Solórzano Hernández Eduardo, Cervantes Alfaro José Miguel, Figueroa Rosales Rosalinda, Gutiérrez Guzmán Blanca Érika, López Vázquez Miguel Ángel, Olvera Cortés María Esther
Laboratorio de Neurociencias, División de Estudios de Posgrado, Facultad de Ciencias Médicas y Biológicas "Dr. Ignacio Chávez", Universidad Michoacana de San Nicolás de Hidalgo, Mexico; Laboratorio de Neurofisiología Experimental, División de Neurociencias, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro Social, Mexico.
Laboratorio de Neurociencias, División de Estudios de Posgrado, Facultad de Ciencias Médicas y Biológicas "Dr. Ignacio Chávez", Universidad Michoacana de San Nicolás de Hidalgo, Mexico.
Behav Brain Res. 2022 Oct 28;435:114056. doi: 10.1016/j.bbr.2022.114056. Epub 2022 Aug 11.
Increases in power and frequency of hippocampal theta activity have been related to efficient place learning and memory acquisition in hippocampal-dependent tests. The complex medial septum-diagonal band of Broca (MS/DBB) is the pacemaker of hippocampal theta activity, influenced by the ascending synchronizing system, and modulated by serotonergic raphe medial afferents, acting on cholinergic and GABAergic septal neurons. The suppression of hippocampal theta expression and the modulation of hippocampal learning and memory are attributed to serotonin. To simultaneously test these hypotheses, a daily local serotonin increase was induced by citalopram (CIT) infusion (100 µM, 0.88 µl, 0.2 µl/m) 15 min before training in the Morris water maze. The theta activity was recorded in the MS/DBB, dentate gyrus (DG) and CA1 of one group infused with artificial cerebrospinal liquid (ACL) and the other with CIT on Days 1-6 of training. After a probe trial (Day 7) and one resting day, the treatments were reversed (Days 8-11). The CIT MS/DBB infusion in the first 6 training days reduced the efficiency of spatial learning in association with reduced power in the DG, reduced MS/DBB-DG coherence, increased DG-CA1 coherence, and a lack of a negative correlation between MS/DBB power and swam distances. No effect of the CIT occurred once the information was acquired under ACL training. These results support a role of serotonin, in acting on the MS/DBB in the fine tuning of hippocampal learning and memory efficiency through the modulation of learning-related theta activity power and septohipocampal synchronization.
海马体θ活动的功率和频率增加与海马体依赖测试中的高效位置学习和记忆获取有关。复杂的内侧隔区-布罗卡斜角带（MS/DBB）是海马体θ活动的起搏器，受上行同步系统影响，并由作用于胆碱能和GABA能隔区神经元的血清素能中缝内侧传入纤维调节。海马体θ表达的抑制以及海马体学习和记忆的调节归因于血清素。为了同时验证这些假设，在莫里斯水迷宫训练前15分钟，通过西酞普兰（CIT）输注（100µM，0.88µl，0.2µl/m）诱导每日局部血清素增加。在训练的第1-6天，记录一组注入人工脑脊液（ACL）和另一组注入CIT的动物在MS/DBB、齿状回（DG）和CA1中的θ活动。在进行一次探索性试验（第7天）和一个休息日之后，处理方式颠倒（第8-11天）。在最初6天的训练中，CIT注入MS/DBB降低了空间学习效率，同时DG功率降低、MS/DBB-DG相干性降低、DG-CA1相干性增加，并且MS/DBB功率与游动距离之间缺乏负相关。一旦在ACL训练下获取了信息，CIT就没有效果。这些结果支持血清素通过调节与学习相关的θ活动功率和隔海马同步，作用于MS/DBB，对海马体学习和记忆效率进行微调。
