Department of Psychology, University of Pittsburgh, 210 S. Bouquet Street, Pittsburgh, PA 15260, USA.
Drug Alcohol Depend. 2012 Oct 1;125(3):307-12. doi: 10.1016/j.drugalcdep.2012.03.006. Epub 2012 Apr 7.
Adolescence is a period of development associated with a peak in an organism's responsiveness to reward. Epidemiological data indicate that the initiation of smoking is high during adolescence and that earlier age of onset is associated with increased incidence of dependence as adults. In rats, nicotine is known to have primary reinforcing and reinforcement enhancing effects. Although the primary reinforcing effects of nicotine have been demonstrated in adolescent rats (self-administration), less is known about its reinforcement enhancing effects during this period. Moreover, the impact of adolescent nicotine exposure on its reinforcement enhancing effects during adulthood has not yet been examined. The objectives of this study were to assess whether (1) nicotine enhances operant responding for an unconditioned visual reinforcer (VS) in adolescent rats, and (2) exposure to nicotine during adolescence affects responsiveness to the VS in adulthood.
Rats were exposed to nicotine (0.32 mg/kg, subcutaneous injection) or saline during adolescence (postnatal day 29-42) and adulthood. Nose-poking for the VS was assessed under fixed and progressive ratio schedules.
Nicotine increased responding for the VS during adolescence. Adolescent nicotine exposure failed to significantly affect adult responsiveness for the VS, regardless of adult nicotine exposure, but early exposure to the VS affected responsiveness to the VS in adulthood.
Nicotine exhibits reinforcement enhancing effects in adolescent rats. Long-term effects of adolescent nicotine on reinforcement enhancement are minimal, but the impact of early exposure to the VS and/or the primary reinforcing effects of nicotine requires further investigation.
青春期是一个与生物体对奖励的反应性达到高峰相关的发展阶段。流行病学数据表明，青少年开始吸烟的比例很高，而且发病年龄越早，成年后依赖的发生率就越高。在老鼠身上，尼古丁已知具有主要的强化和增强强化作用。尽管尼古丁对青春期老鼠的主要强化作用已经得到证实（自我给药），但在这段时间内，它对增强强化作用的了解较少。此外，青春期暴露于尼古丁对其成年后增强强化作用的影响尚未得到检验。本研究的目的是评估（1）尼古丁是否增强青春期大鼠对非条件视觉强化物（VS）的操作性反应，以及（2）青春期暴露于尼古丁是否会影响成年后对 VS 的反应性。
在青春期（出生后第 29-42 天）和成年期，大鼠接受尼古丁（0.32mg/kg，皮下注射）或生理盐水处理。通过固定和递增比率程序评估对 VS 的鼻探测反应。
尼古丁在青春期增加了对 VS 的反应。无论成年期是否暴露于尼古丁，青春期暴露于尼古丁都不会显著影响成年期对 VS 的反应性，但早期暴露于 VS 会影响成年期对 VS 的反应性。
尼古丁在青春期大鼠中表现出增强强化作用。青春期尼古丁对强化增强的长期影响很小，但早期暴露于 VS 和/或尼古丁的主要强化作用需要进一步研究。
