van Haaren F
University of Florida, Department of Psychology, Gainesville 32611.
Pharmacol Biochem Behav. 1994 May;48(1):265-73. doi: 10.1016/0091-3057(94)90526-6.
Intact and gonadectomized male and female Wistar rats pressed a lever on a multiple (tandem Random-Interval 30-s, Differential Reinforcement of High Rate 0.5-s) (tandem Random-Interval 30-s, Differential Reinforcement of Low-Rate 5.0-s) schedule of reinforcement. The pacing requirements maintained high and low response rates under equal reinforcement frequencies. Low doses of cocaine (1 and 3 mg/kg) either did not affect or slightly increased high and low response rates of intact and gonadectomized female rats, while they did not affect or decrease high and low response rates of intact and castrated male rats. Higher doses of cocaine (up to 30 mg/kg) dose-dependently decreased both high and low response rates for all subjects. Intact male rats were less sensitive to the rate-decreasing effects of these doses of cocaine than castrated male rats or intact and ovariectomized female rats. Chronic cocaine administration consistently resulted in behavioral sensitization only in intact male subjects. The results of this experiment provide further support for the notion that the behavioral effects of psychomotor stimulant drugs are not necessarily rate dependent but may depend upon the extent to which schedule contingencies allow for behavioral variability without negatively affecting behavioral outcomes.
完整的和去性腺的雄性及雌性Wistar大鼠在多重（串联随机间隔30秒、高比率0.5秒差异强化）（串联随机间隔30秒、低比率5.0秒差异强化）强化程序下按压杠杆。节奏要求在相等的强化频率下维持高反应率和低反应率。低剂量可卡因（1和3毫克/千克）对完整的和去性腺的雌性大鼠的高反应率和低反应率要么没有影响，要么略有增加，而对完整的和阉割的雄性大鼠的高反应率和低反应率没有影响或使其降低。更高剂量的可卡因（高达30毫克/千克）对所有实验对象的高反应率和低反应率均呈剂量依赖性降低。完整的雄性大鼠对这些剂量可卡因的反应率降低效应不如阉割的雄性大鼠或完整的及卵巢切除的雌性大鼠敏感。长期给予可卡因仅在完整的雄性实验对象中持续导致行为敏化。本实验结果进一步支持了以下观点：精神运动兴奋剂药物的行为效应不一定依赖于反应率，而可能取决于程序意外情况在不对行为结果产生负面影响的情况下允许行为变化的程度。
