Operant responding for conditioned and unconditioned reinforcers in rats is differentially enhanced by the primary reinforcing and reinforcement-enhancing effects of nicotine
Operant responding for conditioned and unconditioned reinforcers in rats is differentially enhanced by the primary reinforcing and reinforcement-enhancing effects of nicotine
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DOI：
10.1007/s00213-006-0522-0
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发表时间：
2006-11-01
影响因子：
3.4
通讯作者：
Sved, Alan F.
中科院分区：
文献类型：
--
作者：
Chaudhri, Nadia;Caggiula, Anthony R.;Sved, Alan F.
在大鼠中，尼古丁自身给药的原理是适度的，当尼古丁单独注射(主要强化)时，尼古丁自身给药是适度的，但当尼古丁注射与温和加强的非药理刺激相结合时，尼古丁自我给药是强大的。此外，非反应性(非偶发)尼古丁给药也提高了对同一非药理刺激的反应性，这表明除了初级强化外，尼古丁还可以增强其他强化的激励价值。目的在本研究中，我们检验了这样的假设，即非偶发尼古丁的强化作用更依赖于非药理刺激的强化强度，而非偶发尼古丁的作用更依赖于偶发尼古丁的强化强度。材料与方法通过在一些大鼠重复地与蔗糖配对，或通过将蔗糖吸入其他大鼠的显式非配对设计中递送，建立了弱强化的光调刺激。随后，两组受试者均按固定比例和累进比例的强化方案，分别施加偶发尼古丁、非偶发尼古丁(0.06 mg kg(-1)/次注射，自由基)或非偶发生理盐水的刺激。条件性和非条件性尼古丁对这种条件性刺激的反应同样升高。相反，对于不那么强烈的刺激(蔗糖不成对的)，或有尼古丁比非或有尼古丁更有效地提高行为。结论尼古丁的强化增强作用增加了受条件和非条件增强剂控制的行为；然而，对于不那么显著的刺激，来自或有尼古丁的初级强化效应的关联过程也可能是重要的。这些数据表明，烟草中存在的尼古丁可能会以不同的方式调节吸烟者的刺激驱动行为。
Rationale Nicotine self-administration in rats is modest when response-contingent nicotine infusions are delivered alone ( primary reinforcement) but robust when nicotine infusions are combined with a mildly reinforcing non-pharmacological stimulus. Furthermore, response-independent (non-contingent) nicotine administration also elevates responding for that same non-pharmacological stimulus, suggesting that in addition to primary reinforcement, nicotine can enhance the incentive value of other reinforcers.Objectives In this study, we tested the hypothesis that the reinforcement-enhancing effects of non- contingent nicotine are more dependent on the reinforcing strength of the nonpharmacological stimulus than are the effects of contingent nicotine.Materials and methods A weakly reinforcing light-tone stimulus was established as a conditioned reinforcer by repeated pairings with sucrose for some rats, or by delivery in an explicitly unpaired design with sucrose to other rats. Subsequently, both groups lever pressed for the stimulus with contingent nicotine, non- contingent nicotine (0.06 mg kg(-1) per infusion, freebase), or non- contingent saline, according to fixed ratio and progressive ratio reinforcement schedules.Results Compared to sucrose-unpaired training, repeated association with sucrose established the light-tone stimulus as a robust conditioned reinforcer. Contingent and non-contingent nicotine equally elevated responding for this conditioned stimulus. Conversely, for the less reinforcing (sucrose-unpaired) stimulus contingent nicotine more effectively elevated behavior compared to non-contingent nicotine.Conclusions The reinforcement-enhancing effect of nicotine increases behavior controlled by both conditioned and unconditioned reinforcers; however, for less salient stimuli associative processes derived from the primary reinforcing effects of contingent nicotine may also be important. These data suggest that nicotine present in tobacco may differentially modulate stimulus-driven behavior in smokers.