Miladi Gorji Hossein, Rashidy-Pour Ali, Fathollahi Yaghoub
Laboratory of Learning and Memory, Department and Research Center of Physiology, Semnan University of Medical Sciences, Semnan, Iran.
Physiol Behav. 2008 Feb 27;93(3):622-7. doi: 10.1016/j.physbeh.2007.11.002. Epub 2007 Nov 9.
Numerous studies have dealt with the role of opiate system in tasks aimed at measurement of cognitive behavior, but the role of morphine dependence on learning and memory is still controversial. In this study chronic exposure to morphine was employed to evaluate learning ability and spatial short-term memory (working memory) and long-term memory (reference memory) in the water maze task. Male albino rats were made dependent by chronic administration of morphine in drinking water that lasted at least 21 days. In Experiment 1, the performance of animals was evaluated in reference memory version of the water maze. Rats were submitted to a session of 6 trials for 6 consecutive days to find the submerged platform that was located in the center of a quadrant. Latency and traveled distance to find the platform were measured as indexes of learning. Memory retention was tested 24 h after the last training session in a probe trial (60 s) in which there was no platform and the time spent in each quadrant of the water maze was recorded. Results indicated that latency and traveled distance to find the platform were same in control and dependent rats during training days, but during the probe test morphine-dependent group spent significantly less time in the target quadrant. In Experiment 2, training on working memory version of the water maze task was started. Only two trials per day were given until the performance of animals was stabilized (at least 5 days). Final test was done at day 6. Acquisition-retention interval was 75 min. No significant differences were found on acquisition and retention trials between morphine and control groups. Our findings indicate that chronic exposure to morphine did not impair learning ability, but partially impaired retention of spatial long-term (reference) memory. Moreover, dependence on morphine did not affect either acquisition or retention of spatial short (working) memory.
许多研究都探讨了阿片系统在旨在测量认知行为的任务中的作用，但吗啡对学习和记忆的影响仍存在争议。在本研究中，采用慢性暴露于吗啡的方法来评估水迷宫任务中的学习能力、空间短期记忆（工作记忆）和长期记忆（参考记忆）。通过在饮用水中慢性给予吗啡至少21天，使雄性白化大鼠产生依赖性。在实验1中，在水迷宫的参考记忆版本中评估动物的表现。大鼠连续6天每天进行6次试验，以找到位于象限中心的水下平台。将找到平台的潜伏期和行进距离作为学习指标进行测量。在最后一次训练 session 后24小时进行记忆保持测试，在一个探测试验（60秒）中没有平台，记录在水迷宫每个象限中花费的时间。结果表明，在训练期间，对照组和依赖组大鼠找到平台的潜伏期和行进距离相同，但在探测测试中，吗啡依赖组在目标象限花费的时间明显更少。在实验2中，开始进行水迷宫任务工作记忆版本的训练。每天只进行两次试验，直到动物的表现稳定（至少5天）。在第6天进行最终测试。获取 - 保持间隔为75分钟。吗啡组和对照组在获取和保持试验中没有发现显著差异。我们的研究结果表明，慢性暴露于吗啡不会损害学习能力，但会部分损害空间长期（参考）记忆的保持。此外，对吗啡的依赖不会影响空间短期（工作）记忆的获取或保持。
