Sarihi A, Motamedi F, Naghdi N, Rashidy-Pour A
Department of Physiology, School of Medical Sciences, Tarbiat Modarres University, Tehran, Iran.
Behav Brain Res. 2000 Sep;114(1-2):1-9. doi: 10.1016/s0166-4328(00)00176-5.
Numerous studies in the past have dealt with the role of serotonergic system lesions in tasks aimed at measurement of cognitive behavior, but the literature concerning the role of serotonin in cognition remains controversial. Rats with electrolytic lesions of the median raphe nucleus (MRN) were found to display a profound impairment in both the acquisition and retention of spatial memory task. In this study, the lidocaine inactivation was employed to evaluate the involvement of the rat's median raphe nucleus in reference and working memory versions of the Morris water maze (MWM) task. Lidocaine (0.5 microl, 2%) was injected through a single cannula aimed at the MRN; control groups were treated in the same way with a 0.5 microl injection of saline. In Experiment 1, rats were trained in a reference memory version of the MWM with two blocks of four trials per day for three consecutive days, with intra-cerebral injection made 5 min before training. No significant difference was found. In Experiment 2, intra-cerebral injection was applied immediately after two blocks of four trials, and in Experiment 3, the drug was injected 5 min before retention test in rats that had received eight trials per day on three consecutive days. Again, no significant difference between control and treatment groups was found. These results indicate that MRN has no role in acquisition, consolidation and retrieval of spatial reference memory. In subsequent experiments, rats were trained in a working memory version of the MWM task to find a new target position in trial 1, and retrieval was tested 75 min later. MRN inactivation 5 min before (Experiment 4) and immediately after the acquisition trial (Experiment 5) enhanced spatial working memory. It is concluded that normal activity of the MRN has no role in formation and retrieval of reference memory, but it has an inhibitory role in working memory. Our results are confirmed with other studies suggesting that the serotonergic system has a different role in long-term and short-term memory. Interaction with other neurotransmitter systems like acetylcholine may be involved in this case.
过去有许多研究探讨了血清素能系统损伤在旨在测量认知行为的任务中的作用，但关于血清素在认知中的作用的文献仍存在争议。发现中缝正中核（MRN）发生电解损伤的大鼠在空间记忆任务的获取和保持方面均表现出严重受损。在本研究中，采用利多卡因失活来评估大鼠中缝正中核在莫里斯水迷宫（MWM）任务的参考记忆和工作记忆版本中的参与情况。通过一根针对MRN的单套管注射0.5微升（2%）的利多卡因；对照组以相同方式注射0.5微升生理盐水。在实验1中，大鼠在MWM的参考记忆版本中进行训练，每天进行两个时段，每个时段四次试验，连续三天，在训练前5分钟进行脑内注射。未发现显著差异。在实验2中，在两个时段、每个时段四次试验后立即进行脑内注射，在实验3中，在连续三天每天接受八次试验的大鼠的保持测试前5分钟注射药物。同样，对照组和治疗组之间未发现显著差异。这些结果表明，MRN在空间参考记忆的获取、巩固和提取中不起作用。在随后的实验中，大鼠在MWM任务的工作记忆版本中进行训练，在试验1中找到一个新的目标位置，并在75分钟后测试提取情况。在获取试验前5分钟（实验4）和获取试验后立即（实验5）进行MRN失活增强了空间工作记忆。得出的结论是，MRN的正常活动在参考记忆的形成和提取中不起作用，但在工作记忆中具有抑制作用。我们的结果得到了其他研究的证实，这些研究表明血清素能系统在长期和短期记忆中具有不同的作用。在这种情况下，可能涉及与其他神经递质系统如乙酰胆碱的相互作用。
