The current study investigated whether the stimulus effects of morphine can function as a positive and negative feature in a Pavlovian occasion setting drug discrimination preparation in male and female rats. Sprague-Dawley rats were assigned to a feature positive (FP) or feature negative (FN) training group and all received intermixed morphine (3.2 mg/kg, IP) or saline injections 15 min before 20-min daily training sessions. For FP rats, on morphine sessions, each of eight 15-s white noise (WN) presentations was followed by 4-s access to sucrose (0.01 ml, 26% w/v); on saline sessions, sucrose was withheld. FN rats learned the reverse contingency. FP discrimination was acquired somewhat sooner than FN discrimination, and females, but not males, became sensitized to the locomotor effects of morphine, which did not influence conditioned responding. Rats then entered dose generalization testing. There was no sex difference in dose generalization for FN groups (ED₅₀ 1.26 for males and 1.57 for females). Yet for FP rats, the dose response curve for females was shifted to the right compared to males (ED₅₀ 0.54 for males and 1.94 for females). FP females exhibited enhanced responding at a dose higher than that of their original training. These findings reveal the need to reassess our notions of drug stimuli that guide appropriate associative behaviours from the perspective of sex differences.

目前的研究调查了吗啡的刺激作用是否可以在巴甫洛夫场合设置雄性和雌性大鼠的药物鉴别制剂中起到积极和消极的作用。Sprague-Dawley 大鼠被分配到特征阳性 (FP) 或特征阴性 (FN) 训练组，并且在每天 20 分钟的训练课程前 15 分钟接受混合吗啡（3.2 毫克/千克，IP）或生理盐水注射。对于 FP 大鼠，在吗啡治疗中，每 8 次 15 秒白噪声 (WN) 演示之后是 4 秒获取蔗糖（0.01 毫升，26% w/v）；在盐水治疗中，蔗糖被扣留。FN 大鼠学会了反向偶然性。FP 识别比 FN 识别要早一些，并且女性，而不是男性，对吗啡的运动效应变得敏感，这不会影响条件反应。然后大鼠进入剂量泛化测试。FN 组（ED₅₀男性为 1.26，女性为 1.57）。然而，对于 FP 大鼠，与雄性相比，雌性的剂量反应曲线向右移动（雄性的 ED _{50 为}0.54，雌性为 1.94）。FP 雌性在高于其原始训练的剂量下表现出增强的反应。这些发现表明需要重新评估我们对药物刺激的概念，这些概念从性别差异的角度指导适当的联想行为。