程序可能是评估此类药物奖赏效应的有用基线。此外，鉴于可卡因和乙醇的差异结果，药物的相对奖赏效应在这种实验准备中也可能有不同的指标。
