Department of Neuroscience, Centre for Addiction and Mental Health, Toronto, Ontario, Canada M5S 2S1.
Behav Brain Res. 2010 Jan 20;206(2):240-4. doi: 10.1016/j.bbr.2009.09.018. Epub 2009 Sep 16.
The initiation of smoking typically begins during adolescence, suggesting that nicotine may have different motivational effects during this developmental stage compared to adulthood. Studies using the conditioned place preference (CPP) procedure have demonstrated that adolescent rats are more sensitive to the conditioned rewarding effects of subcutaneously administered nicotine compared to adult rats, whereas intravenous self-administration studies have not demonstrated consistent age differences in the reinforcing effects of nicotine. This study was designed to evaluate if intravenously administered nicotine has age-dependent conditioned rewarding effects. Using an unbiased CPP procedure, adolescent and adult male Wistar rats were conditioned with one of two intravenous doses of nicotine that are sufficient to maintain self-administration (0.03 or 0.06 mg/kg) or vehicle (saline) over a period of 8 conditioning trials (4 nicotine and 4 vehicle). Adolescent rats conditioned with 0.03 mg/kg nicotine demonstrated a significant CPP, whereas adult rats did not at either dose tested. After 8 extinction trials, reinstatement of the CPP was observed following a nicotine priming injection (0.15 mg/kg, s.c.) in adolescents that had previously been conditioned with 0.03 mg/kg nicotine; vehicle-treated rats did not show a significant preference for either compartment. The present data are consistent with previous CPP studies using subcutaneously administered nicotine and suggest that passively administered intravenous nicotine is more rewarding in adolescent compared to adult rats.
吸烟的开始通常发生在青少年时期，这表明尼古丁在这个发育阶段可能与成年期有不同的动机作用。使用条件位置偏好（CPP）程序的研究表明，与成年大鼠相比，青少年大鼠对皮下给予尼古丁的条件奖赏作用更为敏感，而静脉内自我给药研究并未表明尼古丁的强化作用在年龄上存在一致的差异。本研究旨在评估静脉内给予的尼古丁是否具有年龄依赖性的条件奖赏作用。使用无偏 CPP 程序，雄性 Wistar 青少年和成年大鼠在 8 个条件试验（4 个尼古丁和 4 个载体）期间，用足以维持自我给药的两种静脉内尼古丁剂量之一（0.03 或 0.06mg/kg）或载体（盐水）进行条件训练。用 0.03mg/kg 尼古丁训练的青少年大鼠表现出明显的 CPP，而在测试的两个剂量下，成年大鼠均未表现出 CPP。在 8 次消退试验后，在先前用 0.03mg/kg 尼古丁训练过的青少年大鼠中，给予尼古丁引发注射（0.15mg/kg，皮下）后，CPP 得到了恢复；接受载体治疗的大鼠对任何一个隔间都没有表现出明显的偏好。目前的数据与使用皮下给予尼古丁的 CPP 研究一致，表明与成年大鼠相比，被动给予静脉内尼古丁在青少年中更具奖赏性。
