Hasenöhrl R U, Schwarting R K, Gerhardt P, Privou C, Huston J P
Institute of Physiological Psychology I, Heinrich-Heine-University, Düsseldorf, Germany.
Physiol Behav. 1994 Mar;55(3):541-6. doi: 10.1016/0031-9384(94)90115-5.
In the present study, substance P (SP) was injected intraperitoneally (IP), and its effects on operant behavior were assessed in rats, which had been trained to bar press for food reward on a fixed-ratio (FR) 20 schedule. These effects were compared with IP injection of morphine sulfate, which had previously been shown to strongly suppress operant responding on FR schedules. The IP injection of SP resulted in a dose-related decrement in response rates. SP in a dose range of 250-500 micrograms/kg decreased operant responding, whereas SP in a dose range of 5-50 micrograms/kg did not influence response rates. The IP injection of morphine (10 mg/kg) markedly suppressed operant responding. However, in contrast to the rate-decreasing effects of SP, this suppression was not selective for the reinforced lever as responding on the nonreinforced lever, used as a control, was also decreased. Furthermore, both injection of 10 mg/kg morphine and SP in a dose range of 250-500 micrograms/kg was found to reduce food intake when the animals had free access to food subsequent to the operant conditioning session. The present results provide the first evidence that systemically administered neurokinin SP can affect operant responding for food reward. The suppressive effects on operant behavior and feeding obtained with systemic SP or morphine are discussed with respect to recent findings showing that both drugs can modulate mesolimbic dopamine activity after systemic drug injection.
在本研究中，将P物质（SP）腹腔注射（IP），并在大鼠中评估其对操作性行为的影响，这些大鼠已被训练在固定比率（FR）20的时间表上按压杠杆以获取食物奖励。将这些影响与腹腔注射硫酸吗啡的情况进行比较，硫酸吗啡先前已被证明能强烈抑制FR时间表上的操作性反应。腹腔注射SP导致反应率呈剂量相关的下降。剂量范围为250 - 500微克/千克的SP降低了操作性反应，而剂量范围为5 - 50微克/千克的SP对反应率没有影响。腹腔注射吗啡（10毫克/千克）显著抑制了操作性反应。然而，与SP的降低速率效应相反，这种抑制对强化杠杆没有选择性，因为作为对照的非强化杠杆上的反应也减少了。此外，当动物在操作性条件反射实验后可自由获取食物时，发现注射10毫克/千克吗啡和剂量范围为250 - 500微克/千克的SP都会减少食物摄入量。本研究结果首次证明，全身给药的神经激肽SP可影响获取食物奖励的操作性反应。关于最近的研究结果，即这两种药物在全身注射后均可调节中脑边缘多巴胺活性，讨论了全身给予SP或吗啡对操作性行为和进食的抑制作用。
